NAME:- MOHD. SHAHNAWAZ ALAMROLL NO:-COURSE:-B.SC (IT)SEMESTER: - THIRDBOOK NO:- BT0076(TCP/IP)SESSION:- SPRING 20121.   Br...
2.   Explain the purpose of NCP in PPP.The Network Control Protocol (NCP) phase in the PPP link connection process is used...
There are a large number of proposed standard protocols, which specify the operation of PPP overdifferent kinds of point-t...
1. The DF flag bit is checked to see if fragmentation is allowed. If the bit is set, the datagram will bediscarded and an ...
this timer is called the IP datagram time to live (TTL) value.It is implementation-dependent. Someimplementations allow it...
(do ((line (read-line s) (read-line s)))             ((eof-object? line))           (display line)           (newline)))5....
The process of setting up a proxy transfer begins with the use of a proxy open command. AnyFTP command can then be sent to...
2. HELO (HELO is an abbreviation for hello) is sent, to which the receiver will identify itself bysending back its domain ...
9. Discuss various HTTP protocol parameters.Protocol parameters: We provide some of the HTTP protocol parameters here.· HT...
· HTTP URL: The HTTP URL scheme enables you to locate network resources through theHTTP protocol. It is based on the URI G...
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TCP/IP 3RD SEM.2012 AUG.ASSIGNMENT

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TCP/IP 3RD SEM.2012 AUG.ASSIGNMENT

  1. 1. NAME:- MOHD. SHAHNAWAZ ALAMROLL NO:-COURSE:-B.SC (IT)SEMESTER: - THIRDBOOK NO:- BT0076(TCP/IP)SESSION:- SPRING 20121. Briefly discuss the functions of transport layer.Transport layer accepts data from session layer breaks it into packets and deliversthese packets to the network layer. It is the responsibility of transport layer to guaranteesuccessful arrival of data at the destination device. It provides an end-to-end dialog thatis the transport layer at the source device directly communicates with transport layer atdestination device. Message headers and control messages are used for this purpose.It separates the upper layers from the low level details of data transmission and makessure an efficient delivery. OSI model provides connection-oriented service at transportlayer.It is responsible for the determination of the type of service that is to be provided to theupper layer. Normally it transmits packets in the same order in which they are senthowever it can also facilitate the transmission of isolated messages. There is no suretythat these isolated messages are delivered to the destination devices in case ofbroadcast networks and they will be in the same order as were sent from the source.If the network layer do not provide adequate services for the data transmission. Dataloss due to poor network management is handled by using transport layer. It checks forany packets that are lost or damaged along the way
  2. 2. 2. Explain the purpose of NCP in PPP.The Network Control Protocol (NCP) phase in the PPP link connection process is used for establishingand configuring different network-layer protocols such as IP, IPX or AppleTalk.After a NCP has reached the Opened state, PPP will carry the corresponding network-layer protocolpackets. Any supported network-layer protocol packets received when the corresponding NCP is not inthe Opened state MUST be silently discarded.During this phase, link traffic consists of any possible combination of LCP, NCP, and network-layerprotocol packets.The most common layer 3 protocol negotiated is IP. The routers exchange IP Control Protocol (IPCP)messages negotiating options specific to the protocol. The corresponding network control protocol forIPv6 is IPv6CP.IPCP negotiates two options: compression and IP address assignments. However, IPCP is also used topass network related information such as primary and backup Windows Name Service (WINS) andDomain Name System (DNS) servers.
