RFC 1482 (rfc1482) - Page 2 of 11
Aggregation Support in the NSFNET Policy-Based Routing Database
Alternative Format: Original Text Document
RFC 1482 Routing Aggregation Support July 1993
2. Aggregation Support by the Backbone Service
The NSFNET backbone service includes a Policy-Based Routing Database
system which currently holds the set of network numbers that are
accepted by the backbone service with a list of Autonomous System
numbers from which announcements of these network numbers are
expected. In order to implement CIDR, the database system will be
modified to allow aggregation of routing information to be
configured.
The NSFNET will (initially) not support de-aggregation on its
outbound announcements. See section 2.3.
2.1 Current Configuration Capabilities
2.1.1 Inbound Announcements
An example of the way a network number is currently configured is as
follows:
35 1:237 2:233 3:183 4:266 5:267 6:1225
This shows that network number 35 (ie. 35.0.0.0, a class A net
number) is configured on the T3 backbone such that routing
announcements are expected from up to 6 autonomous systems. The
primary path is via AS 237, secondary is via AS 233, etc.
2.1.2 Outbound Announcements
Currently the NSFNET database has a list of AS's or network numbers
for each neighbor AS that are announced by the backbone to that AS.
These announcements are specified currently by "announcetoAS"
statements--which implement policies submitted by midlevels to
Merit--and then included in the ANSnet router configuration files.
There are two forms of these statements. The first form uses the
"norestrict" clause and indicates that all of the network numbers
within each AS in the list should be announced to the neighbor
midlevel AS. For example:
announcetoAS 42 norestrict ASlist 22 26 38 60 68
In this example, the NSFNET is configured to announce to neighboring
midlevel AS 42, all networks in the routing table that were announced
from AS's 22, 26, 38, 60 and 68.
If the "norestrict" keyword is changed to "restrict", this indicates
that an explicit announce list of network numbers for the AS is
specified in the configuration file. The NSFNET will only announce
Knopper & Richardson