CS4550 Computer Networks II IP : internet protocol, part 3 : routing policies, IPv6

IP routing  routing mechanism - the mechanics of routing -- discussed previously -- review basic routing algorithm  routing policy - how the paths in the network are calculated -- there is no single required routing policy on the Internet -- DV and LS routing already discussed -- some specific IP policies to follow

IP - routing policy topics  interior gateway protocols (IGPs) u RIP u IGRP, EIGRP u OSPF  autonomous systems  exterior gateway protocols u EGP u BGP  IPv6

references  Feit, TCP/IP: architecture, protocols and implementation  many RFCs : RIP : 1058, 1723, 1582 OSPF : 1583,1793, 1586, 1584, 1403 BGP : 1771, 1773, 1772 IGRP :

Automated Routing Protocols Generic Functions Measure route cost Send/receive routing updates compute routes update routing tables

routing information protocol (RIP)  most widely used; now in 2nd version  free, available with Unix as “routed”  DV routing, each hop assigned cost (usually 1)  strong points: simple and available; good for small, simple networks  max path length is 15 hops  not good for very large networks (already discussed DV problems)

IGRP : internet gateway routing protocol  Cisco routers -> proprietary  distance vector protocol also  uses split horizon  updates every 90 seconds (default)  triggered updates  if no update from an adjacent router for 270 sec, entry timed out, destinations using it rerouted  destinations flushed after 540 seconds

more on IGRP  more sophisticated distance metric u delay u bandwidth u congestion (load) u reliability u hop count to destination u biggest MTU (packet) that link/path can carry  can also split traffic over multiple paths  can also support routing between different autonomous systems

EIGRP - enhanced IGRP  same distance metrics and routing calculations  does away with periodic updates; only updated after change, but reliable updates used  used an algorithm to detect loops in routes and remove them  “EIGRP has proven the distance vector routing is far from dead” (Feit)

OSPF : open shortest path first  link state protocol, developed by IETF; non proprietary  low overhead; updates report changes rather than everything  quick detection of topology changes, rap  id updating after changes  traffic splitting over multiple paths  subnet masks supported  authentication supported  widely used, refinements will continue

autonomous systems  a piece of the Internet unified by a routing policy  “somebody’s network” early def: a collection of subnetworks and hosts, interconnected by routes new def: a connected group of 1 or more IP prefixes... which has a SINGLE and CLEARLY DEFINED routing policy

autonomous systems  routing within ASs is done by IGPs, or interior gateway protocols; chosen by the controlling organization  routing between ASs is done by EGPs, or exterior gateway protocols  AS domain is identified by a unique 16-bit AS number administered by ARIN (

AS ASAS ASAS RIP IGRP EIGRP EGP BGP EIGRP autonomous systems

exterior gateway protocols EGP - an early version - simple distance vector: But NO weight used - very limited information passed between routers - useful early when Internet was small; losing its usefulness now BGP - border gateway protocol -report entire paths, avoiding loops -similar to link-state algorithm

Further Internet topics  IPv6  UDP and TCP (in next class)  domain name system  FTP  Telnet   HTTP  internet telephony  integrating TV, voice,video into Internet

Why IP Version 6 IPv4 Proposed in 1975, adopted in 1981 Served well but 24 years old Address Depletion Explosion of in growth of routing tables Non-heirarchical in nature Security Issues Routing Performance New Applications Telephony, video, conferencing Piece of “the Puzzel” to enable new services

IPv6 Challanges Backward Compatibility MUST work with existing equipment Perpetual coexistence with IPv4 MUST Coexist with current standards/protocols will require new v4/v6 aware protocols to take advantage of v6 features

IPv6 Routing Routers CANNOT Fragment guaranteed minimum 576 byte path Shorter & Simplified Header Faster Analysis Most Optional Headers Ignored during routing Hierarchical Addressing Smaller Routing Tables Like international phone system Flow Control Lables

IPv6 Packet Format MUCH Simplified Fixed Length - 40 bytes versionTraffic ClassFlow Label Payload length next header hop limit Source Address ( 4 lines 16 bytes) destination Address (4 lines 16 bytes) Extension Headers 8 Optional headers Defined Authentication (MDS) Encapsulating Security Payload

IPv6 Addressing Address Notation X:X:X:X:X:X:X:X Where X = 16 bits Total 0f 128 bits Three Address Types Unicast Multicast Anycast Global Unicast Address TLA ID RES NLA ID SLA ID Interface ID