  3. 3. There are a large number of proposed standard protocols, which specify the operation of PPP overdifferent kinds of point-to-point links. Each has a status of elective. Point-to-point circuits in the formof asynchronous and synchronous lines have long been the mainstay for data communications. In theTCP/IP world, the de facto standard SLIP protocol has served admirably in this area, and is still inwidespread use for dial-up TCP/IP connections. However, SLIP has a number of drawbacks that areaddressed by the Point-to-Point Protocol. PPP has three main components:• A method for encapsulating datagrams over serial links.• A Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection.• A family of Network Control Protocols (NCPs) for establishing and configuring different network-layerprotocols.3. What is fragmentation? Explain its significance.When an IP datagram travels from one host to another, it can pass through different physicalnetworks. Each physical network has a maximum frame size. This is called the maximum transmissionunit (MTU). It limits the length of a datagram that can be placed in one physical frame. IP implementsa process to fragment datagrams exceeding the MTU. The process creates a set of datagrams withinthe maximum size. The receiving host reassembles theoriginal datagram. IP requires that each link support a minimum MTU of 68 octets. This is the sum ofthe maximum IP header length (60 octets) and the minimum possible length of data in a non-finalfragment (8 octets). If any network provides a lower value than this, fragmentation and reassemblymust be implemented in the network interface layer. This must be transparent to IP. IPimplementations are not required to handle unfragmented datagrams larger than 576 bytes. Inpractice, most implementations will accommodate larger values.An unfragmented datagram has an all-zero fragmentation information field. That is, the morefragments flag bit is zero and the fragment offset is zero. The following steps fragment the datagram:
  4. 4. 1. The DF flag bit is checked to see if fragmentation is allowed. If the bit is set, the datagram will bediscarded and an ICMP error returned to the originator.2. Based on the MTU value, the data field is split into two or more parts. All newly created dataportions must have a length that is a multiple of 8 octets, with the exception of the last data portion.3. Each data portion is placed in an IP datagram. The headers of these datagrams are minormodifications of the original:The more fragments flag bit is set in all fragments except the last.The fragment offset field in each is set to the location this data portion occupied in the originaldatagram,relative to the beginning of the original unfragmented datagram. The offset is measured in8-octet units.If options were included in the original datagram, the high order bit of the option type byte determinesif this information is copied to all fragment datagrams or only the first datagram. For example, sourceroute options are copied in all fragments.– The header length field of the new datagram is set.– The total length field of the new datagram is set.– The header checksum field is re-calculated.4. Each of these fragmented datagrams is now forwarded as a normal IP datagram. IP handles eachfragment independently. The fragments can traverse different routers to the intended destination.They can be subject to further fragmentation if they pass through networks specifying a smaller MTU.At the destination host, the data is reassembled into the original datagram. The identification field setby the sending host is used together with the source and destination IP addresses in the datagram.Fragmentation does not alter this field. In order to reassemble the fragments, the receiving hostallocates a storage buffer when the first fragment arrives. The host also starts a timer. Whensubsequent fragments of the datagram arrive, the data is copied into the buffer storage at the locationindicated by the fragment offset field. When all fragments have arrived, the complete originalunfragmented datagram is restored. Processing continues as for unfragmented datagrams. If thetimer is exceeded and fragments remain outstanding,the datagram is discarded. The initial value of
  5. 5. this timer is called the IP datagram time to live (TTL) value.It is implementation-dependent. Someimplementations allow it to be configured. The netstat command can be used on some IP hosts to listthe details of fragmentation.3. What Is a Socket?A server application normally listens to a specific port waiting for connection requests from a client.When a connection request arrives, the client and the server establish a dedicated connection overwhich they can communicate. During the connection process, the client is assigned a local port number,and binds a socket to it. The client talks to the server by writing to the socket and gets information fromthe server by reading from it. Similarly, the server gets a new local port number (it needs a new portnumber so that it can continue to listen for connection requests on the original port). The server alsobinds a socket to its local port and communicates with