Sales Tel: +63 945 7983492  |  Email Us    
SMDC Residences

Air Residences

Features and Amenities

Reflective Pool
Function Terrace
Seating Alcoves

Air Residences

Green 2 Residences

Features and Amenities:

Wifi ready study area
Swimming Pool
Gym and Function Room

Green 2 Residences

Bloom Residences

Features and Amenities:

Recreational Area
2 Lap Pools
Ground Floor Commercial Areas

Bloom Residences

Leaf Residences

Features and Amenities:

3 Swimming Pools
Gym and Fitness Center
Outdoor Basketball Court

Leaf Residences

Contact Us

Contact us today for a no obligation quotation:


+63 945 7983492
+63 908 8820391

Copyright © 2018 SMDC :: SM Residences, All Rights Reserved.


































































3X0-103 dumps with Real exam Questions and Practice Test - smresidences.com.ph

Great Place to download 100% free 3X0-103 braindumps, real exam questions and practice test with VCE exam simulator to ensure your 100% success in the 3X0-103 - smresidences.com.ph

Pass4sure 3X0-103 dumps | Killexams.com 3X0-103 real questions | http://smresidences.com.ph/

3X0-103 Linux Networking (Level 1)

Study Guide Prepared by Killexams.com Sair Dumps Experts

Exam Questions Updated On :



Killexams.com 3X0-103 Dumps and Real Questions

100% Real Questions - Exam Pass Guarantee with High Marks - Just Memorize the Answers



3X0-103 exam Dumps Source : Linux Networking (Level 1)

Test Code : 3X0-103
Test Name : Linux Networking (Level 1)
Vendor Name : Sair
: 163 Real Questions

Its appropriate to study books for 3X0-103 exam, however make certain your achievement with those .
Nicely I used to spent maximum of my time surfing the internet but it become not all in useless because it emerge as my browsing that added me to this killexams.com right earlier than my 3X0-103 exam. Coming right here end up the extremely good issue that happened to me because it have been given me test rightly and consequently positioned up an super overall performance in my test.


Get fee percent state-of-the-art expertise to prepare 3X0-103 exam.
a few rightly men cant carry an alteration to the worlds way however they are able to best let you know whether you have got been the only guy who knew a way to try this and that i need to be regarded in this world and make my own mark and i have been so lame my entire way but I know now that I wanted to get a skip in my 3X0-103 and this could make me famous perhaps and yes i am brief of glory however passing my A+ exams with killexams.com became my morning and night glory.


Real 3X0-103 questions! I was not expecting such ease in exam.
Well I used to spent most of my time browsing the web but it was not all in vain because it was my browsing that brought me to this killexams.com right before my 3X0-103 exam. Coming here was the best thing that happened to me since it got me study well and consequently put up a good performance in my exams.


I were given great Questions financial institution for my 3X0-103 exam.
killexams.com helped me to score 96 percent in 3X0-103 certification therefore i have entire religion on the products of killexams. My first advent with this website become 12 months ago thru certainly one of my pal. I had made amusing of him for the usage of 3X0-103 exam engine but he guess with me about his highest grades. It was right because he had scored ninety one percent I only scored forty percentage. I am happy that my buddy gained the guess due to the fact now i have complete trust in this website and might come once more for repeated times.


Did you attempted this brilliant source state-of-the-art real examination questions.
i am very glad right now. You must be wondering why i am so satisfied, rightly the purpose is pretty easy, I just got my 3X0-103 test consequences and i have made it via them pretty without difficulty. I write over right here because it was this killexams.com that taught me for 3X0-103 check and i cant pass on with out thanking it for being so beneficiant and helpful to me at some point of.


I were given 3X0-103 licensed in 2 days practise.
I notably advocate this package deal to all people making plans to get 3X0-103 q and a. test for this certification are tough, and it takes a lot of work to skip them. killexams.com does most of it for you. 3X0-103 exam I got from this website had maximum of the questions provided at some point of the exam. with out these dumps, I suppose i would fail, and that is why such a lot of people dont pass 3X0-103 exam from the primary attempt.


what is easiest manner to bypass 3X0-103 examination?
It became genuinely 12 days to attempt for the 3X0-103 exam and i used to be loaded with some factors. I used to be searching out a smooth and powerful manual urgently. In the end, I were given the of killexams. Its brief solutions had been now not difficult to finish in 15 days. Inside the actual 3X0-103 exam, I scored 88%, noting all of the questions in due time and got 90% questions just like the pattern papers that they provided. An awful lot obliged to killexams.


in which can i download 3X0-103 ultra-modern dumps?
An lousy lot obliged to the only and best killexams.com. Its far the most sincere machine to pass the exam. I would thank the killexams.com exam cease end result, for my fulfillment within the 3X0-103. Examination was most effective three weeks beforehand, once I began to test this aide and it labored for me. I scored 89%, identifying how to finish the exam in due time.


wherein can i locate 3X0-103 real take a look at questions questions?
i am running into an IT firm and therefore I infrequently discover any time to put together for 3X0-103 exam. therefore, I ariseto an smooth conclusion of killexams.com dumps. To my wonder it worked like wonders for me. I ought to clear upall of the questions in least possible time than supplied. The questions appear to be quite clean with wonderful reference guide. I secured 939 marks which became sincerely a extremely good wonder for me. remarkable thanks to killexams!


No waste of time on internet! Found exact source of 3X0-103 questions.
I have renewed my membership this time for 3X0-103 exam. I accept my involvement with killexams.com is so important it is not possible surrender by not having a membership. I can just trust killexams.com exams for my exam. Just this site can help me attain my 3X0-103 accredition and help me in getting above 95% marks in the exam. You all are truly making an incredible showing. Keep it up!


Sair Linux Networking (Level 1)

top of the line Networking Tweaks for Linux | killexams.com Real Questions and Pass4sure dumps

A Linux equipment will also be tweaked to a level home windows clients may additionally envy (or concern) certainly for networking. Tweaking a Linux box for networking is somewhat greater mundane than different platforms: there are certain driver settings possible work with however its most reliable flexibility comes from a mix of OS-degree adjustments and adherence to distinctive RFCs.

ifconfig (interface) txqueuelen #

Speedy Linuxapplication buffers for community adapters on Linux birth off at a conservative one thousand packets. community researchers and scientists have mucked round with this, and figured out that they should be the use of 10,000 for anything respectable on a LAN; more when you are working GB or 10GE stuff. slow interfaces, equivalent to modems and WAN links, can default to 0-100, but don't be afraid to bump it up in opposition t 1000 and notice if your efficiency improves. Bumping up this environment does use memory, so be careful if you're the usage of an embedded router or anything (I've used 10,000 on 16MB RAM OpenWRT devices, no prob).

which you could edit /and so forth/rc.native, add an "up" command to /and many others/networking/interfaces, or something your distribution suggests and it be most useful to put a command like this at startup.

/and many others/sysctl.conf

This file governs default habits for a lot of community and file operation settings on Linux and other *nix-based mostly techniques. in case you install Ubuntu or Fedora programs, you will word they're going to add their personal tweaks (continually protection or file-oriented) to the file: do not delete these, until you read up on them, or see any that are contradicted through the advised additions here...

net.ipv4.tcp_rfc1337=1

web.ipv4.tcp_window_scaling=1

internet.ipv4.tcp_workaround_signed_windows=1

internet.ipv4.tcp_sack=1

web.ipv4.tcp_fack=1

internet.ipv4.tcp_low_latency=1

internet.ipv4.ip_no_pmtu_disc=0

web.ipv4.tcp_mtu_probing=1

internet.ipv4.tcp_frto=2

internet.ipv4.tcp_frto_response=2

net.ipv4.tcp_congestion_control=illinois

1. RFC 1337, TIME-WAIT Assassination dangers in TCP, a repair written in 1992 for some theoretically-feasible failure modes for TCP connections. To this present day this RFC nonetheless has americans puzzled if it negatively affects efficiency or not or is supported by any good router. Murphy's legislation is that the only router that it could even have drawback with, is surely your personal.

2. TCP window scaling tries to keep away from getting the community adapter saturated with incoming packets.

3. TCP SACK and FACK confer with alternate options present in RFC 2018 and are also documented lower back to Linux Kernel 2.6.17 with an experimental "TCP-Peach" set of services. These are supposed to get you your facts without excessive losses.

four. The latency atmosphere is 1 if you decide on more packets vs bandwidth, or 0 in case you choose bandwidth. greater packets are ideal for things like far off desktop and VOIP: less for bulk downloading.

5. I discovered RFC 2923, which is a fine evaluation of PMTU. IPv6 uses PMTU with the aid of default to avoid segmenting packets on the router level, however its not obligatory for IPv4. PMTU is meant to notify routers of the best packet sizes to use between links, but its a common admin observe to block ICMP ports that allow pinging, therefore breaking this mechanism. Linux tries to use it, and so do I: in case you have issues, you have got a problem router, and can change the "no" surroundings to 1. "MTU probing" is also part of this: 1 capability are attempting, and nil means don't.

6. FRTO is a mechanism in more moderen Linux kernels to optimize for instant hosts: use it when you have them; delete the setting, or set to 0, in case you don't.

For additional study, there is an outstanding IBM article involving community optimizations: it turned into my supply for some of these settings, as well as following a lot of articles on tweaking Linux networking over the years (SpeedGuide has one from 2003).

