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CS 5565 Network Architecture and Protocols

CS 5565 Network Architecture and Protocols. Godmar Back. Lecture 36. 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. IPv6. IPv6.

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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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