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IPv6 Essentials
book

IPv6 Essentials

by Silvia Hagen
July 2002
Beginner content levelBeginner
360 pages
11h 19m
English
O'Reilly Media, Inc.
Content preview from IPv6 Essentials

ICMP Informational Messages

In RFC 2463, two types of informational messages are defined: the Echo Request and the Echo Reply messages. Other ICMP informational messages are used for Path MTU Discovery and neighbor discovery. These messages are discussed at the end of this chapter and defined in RFC 2461, “Neighbor Discovery for IP Version 6,” and RFC 1981, “Path MTU Discovery for IP version 6.”

The Echo Request and Echo Reply messages are used for one of the most common TCP/IP utilities: Packet INternet Groper (ping). Ping is used to determine if a specified host is available on the network and ready to communicate. The source host issues an Echo Request message to the specified destination. The destination host, if available, responds with an Echo Reply message. In Chapter 11, you can find a screenshot that shows you what an IPv6 ping looks like in the trace file, as well as the command you need to ping over IPv6.

Echo Request Message

The format of the Echo Request message is shown in Figure 4-6.

Format of the Echo Request message

Figure 4-6. Format of the Echo Request message

The Type Field is set to 128, the value for the Echo Request. The Code Field is not used for this message and is therefore set to zero. The Identifier and Sequence Number fields are used to match requests with replies. The reply must always contain the same numbers as the request. Whether an identifier and a sequence number are used and ...

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Publisher Resources

ISBN: 0596001258Catalog PageErrata