TCP Congestion Controls

home windows Vista and more recent received Compound TCP as an alternative choice to usual TCP Reno. Linux Kernel 2.6 has had numerous mechanisms accessible to it for a while: 2.6.19 defaulted to CUBIC which become presupposed to work well over "long hyperlinks."  My two personal favorites: TCP Westwood + and TCP Illinois. however that you could dig in, look at distinctive research papers on-line, and spot what works most excellent for your ambiance.

1. be sure your kernel has the proper module: in my illustration, i take advantage of TCP Illinois, which has been compiled with any typical Ubuntu kernel considering the fact that 2008, and is found as tcp_illinois.

2. Add talked about kernel module to /etc/modules

3. change /and many others/sysctl.conf to use the non "tcp_" a part of your choice.

There you have got it -- some of my favorite Linux tweaks for networking. i'm drawn to listening to how these worked for you. you probably have a few of your own, please publish a comment and share them with other readers.

be part of the community World communities on fb and LinkedIn to touch upon subject matters that are good of mind.

Linux community Programming, part 1 | killexams.com Real Questions and Pass4sure dumps

Like most other Unix-based operating techniques, Linux supports TCP/IP as its native community transport. during this collection, they are able to assume you're pretty usual with C programming on Linux and with Linux themes akin to indicators, forking, and so on.

this article is a simple introduction to using the BSD socket interface for developing networked applications. within the subsequent article, they can cope with considerations concerned in developing (community) daemon methods. Future articles will cowl using faraway process calls and establishing with CORBA/disbursed objects.

short Introduction to TCP/IP

The TCP/IP suite of protocols allows two applications, operating on both the same or separate computers related with the aid of a network, to talk. It was peculiarly designed to tolerate an unreliable network. TCP/IP enables two primary modes of operation—connection-oriented, legit transmission and connectionless, unreliable transmission (TCP and UDP respectively). figure 1 illustrates the different protocol layers in the TCP/IP suite stack.

determine 1. TCP/IP Protocol Layers

TCP provides sequenced, authentic, bi-directional, connection-based mostly bytestreams with transparent retransmission. In English, TCP breaks your messages up into chunks (not more advantageous in dimension than 64KB) and ensures that all of the chunks get to the vacation spot without error and within the correct order. Being connection-based, a digital connection needs to be installation between one community entity and the different earlier than they can talk. UDP gives (very quick) connectionless, unreliable switch of messages (of a hard and fast maximum length).

To enable functions to speak with every different, either on the identical desktop (using loopback) or throughout distinct hosts, each and every application ought to be for my part addressable.

TCP/IP addresses consist of two elements—an IP address to determine the computer and a port number to establish certain applications working on that computer.

The addresses are invariably given in both the “dotted-quad” notation (i.e., 127.0.0.1) or as a bunch identify (foobar.bundy.org). The device can use either the /and so on/hosts file or the area name service (DNS) (if available) to translate host names to host addresses.

Port numbers range from 1 upwards. Ports between 1 and IPPORT_RESERVED (described in /usr/encompass/netinet/in.h—customarily 1024) are reserved for device use (i.e., you have to be root to create a server to bind to these ports).

The simplest network purposes comply with the customer-server mannequin. A server method waits for a shopper method to connect to it. When the connection is dependent, the server performs some project on behalf of the customer after which constantly the connection is damaged.

the usage of the BSD Socket Interface

probably the most normal formula of TCP/IP programming is to make use of the BSD socket interface. With this, network endpoints (IP tackle and port number) are represented as sockets.

The socket interprocess verbal exchange (IPC) amenities (delivered with four.2BSD) have been designed to enable community-primarily based purposes to be developed independently of the underlying communique amenities.

creating a Server application

To create a server software the use of the BSD interface, you have to observe these steps:

  • Create a new socket by typing: socket().

  • bind an address (IP handle and port number) to the socket via typing: bind. This step identifies the server in order that the customer knows the place to go.

  • listen for brand spanking new connection requests on the socket with the aid of typing: pay attention().

  • settle for new connections by using typing: settle for().

  • commonly, the servicing of a request on behalf of a consumer might also take a substantial size of time. it might be greater productive in one of these case to settle for and take care of new connections while a request is being processed. the most common approach of doing here is for the server to fork a brand new reproduction of itself after accepting the new connection.

    figure 2. representation of customer/Server Code

    The code illustration in list 1 indicates how servers are implemented in C. The application expects to be known as with only one command-line argument: the port quantity to bind to. It then creates a new socket to hear on using the socket() device name. This name takes three parameters: the domain wherein to take heed to, the socket class and the network protocol.

    The domain may also be both the PF_UNIX domain (i.e., internal to the local laptop only) or the PF_INET (i.e., all requests from the web). The socket class specifies the conversation semantics of the connection. whereas a number of styles of sockets have been specific, in practice, SOCK_STREAM and SOCK_DGRAM are the most common implementations. SOCK_STREAM gives for TCP reliable connection-oriented communications, SOCK_DGRAM for UDP connectionless conversation.

    The protocol parameter identfies the selected protocol to be used with the socket. while distinctive protocols may also exist within a given protocol family unit (or domain), there's commonly only 1. For TCP here is IPPROTO_TCP, for UDP it is IPPROTO_UDP. You do not have to explicitly specify this parameter when making the characteristic call. as a substitute, the usage of a value of 0 will choose the default protocol.

    as soon as the socket is created, its operation will also be tweaked by potential of socket alternatives. in the above instance, the socket is determined to reuse historical addresses (i.e., IP tackle + port numbers) without looking forward to the required connection shut timeout. If this were now not set, you possibly can should wait 4 minutes in the TIME_WAIT state before using the address again. The 4 minutes comes from 2 * MSL. The recommended value for MSL, from RFC 1337, is 120 seconds. Linux uses 60 seconds, BSD implementations continuously use around 30 seconds.

    The socket can linger to make sure that all facts is examine, as soon as one conclusion closes. This option is grew to become on in the code. The constitution of linger is defined in /usr/include/linux/socket.h. It feels like this:

    struct linger int l_onoff; /* Linger lively */ int l_linger; /* How lengthy to linger */ ;

    If l_onoff is zero, lingering is disabled. whether it is non-zero, lingering is enabled for the socket. The l_linger container specifies the linger time in seconds.

    The server then tries to discover its own host identify. I might have used the gethostname() call, but the use of this feature is deprecated in SVR4 Unix (i.e., solar's Solaris, SCO Unixware and pals), so the native function _GetHostName() provides a more moveable solution.

    once the host identify is centered, the server constructs an address for the socket by means of making an attempt to get to the bottom of the host name to an online area address, using the gethostbyname() name. The server's IP handle could as an alternative be set to INADDR_ANY to allow a consumer to contact the server on any of its IP addresses—used, for example, with a desktop with assorted network cards or diverse addresses per community card.

    After an tackle is created, it is sure to the socket. The socket can now be used to hear for brand spanking new connections. The BACK_LOG specifies the highest dimension of the pay attention queue for pending connections. If a connection request arrives when the pay attention queue is full, it will fail with a connection refused error. [This forms the basis for one type of denial of service attack —Ed.] See sidebar on TCP listen() Backlog.

    Having indicated a willingness to listen to new connection requests, the socket then prepares to settle for the requests and repair them. The illustration code achieves this the use of an unlimited for() loop. as soon as a connection has been permitted, the server can verify the address of the client for logging or other functions. It then forks a toddler reproduction of itself to tackle the request while it (the guardian) continues listening for and accepting new requests.

    The child system can use the read() and write() system calls on this connection to talk with the customer. it is additionally viable to use the buffered I/O on these connections (e.g., fprint()) as long as you be aware to fflush() the output when essential. alternatively, that you may disable buffering altogether for the process (see the setvbuf() (3) man page).

    As you could see from the code, it's reasonably regular (and first rate practice) for the newborn procedures to close the inherited mum or dad-socket file descriptor, and for the dad or mum to close the child-socket descriptor when the usage of this elementary forking model.

    developing the Corresponding customer

    The client code, shown in record 2, is a bit less demanding than the corresponding server code. To delivery the client, you have to deliver two command-line arguments: the host identify or tackle of the desktop the server is running on and the port quantity the server is sure to. obviously, the server should be running before any customer can connect to it.

    within the customer example (list 2), a socket is created like earlier than. the first command-line argument is first assumed to be a number name for the applications of finding the server's handle. If this fails, it is then assumed to be a dotted-quad IP handle. If this also fails, the client cannot resolve the server's handle and will not be in a position to contact it.

    Having located the server, an tackle constitution is created for the client socket. No explicit name to bind() is required right here, as the connect() name handles all of this.

    as soon as the connect() returns successfully, a duplex connection has been dependent. just like the server, the customer can now use examine() and write() calls to obtain data on the connection.

    Be aware of right here facets when sending information over a socket connection:

  • Sending text is constantly satisfactory. remember that diverse systems can have distinctive conventions for the end of line (i.e., Unix is \012, whereas Microsoft makes use of \015\012).