the client by reading from and writing to it.The client and the server must agree on a protocol--that is, they must agree on the language ofthe information transferred back and forth through the socket.Definition: A socket is one end-point of a two-way communication link between two programs runningon the network.The java.net package in the Java development environment provides a class--Socket--thatrepresents one end of a two-way connection between your Java program and another program onthe network. The Socket class implements the client side of the two-way link. If you are writingserver software, you will also be interested in the ServerSocket class which implements theserver side of the two-way link. This lesson shows you how to use the Socket and ServerSocketclasses.If you are trying to connect to the World Wide Web, the URL class and related classes(URLConnection, URLEncoder) are probably more suitable than the socket classes to what youare doing. In fact, URLs are a relatively high level connection to the Web and use sockets as partof the underlying implementation. See Working with URLs for information about connectingto the Web via URLs.Internet Socket Client ExampleThe following example demonstrates an Internet socket client. It connects to the HTTP daemonrunning on the local machine and returns the contents of the root index URL. (let ((s (socket PF_INET SOCK_STREAM 0))) (connect s AF_INET (inet-pton AF_INET "127.0.0.1") 80) (display "GET / HTTP/1.0rnrn" s)
  6. 6. (do ((line (read-line s) (read-line s))) ((eof-object? line)) (display line) (newline)))5. Differentiate between FQDN and PQDN.FQDNA fully qualified domain name (FQDN) is the complete domain name for a specific computer, or host, onthe Internet. The FQDN consists of two parts: the hostname and the domain name. For example, anFQDN for a hypothetical mail server might be mymail.somecollege.edu. The hostname is mymail,and the host is located within the domain somecollege.edu.PQDNIf a label is not terminated by a null string, it is called a partially qualified domain name (PQDN). A PQDNstarts from a node, but it does not reach the root. It is used when the name to be resolved belongs tothe same site as the client. Here the resolver can supply the missing part, called suffix, to create anFQDN.6. What do you mean by option negotiation explain with example?All of the DO/DONT/WILL/WONT stuff above only serves to enable or disable an option. Some optionsare only either off or on, in which case the negotiation above is sufficient. An example would be thebinary transmission option, TRANSMIT-BINARY. Others require that after they are enabled, the clientand server exchange parameters to control how the option works. For example, the TERMINAL-TYPEoption requires some way for the client to send the server the name of the terminal.Telnet allows the client and server to send an arbitrary amount of data related to the option using aprocess called option subnegotiation. A device begins this process by sending a special sequence ofTelnet protocol commands and data. First the command SB is sent, followed by the option number andparameters as defined by the particular option; the end of the subnegotiation data is marked by theprotocol command SE. Of course, both SB and SE must be preceded by the Interpret As Command (IAC)command byte.7. Discuss FTP proxy transfer through firewall.FTP provides the ability for a client to have data transferred from one FTP server to another FTPserver. Several justifications for such a transfer exist, including: To transfer data from one host to another when direct access to the two hosts are not possible. To bypass a slow client connection. To bypass a firewall restriction. To reduce the amount of traffic within the client’s network
  7. 7. The process of setting up a proxy transfer begins with the use of a proxy open command. AnyFTP command can then be sent to the proxy server by preceding the command with proxy. Forexample, executing the dir command lists the files on the primary FTP server. Executing theproxy dir command lists the files on the proxy server. The proxy get and proxy put commandscan then be used to transfer data between the two hosts.1. The FTP client opens a connection and logs on to the FTP server A.2. The FTP client issues a proxy open command, and a new control connection is establishedwith FTP server B.3. The FTP client then issues a proxy get command (though this can also be a proxy put).4. A data connection is established between server A and server B. Following data connectionestablishment, the data flows from server B to server A.8. Explain various steps involved in SMTP Mail Transaction flow.Although mail commands and replies are rigidly defined, the exchange can easily be followed inFig. 8.2. All exchanged commands, replies, and data are text lines delimited by a <CRLF>. Allreplies have a numeric code at the beginning of the line. The steps of this flow are:1. The sender SMTP establishes a TCP connection with the destination SMTP and then waits forthe server to send a 220 Service ready message or a 421 Service not available message when thedestination is temporarily unable to proceed.
