CSC 600 Internetworking with TCP/IP Unit 7: IPv6 (ch. 33) Dr. Cheer-Sun Yang Spring 2001

IP v6 - Version Number 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 –Next Generation

Why Change IP? New computer and communication technologies New applications – VoIP requires real-time data delivery Increase in size and load – too many hosts!

Why Change IP? Address space exhaustion –Two level addressing (network and host) wastes space –Network addresses used even if not connected to Internet –Growth of networks and the Internet –Extended use of TCP/IP –Single address per host Requirements for new types of service

Why Change IP? New technologies : since 1970s, –processor performance has increased over two orders of magnitude –Memory sizes have increased by over a factor of 100 –Network bandwidth of the Internet backbone has risen by a factor of 7000 –LAN technologies have emerged Increase in size – the number of hosts has risen from a handful to 56 million; the current 32-bit IP address space cannot accommodate projected growth of the global Internet beyond 2002.

IPv6 RFCs Recommendations for the IP Next Generation Protocol Overall specification addressing structure Others : 2462, 2463, 2464, 2374, 2375, 2526, etc.

IPv6 Enhancements (1) Expanded address space –128 bit Improved option mechanism –Separate optional headers between IPv6 header and transport layer header –Most are not examined by intermediate routes Improved speed and simplified router processing Easier to extend options Address autoconfiguration –Dynamic assignment of addresses

IPv6 Enhancements (2) Increased addressing flexibility –Anycast - delivered to one of a set of nodes –Improved scalability of multicast addresses Support for resource allocation –Replaces type of service –Labeling of packets to particular traffic flow –Allows special handling –e.g. real time video

Structure

Base Header Alignment has been changed from 32-bit to 64-bit multiples. The header length has been eliminated and the datagram length field has been replaced by a PAYLOAD LENGTH field. The size of source and destination address fields has been increased to 16 octets each.

Base Header (cont’d) Fragmentation information has been removed out of fixed fields into an extension header. The TIME-TO-LIVE field has been rep[laced by a HOP LIMIT field. The SERVICE TYPE is renamed to be a TRAFFIC CLASS field, and extended with a FLOW LABEL field. The PROTOCOL field has been replaced by the type of the next header.

Extension Headers Hop-by-Hop Options –Require processing at each router Routing –Similar to v4 source routing Fragment Authentication Encapsulating security payload Destination options –For destination node

Extension Headers (cont’d) IPv6 extension headers are similar to IPv4 options. Each datagram includes extension headers for only those facilities that the datagram uses.

IP v6 Header

IP v6 Header Fields (1) Version –6 Traffic Class –Classes or priorities of packet –Still under development –See RFC 2460 Flow Label –Used by hosts requesting special handling Payload length –Includes all extension headers plus user data

IP v6 Header Fields (2) Next Header –Identifies type of header Extension or next layer up Source Address Destination address

IPv6 Base Header From now on, they can’t call me Junior!

Fragmentation Header Fragmentation only allowed at source No fragmentation at intermediate routers Node must perform path discovery to find smallest MTU of intermediate networks Source fragments to match MTU Otherwise limit to 1280 octets

Fragmentation Header Fields Next Header Reserved Fragmentation offset Reserved More flag Identification

End-to-End Fragmentation An internet protocol that uses end-to-end fragmentation requires a sender to discover the path MTU to each destination, and to fragment any outgoing datagram that is larger than the path MTU. End-to-end fragmentation does not accommodate route changes. To solve the problem of route changes that affect the path MTU, IPv6 includes a new ICMP error message. When a route discovers that fragmentation is needed, it sends the message back to the source. The source will fragment the datagrams based on the new minimum MTU.

Source Routing Header List of one or more intermediate nodes to be visited Next Header Header extension length Routing type Segments left –i.e. number of nodes still to be visited

IPv6 Options

Hop-by-Hop Options Next header Header extension length Options –Jumbo payload Over 2 16 = 65,535 octets –Router alert Tells the router that the contents of this packet is of interest to the router Provides support for RSPV (chapter 16)

Destination Options Same format as Hop-by-Hop options header

IPv6 Addresses 128 bits long Assigned to interface Single interface may have multiple unicast addresses Three types of address

Types of address Unicast –Single interface Anycast –Set of interfaces (typically different nodes) –Delivered to any one interface –the “nearest” Multicast –Set of interfaces –Delivered to all interfaces identified

Aggregatable Global Unicast Address Structure

Interface Identifier

Multicasting Addresses that refer to group of hosts on one or more networks Uses –Multimedia “broadcast” –Teleconferencing –Database –Distributed computing –Real time workgroups

Group Membership in IPv6 Multicast addresses are used to define a group of hosts instead of one. All use the prefix in the first field. The second field is a flag that defines the group address as either permanent or transient. The third field is a SCOPE field which indicates the scope to be node local(0001), link local (0010), site local(0101), organizational local (1000), or global(1110).

ICMP v6 Function of IGMP included in ICMP v6 New group membership termination message to allow host to leave group