  • distinct architectures might also use different byte-ordering for integers etc. happily, the BSD guys notion of this problem already. There are routines (htons and nstoh for short integers, htonl and ntohl for long integers) which function host-to-network order and community-to-host order conversions. whether the network order is little-endian or huge-endian doesn't in fact matter. It has been standardized across all TCP/IP community stack implementations. unless you persistently flow simplest characters throughout sockets, you're going to run into byte-order complications in case you don't use these routines. reckoning on the computing device structure, these routines can be null macros or may additionally in fact be purposeful. curiously, a standard source of bugs in socket programming is to forget to use these byte-ordering routines for filling the handle container within the sock_addr structures. possibly it isn't intuitively evident, but this ought to even be achieved when the usage of INADDR_ANY (i.e., htonl(INADDR_ANY)).

  • A key aim of community programming is to make sure methods do not intrude with each different in sudden methods. In certain, servers must use applicable mechanisms to serialize entry through essential sections of code, evade impasse and give protection to information validity.

  • You cannot (commonly) move a pointer to reminiscence from one machine to one other and are expecting to use it. it is not going you're going to want to try this.

  • similarly, you cannot (generally) flow a file descriptor from one process to a different (non-child) technique via a socket and use it straightaway. each BSD and SVR4 deliver alternative ways of passing file descriptors between unrelated processes; although, the easiest method to do that in Linux is to use the /proc file gadget.

  • moreover, you need to make sure that you address brief writes appropriately. short writes occur when the write() call best partly writes a buffer to a file descriptor. They ensue due to buffering in the working system and to stream control within the underlying transport protocol. certain gadget calls, termed gradual equipment calls, may well be interrupted. Some might also or may additionally not be instantly restarted, so make sure to explicitly tackle this when community programming. The code excerpt in listing three handles brief writes.

    the usage of distinctive threads instead of diverse techniques may lighten the weight on the server host, thereby expanding efficiency. Context-switching between threads (in the same method tackle house) often has tons much less linked overhead than switching between distinct methods. however, considering most of the slave threads during this case are doing network I/O, they need to be kernel-stage threads. if they had been person-stage threads, the first thread to dam on I/O would cause the entire method to dam. this would outcome in starving all other threads of any CPU attention until the I/O had achieved.

    it's ordinary to close pointless socket file descriptors in newborn and dad or mum strategies when using the standard forking model. This prevents the newborn or mum or dad from skills faulty reads or writes and additionally frees up descriptors, which might be a limited aid. however do not try this when the use of threads. multiple threads inside a technique share the equal memory area and set of file descriptors. if you shut the server socket in a slave thread, it closes for all other threads in that process.

    Connectionless statistics—UDP

    listing 4 suggests a connectionless server the use of UDP. while UDP applications are comparable to their TCP cousins, they have some critical changes. optimum, UDP doesn't guarantee legit beginning—in case you require reliability and are the usage of UDP, you both have to enforce it yourself for your software common sense or switch to TCP.

    Like TCP applications, with UDP you create a socket and bind an handle to it. (Some UDP servers do not deserve to name bind(), but it surely does no hurt and may save you from making a mistake.) UDP servers do not hear or accept incoming connections, and customers do not explicitly connect to servers. really, there is terribly little difference between UDP valued clientele and servers. The server ought to be bound to a primary port and tackle most effective in order that the client knows where to send messages. additionally, the order of expected facts transmissions is reversed, i.e., for those who send records the use of send() in the server, your client may still are expecting to acquire records the use of recv().

    it is normal for UDP clients to fill within the sockaddr_in constitution with a sin_port price of 0. (notice that 0 in both byte-order is 0.) The gadget then automatically assigns an unused port number (between 1024 and 5000) to the customer. i'm leaving it as an pastime to the reader to convert the server in listing four into a UDP customer.

    /etc/features

    in order to connect with a server, you ought to first know each the handle and port number on which it is listening. Many standard services (FTP, TELNET, and so forth.) are listed in a textual content database file referred to as /and many others/features. An interface exists to request a service by means of name and to obtain the port number (accurately formatted in community byte-order) for that carrier. The feature is getservbyname(), and its prototype is in the header file /usr/encompass/netdb.h. This instance takes a carrier name and protocol classification and returns a pointer to struct servent.

    struct servent char *s_name; /* respectable carrier name */ char **s_aliases; /* alias list */ int s_port; /* port number, network<\n> * byte-order--so do not * use host-to-community macros */ char *s_proto; /* protocol to make use of */ ;

    Conclusions

    this article has added network programming in Linux, the use of C and the BSD Socket API. In general, coding with this API tends to be rather laborious, certainly when compared to one of the most different suggestions available. In future articles, i will be able to examine two options to the BSD Socket API for Linux: the use of far off technique Calls (RPCs) and the regular Object Request broker structure (CORBA). RPCs have been added in Ed Petron's article “remote technique Calls” in Linux Journal problem #forty two (October, 1997).

    elements

    TCP hear() Backlog

    fundamental gadget Calls The subsequent article in this collection will cowl the issues worried in establishing lengthy-lived community functions (daemons) in Linux.

    All listings talked about listed here are available by nameless download in the file ftp://ftp.linuxjournal.com/lj/listings/issue46/2333.tgz.


    the way to generate SSH keys in OpenSSH for windows 10 | killexams.com Real Questions and Pass4sure dumps

    further prolong Microsoft's implementation of OpenSSH in windows 10 by using producing your personal secure keys.

    istock-859761306.jpg

    picture: Jakarin2521, Getty images/iStockphoto

    the use of OpenSSH is ubiquitous with secured access to customer gadgets over a network. The aim of SSH is straight-forward: to securely encapsulate the administration site visitors between two conclusion-elements, during this case using the server-client model for authentication.

    while SSH may be enabled to work over customers, which might be joined to the equal area, say using energetic listing credentials, here's not feasible when attempting to speak to contraptions reminiscent of community switches or routers, which are not natively part of any area infrastructure. instead, these contraptions and Linux-primarily based purchasers use a public/deepest key pair to investigate the person trying to connect with the client and operate authentication before featuring remote entry.

    SEE: assistance security coverage (Tech seasoned research)

    listed here, they can use this use case as it is often considered to be a extra relaxed formula of obtaining access, which lends itself seamlessly to windows and non-windows devices alike. by means of generating and managing SSH key pairs, IT could be capable of remotely connect with shoppers in a relaxed method while ensuring confidentiality and non-repudiation for each user, using a special key pair tied to the individual's windows login account for comfortable storage.

    install the OpenSSH module for PowerShell

    1. Log in to the home windows laptop with an admin-stage account and launch PowerShell with admin privileges.

    2. Enter here cmdlet to installation the OpenSSH module. If this is the first time the module has been put in on the gadget, you may be prompted to down load and deploy some additional tools. class "Y" to allow the equipment to be put in.

    install-Module -drive OpenSSHUtils

    3. subsequent, enter the cmdlet to delivery the ssh-agent service for securely storing privately generated SSH keys.

    beginning-provider ssh-agent

    four. last, enter the cmdlet to beginning the sshd provider, for you to generate the primary pair of host keys automatically.

    birth-provider sshd

    note: by default, the OpenSSH Server app in not installed, so it must first be installed. also, the ssh-agent carrier is set to Disabled and should be modified before the cmdlets above will work. Host keys are saved at the %HOMEDRIVE%\ProgramData\ssh listing.

    SEE: PowerShell scripting: Seven tips to in the reduction of error (free PDF) (TechRepublic)

    Generate consumer key pair

    1. In PowerShell, exchange directories to the route above the place the SSH keys are stored, then enter the cmdlet beneath to being generating the key pair.

    ssh-keygen

    2. to be able to generate a distinct set of key pairs and shop them, you may be caused to supply a listing where the important thing pair can be saved, or you might also press enter to choose the default place provided.

    3. subsequent, you are going to be prompted to select a passphrase to encrypt the key pair with. while providing a passphrase is not obligatory, it's incredibly counseled to enter one because it serves the secondary goal of appearing as a variety of two-component authentication when employing the key pair to set up remote connections.

    4. once the method is achieved, two files will be generated alongside the SHA256 fingerprint, and the key is random paintings image might be displayed on-reveal and will look like this (figure A):

    201916-figure-a.jpg

    201916-figure-a.jpg

    Copying the general public key securely

    The OpenSSH equipment include the SCP and SFTP utilities to make transferring keys absolutely secure. with a purpose to accurately configure a windows customer for authenticating by the use of SSH keys, the general public key (.PUB) file have to be transferred to the client equipment's .ssh directory and saved within the authorized_keys textual content file.

