Network Working Group Jon Postel
Request for Comments: 890 ISI
February 1984 Exterior Gateway Protocol Implementation Schedule
Status of this Memo
This memo is a policy statement on the implementation of the Exterior
Gateway Protocol in the Internet. This is an official policy
statement of ICCB and DARPA.
The Current Situation
Currently the Internet has a number of smart gateways and a number of
dumb gateways. The smart gateways dynamically exchange routing
information among themselves using the Gateway Gateway
Protocol (GGP) . The dumb gateways do not exchange routing
The dumb gateways must be listed in the smart gateway routing tables,
and changes in dumb gateways status (e.g., adding new dumb gateways)
in the smart gateways tables requires human intervention.
The amount of routing traffic between smart gateways depends on the
number of smart gateways and the total number of networks. Since
dumb gateways typically connect a single network at the edge of the
Internet, there is typically one more network in the routing table
for each dumb gateway.
Gateways that connect a single network to the edge of the Internet
may be called "stub" gateways.
The current GGP procedures used by the smart gateways are at the
limits of their capacity. A significant change to these procedures
is urgently required. This is difficult to perform because the smart
gateways are maintained by several different groups, and because it
is difficult to isolate a subset of these gateways for testing new
The Future Situation
In the future, as it is currently envisioned, there will be a number
of co-equal autonomous systems of gateways. Each as will have its
own private internal procedures for maintaining routing information,
perhaps via an Interior Gateway Protocol (IGP). The smartness of a
gateway will be the smartness of the IGP used in the autonomous
system the gateway participates in. Some gateways of each autonomous
system will exchange routing informations with some gateways of other
autonomous systems via an Exterior Gateway Protocol (EGP) .
The factoring of the old set of smart gateways into a number of
autonomous systems allows more flexibility for the development and
testing of improved routing procedures. Different autonomous systems
can adopt different routing procedures internally, as long as they
communicate with other autonomous systems via the EGP.
The Transition Situation
The first step in the transition from the current situation to the
future situation is the replacement of all dumb gateways with
gateways that implement at least a subset of the EGP.
This subset is called the "Stub Exterior Gateway Protocol", and is
described in RFC-888 .
The second step is to factor the existing smart gateways into
autonomous systems. The gateways programmed and maintained by
different groups will become distinct autonomous systems. As things
are, this will result in one fairly large autonomous system and three
or four small autonomous systems. At this step the large autonomous
system will be referred to as the "core" autonomous system. All
other autonomous systems will be stubs attached to this core via EGP.
The third step is to specify the full EGP protocol, and to allow a
rich connectivity between co-equal autonomous systems.
After 1-Aug-84 there shall be no dumb gateways in the Internet.
Every gateway must be a member of some autonomous system. Some
gateway of each autonomous system must exchange routing information
with some gateway of the core autonomous system using the Exterior
If you have a dumb gateway now, you should start doing something
today to get it upgraded to, or replaced by, an EGP gateway.
There may be a gateway you can use already developed by someone.
People at the following places are working on EGP gateways: BBN,
MIT, Linkabit, ISI, Honeywell, and Symbolics. For more information
send a message to Joyce Reynolds at mailbox "JKReynolds@USC-ISIF".
There are plans to provide EGP functionality in Berkeley 4.2 Unix.
Berkeley has indicated an intention to have EGP capability available
in the standard release of 4.2 Unix before the cut off date for dumb
The is a mailing list for EGP implementers called "egp-people". To
get on or off this list send a message to the mailbox
There is a EGP testing program available on TOPS20. For information
about using it send a message to Jim Mathis at mailbox
If you need an autonomous system number send a request to Joyce
Reynolds at mailbox "JKReynolds@USC-ISIF".
 Seamonson, L., and E. Rosen, "Stub Exterior Gateway Protocol",
RFC-888, BBN Communications Company, January 1984.
 Rosen, E., "Exterior Gateway Protocol", RFC-827, Bolt Beranek
and Newman, October 1982.
 Hinden, R., and A. Sheltzer, "The DARPA Internet Gateway",
RFC-823, Bolt Beranek and Newman, September 1982.