The Future of TCP/IP (IPv6)

© MMII JW Ryder CS 428 Computer Networking 1

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


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


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


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


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


Features of IPv6 Includes facilities for fragmentation and source

routing Main changes introduced are1. Larger Addresses: IPv6 quadruples the size from 32

bits to 128 bits2. 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


Features of IPv63. 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


Features of IPv66. 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


Features of IPv67. Support for Resource Allocation:

Two facilities for pre-allocation of network resources a Flow abstraction a Differentiated Services specification


IPv6 Address Space How big is 2128 ? 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 1024 internet addresses per each square meter on earth

So large that the address space is greater than 3.4 * 1038 If addresses are assigned at the rate of 1,000,000 every

microsecond (1/1,000,000th of a second), it would take more than 1020 years to assign all possible addresses


IPv6 Colon Hexadecimal Notation 128 bit number expressed as dotted decimal 104.230.140.100.255.255.255.255.0.0.17.128.150.10.255.255 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


Zero Suppression 0:0:0:0:0:0:128.10.2.1 becomes ::128.10.2.1 Looks quite similar to IPv4 12AB::CD30:0:0:0:0/60 says use first 60 bits

and becomes 12AB00000000CD3


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)


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.


Encoding IPv4 Addresses in IPv6

DATAGRAM IDENTIFICATION

16 bits

IPv4 Address 0000 . . . . . . . . . . . . . . . . . . . . . . . . 0000

RESERVED

0000

FFFF IPv4 Address 0000 . . . . . . . . . . .. . . . . . . . . . . . . . 0000

32 bits80 zero bits

• 16-bit field contains 0000 if node also has a conventional IPv6 address and FFFF if it does not.


General Form of IPv6 Datagram

Base

Header

Extension

Header 1

Extension

Header N Data

Optional

40 octets


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


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


Base Header Format

NEXT HEADER HOP LIMITPAYLOAD LENGTH

FLOW LABELTRAFFIC CLASSVERS

SOURCE ADDRESS

DESTINATION ADDRESS

160 4 12 24 31

Base Header Size: 4 + 4 + 16 + 16 = 40 Octets


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


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


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


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


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


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


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

160 8 24 31

RESERVED RS 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.

The Future of TCP/IP (IPv6)

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