    1. begin the manner via executing here command in PowerShell to create the .ssh directory within the consumer's profile folder.

    ssh username@area.com mkdir C:\clients\username\.ssh

    2. the use of the SCP utility, enter here command to soundly reproduction the public key from the server to the client device.

    scp C:\clients\username\.ssh\id_rsa.pub username@area.com:C:\users\username\.ssh\authorized_keys

    three. ultimately, adjust the ACL on the authorized_keys file on the server by using entering here command.

    ssh —% username@domain.com powershell -c $ConfirmPreference = 'None'; restoration-AuthorizedKeyPermission C:\users\username\.ssh\authorized_keys

    Microsoft Weekly e-newsletter

    Be your enterprise's Microsoft insider with the aid of those windows and office tutorials and their specialists' analyses of Microsoft's commercial enterprise products. Delivered Mondays and Wednesdays

    check in these days check in nowadays additionally see

    Unquestionably it is hard assignment to pick dependable certification questions/answers assets regarding review, reputation and validity since individuals get sham because of picking incorrectly benefit. Killexams.com ensure to serve its customers best to its assets concerning exam dumps update and validity. The vast majority of other's sham report dissension customers come to us for the brain dumps and pass their exams joyfully and effortlessly. They never trade off on their review, reputation and quality on the grounds that killexams review, killexams reputation and killexams customer certainty is imperative to us. Uniquely they deal with killexams.com review, killexams.com reputation, killexams.com sham report objection, killexams.com trust, killexams.com validity, killexams.com report and killexams.com scam. On the off chance that you see any false report posted by their rivals with the name killexams sham report grievance web, killexams.com sham report, killexams.com scam, killexams.com protest or something like this, simply remember there are constantly awful individuals harming reputation of good administrations because of their advantages. There are a huge number of fulfilled clients that pass their exams utilizing killexams.com brain dumps, killexams PDF questions, killexams hone questions, killexams exam simulator. Visit Killexams.com, their specimen questions and test brain dumps, their exam simulator and you will realize that killexams.com is the best brain dumps site.

    Back to Braindumps Menu


    156-730 dumps questions | 920-131 exam prep | 0B0-108 real questions | C2180-279 real questions | 000-834 braindumps | HP0-Y25 test prep | CSQE dump | M2090-744 practice exam | A2090-422 practice questions | 9L0-206 brain dumps | 250-430 test questions | 1Z0-325 practice test | 1Z0-515 braindumps | HP0-S40 pdf download | LOT-989 brain dumps | 9A0-056 study guide | HP0-J56 exam questions | 1Z0-605 questions and answers | VCI510 questions answers | HP0-J19 free pdf |


    Memorize these 3X0-103 dumps and register for the test
    We are doing fight to giving you actual Linux Networking (Level 1) exam questions and answers, close by clarifications. Each on killexams.com has been affirmed by Sair confirmed authorities. They are extraordinarily qualified and affirmed individuals, who have various occasions of master encounter related to the Sair exams.

    If you are interested in successfully completing the Sair 3X0-103 exam to start earning? killexams.com has leading edge developed Linux Networking (Level 1) exam questions that will ensure you pass this 3X0-103 exam! killexams.com delivers you the most accurate, current and latest updated 3X0-103 exam questions and available with a 100% money back guarantee. There are many companies that provide 3X0-103 brain dumps but those are not accurate and latest ones. Preparation with killexams.com 3X0-103 new questions is a best way to pass this certification exam in easy way.

    We are all well aware that a major problem in the IT industry is that there is a lack of quality study materials. Their exam preparation material provides you everything you will need to take a certification exam. Their Sair 3X0-103 Exam will provide you with exam questions with verified answers that reflect the actual exam. These questions and answers provide you with the experience of taking the actual test. High quality and value for the 3X0-103 Exam. 100% guarantee to pass your Sair 3X0-103 exam and get your Sair certification. They at killexams.com are committed to help you pass your 3X0-103 exam with high scores. The chances of you failing your 3X0-103 test, after going through their comprehensive exam dumps are very little.

    Sair 3X0-103 is rare all around the globe, and the business and programming arrangements gave by them are being grasped by every one of the organizations. They have helped in driving a large number of organizations on the beyond any doubt shot way of achievement. Far reaching learning of Sair items are viewed as a critical capability, and the experts certified by them are exceptionally esteemed in all associations.

    We give genuine 3X0-103 pdf exam questions and answers braindumps in two arrangements. Download PDF and Practice Tests. Pass Sair 3X0-103 real Exam rapidly and effectively. The 3X0-103 braindumps PDF sort is accessible for perusing and printing. You can print increasingly and practice ordinarily. Their pass rate is high to 98.9% and the comparability rate between their 3X0-103 study guide and genuine exam is 90% in light of their seven-year teaching background. Do you need successs in the 3X0-103 exam in only one attempt? I am right now examining for the Sair 3X0-103 real exam.

    As the only thing that is in any way important here is passing the 3X0-103 - Linux Networking (Level 1) exam. As all that you require is a high score of Sair 3X0-103 exam. The just a single thing you have to do is downloading braindumps of 3X0-103 exam prep directs now. They will not let you down with their unconditional guarantee. The experts likewise keep pace with the most up and coming exam so as to give the greater part of updated materials. Three Months free access to have the capacity to them through the date of purchase. Each applicant may bear the cost of the 3X0-103 exam dumps through killexams.com at a low cost. Frequently there is a markdown for anybody all.

    killexams.com Huge Discount Coupons and Promo Codes are as under;
    WC2017 : 60% Discount Coupon for all exams on website
    PROF17 : 10% Discount Coupon for Orders greater than $69
    DEAL17 : 15% Discount Coupon for Orders greater than $99
    DECSPECIAL : 10% Special Discount Coupon for All Orders


    Quality and Value for the 3X0-103 Exam: killexams.com Practice Exams for Sair 3X0-103 are composed to the plain best necessities of specialized precision, utilizing just guaranteed issue tally experts and distributed creators for improvement.

    100% Guarantee to Pass Your 3X0-103 Exam: If you don't pass the Sair 3X0-103 exam the utilization of their killexams.com experimenting with engine, they will give you a FULL REFUND of your purchasing charge.

    Downloadable, Interactive 3X0-103 Testing engines: Their Sair 3X0-103 Preparation Material presents you all that you will need to take Sair 3X0-103 exam. Points of interest are investigated and created by utilizing Sair Certification Experts who're continually the use of industry delight in to give extraordinary, and legitimate.

    - Comprehensive questions and answers about 3X0-103 exam - 3X0-103 exam questions joined by displays - Verified Answers by Experts and very nearly 100% right - 3X0-103 exam questions updated on general premise - 3X0-103 exam planning is in various decision questions (MCQs). - Tested by different circumstances previously distributing - Try free 3X0-103 exam demo before you choose to get it in killexams.com

    killexams.com Huge Discount Coupons and Promo Codes are as under;
    WC2017: 60% Discount Coupon for all exams on website
    PROF17: 10% Discount Coupon for Orders greater than $69
    DEAL17: 15% Discount Coupon for Orders greater than $99
    DECSPECIAL: 10% Special Discount Coupon for All Orders


    Snap http://killexams.com/pass4sure/exam-detail/3X0-103

    3X0-103 | 3X0-103 | 3X0-103 | 3X0-103 | 3X0-103 | 3X0-103


    Killexams ST0-94X study guide | Killexams 101-01 braindumps | Killexams C2020-615 practice questions | Killexams 9A0-088 real questions | Killexams SD0-101 dumps | Killexams IBQH001 pdf download | Killexams EX0-116 Practice test | Killexams 000-270 free pdf | Killexams C4040-109 real questions | Killexams C2140-820 cheat sheets | Killexams HP0-Y47 braindumps | Killexams VCP410-DT questions and answers | Killexams 000-586 dumps questions | Killexams 9L0-620 questions and answers | Killexams C2150-624 cram | Killexams 70-703 study guide | Killexams HP2-Z27 brain dumps | Killexams HP2-H09 bootcamp | Killexams 70-343 questions answers | Killexams 210-250 dump |


    killexams.com huge List of Exam Braindumps

    View Complete list of Killexams.com Brain dumps


    Killexams ST0-100 examcollection | Killexams 4A0-108 practice test | Killexams LE0-628 practice questions | Killexams 000-821 practice exam | Killexams C2040-440 questions and answers | Killexams HP0-J23 test prep | Killexams 1Z0-859 dumps questions | Killexams 300-360 cram | Killexams 1Z0-055 Practice test | Killexams SC0-402 free pdf download | Killexams LOT-914 questions answers | Killexams ST0-057 bootcamp | Killexams 920-471 brain dumps | Killexams II0-001 Practice Test | Killexams 190-610 exam questions | Killexams ANCC-MSN VCE | Killexams ST0-174 exam prep | Killexams 648-385 real questions | Killexams JN0-660 study guide | Killexams 650-302 practice questions |


    Linux Networking (Level 1)

    Pass 4 sure 3X0-103 dumps | Killexams.com 3X0-103 real questions | http://smresidences.com.ph/

    Network Engineer with Linux Skills Salary | killexams.com real questions and Pass4sure dumps

    The average pay for a Network Engineer with Linux skills is $28.66 per hour.

    The average pay for a Network Engineer with Linux skills is $71,727 per year.

    Salary $48,003 - $102,315 Bonus $235 - $10,750 Profit Sharing $974 - $10,166 Total Pay (? XTotal Pay combines base annual salary or hourly wage, bonuses, profit sharing, tips, commissions, overtime pay and other forms of cash earnings, as applicable for this job. It does not include equity (stock) compensation, cash value of retirement benefits, or the value of other non-cash benefits (e.g. healthcare). ) $44,877 - $107,919 Hourly Rate $16.22 - $51.79 Overtime $22.04 - $77.28 Bonus $235 - $10,750 Profit Sharing $974 - $10,166 Total Pay (? XTotal Pay combines base annual salary or hourly wage, bonuses, profit sharing, tips, commissions, overtime pay and other forms of cash earnings, as applicable for this job. It does not include equity (stock) compensation, cash value of retirement benefits, or the value of other non-cash benefits (e.g. healthcare). ) $44,877 - $107,919 Job Description for Network Engineer

    The work of network engineers revolves around their employers' computer network designs and implementations, and they are salaried instead of paid on an hourly basis. They generally work in offices to troubleshoot problems related to their company’s enterprise-wide network, and they must ensure that their systems' security and firewall software is up-to-date.

