From GEANT2-JRA1 Wiki

L3 network discovery

The objective is to have a tool which discovers the L3 topology and populate the topology DB in an automated way.

The information which should be provided is described Prototype Participation and is a subset of the information needed in the JRA1_D1.4_Database_Schema.

Methods

1. ESnet method
   • A script which contact a router and download the IGP database. This allow to get the list of routers (alive) in the network, the connections between routers, the IP addresses and the link capacity. The script is being run once a day. (*) (**)
   • Then they contact each router using SNMP and try to figure out the router type. Once they got the type, they know which OIDs they need to use to retrieve information from the router.
   • Then they perform a SNMPwalk to figure out the list of interfaces. They also gather the link capacity, the description and the utilisation counters. (***)
2. CNM method
   • This requires Cisco Discovery Protocol to be turned on on all the routers/switches in the network. This protocol is not only supported by Cisco equipment, but also by other vendors like HP (switches). Juniper does not support CDP.
   • Starting from an initial known network element its neighbors are discovered. This is done by retrieving the SNMP variables corresponding to CDP which show the directly connected neighbors. After that, the neighbors are requested to provide information about their neighbors and so on.
   • Network metrics are retrieved independent from the discovery procedure by requesting SNMP variables from all known network elements.

(*) You could also use an IGP listener which would provide you the same information, but you would be notified near real time about changes and those could be tracked in the topology DB. (**) Drawback, you may loose the equipment which are down when you run the script. (***) You could instead of using SNMP, use ssh and have access to the router configuration.

Student work description

Amongst the services defined for the perfSONAR infrastructure, the Topology Service aims at providing a network topological information in a pre-defined format to any services requesting topological information. The topological information needs to be retrieved from the routers and populates the Topology Service information repository. The goal of this student project is to build a tool to discover the IP network topology and to retrieve topological information from the network (routers, interfaces name, link capacity, IP prefixes , etc). The tools should be designed to be able to deal with different type of routers, however it's implementation would be limited to GEANT router types.

This will be achieved by:

• Investigating different techniques to discover the topology and

retrieve topological information (IGP listener, SNMP MIB browsing).

• Investigate how the information can be retrieved and presented from

several routing platforms (in particular Cisco and Juniper routers).

• Provide a modular and scalable design.
• Implement a Topology Discovery system for the GEANT network.