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CS 5565 Network Architecture and Protocols

Learn about the IPv6 protocol, its key features, benefits, and transition from IPv4. Understand addressing, autoconfiguration, headers, and routing in the context of network architecture. Explore broadcast and multicast routing protocols.

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CS 5565 Network Architecture and Protocols

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  1. CS 5565Network Architecture and Protocols Godmar Back Lecture 36

  2. Announcements • Donghang graded 2A, will check & return by Friday • Project 2B due Apr 26 & May 3 • Do not procrastinate • Reading Assignment Chapter 4.1-4.6 CS 5565 Spring 2006

  3. IPv6

  4. IPv6 • Initial motivation:32-bit address space soon to be completely allocated. • Additional motivation: • header format helps speed processing/forwarding • header changes to facilitate QoS • easier configuration of both hosts & backbone routers IPv6 datagram format: • fixed-length 40 byte header • no fragmentation allowed CS 5565 Spring 2006

  5. IPv6 Header (Cont) Priority: identify priority among datagrams in flow Flow Label: identify datagrams in same “flow.” (concept of “flow” not well defined). Next header: identify upper layer protocol for data CS 5565 Spring 2006

  6. Other Changes from IPv4 • Checksum:removed entirely to reduce processing time at each hop • ICMPv6: new version of ICMP • additional message types, e.g. “Packet Too Big” • multicast group management functions • Options: allowed, but outside of header, indicated by “Next Header” field CS 5565 Spring 2006

  7. Extension Headers • Grouped in six types: • Hop-by-hop options, e.g. Jumbograms • Destination options • Routing, e.g. source routing • Fragment – can be done, but end hosts only! • Authentication • Encapsulation • Routers quickly know which headers they must examine and which they can skip CS 5565 Spring 2006

  8. IPv6 Addresses • Written as eight 16bit values • e.g. fe80::020e:7bff:fe32:d716 (made from 00:0E:7B:32:D7:16) CS 5565 Spring 2006

  9. IPv6 autoconf • stateless autoconfiguration see [Donzé 2004] • Plug in and interface creates link-local address based on adapter MAC • Interface can have link-local (fe80::…), site-local & global (2001::…) addresses • VT’s campus has had IPv6 testbed since 1998, now connected to public IPv6 network • Try it out yourself! • MacOS, Linux: enabled by default of recent installations • Windows XP: “ipv6 install” at command prompt • Tools add 6: ping6, traceroute6, etc.. CS 5565 Spring 2006

  10. Transition From IPv4 To IPv6 • Not all routers can be upgraded simultaneously • no “flag days” • How will the network operate with mixed IPv4 and IPv6 routers? • Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers CS 5565 Spring 2006

  11. Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data Flow: X Src: A Dest: F data A B E F D C A B F E tunnel Logical view: IPv6 IPv6 IPv6 IPv6 Physical view: IPv6 IPv6 IPv6 IPv6 IPv4 IPv4 Src:B Dest: E Src:B Dest: E A-to-B: IPv6 E-to-F: IPv6 B-to-C: IPv6 inside IPv4 B-to-C: IPv6 inside IPv4 Tunneling CS 5565 Spring 2006

  12. IPv6 – Opposing View • Bernstein points out some hindrances [The IPv6 mess] • Lack of interoperability b/c no embedding of addresses • Transition path (comparison to MX records) • IPv6 – the next OSI? • DoD requirement by 2008 • Asian countries are pushing for transition CS 5565 Spring 2006

  13. Other Routing Protocols • Ad-hoc Routing • Broadcast Routing • Multicast Routing CS 5565 Spring 2006

  14. duplicate creation/transmission duplicate duplicate (b) (a) R2 R3 R4 R2 R3 R4 R1 R1 Broadcast Routing • Motivation: • Use in-network duplication (b) rather than source-duplication (a) CS 5565 Spring 2006

  15. Broadcast Routing (2) • Simplest approach: simple flooding • Forward every packet from every link to all other links every time • Inefficient, loops, “broadcast storms” • Sequence-number controlled flooding • Only forward new packets to all other links CS 5565 Spring 2006

  16. A D G B E C F Reverse Path Forwarding • Only forward packets from link that lies on shortest path to the source • Assume unicast routing has run & every node knows shortest path to source CS 5565 Spring 2006

  17. A A D D G G E B B E F F C C Broadcast using spanning tree • Same spanning tree can be used for all sources! CS 5565 Spring 2006

  18. 3 4 2 5 1 A D G A D B E G F C B E F C Spanning Tree Construction • Center-based: all nodes send “tree-join” message to known or elected center node CS 5565 Spring 2006

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