    Read More...

    Network engineers must be knowledgeable of a variety of networking technologies, such as routing, cryptographic tunneling, firewalls, and others. A bachelor's degree in information technology, computer science, or a related field is generally required for this position; however, some companies may accept candidates with significant prior experience instead of a degree. Network engineers should also be proficient in Microsoft Office programs (Word, Excel, PowerPoint and Outlook) and be able to troubleshoot various network and computer system problems. They must also ensure that their employers' computer networks, perhaps including their corporate office, regional office, and other sites, are optimal and efficient.

    Strong verbal and written communication skills and the ability to work well in a team environment are important in this position, and they must be able to speak clearly, by phone or in-person, with various network users regarding their companies' computer network issues. They also keep records of system problems and resolutions using databases or similar software and generate reports to be presented to managers or executives. They must always stay up-to-date with ever-changing technology in the marketplace and continuously learn new skills by attending college classes, workshops, conferences, etc. They are also encouraged to read professional journals relevant to their field, and some may be required to train and coach new or junior network engineers. They may also occasionally need to travel to vendors' or clients' offices. (Copyright 2019 PayScale.com)

    Network Engineer Tasks

  • Plan, design, and troubleshoot local and wide area network infrastructure, including routers, firewalls, switches, gateways, DNS servers, DHCP servers, clustering solutions, and related hardware, software, and services.
  • Test and document system behavior, performance, and security.
  • Providing tier 4 support and network disaster recovery expertise.
  • Pay by Experience Level for Network Engineer

    Pay by Experience for a Network Engineer has a positive trend. An entry-level Network Engineer with less than 5 years of experience can expect to earn an average total compensation of $63,000 based on 191 salaries provided by anonymous users. Average total compensation includes tips, bonus, and overtime pay. A Network Engineer with mid-career experience which includes employees with 5 to 10 years of experience can expect to earn an average total compensation of $75,000 based on 162 salaries. An experienced Network Engineer which includes employees with 10 to 20 years of experience can expect to earn an average total compensation of $80,000 based on 125 salaries. A Network Engineer with late-career experience which includes employees with greater than 20 years of experience can expect to earn an average total compensation of $81,000 based on 33 salaries.


    Installing Ubuntu in Level 1 of the Stairway to SQL Server on Linux | killexams.com real questions and Pass4sure dumps

    SQL Server 2017 is the first SQL Server version that can be installed on Windows, Linux and a Docker container. This stairway series serves as a guide for the experienced SQL Server DBA to acquire skills and knowledge on this platform.

    This is the first article in a new stairway series that will explore SQL Server on Linux using the most common best practices and comparing both the versions for Windows and Linux.

    This series will cover the following topics:

  • Linux installation
  • Linux commands for DBA
  • SQL Server installation
  • Using the new SQL Server instance
  • Installing and using SQL Server Agent on Linux
  • HA/DR basics: Log Shipping
  • Monitoring SQL Server on Linux
  • Troubleshooting
  • Advanced HA/DR: AlwaysOn Availability Groups
  • For the first installment of this stairway series, let’s go through the first step: the Linux server installation.

    Which Linux distribution to choose?

    SQL Server 2017 is currently supported only on these Linux distributions:

  • RedHat Enterprise Linux 7.3 o 7.4
  • Ubuntu 16.04
  • Suse Linux Enterprise Server v12 SP2
  • SQL Server 2017 is also supported as a Docker image, which can run on Docker Engine on Linux or Docker for Windows/Mac. The docker image is based on Ubuntu 16.04.

    But, which is the best Linux distribution among those supported by SQL Server 2017 ? Well, it depends on what your company needs and the confidence level you already have with the supported Linux distros.

    Today, Linux is not only a free OS, but a platform to run business applications. When comparing the best Linux distros, corporate Linux users usually take care not only about the feature matrix supported by that distro, but also about support and lifetime of the product.

    Red Hat is one of the market leaders of Linux distributions. Red Hat Enterprise Linux, or RHEL, entered many data centers via support deals with hardware and software vendors. Today is a stable, proven foundation that’s versatile enough for rolling out new applications, virtualizing environments, and creating a secure hybrid cloud. RHEL 7.x deliver 10 years of support, with 5 and a half years of Full support, 1 year of so-called Maintenance Support 1 and further 3 years and half for the Maintenance Support 2.

    Ubuntu is a free and open source operating system and Linux distribution based on Debian. Canonical, the company behind Ubuntu, has a mission to make open source available to people everywhere, generates revenue from the sale of professional services around the distribution. New releases of Ubuntu occur every six months, while long-term support (LTS) releases occur every two years.

    Suse Linux Enterprise Server (SLES) is a Linux-based operating system developed by SUSE. Major versions are released at an interval of 3–4 years, while minor versions (called “Service Packs”) are released about every 18 months. From a technical perspective, SUSE Linux is more accessible than the other supported Linux distributions. SUSE is also the most administrator-friendly, thanks to its integrated YaST platform. SUSE is one of the main developers for Pacemaker High Availability, the standard tool for high-availability clusters in all current Linux distributions, used also by SQL Server 2017 to implement AlwaysOn or Failover clustering. Long term support for the supported version (v12 with SP2) is 31 March 2021.

    From the SQL Server DBA point of view, there are no significant differences among the three operating systems and choosing one of them could be based on your internal knowledge, if the company already have a Linux-based machine, or the list of the features you want to implement together with your SQL Server.

    For this series I chose to install an Ubuntu server 16.04. Generally speaking, this distribution is well-know for some of the included services like OpenStack cloud services, Ceph scalable distributed file system or the Metal-as-a-Service (MAAS) tool, which can be used to easily deploy OpenStack or other server types on bare-metal, all programmatically. They don’t need all these services for their purposes, but they can use Ubuntu Server just because it’s easy to setup, well-documented and supported among the Linux communities.

    Installing Ubuntu

    To install Ubuntu on your own machine, either physical or virtual, you have to use to the past releases download page: http://releases.ubuntu.com/16.04.4/ due to the fact that the current release is the 18.04 LTS, which is not supported by Microsoft.

    I want to point out that is very important for a server to choose the long-term support (LTS) release of the Linux distribution, because it’s more stable and supported for the years to come by its vendor, with further security or feature updates.

    Before starting the installation, let’s take a look at the prerequisites: Ubuntu requires a minimum of 512MB of RAM and 5GB of disk space, while SQL Server itself requires at least 3.25GB of RAM and additional 3GB of disk for the binaries. Considering that they should have at least space to save OS and SQL Server logs, system databases and a few other things, I would not create a server with less than 4GB of RAM and 20GB of disk space.

    In a later level of this series we’ll see which best practices they should apply to their new SQL Server on Linux, including a multiple disk configuration to spread their data files, transaction logs and TempDB files. For now, they are assuming this is a very basic server configuration.

    Let’s start with the installation: boot the system from the media containing the ISO file (for example an USB key if you are using a physical server) or connect the ISO to the virtual machine if you are creating a virtual server.

    At the boot prompt you will be asked to select a language for the setup.

    From the main boot menu you can choose further options to install Ubuntu on your system, do some check or rescue a broken system. We’ll cover only the basic installation of a fresh Ubuntu server.

    The installer asks which language is should use and the keyboard layout (by auto-detecting the layout or by entering manually).

    The installer then discovers the hardware configuration and configures the network settings using a DHCP server or gives you the option to configure it manually by going back and selecting the option “Configure the network manually”.

    Next, the installer asks for the system’s name and sets up a new user that will have root access through the sudo utility. You are required to choose and confirm username and password.

    For Windows users: let me explain some concepts before going further. In a Linux operating system root is the user name that by default has access to all commands and files, like the Administrator user in a Windows operating system.

    At this point of the installation, they are providing the system the name of a new unprivileged user that can be used for everyday tasks. When they need superpowers, they can still run a command with the sudo utility, which elevates the privileges to the root user level and runs the specific command. This is just like the “RunAs Administrator” command in Windows.

    You will be asked then if you want to encrypt your home directory, so that your stored files are not readable if the computer is stolen.

    After being asked to choose the timezone, you are entered into the disk layout configuration. They have four choices, with a guided partitioning method or a manual one.  I chose to use the entire disk and set up a Logical Volume Manager (LVM). Logical Volume Management is a storage device management technology that gives users the power to pool and abstract the physical layout of component storage devices for easier and flexible administration. This is like gathering existing storage devices into groups and allocate logical units from the combined space as needed.

    Logical volumes can have meaningful names like “databases” or “backups”. Volumes can be resized dynamically as space requirements change and migrated between physical devices within the pool on a running system or exported easily. LVM also offers advanced features like snapshotting, striping, and mirroring.

    You can learn more about LVM here: http://tldp.org/HOWTO/LVM-HOWTO/index.html.

