Novell Link-State Protocol (NLSP)

Novell Link-State Protocol (NLSP) is used exclusively to route IPX traffic. It is a link-state routing protocol, not a distance-vector protocol like IPX RIP. The current version of NLSP, version 1.1, supports a multitude of advanced routing features, such as:

• Multiple areas

• Route aggregation

• Hierarchical addressing

• Network summarization

NLSP is similar to IS-IS and OSPF in that it defines areas. NLSP offers solutions to many of the problems that we discussed with RIP and SAP, and it can actually work as a replacement for all RIP and SAP communication between servers (or routers). Every NLSP router (remember that NLSP- enabled NetWare servers are NLSP routers) builds and maintains three databases:

• Adjacency

• Link-state

• Forwarding

These three databases are listed in the order in which they are built. The adjacency database can be unique on every router. Each router will, on each of its NLSP-enabled interfaces, meet every other NLSP router on that network segment. On an Ethernet interface, for example, there can be several other NLSP-enabled devices (other routers, servers, etc.). On a point-to-point WAN interface, there is only one other device. All of this information goes into the adjacency database, and once it is built, each router knows all of its NLSP neighbors on all connected networks.

The information in the adjacency database is used to create the link-state database. Once the routers know all of their adjacencies, they share that information with every other router in what is called the area (we will cover this process and define an area in the next section). At that point, every router knows not only its own adjacencies, but every other router’s adjacencies as well. From this, each router builds a link-state database that represents every router in the area and every path between them. Since every router builds this database with the same information (all unique adjacency databases from all routers), the link-state database will be identical on every router in the area.

Once the link-state database is built and all routers agree upon it, each router builds from the link-state database a forwarding database. This is really just a route table. It lists all networks and the best path for each individual router to take to get to these networks. Because each router can occupy a unique position in the area, each router will have a unique forwarding database.