1 Chapter 3 TCP and IP. Chapter 3 TCP and IP 2 Introduction Transmission Control Protocol (TCP) Transmission Control Protocol (TCP) User Datagram Protocol

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Chapter 3Chapter 3

TCP and IPTCP and IP

Chapter 3 TCP and IP2

Introduction Introduction

Transmission Control Protocol Transmission Control Protocol (TCP)(TCP)

User Datagram Protocol (UDP)User Datagram Protocol (UDP) Internet Protocol (IPv4)Internet Protocol (IPv4) IPv6IPv6


TCPTCPDefined in Defined in RFC 793RFC 793, RFC 1122, RFC 1122Provides the Internet’s primary Provides the Internet’s primary

reliable host-to-host delivery reliable host-to-host delivery mechanismmechanism

Services offered:Services offered:– basic data transferbasic data transfer– reliability (reliable data transfer)reliability (reliable data transfer)– flow controlflow control– multiplexing/de-multiplexingmultiplexing/de-multiplexing– connections (maintains state)connections (maintains state)– precedence and securityprecedence and security

http://www.ietf.org/rfc/rfc0793.txt?number=793


TCP HeaderTCP Header


TCP Fields/FunctionsTCP Fields/Functions Source Port # (16 bits):Source Port # (16 bits): source source

application (application (multiplexingmultiplexing)) Destination Port # (16 bits):Destination Port # (16 bits): target target

application (application (de-multiplexingde-multiplexing)) Sequence # (32 bits):Sequence # (32 bits): number of the number of the

first data octet (first data octet (reliable data transferreliable data transfer)) Acknowledgement # (32 bits):Acknowledgement # (32 bits): next next

data octet expected by receiver data octet expected by receiver ((reliable data transferreliable data transfer))

Data offset/header length (4 bits):Data offset/header length (4 bits): number of 32bit words in the header number of 32bit words in the header ((basic data transferbasic data transfer))


TCP Fields/FunctionsTCP Fields/Functions Flags (6 or 8 bits):Flags (6 or 8 bits): source application source application

((precedence, connection managementprecedence, connection management)) Window size (16 bits):Window size (16 bits): number data number data

octets receiver is willing to accept (octets receiver is willing to accept (flow flow controlcontrol))

Checksum (16 bits):Checksum (16 bits): error detection error detection code (code (reliable data transferreliable data transfer))

Urgent pointer (16 bits):Urgent pointer (16 bits): pointer to last pointer to last data octet in sequence of urgent data data octet in sequence of urgent data (precedence)(precedence)

Header length (variable):Header length (variable): number of number of 32bit words in the header – indicates 32bit words in the header – indicates presence or absence of options (presence or absence of options (variousvarious))

more ->more ->

more ->more ->

more ->more ->

more ->more ->


TCP Fields/Functions (Flags)TCP Fields/Functions (Flags) URG:URG: urgent pointer field is significant urgent pointer field is significant ACK:ACK: acknowledgement field is significant acknowledgement field is significant PSH:PSH: push function specified by app push function specified by app RST:RST: reset the connection reset the connection SYN:SYN: synchronize the sequence number synchronize the sequence number FIN: FIN: no more data from senderno more data from sender

CWR:CWR: congestion warning congestion warning

acknowledgement acknowledgement ECE: ECE: Explicit congestion notificationExplicit congestion notification

more ->more ->

more ->more ->

RFC RFC 31683168


TCP Data FlowTCP Data Flow

Outgoing data is logically a stream Outgoing data is logically a stream of octets from an end user (SEND)of octets from an end user (SEND)

Stream is broken into blocks of Stream is broken into blocks of data, called segmentsdata, called segments

TCP accumulates octets from user TCP accumulates octets from user until segment is large enough, or until segment is large enough, or data is marked with PUSH flagdata is marked with PUSH flag

User (i.e. the application) can mark User (i.e. the application) can mark data as URGENTdata as URGENT


Similarly, incoming data is a Similarly, incoming data is a stream of octets presented to stream of octets presented to user (application)user (application)

Data marked with PUSH flag Data marked with PUSH flag triggers delivery of data to user, triggers delivery of data to user, otherwise TCP decides when to otherwise TCP decides when to deliver data (RECEIVE)deliver data (RECEIVE)

Data marked with URGENT flag Data marked with URGENT flag causes user to be signaledcauses user to be signaled

TCP Data Flow (cont.)TCP Data Flow (cont.)