    The Ubuntu base system installation then starts. During this phase of the installation process, you may be given the opportunity to select additional software to install, by selecting predefined collections of software (for example DNS server or OpenSSH server) to quickly set up your computer to perform various tasks. They can simply “continue” and skip this task, as they only need a base system.

    A last step requires us to install the GRUB loader, and then they are ready to start with their new server.

    GRUB or GRand Unified Bootloader, is a multiboot boot loader. A boot loader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the operating system kernel software (such as Windows or Linux). This can add the flexibility, for example,  to run different operating systems from the same physical (or virtual) disk or to run specialized Linux distributions (for example to troubleshoot a failed system or to run diagnostic tools).

    At the end of the installation process, you will be asked to reboot the system to start from your new Ubuntu server.

    As you can see, this process is really straightforward and doesn’t require particular skills. There are a number of options that you can change by choosing the advanced installation, and we’ll learn about some of them when we’ll be talking about the best practices and the perfomance tuning.

    Now, let’s log in and take a look at their new Linux machine.

    After rebooting the server, when prompted type sqladmin as the username they are using to enter the system and the password you provided during the setup to enter the machine.

    One of the most evident differences moving from Windows to Linux is case sensitivity, especially when creating or navigating a folder structure. The directory “Data” is not the same as “data” !

    Once logged in, they can use a lot of commands, provided by the command-line interpreter, known as shell), they are using. The Bash shell is one of the most commonly used (but you can obviously change it whenever you want).

    Let’s see some example. With the command pwd, short for print working directory, they can show where they are located in the directory tree and then moving, for example, to another directory by using the cd command (change directory), like they do in a Windows command prompt.

    We can create or edit a file from the command shell by using the program vi (visual editor), which is included in Linux/UNIX operating system since its early days, or switch to a “modern” editor like nano or vim.

    We’ll talk about Linux commands in a future article: this brief introduction was intended only to show you how to log into your newly installed system and check if it works.

    If you want to know more about the Ubuntu Server Linux and how to do a particular task, you can use the official documentation site at help.ubuntu.com and click on 16.04 LTS version, which is the supported edition at the time they are writing this article.

    Update

    With the release of the Cumulative Update 10 for SQL Server 2017 (build 14.0.3037.1) in late August, Microsoft has updated the package dependecies that prevented the installation of SQL Server 2017 on servers with Ubuntu 18.04 LTS. There may be additional actions required on some systems: if the library libcurl4 is installed, you need to remove it and install libcurl3, using the following commands:

    $ sudo apt-get remove libcurl4

    $ sudo apt-get install libcurl3

    Microsoft recommends to install SQL Server 2017 on Ubuntu 18.04 for non-production purpose only, until thorough testing has been completed and full support has been documented.

    You can find additional info on the original blog page: https://blogs.msdn.microsoft.com/sql_server_team/installing-sql-server-2017-for-linux-on-ubuntu-18-04-lts/

    Summary

    We learned how to setup a fresh Linux machine with Ubuntu Server 16.04, bearing in mind which prerequisites they do need to move to the next step: the SQL Server 2017 installation.

    Related links


    Linux Network Programming, Part 1 | killexams.com real questions and Pass4sure dumps

    Like most other Unix-based operating systems, Linux supports TCP/IP as its native network transport. In this series, they will assume you are fairly familiar with C programming on Linux and with Linux topics such as signals, forking, etc.

    This article is a basic introduction to using the BSD socket interface for creating networked applications. In the next article, they will deal with issues involved in creating (network) daemon processes. Future articles will cover using remote procedure calls and developing with CORBA/distributed objects.

    Brief Introduction to TCP/IP

    The TCP/IP suite of protocols allows two applications, running on either the same or separate computers connected by a network, to communicate. It was specifically designed to tolerate an unreliable network. TCP/IP allows two basic modes of operation—connection-oriented, reliable transmission and connectionless, unreliable transmission (TCP and UDP respectively). Figure 1 illustrates the distinct protocol layers in the TCP/IP suite stack.

    Figure 1. TCP/IP Protocol Layers

    TCP provides sequenced, reliable, bi-directional, connection-based bytestreams with transparent retransmission. In English, TCP breaks your messages up into chunks (not greater in size than 64KB) and ensures that all the chunks get to the destination without error and in the correct order. Being connection-based, a virtual connection has to be set up between one network entity and the other before they can communicate. UDP provides (very fast) connectionless, unreliable transfer of messages (of a fixed maximum length).

    To allow applications to communicate with each other, either on the same machine (using loopback) or across different hosts, each application must be individually addressable.

    TCP/IP addresses consist of two parts—an IP address to identify the machine and a port number to identify particular applications running on that machine.

    The addresses are normally given in either the “dotted-quad” notation (i.e., 127.0.0.1) or as a host name (foobar.bundy.org). The system can use either the /etc/hosts file or the Domain Name Service (DNS) (if available) to translate host names to host addresses.

    Port numbers range from 1 upwards. Ports between 1 and IPPORT_RESERVED (defined in /usr/include/netinet/in.h—typically 1024) are reserved for system use (i.e., you must be root to create a server to bind to these ports).

    The simplest network applications follow the client-server model. A server process waits for a client process to connect to it. When the connection is established, the server performs some task on behalf of the client and then usually the connection is broken.

    Using the BSD Socket Interface

    The most popular method of TCP/IP programming is to use the BSD socket interface. With this, network endpoints (IP address and port number) are represented as sockets.

    The socket interprocess communication (IPC) facilities (introduced with 4.2BSD) were designed to allow network-based applications to be constructed independently of the underlying communication facilities.

    Creating a Server Application

    To create a server application using the BSD interface, you must follow these steps:

  • Create a new socket by typing: socket().

  • bind an address (IP address and port number) to the socket by typing: bind. This step identifies the server so that the client knows where to go.

  • listen for new connection requests on the socket by typing: listen().

  • accept new connections by typing: accept().

  • Often, the servicing of a request on behalf of a client may take a considerable length of time. It would be more efficient in such a case to accept and deal with new connections while a request is being processed. The most common way of doing this is for the server to fork a new copy of itself after accepting the new connection.

    Figure 2. Representation of Client/Server Code

    The code example in Listing 1 shows how servers are implemented in C. The program expects to be called with only one command-line argument: the port number to bind to. It then creates a new socket to listen on using the socket() system call. This call takes three parameters: the domain in which to listen to, the socket type and the network protocol.

    The domain can be either the PF_UNIX domain (i.e., internal to the local machine only) or the PF_INET (i.e., all requests from the Internet). The socket type specifies the communication semantics of the connection. While a few types of sockets have been specified, in practice, SOCK_STREAM and SOCK_DGRAM are the most popular implementations. SOCK_STREAM provides for TCP reliable connection-oriented communications, SOCK_DGRAM for UDP connectionless communication.

    The protocol parameter identfies the particular protocol to be used with the socket. While multiple protocols may exist within a given protocol family (or domain), there is generally only one. For TCP this is IPPROTO_TCP, for UDP it is IPPROTO_UDP. You do not have to explicitly specify this parameter when making the function call. Instead, using a value of 0 will select the default protocol.

    Once the socket is created, its operation can be tweaked by means of socket options. In the above example, the socket is set to reuse old addresses (i.e., IP address + port numbers) without waiting for the required connection close timeout. If this were not set, you would have to wait four minutes in the TIME_WAIT state before using the address again. The four minutes comes from 2 * MSL. The recommended value for MSL, from RFC 1337, is 120 seconds. Linux uses 60 seconds, BSD implementations normally use around 30 seconds.

    The socket can linger to ensure that all data is read, once one end closes. This option is turned on in the code. The structure of linger is defined in /usr/include/linux/socket.h. It looks like this:

    struct linger { int l_onoff; /* Linger active */ int l_linger; /* How long to linger */ };

    If l_onoff is zero, lingering is disabled. If it is non-zero, lingering is enabled for the socket. The l_linger field specifies the linger time in seconds.

    The server then tries to discover its own host name. I could have used the gethostname() call, but the use of this function is deprecated in SVR4 Unix (i.e., Sun's Solaris, SCO Unixware and buddies), so the local function _GetHostName() provides a more portable solution.

    Once the host name is established, the server constructs an address for the socket by trying to resolve the host name to an Internet domain address, using the gethostbyname() call. The server's IP address could instead be set to INADDR_ANY to allow a client to contact the server on any of its IP addresses—used, for example, with a machine with multiple network cards or multiple addresses per network card.

    After an address is created, it is bound to the socket. The socket can now be used to listen for new connections. The BACK_LOG specifies the maximum size of the listen queue for pending connections. If a connection request arrives when the listen queue is full, it will fail with a connection refused error. [This forms the basis for one type of denial of service attack —Ed.] See sidebar on TCP listen() Backlog.

    Having indicated a willingness to listen to new connection requests, the socket then prepares to accept the requests and service them. The example code achieves this using an infinite for() loop. Once a connection has been accepted, the server can ascertain the address of the client for logging or other purposes. It then forks a child copy of itself to handle the request while it (the parent) continues listening for and accepting new requests.

    The child process can use the read() and write() system calls on this connection to communicate with the client. It is also possible to use the buffered I/O on these connections (e.g., fprint()) as long as you remember to fflush() the output when necessary. Alternatively, you can disable buffering altogether for the process (see the setvbuf() (3) man page).

