|GGP, Gateway to Gateway Protocol|
|Protocol type:||Transport layer routing protocol.|
This protocol was used mainly for routing datagrams and other gateway tasks.
GGP is an obsolete protocol and SHOULD NOT be implemented.
The IP protocol is used for host-to-host datagram service in a system of interconnected networks called the Catenet. The network connecting devices are called Gateways. These gateways communicate between themselves for control purposes via a Gateway to Gateway Protocol (GGP). Occasionally a gateway or destination host will communicate with a source host, for example, to report an error in datagram processing. For such purposes ICMP is used.
RFC 1009, pages 22 and 23:
GGP was designed and implemented by BBN for the first experimental Internet gateways. It is still in use in the BBN LSI/11 gateways, but is regarded as having serious drawbacks. GGP is based upon an algorithm used in the early ARPANET IMPs and later replaced by SPF.
GGP is a "min-hop" algorithm, i.e., its length measure is simply the number of network hops between gateway pairs. It implements a distributed shortest-path algorithm, which requires global convergence of the routing tables after a change in topology or connectivity. Each gateway sends a GGP routing update only to its neighbors, but each update includes an entry for every known network, where each entry contains the hop count from the gateway sending the update.
|MAC header||IP header||GGP packet|
|Gateway type||unused||Sequence number|
|GGP message :::|
Specifies the format of the GGP message.
|9||Network interface status.|
Must be cleared to zero.
Sequence number. 16 bits.
GGP message. Variable length.
[RFC 778] DCNET Internet Clock Service.
[RFC 792] INTERNET CONTROL MESSAGE PROTOCOL.
[RFC 823] THE DARPA INTERNET GATEWAY.
[RFC 1812] Requirements for IP Version 4 Routers.
[IEN 109] HOW TO BUILD A GATEWAY.
[RFC 1009] Requirements for Internet Gateways.
[RFC 1716] Towards Requirements for IP Routers.