1. 1 Review – The Internet’s Protocol Architecture

2. Protocols, Internetworking & the Internet 2 Introduction Internet standards Internet standards Layered protocol architecture Layered protocol architecture TCP/IP protocol suite TCP/IP protocol suite Internetworking Internetworking

3. Protocols, Internetworking & the Internet 3 Standards/Standards Bodies The Internet Society The Internet Society –Internet Architecture Board (IAB) defines overall architecture of the Internet defines overall architecture of the Internet provides broad guidance for IETF provides broad guidance for IETF –Internet Engineering Steering Group (IESG) provides technical management of IETF and the Internet standards process provides technical management of IETF and the Internet standards process –Internet Engineering Task Force (IETF) IETF designs and develops Internet protocols designs and develops Internet protocols charters standards working groups charters standards working groups publishes RFCs, with approval of IESG publishes RFCs, with approval of IESGRFCs Eight areas defined: General, Applications, Internet, Operations & Management, Routing, Security, Transport, User Services Eight areas defined: General, Applications, Internet, Operations & Management, Routing, Security, Transport, User Services

4. Protocols, Internetworking & the Internet 4 Internet RFC Process Historic Experimental Best Current Practice Informational Internet Standard Draft Standard Proposed Standard Internet Draft

5. Protocols, Internetworking & the Internet 5 Key Features of a Protocol (as defined by standards) Set of rules or conventions to exchange blocks of formatted data Set of rules or conventions to exchange blocks of formatted data Syntax: data format Syntax: data format Semantics: control information (coordination, error handling) Semantics: control information (coordination, error handling) Timing: order, speed matching, sequencing Timing: order, speed matching, sequencing Actions: what happens when an event occurs Actions: what happens when an event occurs

6. Protocols, Internetworking & the Internet 6 Internet Protocol Stack Layers (a.k.a. TCP/IP stack) Physical Physical Network Access Network Access Internet Internet Transport Transport Application Application Physical Link Network Transport Application or…

7. Protocols, Internetworking & the Internet 7 TCP and UDP TCP: TCP: –connection-oriented, handshake required –reliable packet delivery in sequence UDP: UDP: –connectionless (datagram), no handshake –unreliable packet delivery –packets may arrive out of sequence or duplicated

8. Chapter 3 TCP and IP 8 TCP Defined in RFC 793, RFC 1122 Defined in RFC 793, RFC 1122RFC 793RFC 1122RFC 793RFC 1122 Provides the Internet’s primary reliable host-to-host delivery mechanism Provides the Internet’s primary reliable host-to-host delivery mechanism Services offered: Services offered: –basic data transfer –reliability (reliable data transfer) –flow control –multiplexing/de-multiplexing (one-to-one) –connections (maintains state) –precedence and security

9. Chapter 3 TCP and IP 9 TCP Header

10. Chapter 3 TCP and IP 10 UDP RFC 768 RFC 768 RFC 768 RFC 768 Connectionless, unreliable Connectionless, unreliable Less overhead Less overhead Simply adds port addressing to IP Simply adds port addressing to IP Checksum is optional Checksum is optional

11. Protocols, Internetworking & the Internet 11 TCP Applications FTP client FTP server TCP control connection port 21 TCP data connection port 20 mail server user agent user agent user agent mail server user agent user agent mail server user agent SMTP SMTP SMTP PC running Explorer Serverrunning Apache Web Server Mac running Navigator http request http response email Web browsing file transfer

12. TCP/UDP Service Comparison ServiceTCPUDP Basic data transferYes Reliable data transferYesNo Flow controlYesNo Multiplexing/de-multiplexingYes, one-to-oneYes, many-to-one Connection managementYes (state)No Congestion controlYesNo Delivery precedence/priorityYesNo Optional processing informationYesNo Protocols, Internetworking & the Internet 12

13. Protocols, Internetworking & the Internet 13 IP Headers – IPv4 IP Version 4 Header

14. Chapter 3 TCP and IP 14 IPv6 Increase IP address from 32 bits to 128 bits Increase IP address from 32 bits to 128 bits Accommodate variable QoS flow information and packet handling Accommodate variable QoS flow information and packet handling Fixed size 40-octet header for performance, followed by optional extension headers Fixed size 40-octet header for performance, followed by optional extension headers Longer header but fewer fields (8 vs 12), so routers should have less processing Longer header but fewer fields (8 vs 12), so routers should have less processing

15. Protocols, Internetworking & the Internet 15 IP Headers – IPv6 IP Version 6 Header

16. Chapter 3 TCP and IP 16 IPv6 Header Version: 6 Version: 6 Traffic class: e.g. DSCP (more later) Traffic class: e.g. DSCP (more later) Flow label: identifies packets in a sequence from a particular source to destination that need special handling (more later) Flow label: identifies packets in a sequence from a particular source to destination that need special handling (more later) Payload length: total length of packet in octets, minus 40 octets (max 65535) Payload length: total length of packet in octets, minus 40 octets (max 65535) Next header: specifies how to interpret next field following the header Next header: specifies how to interpret next field following the header Hop limit: max number of hops for this packet, decremented field, discard at 0 Hop limit: max number of hops for this packet, decremented field, discard at 0 Source address: packet originator Source address: packet originator Destination address: intended recipient Destination address: intended recipient

17. Protocols, Internetworking & the Internet 17 Operation of TCP and IP IP implemented in end systems and routers, relaying data between hosts IP implemented in end systems and routers, relaying data between hosts TCP implemented for end-to-end data transfer only in end systems*, assuring reliable delivery of blocks of data TCP implemented for end-to-end data transfer only in end systems*, assuring reliable delivery of blocks of data Each host on sub-network has a unique IP address Each host on sub-network has a unique IP address Each process on each host has a unique TCP port number Each process on each host has a unique TCP port number * Except when?

18. Protocols, Internetworking & the Internet 18 TCP/IP Protocol Data Units (PDUs)

19. Protocols, Internetworking & the Internet 19 TCP/IP Concepts – Data Flow application transport network link physical application transport network link physical application transport network link physical application transport network link physical network link physical data

20. Protocols, Internetworking & the Internet 20 TCP/IP Concepts

21. Protocols, Internetworking & the Internet 21 Routers Provide connections between networks Provide connections between networks Accommodate network differences: Accommodate network differences: –Addressing schemes –Maximum packet sizes –Hardware and software interfaces –Network reliability –Congestion/Traffic Management

22. Protocols, Internetworking & the Internet 22 TCP/IP Internetworking Example

23. Protocols, Internetworking & the Internet 23 Figure 2-8

24. Protocols, Internetworking & the Internet 24 Figure 2-9

25. Protocols, Internetworking & the Internet 25 Figure 2-10