  8. 8. 2. HELO (HELO is an abbreviation for hello) is sent, to which the receiver will identify itself bysending back its domain name. The sender-SMTP can use this to verify that it contacted the rightdestination SMTP. The sender SMTP can substitute an EHLO command in place of the HELOcommand. A receiver SMTP that does not support service extensions will respond with a 500Syntax Error, command unrecognized message. The sender SMTP then retries with HELO, or ifit cannot transmit the message without one or more service extensions, it sends a QUIT message.If a receiver-SMTP supports service extensions, it responds with a multiline 250 OK message,which includes a list of service extensions that it supports.3. The sender now initiates the start of a mail transaction by sending a MAIL command to thereceiver. This command contains the reverse-path that can be used to report errors. Note that apath can be more than just the user mailbox@host domain name pair. In addition, it can contain alist of routing hosts. Examples of this are when we pass a mail bridge, or when explicit routinginformation is provided in the destination address. If accepted, the receiver replies with a 250OK.4. The second step of the actual mail exchange consists of providing the server SMTP with thedestinations for the message. There can be more than one recipient. This is done by sending oneor more RCPTTO:<forward-path> commands. Each of them will receive a reply 250 OK if thedestination is known to the server, or a 550 No such user here if it is not.5. When all RCPT commands are sent, the sender issues a DATA command to notify thereceiver that the message contents will follow. The server replies with 354 Start mail input, endwith <CRLF>.<CRLF>. Note the ending sequence that the sender should use to terminate themessage data.6. The client now sends the data line by line, ending with the 5-character sequence<CRLF>.<CRLF> line, upon which the receiver will acknowledge with a 250 OK, or anappropriate error message if anything went wrong.7. At this juncture, the client now has several possible actions: If the client has no more messages to send, it can end the connection with a QUIT command, which will be answered with a 221 Service closing transmission channel reply. If the sender has no more messages to send, but is ready to receive messages (if any) from the other side, it can issue the TURN command. The two SMTPs now switch their role of sender/receiver, and the sender (previously the receiver) can now send messages by starting with step 3. If the sender has another message to send, it returns to step 3 and sends a new MAIL command.Fig. 8.2 illustrates the normal transmission of a single message from a client to a server.Additionally, we provide a textual scenario in Fig. 8.3.
  9. 9. 9. Discuss various HTTP protocol parameters.Protocol parameters: We provide some of the HTTP protocol parameters here.· HTTP version: HTTP uses a <major>.<minor> numbering scheme to indicate the versions ofthe protocol. The furthermost connection is performed according to the protocol versioningpolicy. The <major> number is incremented when there are significant changes in protocol, suchas changing a message format. The <minor> number is incremented when the changes do notaffect the message format. The version of HTTP messages is sent by an HTTP-Version field inthe first line of the message. The HTTP-Version field is in the following format: HTTP-Version= "HTTP" "/" 1*DIGIT "." 1*DIGIT· Uniform Resource Identifiers (URIs): Uniform Resource Identifiers are generally referred to asWWW addresses and a combination of Uniform Resource Locators (URLs) and UniformResource Names (URNs). In fact, URIs are strings that indicate the location and name of thesource on the server.
  10. 10. · HTTP URL: The HTTP URL scheme enables you to locate network resources through theHTTP protocol. It is based on the URI Generic Syntax and described in RFC 3986. The generalsyntax of a URL scheme is: HTTP_URL = "http" "//" host [ ":" port ] [ abs_path ]. The portnumber is optional. If it is not specified, the default value is 80.10. with example, explain how OIDs are assigned to managed objects? 1. The original intention of the Recommendation ITU-T X.660 | ISO/IEC 9834 series was that anyone should be able to get an OID if they needed one. There are registrars from which it is easy and quite cheap (sometimes even free!) to have an OID assigned, such as: o Several countries are handling out OIDs under their country arc {joint-iso-itu- t(2) country(16)} and/or {iso(1) member-body(2)}. o If you are representing a country and want to allocate an arc under {iso(1) member- body(2)} or {joint-iso-itu-t(2) country(16)}, please see question 11 below. o IANA (Internet Assigned Numbers Authority) hands out OIDs for free under {iso(1) identified-organization(3) dod(6) internet(1) private(4) enterprise(1)}; these OIDs are mainly intended for identifying MIBs in an SNMP context. o You can generate a UUID (or use a UUID that you already hold) and append it as a subsequent arc of {joint-iso-itu-t(2) uuid(25)} (without registering it because it is guaranteed to be globally unique with a high probability) according to Recommendation ITU-T X.667 | ISO/IEC 9834-8 (but see question 30 about size limitations of OID encodings). o ETSI (European Telecommunication Standards Institute) hands out OIDs under {itu-t(0) identified-organization(4) etsi(0) reserved(127) etsi-identified-organization(0)} even for non- ETSI-members. o You can obtain an OID from Microsoft to extend the Active Directory schema . o Network operators can have an OID assigned by ITU-T under {itu-t(0) network- operator(3)}; telecom operators can have an OID assigned by their national PTT administration under {itu-t(0) administration(2)}. o Dave Harvey (UK) has offered to sub-delegate ranges of his own root to anyone who uses a DICOM toolkit (communication in medicine).

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