    As you can see from the code, it is quite common (and good practice) for the child processes to close the inherited parent-socket file descriptor, and for the parent to close the child-socket descriptor when using this simple forking model.

    Creating the Corresponding Client

    The client code, shown in Listing 2, is a little simpler than the corresponding server code. To start the client, you must provide two command-line arguments: the host name or address of the machine the server is running on and the port number the server is bound to. Obviously, the server must be running before any client can connect to it.

    In the client example (Listing 2), a socket is created like before. The first command-line argument is first assumed to be a host name for the purposes of finding the server's address. If this fails, it is then assumed to be a dotted-quad IP address. If this also fails, the client cannot resolve the server's address and will not be able to contact it.

    Having located the server, an address structure is created for the client socket. No explicit call to bind() is needed here, as the connect() call handles all of this.

    Once the connect() returns successfully, a duplex connection has been established. Like the server, the client can now use read() and write() calls to receive data on the connection.

    Be aware of the following points when sending data over a socket connection:

  • Sending text is usually fine. Remember that different systems can have different conventions for the end of line (i.e., Unix is \012, whereas Microsoft uses \015\012).

  • Different architectures may use different byte-ordering for integers etc. Thankfully, the BSD guys thought of this problem already. There are routines (htons and nstoh for short integers, htonl and ntohl for long integers) which perform host-to-network order and network-to-host order conversions. Whether the network order is little-endian or big-endian doesn't really matter. It has been standardized across all TCP/IP network stack implementations. Unless you persistently pass only characters across sockets, you will run into byte-order problems if you do not use these routines. Depending on the machine architecture, these routines may be null macros or may actually be functional. Interestingly, a common source of bugs in socket programming is to forget to use these byte-ordering routines for filling the address field in the sock_addr structures. Perhaps it is not intuitively obvious, but this must also be done when using INADDR_ANY (i.e., htonl(INADDR_ANY)).

  • A key goal of network programming is to ensure processes do not interfere with each other in unexpected ways. In particular, servers must use appropriate mechanisms to serialize entry through critical sections of code, avoid deadlock and protect data validity.

  • You cannot (generally) pass a pointer to memory from one machine to another and expect to use it. It is unlikely you will want to do this.

  • Similarly, you cannot (generally) pass a file descriptor from one process to another (non-child) process via a socket and use it straightaway. Both BSD and SVR4 provide different ways of passing file descriptors between unrelated processes; however, the easiest way to do this in Linux is to use the /proc file system.

  • Additionally, you must ensure that you handle short writes correctly. Short writes happen when the write() call only partially writes a buffer to a file descriptor. They occur due to buffering in the operating system and to flow control in the underlying transport protocol. Certain system calls, termed slow system calls, may be interrupted. Some may or may not be automatically restarted, so you should explicitly handle this when network programming. The code excerpt in Listing 3 handles short writes.

    Using multiple threads instead of multiple processes may lighten the load on the server host, thereby increasing efficiency. Context-switching between threads (in the same process address space) generally has much less associated overhead than switching between different processes. However, since most of the slave threads in this case are doing network I/O, they must be kernel-level threads. If they were user-level threads, the first thread to block on I/O would cause the whole process to block. This would result in starving all other threads of any CPU attention until the I/O had completed.

    It is common to close unnecessary socket file descriptors in child and parent processes when using the simple forking model. This prevents the child or parent from potential erroneous reads or writes and also frees up descriptors, which are a limited resource. But do not try this when using threads. Multiple threads within a process share the same memory space and set of file descriptors. If you close the server socket in a slave thread, it closes for all other threads in that process.

    Connectionless Data—UDP

    Listing 4 shows a connectionless server using UDP. While UDP applications are similar to their TCP cousins, they have some important differences. Foremost, UDP does not guarantee reliable delivery—if you require reliability and are using UDP, you either have to implement it yourself in your application logic or switch to TCP.

    Like TCP applications, with UDP you create a socket and bind an address to it. (Some UDP servers do not need to call bind(), but it does no harm and will save you from making a mistake.) UDP servers do not listen or accept incoming connections, and clients do not explicitly connect to servers. In fact, there is very little difference between UDP clients and servers. The server must be bound to a known port and address only so that the client knows where to send messages. Additionally, the order of expected data transmissions is reversed, i.e., when you send data using send() in the server, your client should expect to receive data using recv().

    It is common for UDP clients to fill in the sockaddr_in structure with a sin_port value of 0. (Note that 0 in either byte-order is 0.) The system then automatically assigns an unused port number (between 1024 and 5000) to the client. I'm leaving it as an exercise to the reader to convert the server in Listing 4 into a UDP client.

    /etc/services

    In order to connect to a server, you must first know both the address and port number on which it is listening. Many common services (FTP, TELNET, etc.) are listed in a text database file called /etc/services. An interface exists to request a service by name and to receive the port number (correctly formatted in network byte-order) for that service. The function is getservbyname(), and its prototype is in the header file /usr/include/netdb.h. This example takes a service name and protocol type and returns a pointer to struct servent.

    struct servent { char *s_name; /* official service name */ char **s_aliases; /* alias list */ int s_port; /* port number, network<\n> * byte-order--so do not * use host-to-network macros */ char *s_proto; /* protocol to use */ };

    Conclusions

    This article has introduced network programming in Linux, using C and the BSD Socket API. In general, coding with this API tends to be quite laborious, especially when compared to some of the other techniques available. In future articles, I will compare two alternatives to the BSD Socket API for Linux: the use of Remote Procedure Calls (RPCs) and the Common Object Request Broker Architecture (CORBA). RPCs were introduced in Ed Petron's article “Remote Procedure Calls” in Linux Journal Issue #42 (October, 1997).

    Resources

    TCP listen() Backlog

    Major System Calls The next article in this series will cover the issues involved in developing long-lived network services (daemons) in Linux.

    All listings referred to in this article are available by anonymous download in the file ftp://ftp.linuxjournal.com/lj/listings/issue46/2333.tgz.



