Protocol Description

Internet Protocol version 6 (IPv6) is the new version of Internet Protocol (IP) based on IPv4. It is a network-layer (Layer 3) protocol that contains addressing information and some control information enabling packets to be routed in the network. IPv6 is also called the next generation IP or IPng.

The most significant change in IPv6 is increasing the IP address size from 32 bits in IPv4 to 128 bits, to support more levels of addressing hierarchy, a much greater number of addressable nodes, and simpler auto-configuration of addresses. There are three types of IP addresses in IPv6: Unicast, Multicast and Anycast. Broadcast no longer exists in IPv6, which becomes a special form of multicast. IPv6 addresses are expressed in hexadecimal format (base 16), which allows not only numerals (0-9) but a few characters as well (a-f).

IPv6 fixes many shortages in IPv4 in addition to the limited number of available IPv4 addresses. IPv6 has enhanced network layer routing in two main areas: 1) Improved support for extensions and
options; 2) Flow labeling capability to differenciate the packets at network layer. The key benefits of introducing IPv6 are:

• 340 undecillion IP addresses for the whole world network devices

• Plug and Play configuration with or without DHCP

• Better network bandwidth efficiency using multicast and anycast without broadcast

• Better QOS support for all types of applications

• Improved support for extensions and options with better routing efficiency

• Native information security framework for both data and control packets

• Enhanced mobility with fast handover, better route optimization and hierarchical mobility

The following table compares the key characters of IPv6 vs. IPv4:

Subjects	IPv4	IPv6	IPv6 Advantages
Address Space	4 Billion Addresses	3.4 x 1038 addresses	79 Octillion times the IPv4 address space
Configuration	Manual or use DHCP	Universal Plug and Play (UPnP) with or without DHCP	Lower Operation Expenses and less error
Broadcast / Multicast	Both	Broadcast is a form of multicast	Better bandwidth efficiency
Anycast	Not part of the original protocol	Explicit support of anycast	Allows for newer applications in mobility, data center, etc.
Routing efficiency	Need to process Option and Checksum by every router	No checksum; Extended header for options.	Flexible extensions and options; better routing efficiency.
Network Reconfiguration	Mostly manual & Labor intensive	By design; Facilitate the re-numbering of hosts and routers	Lower operation expenses and facilitate migration
QoS support	ToS using DIFFServ	Flow classes and flow labels	More Granular control of QoS
Security	IPsec for data packet protection	IPsec is the native technology to protect data and control packets	Unified framework for security and more secure computing environment
Mobility	Mobile IPv4	Mobile IPv6	Better efficiency and scalability; Work with the latest 3G mobile technologies and beyond.

Few in the industry would argue with the principle that IPv6 represents a major leap forward for the Internet and the users. However, given the magnitude of a migration that affects so many millions of network devices, it is clear that IPv4 and IPv6 will coexist for a long period of time.

Protocol Structure

4	12	16	24	32bit
Version	Traffic Class	Flow label
Payload length			Next header type	Hop limit
Source address (128 bits)
Destination address (128 bits)
Next header		Extension Header Information (optional and variable length)
Data (Variable Length)

• Version — Internet Protocol Version number (For IPv6 it is 6).

• Traffic Class — enables a source to identify the desired delivery priority of the packets. Priority values are divided into ranges: traffic where the source provides congestion control and non-congestion control traffic.

• Flow label — used by a source to label those packets for special handling by the IPv6 router. The flow is uniquely identified by the combination of a source address and a non-zero flow label.

• Payload length — the length of the data portion of the packet.

• Next headertype — identifies the type of header immediately following the IPv6 header. Hop limit specifies the maximum number of routers (hops) through which a packet can traverse before discarded. It is decremented by one by each node that forwards the packet. Source address – 128-bit address of the originator of the packet.Destination address – 128-bit
  address of the intended recipient of the packet (possibly not the ultimate recipient, if a Routing header is present). Extension Header Information – an optional field with variable length. The following IPv6 extension headers are currently defined.

• Routing — Extended routing, like IPv4 loose source route

• Fragmentation — Fragmentation and reassembly

• Authentication — Integrity and authentication, security

• Encapsulation — Confidentiality

• Hop-by-Hop Option — Special options that require hop-by-hop processing

• Destination Options — Optional information to be examined by the destination node

The format of IPv6 address is:

16 bits	16 bits	16 bits	16 bits	16 bits	16 bits	16 bits	16 bits
aaaa	aaaa	aaaa	aaaa	aaaa	aaaa	aaaa	aaaa

IPv6 address is classified in three types: Unicast, Multicast and Anycast. Unicast Address is applied to one network interface. The common global unicast address divisions:

Global Routing Prefix (N bits)	Subnet ID (64-N bits)	Interface ID (64 bits)

Link-local unicast address divisions:

1111111010 (10 bits)	0×00…0 (54bits)	Interface ID (64 bits)

Site-local unicast address divisions:

1111111011 (10 bits)	0×00…0	SLA	Interface ID (64 bits)

(Interface ID is based on hardware MAC address.)

Multicast Address: applied for multiple network interfaces, and communication is conducted with all hosts with the same address.

0xFF (8 bits)	Flag (4bits)	Scope(4bits)	Group ID (64 bits)

Anycast Address: applied for multiple network interfaces, but actual communication is conducted with one of them. It has the same format as the Unicast.

