Ipv6_shanghaiipv6 specification Semantics

1: semantics Semantics

 

I. Introduction

1. changes form IPv6 to IPv6.

1) expanded addressing capabilities

32 bit to 128 bits to support

A) more levels of addressing hiearchy

B) a much greater number of address nodes

C) Simpler auto-configration of address nodes.

D) add"Scope"FieldMulticast addresses.

E) define a new type of addresses called"Anycast address"To send a packet to anyone of a group of nodes.

 

2) Header Format simplication

Drop or make optionalSome IPv4 header field.

A) Reduce the common-case processing cost of Packet Handling.

B) Limit the bandwidth cost of the IPv6 Header.

 

3) improved support for extensions and options

Changes in the way IP Header Options

A) More efficient forwarding.

B) less stringent limits on the length of options. (The option length is relaxed)

C) greater flexibility for introducing new options in the future.

4) flow labeling capability

A) add a capability to enable the labeling of packets, for which the senderRequests special handling,

SuchNon-default QualityOr"Real-time"Service.

 

5) authentication and privacy capabilities

A) extensions to supportAuthentication data integraty (complete data ),

Optional Data Confidentiality (data confidentiality).

 

Ii. Terminology

1: node-A device that implements limit 6.

2: Router-a node that forwards IPv6 packets not explicitly addressed to itself.

3: Host-any node that is not a router.

4: upper layer-A protocol layer immediatlyAbove IPv6, ICMP, TCP, UDP, OSPF, IPX, appletalk or IPv6 intself.

5.Link-a communication facility at the same link.

Below limit 6.

Ethernets (bridged), PPP links, X.25, frame, relay.

6.Neighbors-nodes attached to the same link.

7. Interface-A node's attachment to a link.

8.Packet-an IPv6 Header plus Payload.

9. Link Mtu-the maximum transmission unit.

MaximumPacketSize in octets.

10. Path Mtu-Minimum link MTU of all the linksIn a path between a source node and a destination node.

 

Iii. IPv6 Header Format (40 ETS)

 

8 parts

A) version, traffic class, Flow Label (4, 8, 20)

B) payload, next header, hop limit (16, 8, 8)

C) Source Address (128 ).

D) Destination Address (128 ).

 

1: version-4 bits

2: Traffic class-8 bits

3: Flow Label-20 bits

4: payload-16 bits

5: Next header-8 bits

6: Hop limit-8 bitsThe packet is discarded if hop limit is decremented to zero.

7. Source Address-128 bits.

8. Destination Address-128 bits.

 

Iv. IPv6 extension header

OptionaL IPv6 Internet-layer is encodedIn separate HeadersThat may be placedBetween the IPv6 Header and the upper layer HeaderIn a packet.

 

?

With one hop ition (HOP by Hop), Extension headers are not examined or processed by any node along a packets delivery path,

Until the packet reaches the node(OR each set of nodes in the case of municast).

 

Extension HeadersMust beProcessed strictly in the order they appear in the packet.

 

Hop by Hop OptionCarries information thatMust be examined and processed by every node along a packets delivery path,

Including the source and destination nodes.