Transmission Control Protocol (TCP) / Internet Protocol (IP)

Transcription

1 Transmission Control Protocol (TCP) / Internet Protocol (IP)

2 Overview of TCP/IP Oldest networking standard developed for US department s ARPANET Most popular network protocol Allows reasonably efficient and error free transmission A file transfer protocol, sends large files uncorrupted across unreliable networks Compatible with a variety of data link protocols hence popular

3 An Internet F B A C a 2 1 b e f 3 5 c d 4 E A, B, C, D, E, F host (computers) D 1, 2, 3, 4, 5 physical networks a, b, c, d, e, f routers/gateways For TCP/IP, the same internet appears differently. TCP/IP considers all interconnected physical networks as one huge network ( )

4 TCP/IP and OSI model Application Application Presentation Session SMTP Applications FTP TELNET DNS SNMP NFS RPL TFTP Data units known as Message creates Transport layer (2protocols) Network layer Data link layer Physical layer ICMP ARP TCP RARP Protocols defined by the underlying networks UDP IP (Supports 4 protocols) H Segment or user diagram Creates H Datagram Encapsulated Frame Bits H

5 NETWORK LAYER ICMP (Internet control message protocol) - handles error & controls messages IGMP ARP (Address resolution protocol) obtaining the physical address of a mode when the internet address is known RARP (Reverse address resolution protocol) allows a host to discover its internet address when it knows only its physical address

6 Internet Protocol (IP) -1 Transmission mechanism used for TCP/IP Unreliable & connectionless datagram protocol Assumes the unreliability of the underlying layers & gives best to get a transmission through to its destination For good quality IP must be paired with a reliable protocol like TCP

7 Internet Protocol (IP) 2 IP transports data in packets known as datagrams IP functionality in a limited way is not a weakness IP provides bare-bone transmission functions ; frees the user to add only those facilities necessary for a given application; allows for maximum efficiency

8 IP Datagram bytes bytes Header Data (a) Datagram VER Version HLEN Header length VER 4 bits HLEN Service type Total length of the IP Datagram 16 bits 4 bits 8 bits (2 byte field) Flags Identification 16 bits 3 bits Protocol Header checksum 8 bits 16 bits Source IP address Destination IP address Option Time to live 8 bits Fragmentation Offset 13 bits (b) Header

9 IP datagram- 1 Service type : defines how the datagram should be handled; includes bits that define the priority of the datagram; also contains bits that specify type of service the sender desires such as the level of throughput, reliability and delay Total length : can define up to 65,536 bytes;two byte field.

10 IP datagram- 2 Flags : Bits in the flags deal with fragmentation. (Datagram can/cannot be fragmented; can be the first, middle or last fragment etc.) Fragmentation offset : A pointer shows the offset of the data in the original datagram Time to live : This field defines the number of hops a datagram can travel before it is discarded; source host, when it creates the datagram sets this field to an initial value; when the datagram travels through the internet router by router each router decrements this value by 1. If this value becomes 0 before the datagram reaches its final destination, the datagram is discarded. This prevents a datagram from going back & forth between routers

11 Internet address - 1 Protocol : field defines which upper layer protocol data are encapsulated Source address, destination address : Each field is a four byte(32 bit) Internet address. It identifies the original source & final destination of the datagram respectively. Options : The field gives more functionality to the IP datagram. It carries field that control routing, timing, management and alignment.

12 Internet address - 2 Addressing : Physical addresses are on NICs. It identifies individual devices. The internet requires an additional addressing constituent : An address that identifies the connection of a host to its network Each internet consists of four bytes (32 bits) defining three fields : I. Class type II. Netid III. Hostid

13 Internet address - each internet consists of four bytes (32 bits) defining three fields : 1) Class type 2) Netid 3) Hostid varying lengths & depends on the Class of the address Class type Netid Hostid

14 Internet classes byte 1 byte 2 byte 3 byte 4 Address Class A Class B Netid Hostid Netid Hostid Hostid Hostid Lowest Class C Netid Hostid Class D Multicast address Class E Reserved for future use

15 Class range of internet addresses Class A Class B Class C Class D From Netid Hostid Netid Hostid Netid Hostid To Netid Hostid Netid Hostid Netid Hostid Hostid Class E

16 Network & hosts addresses in an internet Network 1 C 1 C 2 C C G Gateway C 6 Router R G Gateway Network C 7 C 3 C 4 Network C 9 C

17 ARP request/response ARP packet Router or host ARP packet questions about the physical address of a node. IP address it gives Host Hos 1 Host 2 Host Host 3 One of the nodes responds identifying itself as the right node & gives the physical address

18 UDP Datagram Format 8 bytes variable Header Data Source port address 16 bits Total length 16 bits Destination port Address 16 bits Clocksum 16 bits

