Understanding IPv6
Based on the latest IETF meetings, this text provides professionals with a practical and detailed reference and introduction that explains the new capabilities and changes of the next-generation internet protocol.
TABLE OF CONTENTS Understanding IPv6
10.8: CHANGES IN IPv6 NEIGHBOR DISCOVERY PROTOCOL
10.8 CHANGES IN IPv6 NEIGHBOR DISCOVERY PROTOCOL
To support dynamic home agent discovery, MIPv6 modifies some parts of IPv6 Neighbor Discovery Protocol. At first, Router Advertisement message is modified. Two options for the Advertisement message are also modified, and Home Agent Information option is defined.
10.8.1 Modified Router Advertisement message
The Router Advertisement message defined in RFC 2461 is modified as follows:
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H (Home Agent) bit is defined in the Reserved field of ICMP Header to indicate that the router sending the Advertisement message is also operating as a home agent on the link.
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The Reserved field is reduced from 6-bit field to a 5-bit field. The header format is shown in Fig. 10-27.
Figure 10-27: Modified Router Advertisement message format. -
In the Options field, Modified Prefix Information option, Advertisement Interval option and Home Agent Information option may be included.
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Remaining fields have the same feature in the original Router Advertisement message.
10.8.2 Modified Prefix Information option
In IPv6 Neighbor Discovery mechanism, only link-local address is used in the Source Address field of IP Header to send Router Advertisement message. To support IP mobility, a new single flag, R (Router Address) is defined in the previous Reserved field of Prefix Information option, which allows a router to advertise its prefix information to mobile nodes away from home link. The option format is shown in Fig. 10-28.
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R flag indicates that the Prefix field in the option carries a complete IP address assigned to the home agent. When...
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