© MMII JW RyderCS 428 Computer Networking1 The Future of TCP/IP (IPv6)  Chapter 33  Evolution of TCP/IP intertwined with evolution of the global Internet  Internet is largest installed internet  Funding comes from organizations that are Internet users  Most researchers use Internet daily  Chapter purpose is to consider ongoing evolution of TCP/IP

© MMII JW RyderCS 428 Computer Networking2 Why Change?  New computer and communication technologies  New technologies = new possibilities and needs  New applications  New ways to use Internet means new protocols needed  Increases in size and load  Massive growth means old ways strained

© MMII JW RyderCS 428 Computer Networking3 Motivation for Changing IPv4  New countries with differing administrative policies  IPv4 same for about 20 years  Since IPv4 designed  Enhanced processor performance  Memory size increased  Network bandwidth for Internet backbone increased  New LAN technologies  Number of hosts on Internet risen to over 56 million

© MMII JW RyderCS 428 Computer Networking4 Road to New Version of IP  Several suggested designs  Make IP more sophisticated at expense of increased complexity and processing overhead  Use a modification of OSI CLNS protocol  Retain most of ideas in IP but make simple extensions to accommodate larger addresses  Simple IP – (SIP)  Still include new ideas from other suggested protocols

© MMII JW RyderCS 428 Computer Networking5 Features of IPv6  Despite many conceptual similarities IPv6 changes most protocol details  Completely revises datagram format  Replace IPv4 variable length fields with a series of fixed format headers  Still supports connectionless delivery  Allows sender to choose datagram size but requires sender to specify maximum hops

© MMII JW RyderCS 428 Computer Networking6 Features of IPv6  Includes facilities for fragmentation and source routing  Main changes introduced are 1. Larger Addresses: IPv6 quadruples the size from 32 bits to 128 bits 2. Extended Address Hierarchy: Creates ability to have additional address levels on an internet  IPv4 Addresses – 2 levels, Network and Host  IPv6 Addresses – Can define a hierarchy of ISPs as well as hierarchy within a site

© MMII JW RyderCS 428 Computer Networking7 Features of IPv6 3. Flexible Header Format: Datagram format entirely different  Defines a fixed size (40 octets) header with optional extended headers 4. Improved Options:  Has same options as IPv4 plus some new ones 5. Provision for Protocol Extension:  Move away from protocol that fully specifies all details to one that permits additional features

© MMII JW RyderCS 428 Computer Networking8 Features of IPv6 6. Support for Autoconfiguration and Renumbering:  Allows computers on an isolated network to assign themselves addresses and begin communicating without depending on a router or manual configuration  Facility to permit a manager to renumber networks dynamically

© MMII JW RyderCS 428 Computer Networking9 Features of IPv6 7. Support for Resource Allocation:  Two facilities for pre-allocation of network resources  a Flow abstraction  a Differentiated Services specification

© MMII JW RyderCS 428 Computer Networking10 IPv6 Address Space  How big is ?  So large that everyone on earth will have enough addresses to have their own internets with as many addresses as the current Internet has  So large that there would be internet addresses per each square meter on earth  So large that the address space is greater than 3.4 *  If addresses are assigned at the rate of 1,000,000 every microsecond (1/1,000,000 th of a second), it would take more than years to assign all possible addresses

© MMII JW RyderCS 428 Computer Networking11 IPv6 Colon Hexadecimal Notation  128 bit number expressed as dotted decimal  becomes  68E6:8C64:FFFF:FFFF:0:1180:96A:FFFF  Hex notation allows zero compression  A string of repeated zeros is replaced with a pair of colons  FF05:0:0:0:0:0:0:B3 becomes FF05::B3  Can be applied only once in any address

© MMII JW RyderCS 428 Computer Networking12 Zero Suppression  0:0:0:0:0:0: becomes ::  Looks quite similar to IPv4  12AB::CD30:0:0:0:0/60 says use first 60 bits and becomes  12AB CD3

© MMII JW RyderCS 428 Computer Networking13 Basic IPv6 Address Types  Unicast – Destination address specifies a single computer. Route datagram along shortest path.  Anycast – Destination is a set of computers, possibly at different locations, that all share a single address. Route datagram along shortest path and deliver to exactly one member of the group (i.e. closest member)

© MMII JW RyderCS 428 Computer Networking14 Basic IPv6 Address Types  Multicast - Destination is a set of computers, possibly at different locations. One copy of the datagram will be delivered to each member of the group using hardware multicast or broadcast if viable.

