TECHNOLOGY

MPLS

OSPF

OSPF is a link state routing protocol supported in the HSX 6000 that is used as an interior gateway protocol (IGP). OSPF is defined in RFC2328 and is used within a single autonomous system (AS) for routing within the AS. OSPF supports a two level hierarchy using areas that enables a router to minimize their routing table sizes. OSPF areas are delineated on the interface such that an area border router (ABR) is actually in two or more areas at once, effectively creating the border between areas, inside an ABR.

An OSPF network can be divided into smaller networks. A special area, known as the backbone area (called area zero), forms the core of the network. The other areas are connected to the backbone. Inter-area routing goes through the backbone, and all areas must connect to it; if a direct connection is not possible, then a virtual link can be established. OSPF-TE is defined in RFC3630 and provides traffic engineering extensions to OSPF. Using these extensions, OSPF can be used to distribute traffic engineering information within an AS. Traffic engineering information is maintained in a separate database known as the traffic engineering database (TED). The TED can be queried to compute constraint-based paths that are used to create traffic engineered connections through the network.