1. CSCI 465 D ata Communications and Networks Lecture 25 Martin van Bommel CSCI 465 Data Communications & Networks 1

2. IP Versions IP v 1-3 defined and replaced IP v4 - current version IP v5 - streams protocol IP v6 - replacement for IP v4 – during development it was called IPng (IP Next Generation) CSCI 465 Data Communications & Networks 2

3. Why Change IP Versions? Address space exhaustion: – 2 level addressing (network and host) wastes space – IP network addresses used even if not connected Growth of networks and the Internet – extended use of TCP/IP – e.g. TV, point-of-sale – single address per host not flexible Requirements for new types of service – address configuration Routing flexibility - traffic support CSCI 465 Data Communications & Networks 3

4. IPv6 Enhancements expanded 128 bit address space improved option mechanism – most not examined by intermediate routes dynamic address assignment increased addressing flexibility – unicast, anycast, and multicast support for resource allocation labeled packet flows CSCI 465 Data Communications & Networks 4

5. 5 IPv6 PDU (Packet) Structure

6. IPv6 Header CSCI 465 Data Communications & Networks 6

7. IP v6 Flow Label related sequence of packets - special handling – identified by source and destination address + flow label – flow number generated randomly make sure not to reuse within lifetime of old flow router treats packets of flow the same – treatment pre-negotiated with router(s) CSCI 465 Data Communications & Networks 7

8. IPv6 Addresses 128 bits long – Assigned to interface – Same interface may have multiple addresses Types of addresses – Unicast – single interface address – Anycast – one of a set of interface addresses – Multicast – all of a set of interface addresses CSCI 465 Data Communications & Networks 8

9. Hop-by-Hop Options must be examined by every router – if unknown discard/forward handling is specified next header – type of header that follows header extension length – length of this header Options – Jumbo payload IPv6 packet is longer than 65,535 octets – Router alert Tells router(s) that packet contains router control data CSCI 465 Data Communications & Networks 9

10. Fragmentation Header fragmentation only allowed at source no fragmentation at intermediate routers node must perform path discovery to find smallest MTU (maximum transmission unit) of intermediate networks set source fragments to match MTU otherwise limit to 1280 octets – minimum MTU must be supported by networks CSCI 465 Data Communications & Networks 10

11. Routing Header contains a list of one or more intermediate nodes to be visited on the way to a packet’s destination Includes – Next header identification, Header length, Routing type – Segments left – number of route segments left Type 0 routing – IPv6 header has address of router – Routing header contains list of router addresses – Next destination address first on list – Final destination address last on list – Each router on path moves address to IPv6 header and shortens list CSCI 465 Data Communications & Networks 11

12. IPv6 Extension Headers CSCI 465 Data Communications & Networks 12