An OSPF Autonomous System (AS) is divided into areas, connected by Area Border Routers (ABRs). One area, usually called "zero" area, is the backbone of the network. A router has complete knowledge of the topology only of the areas where it is located. An OSPF autonomous system exchange information (routes) with other autonomous systems through AS Boundary Routers (ASBRs).

The main features of Polyphemus are the following:

• Inter/Intra Area Exploration

A user can ask for the exploration of a specific area (intra-area exploration) or for the interconnection relationships between areas (inter-area exploration). Areas are explored by directly accessing the Management Information Base (MIB) of the routers with the Simple Network Management Protocol (SNMP). Supposing you have the AS depicted in Figure a. In this case, an inter area exploration gives the topology illustrated by Figure b while an intra area exploration results in the topology shown in Figure c.

 

• Inter/Intra Area Visualization

The user can visualize routers, local-area networks, areas, and inter-area relationships. For each item on the map a rich set of information can be displayed (see below).

 

• Detailed Node Information

Polyphemus show maps representing the interconnections  between the elements of the autonomous system we are exploring. There are three types of elements: routers, networks and areas; for each of them the user can ask for detailed information. The available data are summarized as follows:

Router data (see Figures 14,15,16,17,18):

• Router ID (RID) and current working status: the Router ID is an IP address used to identify the router within the OSPF protocol. Current working status can help  administrators to know if the router is an Area Border Router (ABR), an AS Boundary Router (ASBR) or both.

• Network interfaces: for each  network interface of the router it is possible to obtain its type (ethernet csma-cd, frame relay, token ring, fddi, etc.), its transfer speed, its MAC address, its IP assigned address(es),  and other related information.

• Router connections: it is possible to visualize all router links. They may be stub, transit, virtual links, and point-to-point. For each of them Polyphemus allows to get detailed information (e.g. netmask, designated router, etc.).

• Summary and external routes: it is possible to know the list of summary routes injected inside areas by each ABR, or similarly to obtain the list of all routes injected inside the AS by each ASBRs. For each route it is possible to obtain  more detailed information.

Nework Information (see Figure 21):

• General network information: for each network it is possible to know the IP Address/Netmask, the working status (transit/stub) and, for transit networks, also the Designated Router ID and the Designated Router IP.

• Routers connections: for each network it is possible to visualize the list of all connected routers and their RIDs.

Area Information (see Figure 13):

• General area information: for each OSPF area it is possible to know its Area ID, the AS number, the number of ABRs/ASBRs inside the area, its working status as transit area (in presence of virtual links) and the capability to accept external routing information.

• Routers inside an area: for each OSPF area it is possible to visualize the list of all routers belonging to it and for each of them its RID and its current working status (ABR/ASBR).