Cisco Systems 8600 Series BPX Switch and ESP Interfaces, Interim Inter-switch Protocol Routing

BPX Switch and ESP Interfaces

BPX Switch and ESP Interfaces

The BPX switch supports the UNI and NNI interfaces for SVC operations as described in the following:

•UNI, that is the User Network Interface, is the interface for either ATM or Frame Relay customer premise equipment (CPE) to the BPX switch. The UNI is defined as any interface between a user device and an ATM network (i.e., an ATM switch). The UNI defines the signaling method which the CPE must use to request and setup SVCs through the wide-area ATM network. In addition, the UNI is used to send messages from the network to the CPE (i.e., user device) on the status of the circuit and rate control information to prevent network congestion.

For ATM SVCs, the UNI supports either the ATM Forum 3.0 or 3.1 signaling standards as well as traditional ATM PVCs. (Remember the BPX switch also supports high-speed ATM UNI ports.)

For Frame Relay, the UNI supports Frame Relay Forum Frame Relay User-to-Network SVC Implementation Agreement (FRF.4), which specifies the Frame Relay SVC signaling protocols. BPX switch Frame Relay UNIs (FRSMs) also support traditional Frame Relay PVCs.

•Network-to-Network Interface (NNI). The NNI is the interface to other BPX switch or foreign ATM Switches. The BPX switch supports Interim Inter-switch Protocol (IISP) 3.0 /3.1 or the Private Network to Network Interface (PNNI). These NNI interfaces provide the switching and routing functions between Cisco StrataCom wide-area networks and other networks. Information passing across a NNI is related to circuit routing and status of the circuit in the adjacent network. (Note that NNI could refer to both a connection between a BPX switch with ESP, and a connection between a BPX switch with ESP and a foreign switch.)

Interim Inter-switch Protocol Routing

Interim Inter-switch Protocol (IISP) is an interim static routing protocol defined by the ATM Forum to provide base level capability until the Private Network to Network Interface (PNNI) was specified. The IISP provides users with some level of multi-vendor switch interoperability based on the existing ATM Forum UNI 3.1 specifications. IISP assumes no exchange of routing information between switching systems. It uses a a fixed routing algorithm with static routes. Routing is done on a hop-by-hop basis by making a best match of the destination address in the call setup with address entries in the next hop routing table at a given switching system. Entries in the next hop routing table are configured by the user.

PNNI

The Private Network to Network Interface standards essentially define two protocols:

•Topology

The Private Network to Network Interface (PNNI) defines a protocol for distributing topology information between switches and clusters of switches. This information is used to compute paths through the network. A key feature of the PNNI mechanism is its ability to automatically configure itself in networks in which the address structure reflects the topology. PNNI topology and routing are based on the well-known link-state routing technique.

•Signaling

PNNI also defines a second protocol for signaling, that is message flows used to establish point-to-point connections across the ATM network. This protocol is based on the ATM Forum UNI signaling, with mechanisms added to support source routing, crankback, and alternate routing of call setup requests in case of connection setup failure.

8-4Cisco BPX 8600 Series Reference