Chapter 13. IGMP: Internet Group Management Protocol

13.1. Introduction

IGMP conveys group membership information between hosts and routers on a local network. Routers periodically multicast IGMP queries to the all-hosts group. Hosts respond to the queries by multicasting IGMP report messages. The IGMP specification appears in RFC 1112. Chapter 13 of Volume 1 describes the specification of IGMP and provides some examples.

From an architecture perspective, IGMP is a transport protocol above IP. It has a protocol number (2) and its messages are carried in IP datagrams (as with ICMP). IGMP usually isn’t accessed directly by a process but, as with ICMP, a process can send and receive IGMP messages through an IGMP socket. This ...

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