© MMII JW RyderCS 428 Computer Networking15 Encoding IPv4 Addresses in IPv6 DATAGRAM IDENTIFICATION 16 bits IPv4 Address RESERVED 0000 FFFF IPv4 Address bits80 zero bits 16-bit field contains 0000 if node also has a conventional IPv6 address and FFFF if it does not.

© MMII JW RyderCS 428 Computer Networking16 General Form of IPv6 Datagram Base Header Extension Header 1 Extension Header N Data Optional 40 octets

© MMII JW RyderCS 428 Computer Networking17 IPv6 Base Header Format  See Base Header figure  Alignment changed from 32 bit to 64 bit multiples  Header length eliminated – Replaced with PAYLOAD LENGTH field  Size of source and destination addresses changed to 16 octets  Fragmentation information moved out of fixed fields in base header to extension header

© MMII JW RyderCS 428 Computer Networking18 IPv6 Base Header Format  TIME-TO-LIVE field changed to HOP LIMIT  SERVICE-TYPE field renamed to TRAFFIC CLASS and extended with FLOW LABEL field  PROTOCOL field replaced with a field that specifies type of next header

© MMII JW RyderCS 428 Computer Networking19 Base Header Format NEXT HEADERHOP LIMITPAYLOAD LENGTH FLOW LABELTRAFFIC CLASSVERS SOURCE ADDRESS DESTINATION ADDRESS Base Header Size: = 40 Octets

© MMII JW RyderCS 428 Computer Networking20 Base Header Format  PAYLOAD LENGTH is length of all extension headers plus data  i.e. Total length – 40 octets (Base Header)  IPv6 datagram can contain up to 64K octets of data

© MMII JW RyderCS 428 Computer Networking21 Traffic Class  IPv4 SERVICE CLASS renamed to TRAFFIC CLASS  New IPv6 mechanism allows for resource reservation!  A router can associate with each datagram a given resource allocation  Abstraction called a FLOW  A FLOW is a path through an internet along which intermediate routers guarantee a certain level of quality of service

© MMII JW RyderCS 428 Computer Networking22 Traffic Class  FLOW LABEL in the base header contains a label that routers use to map a datagram to a certain specific flow and priority  Flows can also be used within an organization to manage network resources  Example  Two applications that need to send and receive video can establish a flow over which the bandwidth and delay are guaranteed

© MMII JW RyderCS 428 Computer Networking23 IPv6 Extension Headers Base Header NEXT=ROUTE Route Header NEXT=AUTH Auth Header NEXT=TCP TCP Segment Base Header NEXT=TCP TCP Segment Base Header NEXT=ROUTE Route Header NEXT=TCP TCP Segment One Base Header Two Base Headers Three Base Headers

© MMII JW RyderCS 428 Computer Networking24 IPv6 Fragmentation  As with IPv4, IPv6 arranges for destination to perform re-assembly  In IPv6 however, changes were made that avoid fragmentation by routers  IPv4 requires intermediate routers to fragment any datagram that is too large for the maximum transfer/transmission unit (MTU) of network over which it must travel  IPv6 fragmentation is end-to-end

© MMII JW RyderCS 428 Computer Networking25 IPv6 Fragmentation  No fragmentation done on intermediate routers  Source which is responsible for fragmentation has two choices  Use guaranteed minimum MTU (1280 octets)  Perform Path MTU Discovery  Identifies minimum MTU along path to the destination

© MMII JW RyderCS 428 Computer Networking26 IPv6 Fragmentation  Either case, the source fragments data  IPv6 fragmentation inserts a small extension header after the base header in each fragment DATAGRAM IDENTIFICATION FRAG. OFFSETNEXT HEADER RESERVEDRS M 29 RS is set t 0 and reserved. M marks last fragment. ID unique for re-assembly. Fragments must be a multiple of 8 octets.