Routing between the NSFNET and the DDN
RFC 1133
|
Document |
Type |
|
RFC - Informational
(November 1989; No errata)
|
|
Authors |
|
Jessica Yu
,
Hans-Werner Braun
|
|
Last updated |
|
2013-03-02
|
|
Stream |
|
Legacy
|
|
Formats |
|
plain text
html
pdf
htmlized
bibtex
|
Stream |
Legacy state
|
|
(None)
|
|
Consensus Boilerplate |
|
Unknown
|
|
RFC Editor Note |
|
(None)
|
IESG |
IESG state |
|
RFC 1133 (Informational)
|
|
Telechat date |
|
|
|
Responsible AD |
|
(None)
|
|
Send notices to |
|
(None)
|
Network Working Group J. Yu
Request for Comments: 1133 H-W. Braun
Merit Computer Network
November 1989
Routing between the NSFNET and the DDN
Status of this Memo
This document is a case study of the implementation of routing
between the NSFNET and the DDN components (the MILNET and the
ARPANET). We hope that it can be used to expand towards
interconnection of other Administrative Domains. We would welcome
discussion and suggestions about the methods employed for the
interconnections. No standards are specified in this memo.
Distribution of this memo is unlimited.
1. Definitions for this document
The NSFNET is the backbone network of the National Science
Foundation's computer network infrastructure. It interconnects
multiple autonomously administered mid-level networks, which in turn
connect autonomously administered networks of campuses and research
centers. The NSFNET connects to multiple peer networks consisting of
national network infrastructures of other federal agencies. One of
these peer networks is the Defense Data Network (DDN) which, for the
sake of this discussion, should be viewed as the combination of the
DoD's MILNET and ARPANET component networks, both of which are
national in scope.
It should be pointed out that network announcements in one direction
result in traffic the other direction, e.g., a network announcement
via a specific interconnection between the NSFNET to the DDN results
in packet traffic via the same interconnection between the DDN to the
NSFNET.
2. NSFNET/DDN routing until mid '89
Until mid-1989, the NSFNET and the DDN were connected via a few
intermediate routers which in turn were connected to the ARPANET.
These routers exchanged network reachability information via the
Exterior Gateway Protocol (EGP) with the NSFNET nodes as well as with
the DDN Mailbridges. In the context of network routing these
Mailbridges can be viewed as route servers, which exchange external
network reachability information via EGP while using a proprietary
protocol to exchange routing information among themselves.
Currently, there are three Mailbridges at east coast locations and
Yu & Braun [Page 1]
RFC 1133 Routing between the NSFNET and the DDN November 1989
three Mailbridges at west coast locations. Besides functioning as
route servers the Mailbridges also provide for connectivity, i.e,
packet switching, between the ARPANET and the MILNET.
The intermediate systems between the NSFNET and the ARPANET were
under separate administrative control, typically by a NSFNET mid-
level network.
For a period of time, the traffic between the NSFNET and the DDN was
carried by three ARPANET gateways. These ARPANET gateways were under
the administrative control of a NSFNET mid-level network or local
site and had direct connections to both a NSFNET NSS and an ARPANET
PSN. These routers had simultaneous EGP sessions with a NSFNET NSS
as well as a DDN Mailbridge. This resulted in making them function
as packet switches between the two peer networks. As network routes
were established packets were switched between the NSFNET and the
DDN.
The NSFNET used three NSFNET/ARPANET gateways which had been provided
by three different sites for redundancy purposes. Those three sites
were initially at Cornell University, the University of Illinois
(UC), and Merit. When the ARPANET connections at Cornell University
and the University of Illinois (UC) were terminated, a similar setup
was introduced at the Pittsburgh Supercomputer Center and at the John
von Neumann Supercomputer Center which, together with the Merit
connection, allowed for continued redundancy.
As described in RFC1092 and RFC1093, NSFNET routing is controlled by
a distributed policy routing database that controls the acceptance
and distribution of routing information. This control also extends
to the NSFNET/ARPANET gateways.
2.1 Inbound announcement -- Routes announced from the DDN to the
NSFNET
In the case of the three NSFNET/ARPANET gateways, each of the
associated NSSs accepted the DDN routes at a different metric. The
route with the lowest metric then was favored for the traffic towards
the specific DDN network, but had that specific gateway to the DDN
experienced problems with loss of routing information, one of the
redundant gateways would take over and carry the load as a fallback
path. Assuming consistent DDN routing information at any of the
three gateways, as received from the Mailbridges, only a single
NSFNET/ARPANET gateway was used at a given time for traffic from the
Show full document text