    Direct Download of over 5500 Certification Exams

    3COM [8 Certification Exam(s) ]
    AccessData [1 Certification Exam(s) ]
    ACFE [1 Certification Exam(s) ]
    ACI [3 Certification Exam(s) ]
    Acme-Packet [1 Certification Exam(s) ]
    ACSM [4 Certification Exam(s) ]
    ACT [1 Certification Exam(s) ]
    Admission-Tests [13 Certification Exam(s) ]
    ADOBE [93 Certification Exam(s) ]
    AFP [1 Certification Exam(s) ]
    AICPA [2 Certification Exam(s) ]
    AIIM [1 Certification Exam(s) ]
    Alcatel-Lucent [13 Certification Exam(s) ]
    Alfresco [1 Certification Exam(s) ]
    Altiris [3 Certification Exam(s) ]
    Amazon [2 Certification Exam(s) ]
    American-College [2 Certification Exam(s) ]
    Android [4 Certification Exam(s) ]
    APA [1 Certification Exam(s) ]
    APC [2 Certification Exam(s) ]
    APICS [2 Certification Exam(s) ]
    Apple [69 Certification Exam(s) ]
    AppSense [1 Certification Exam(s) ]
    APTUSC [1 Certification Exam(s) ]
    Arizona-Education [1 Certification Exam(s) ]
    ARM [1 Certification Exam(s) ]
    Aruba [8 Certification Exam(s) ]
    ASIS [2 Certification Exam(s) ]
    ASQ [3 Certification Exam(s) ]
    ASTQB [8 Certification Exam(s) ]
    Autodesk [2 Certification Exam(s) ]
    Avaya [101 Certification Exam(s) ]
    AXELOS [1 Certification Exam(s) ]
    Axis [1 Certification Exam(s) ]
    Banking [1 Certification Exam(s) ]
    BEA [5 Certification Exam(s) ]
    BICSI [2 Certification Exam(s) ]
    BlackBerry [17 Certification Exam(s) ]
    BlueCoat [2 Certification Exam(s) ]
    Brocade [4 Certification Exam(s) ]
    Business-Objects [11 Certification Exam(s) ]
    Business-Tests [4 Certification Exam(s) ]
    CA-Technologies [20 Certification Exam(s) ]
    Certification-Board [10 Certification Exam(s) ]
    Certiport [3 Certification Exam(s) ]
    CheckPoint [43 Certification Exam(s) ]
    CIDQ [1 Certification Exam(s) ]
    CIPS [4 Certification Exam(s) ]
    Cisco [318 Certification Exam(s) ]
    Citrix [48 Certification Exam(s) ]
    CIW [18 Certification Exam(s) ]
    Cloudera [10 Certification Exam(s) ]
    Cognos [19 Certification Exam(s) ]
    College-Board [2 Certification Exam(s) ]
    CompTIA [76 Certification Exam(s) ]
    ComputerAssociates [6 Certification Exam(s) ]
    Consultant [2 Certification Exam(s) ]
    Counselor [4 Certification Exam(s) ]
    CPP-Institute [4 Certification Exam(s) ]
    CSP [1 Certification Exam(s) ]
    CWNA [1 Certification Exam(s) ]
    CWNP [13 Certification Exam(s) ]
    CyberArk [1 Certification Exam(s) ]
    Dassault [2 Certification Exam(s) ]
    DELL [11 Certification Exam(s) ]
    DMI [1 Certification Exam(s) ]
    DRI [1 Certification Exam(s) ]
    ECCouncil [22 Certification Exam(s) ]
    ECDL [1 Certification Exam(s) ]
    EMC [128 Certification Exam(s) ]
    Enterasys [13 Certification Exam(s) ]
    Ericsson [5 Certification Exam(s) ]
    ESPA [1 Certification Exam(s) ]
    Esri [2 Certification Exam(s) ]
    ExamExpress [15 Certification Exam(s) ]
    Exin [40 Certification Exam(s) ]
    ExtremeNetworks [3 Certification Exam(s) ]
    F5-Networks [20 Certification Exam(s) ]
    FCTC [2 Certification Exam(s) ]
    Filemaker [9 Certification Exam(s) ]
    Financial [36 Certification Exam(s) ]
    Food [4 Certification Exam(s) ]
    Fortinet [14 Certification Exam(s) ]
    Foundry [6 Certification Exam(s) ]
    FSMTB [1 Certification Exam(s) ]
    Fujitsu [2 Certification Exam(s) ]
    GAQM [9 Certification Exam(s) ]
    Genesys [4 Certification Exam(s) ]
    GIAC [15 Certification Exam(s) ]
    Google [4 Certification Exam(s) ]
    GuidanceSoftware [2 Certification Exam(s) ]
    H3C [1 Certification Exam(s) ]
    HDI [9 Certification Exam(s) ]
    Healthcare [3 Certification Exam(s) ]
    HIPAA [2 Certification Exam(s) ]
    Hitachi [30 Certification Exam(s) ]
    Hortonworks [4 Certification Exam(s) ]
    Hospitality [2 Certification Exam(s) ]
    HP [752 Certification Exam(s) ]
    HR [4 Certification Exam(s) ]
    HRCI [1 Certification Exam(s) ]
    Huawei [21 Certification Exam(s) ]
    Hyperion [10 Certification Exam(s) ]
    IAAP [1 Certification Exam(s) ]
    IAHCSMM [1 Certification Exam(s) ]
    IBM [1533 Certification Exam(s) ]
    IBQH [1 Certification Exam(s) ]
    ICAI [1 Certification Exam(s) ]
    ICDL [6 Certification Exam(s) ]
    IEEE [1 Certification Exam(s) ]
    IELTS [1 Certification Exam(s) ]
    IFPUG [1 Certification Exam(s) ]
    IIA [3 Certification Exam(s) ]
    IIBA [2 Certification Exam(s) ]
    IISFA [1 Certification Exam(s) ]
    Intel [2 Certification Exam(s) ]
    IQN [1 Certification Exam(s) ]
    IRS [1 Certification Exam(s) ]
    ISA [1 Certification Exam(s) ]
    ISACA [4 Certification Exam(s) ]
    ISC2 [6 Certification Exam(s) ]
    ISEB [24 Certification Exam(s) ]
    Isilon [4 Certification Exam(s) ]
    ISM [6 Certification Exam(s) ]
    iSQI [7 Certification Exam(s) ]
    ITEC [1 Certification Exam(s) ]
    Juniper [65 Certification Exam(s) ]
    LEED [1 Certification Exam(s) ]
    Legato [5 Certification Exam(s) ]
    Liferay [1 Certification Exam(s) ]
    Logical-Operations [1 Certification Exam(s) ]
    Lotus [66 Certification Exam(s) ]
    LPI [24 Certification Exam(s) ]
    LSI [3 Certification Exam(s) ]
    Magento [3 Certification Exam(s) ]
    Maintenance [2 Certification Exam(s) ]
    McAfee [8 Certification Exam(s) ]
    McData [3 Certification Exam(s) ]
    Medical [68 Certification Exam(s) ]
    Microsoft [375 Certification Exam(s) ]
    Mile2 [3 Certification Exam(s) ]
    Military [1 Certification Exam(s) ]
    Misc [1 Certification Exam(s) ]
    Motorola [7 Certification Exam(s) ]
    mySQL [4 Certification Exam(s) ]
    NBSTSA [1 Certification Exam(s) ]
    NCEES [2 Certification Exam(s) ]
    NCIDQ [1 Certification Exam(s) ]
    NCLEX [3 Certification Exam(s) ]
    Network-General [12 Certification Exam(s) ]
    NetworkAppliance [39 Certification Exam(s) ]
    NI [1 Certification Exam(s) ]
    NIELIT [1 Certification Exam(s) ]
    Nokia [6 Certification Exam(s) ]
    Nortel [130 Certification Exam(s) ]
    Novell [37 Certification Exam(s) ]
    OMG [10 Certification Exam(s) ]
    Oracle [282 Certification Exam(s) ]
    P&C [2 Certification Exam(s) ]
    Palo-Alto [4 Certification Exam(s) ]
    PARCC [1 Certification Exam(s) ]
    PayPal [1 Certification Exam(s) ]
    Pegasystems [12 Certification Exam(s) ]
    PEOPLECERT [4 Certification Exam(s) ]
    PMI [15 Certification Exam(s) ]
    Polycom [2 Certification Exam(s) ]
    PostgreSQL-CE [1 Certification Exam(s) ]
    Prince2 [6 Certification Exam(s) ]
    PRMIA [1 Certification Exam(s) ]
    PsychCorp [1 Certification Exam(s) ]
    PTCB [2 Certification Exam(s) ]
    QAI [1 Certification Exam(s) ]
    QlikView [1 Certification Exam(s) ]
    Quality-Assurance [7 Certification Exam(s) ]
    RACC [1 Certification Exam(s) ]
    Real Estate [1 Certification Exam(s) ]
    Real-Estate [1 Certification Exam(s) ]
    RedHat [8 Certification Exam(s) ]
    RES [5 Certification Exam(s) ]
    Riverbed [8 Certification Exam(s) ]
    RSA [15 Certification Exam(s) ]
    Sair [8 Certification Exam(s) ]
    Salesforce [5 Certification Exam(s) ]
    SANS [1 Certification Exam(s) ]
    SAP [98 Certification Exam(s) ]
    SASInstitute [15 Certification Exam(s) ]
    SAT [1 Certification Exam(s) ]
    SCO [10 Certification Exam(s) ]
    SCP [6 Certification Exam(s) ]
    SDI [3 Certification Exam(s) ]
    See-Beyond [1 Certification Exam(s) ]
    Siemens [1 Certification Exam(s) ]
    Snia [7 Certification Exam(s) ]
    SOA [15 Certification Exam(s) ]
    Social-Work-Board [4 Certification Exam(s) ]
    SpringSource [1 Certification Exam(s) ]
    SUN [63 Certification Exam(s) ]
    SUSE [1 Certification Exam(s) ]
    Sybase [17 Certification Exam(s) ]
    Symantec [135 Certification Exam(s) ]
    Teacher-Certification [4 Certification Exam(s) ]
    The-Open-Group [8 Certification Exam(s) ]
    TIA [3 Certification Exam(s) ]
    Tibco [18 Certification Exam(s) ]
    Trainers [3 Certification Exam(s) ]
    Trend [1 Certification Exam(s) ]
    TruSecure [1 Certification Exam(s) ]
    USMLE [1 Certification Exam(s) ]
    VCE [6 Certification Exam(s) ]
    Veeam [2 Certification Exam(s) ]
    Veritas [33 Certification Exam(s) ]
    Vmware [58 Certification Exam(s) ]
    Wonderlic [2 Certification Exam(s) ]
    Worldatwork [2 Certification Exam(s) ]
    XML-Master [3 Certification Exam(s) ]
    Zend [6 Certification Exam(s) ]





    References :


    Dropmark : http://killexams.dropmark.com/367904/11892563
    Wordpress : http://wp.me/p7SJ6L-23S
    Dropmark-Text : http://killexams.dropmark.com/367904/12875633
    Blogspot : http://killexamsbraindump.blogspot.com/2017/12/real-3x0-103-questions-that-appeared-in.html
    RSS Feed : http://feeds.feedburner.com/FreePass4sure3x0-103QuestionBank
    Box.net : https://app.box.com/s/ukrdjg11phcxkj8jh3a9xy1rpul4h9g6






    Back to Main Page





    Killexams exams | Killexams certification | Pass4Sure questions and answers | Pass4sure | pass-guaratee | best test preparation | best training guides | examcollection | killexams | killexams review | killexams legit | kill example | kill example journalism | kill exams reviews | kill exam ripoff report | review | review quizlet | review login | review archives | review sheet | legitimate | legit | legitimacy | legitimation | legit check | legitimate program | legitimize | legitimate business | legitimate definition | legit site | legit online banking | legit website | legitimacy definition | pass 4 sure | pass for sure | p4s | pass4sure certification | pass4sure exam | IT certification | IT Exam | certification material provider | pass4sure login | pass4sure exams | pass4sure reviews | pass4sure aws | pass4sure security | pass4sure cisco | pass4sure coupon | pass4sure dumps | pass4sure cissp | pass4sure braindumps | pass4sure test | pass4sure torrent | pass4sure download | pass4surekey | pass4sure cap | pass4sure free | examsoft | examsoft login | exams | exams free | examsolutions | exams4pilots | examsoft download | exams questions | examslocal | exams practice |

    www.pass4surez.com | www.killcerts.com | www.search4exams.com | http://smresidences.com.ph/