OptionsOptions Maximum segment size (RFC793)Maximum segment size (RFC793)

– specifies the maximum segment size in specifies the maximum segment size in octets to be used in the connection (16 bits)octets to be used in the connection (16 bits)

– used during connection establishmentused during connection establishment Window scale factorWindow scale factor

– receiver window scale factor F (max. 14)receiver window scale factor F (max. 14)– scales receiver window size by 2scales receiver window size by 2FF

– used during connection establishmentused during connection establishment TimestampTimestamp

– used by TCP to monitor RTTused by TCP to monitor RTT– Timestamp… Timestamp Echo ReplyTimestamp… Timestamp Echo Reply


UDPUDP

RFC 768RFC 768Connectionless, unreliableConnectionless, unreliableLess overheadLess overheadSimply adds port addressing to IPSimply adds port addressing to IPChecksum is optionalChecksum is optional


Appropriate Uses of UDPAppropriate Uses of UDP Inward data collectionInward data collectionOutward data disseminationOutward data disseminationRequest-responseRequest-responseReal-time applicationsReal-time applicationsExamples?Examples?

DNSDNS SNMPSNMP Streaming audio/videoStreaming audio/video VoIPVoIP RIPRIP

• Timeliness/ Timeliness/ timingtiming of of data data criticalcritical

• Occasional Occasional lossloss or or significant significant delaydelay is is acceptableacceptable


IPIPDefined in RFC 791Defined in RFC 791


IPv4 Address ClassesIPv4 Address Classes


IPv6IPv6

Increase IP address from 32 bits Increase IP address from 32 bits to 128 bitsto 128 bits

Accommodate higher network Accommodate higher network speeds, mix of data streams speeds, mix of data streams (graphics, video, audio)(graphics, video, audio)

Fixed size 40-octet header for Fixed size 40-octet header for performance, followed by optional performance, followed by optional extension headersextension headers

Longer header but fewer fields (8 Longer header but fewer fields (8 vs 12), so routers should have vs 12), so routers should have less processingless processing


IPv6 HeaderIPv6 Header


IPv6 HeaderIPv6 Header VersionVersion: 6: 6 Traffic classTraffic class: e.g. DSCP (more later): e.g. DSCP (more later) Flow labelFlow label: identifies packets in a sequence : identifies packets in a sequence

from a particular source to destination that from a particular source to destination that need special handling (more later)need special handling (more later)

Payload lengthPayload length: total length of packet in : total length of packet in octets, minus 40 octets (max 65535)octets, minus 40 octets (max 65535)

Next headerNext header: specifies how to interpret next : specifies how to interpret next field following the headerfield following the header

Hop limitHop limit: max number of hops for this : max number of hops for this packet, decremented field, discard at 0 packet, decremented field, discard at 0

Source addressSource address: packet originator: packet originator Destination addressDestination address: intended recipient: intended recipient


IPv6 AddressesIPv6 Addresses128 bits128 bitsLonger addresses can have Longer addresses can have

structure that assists routingstructure that assists routing3 types:3 types:

– UnicastUnicast: single address for a : single address for a single single interfaceinterface

– AnycastAnycast: aggregate address for : aggregate address for any any one of a related setone of a related set of interfaces of interfaces

– MulticastMulticast: single address for : single address for all of a all of a groupgroup of interfaces of interfaces


IPv6 Packet & Extension IPv6 Packet & Extension HeadersHeaders


Optional Extension HeadersOptional Extension HeadersHop-by-hop optionsHop-by-hop options: : instructions for instructions for

each router (RFCs 2675 and 2711)each router (RFCs 2675 and 2711)RoutingRouting: : explicit list of intermediate explicit list of intermediate

nodesnodesFragmentFragment: : only at source nodesonly at source nodesAuthenticationAuthentication: : (IPsec) packet integrity (IPsec) packet integrity

and authenticationand authenticationEncapsulating security payloadEncapsulating security payload: :

(IPsec) payload privacy(IPsec) payload privacyDestination optionsDestination options: : examined only examined only

by destination nodeby destination node


IPv6 Extension HeadersIPv6 Extension Headers

Documents

1 Chapter 3 TCP and IP. Chapter 3 TCP and IP 2 Introduction Transmission Control Protocol (TCP) Transmission Control Protocol (TCP) User Datagram Protocol