19 UDP Source host IP Host-to-host protocol Delivers a datagram Destination host

20 Port-to-port addresses app 1 app 2 app 3 TCP or UDP IP Data Link Physical app 4 app 1 app 2 app 3 TCP or UDP IP Data Link Physical app 4

21 TCP segment Header Data (a) Datagram HLEN Header length HLEN 4 bits Source port address 16 bits Reserved 16 bits g Control checksum 16 bits Sequence number 32 bits Acknowledge number 32 bits u r s c k p s n Options and padding Destination port address 16 bits r s t s y n f l n Window size 16 bits Urgent pointer 16 bits

22 Client/server Paradigm Client program Server TCP/IP Server program Result

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24 Using TELNET to login User working online New Delhi Mumbai Hyderabad Calcutta Terminal Host Banglore Chennai

25 Steps involved in TELNET (remote login) - 1 Terminal (Real) Local host TELNET Client TELNET server Remote host Standard code TCP/IP Standard code

26 Steps involved in TELNET (remote login) TELNET client transforms the output from the actual terminal to standard code 2. TELNET server in the remote host receives the information in the standard code 3. TELNET server will transform the information into character accepted by remote host 4. The remote host is pooled into thinking that a terminal is locally connected to it. (in other words a virtual terminal is connected to the local host)

27 FTP User interface Protocol interpreter Data transfer unit Local host Control connection TCP/IP Data connection Protocol interpreter Data Transfer unit Remote host Local disk Remote disk

28 Local procedure call C program calling the open Function is used here User application program C program to access a disk Local procedure Local Disk Local host

29 Remote procedure call - 1 C program Calling the Open Function Is used here C program to access a disk NFS client RPC Client NFS Server RPC Client C program Local Disk Local host TCP/IP Remote host Local Disk

30 Remote procedure call A program issues a call to the NFS client process. NFS client formats the call for the RPC client and passes it. 2. RPC client transforms the data to a format called XDR.(external data presentation) & provides the interface with TCP/IP transport mechanisms.

31 Remote procedure call At the remote host, RPC server retrieves the call translates it out of XDR and passes it to the NFS server. 4. NFS server relays the call to the remote disk. 5. The remote disk finally responds as if to a call & opens the file to the NFS server. Similar process is followed in the reverse order to work in the opposite way.

32 User A Interface Electronic Mail (Sending & Receiving) User B Interface User agent User agent Spool Mail boxes Mail boxes Spool Database Or disk Alias expansion Alias expansion Database or disk Mail transfer agents (MTA) Mail transfer Agents (MTA) Mail transfer agents (MTA) Mail transfer Agents (MTA) Internet

33 SNMP Network 3 Manager Router R 3 Router R 2 Router R 4 Router R 1 Router R Router R 5 Managed (Agent) Manager Network 1 Routers R 1 to R 4 are Managed (Agent) Managed (Agent)

34 World Wide Web Web server A (Mumbai) Web server B (Denmark) Web server C (Japan) Web server D (Chennai)

35 World wide web Requires A functional architecture A structural architecture A navigational architecture

36 A Functional Architecture <html> <head> <title> DATAMATION Plugin </title> </head> <body> <hp> newswire</hl> <hl> DATAMATION Magazine </hl> <hl> Media kit </hl> LAN HTML documents interpreted by browsers Proxy server Fire wall From & to the internet

37 A structural architecture D: \ Newswire Live wire DATAMATION MANAGEMENT Table of contents Feature index Cover story Management Desktops Networks Software Servers

38 Browser architecture Many commercial browsers exist These interpret and display a web document. Each of these use the same architecture Browser has three parts : 1. Controller 2. Client programs 3. Interpreters

39 Browser architecture BROWSER HTTP FTTP controller GOPHER TELNET SMTP HTML CGI Java INTERPRETERS

40 Static documents Fixed content documents are created and stored in a server Client accesses the document, a copy of the document is received User can use a browsing program to display the document User cannot change the contents;but the contents can be changed in the server

41 Static documents Client Response URL Document Request for a document Server Web document

42 Dynamic documents -1 These do not exist in predefined format Documents are created by a web server when a browser requests the document When the request arrives, the web server runs an application program to create the dynamic document Server then returns the output in response to the browsers request for document

43 Dynamic documents - 2 Contents of document varies as these are created for each request. Time and date are types of dynamic information. Client can request that the server run a program in UNIX and send the result back

44 Dynamic documents Client Response URL Document Request for a document Server

45 Dynamic documents Client requests for running a program. Steps Running the program creates document. Respond

46 Active documents Produce the document D D Client Running the program P1 Response URL P1 Request for a document Copy of the program P1 sent P Server

47 Active documents Steps Client requests for a copy of the program Copy of the program is sent by server. Running the program and creating the document at the client s end.