Address Summarization and Suppression

Address summarization prevents every routing node in the entire PNNI domain from maintaining a dynamic list of all the AESAs of every other node and attached ATM end system. By default, every PNNI routing node, logical or physical, advertises a summary address equal to its level in the PNNI hierarchy. For example, a node residing in the lowest layer of the previous example would advertise the most significant 88 bits of its AESA as a summary address. All end systems attached to this node will have the identical 88-bit pattern in their AESAs.

If a routing node only performs local switching for a group of attached end systems or external PNNI networks, the network administrator can configure a suppression summary address in the node performing the local switching. This suppression summary address prevents the routing node from advertising those locally switched AESAs to other routing nodes, thus lowering routing traffic in the domain and lessening memory demands on other nodes.

PNNI routing follows a prefix longest-match algorithm similar to IP routing. A default prefix is defined as a prefix with a length of zero, and it matches all addresses. A default route can be configured on domain border nodes and redistributed into PNNI. This is particularly useful in stub areas.