HP-UX Mobile IPv6 A.01.00 Administrator's Guide

Chapter 1

Introducing HP-UX Mobile IPv6

Establishing Route Optimization

Route Optimization Data Paths

Mobile Node to Correspondent Node Data Path in Route Optimization

In route optimization mode, the Mobile Node sends data-packets directly to the Correspondent Node. The

Mobile Node uses its Care-of Address as the source IP address and puts its home address in a special IPv6

header option for Mobile IPv6—the Home Address destination option. The Home Address option is part of

an IPv6 Destination Option extension header. The following list describes the sequence of events shown in

Figure 1-9, Data Path: Mobile Node to Correspondent Node in Route Optimization:

1. The Mobile Node builds an IPv6 data-packet with its home address as the source address and calculates

any upper-layer checksum values (such as an IPSec authentication value) using its home address.

2. The Mobile Node appends a Home Address destination option to the IPv6 header with its home address.

3. The Mobile Node replaces its home address in the IPv6 data-packet header with its Care-of Address.

The data-packet is able to pass through routers with ingress routing, because data-packet source address

is the Care-of Address and is topologically correct (the source address will be an address on the foreign

network).

4. When the Correspondent Node receives the data-packet, it replaces the Care-of Address with the Mobile

Node home address in the source address field. This allows upper-layer protocols to correctly calculate

checksum values. The upper-layer protocols can also use the Mobile Node home address to identify the

Mobile Node and maintain connectivity and state information for the Mobile Node. The Mobile Node

home address is also useful for applications that use incoming source IP addresses for verification.

Figure 1-9 Data Path: Mobile Node to Correspondent Node in Route Optimization

Omitting Home Address Information

A Mobile Node is not required to send its home address to the Correspondent Node in a Home Address

destination option. The Mobile Node is required to use the Home Address destination option only when it is

using a transport-level connection (such as a TCP connection) with the Correspondent Node that it

established while attached to its home network, or when it is using a connection that must be maintained

when the Mobile Node attaches to a new foreign network. If the Mobile node is using a short-lived connection

or a connectionless communication with the Correspondent Node, the Mobile Node can send only its Care-of

Address to the Correspondent Node.

Foreign Network

Home Network

Home Agent

Mobile Node

Correspondent

Node

Home Address Option:

Home Address

Src: Care-of Address

Dest: Correspondent Node