IPv4 mapped to IPv6 address:

0×00…0 (80 bits)	0×00…0 (16 bits)	IPv4 Address (32 bits)

IPv4-compatible IPv6 address:

0×00…0 (80 bits)	0×00…0 (16 bits)	IPv4 Address (32 bits)

Related Protocols IPv4, TCP, UDP, ICMPv6, Mobile IPv6, OSPFv3, BGP-MP, IPsec, RIPng

Sponsor Source IPv6 is defined by IETF (http://www.ietf.org) RFC 1883 (original) and RFC 2460 (latest).

Reference

http://www.javvin.com/protocol/rfc1883.pdf
IPv6 Specifications (original)

http://www.javvin.com/protocol/rfc2460.pdf
IPv6 specifications (the latest)

http://www.ipv6forum.com
A good informational site

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Protocol Description

The Internet Protocol (IP) is a network-layer (Layer 3 in the OSI model) protocol that contains addressing information and some control information to enable packets to be routed in a network. IP is the primary network-layer protocol in the TCP/IP protocol suite. Along with the Transmission Control Protocol (TCP), IP represents the heart of the Internet protocols. IP is equally well suited for both LAN and WAN communications.

IP has two primary responsibilities: providing connectionless, best-effort delivery of datagrams through a network; and providing fragmentation and reassembly of datagrams to support data links with different maximum-transmission unit (MTU) sizes. The IP addressing scheme is integral to the process of routing IP datagrams through an internetwork. Each IP address has specific components and follows a basic format. These IP addresses can be subdivided and used to create addresses for subnetworks. Each computer (known as a host) on a TCP/IP network is assigned a unique 32-bit logical address that is divided into two main parts: the network number and the host number. The network number identifies a network and must be assigned by the Internet Network Information Center (InterNIC) if the network is to be part of the Internet. An Internet Service Provider (ISP) can obtain blocks of network addresses from the InterNIC and can itself assign address space as necessary. The host number identifies a host on a network and is assigned by the local network administrator.

When you send or receive data (for example, an e-mail note or a Web page), the message gets divided into little chunks called packets. Each of these packets contains both the sender’s Internet address and the receiver’s address. Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different route across the Internet. Packets can arrive in a different order than the order they were sent in. The Internet Protocol just delivers them. It’s up to another protocol, the Transmission Control Protocol (TCP) to put them back in the right order.

All other protocols within the TCP/IP suite, except ARP and RARP, use IP to route frames from host to host. There are two basic IP versions, IPv4 and IPv6. This document describes the IPv4 details. The IPv6 details are described in a separate document.

Protocol Structure

4	8	16		32bit
Version	IHL	Type of service		Total length
Identification				Flags		Fragment offset
Time to live		Protocol		Header checksum
Source address
Destination address
Option + Padding
Data

• Version — indicates the version of IP currently used (4 for IPv4).
• IP Header Length (IHL) — is the datagram header length in 32-bit words. Points to the beginning of the data. Minimum value is 5 (20bytes) and maximum value is 15 (60 bytes).
• Type-of-Service — indicates the quality of service desired by specifying how an upper-layer protocol would like a current datagram to be handled and assigns datagrams various levels of importance. These 8 bits fields are used for the assignment of Precedence, Delay, Throughput and Reliability.

Type of service	Differentiated Services
Precedence (000 – 111)	000
D (1 = minimize delay)	0
T (1 = maximize throughout)	0
R (1 = maximize reliability)	0
C (1 = minimize cost)	1 = ENC capable
x (reserved and set to 0)	1 = congestion experienced

• Total Length — specifies the length, in bytes, of the entire IP packet, including the data and header. The maximum length is 65,535 bytes. Typically, hosts are prepared to accept datagrams up to 576 bytes.
• Identification — contains an integer that identifies the current datagram. This field is assigned by sender to help receiver to assemble the datagram fragments.
• Flags — consists of a 3-bit field of which the two low-order (least-significant) bits control fragmentation.

  	X (reserved and set to 0
  	D (1 = don't fragment)
  	M (1 = more fragment)

• Fragment Offset — This 13-bits field indicates the position of the fragment’s data relative to the beginning of the data in the original datagram, which allows the destination IP process to properly reconstruct the original datagram.
• Time-to-Live — is a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly.
• Protocol — indicates which upper-layer protocol receives incoming packets after IP processing is complete. Some sample protocols:

  	1 -- ICMP     2 -- IGMP    6 -- TCP
  	9 -- IGRP     17 -- UDP    47 --GRE
  	50 -- ESP     51 -- AH     57 -- SKIP
  	88 -- EIGRP   89 -- OSPF   115 -- L2TP

• Header Checksum — helps ensure IP header integrity. Since some header fields change, e.g., Time to Live, this is recomputed and verified at each point the Internet header is processed.
• Source Address — specifies the sending node.
• Destination Address — specifies the receiving node.
• Options — allows IP to support various options.

  	0 -- End of option list
  	1 -- No operation (PAD)
  	7 -- Record route
  	68 -- timestamp
  	131 -- Loose source route
  	137 -- Strict source route

• Data — contains upper-layer information.

Related Protocols IPv6, TCP, UDP, ICMP, SNMP, FTP,
TELNET, SMTP, ARP, RARP, RPC, XDR, and NFS

Sponsor Source The Internet Protocol is defined by IETF
(http://www.ietf.org) RFC 791.

Reference

http://www.javvin.com/protocol/rfc791.pdf
Internet Protocol Specifications

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ip.htm
IP Overview

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