IBM SG24-4817-00 manual SSI Connection TRS Capacity, NNI Connection

This soft copy for use by IBM employees only.

Notes:

￿1￿ Any two combinations of token-ring (IEEE 802.5) and Ethernet / IEEE802.3 LAN Emulation.

￿2￿ Sum of the LECs when two sets of LES/BUS configured.

￿3￿ Average value based on the performance test.

6.2.1.4 SSI Connection (TRS Capacity)

The IBM 8285 implements a dynamic routing mechanism between ATM switches. This mechanism, called the switch-to-switch interface (SSI) protocol, was developed by IBM based on the ATM Forum PNNI Phase 1 specification, and is an IBM exclusive. SSI provides many benefits, such as reducing the workload of route definition, enabling link aggregation between switches, and enabling automatic route backup should the primary route fail. However, as with any dynamic routing protocol, the need to exchange information between nodes can consume bandwidth and processing resources. The IBM 8285 has the following capacity limitations for SSI connection:

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Maximum number of ATM switches per cluster

Maximum number of ATM switch hops in a cluster

Call setup and cell transmit time are proportional to the number of hops.

Parallel / Multiple SSI link

Parallel SSI links between two hubs are supported but the bandwidth cannot be shared. This means a data path between two switches is assigned to a specific SSI link even if you have parallel SSI links. But parallel SSI links increase the total bandwidth available between switches. There is no limit for the number of the parallel SSI links but excessive links provide little additional benefit.

Multiple SSI links which provide alternate paths are supported. There is no limit to the number of multiple SSI links allowed as long as the network is designed within the restrictions of the maximum number of ATM switches and ATM switch hops in a cluster.

Table 25 shows the summary of the TRS capacity of the IBM 8285 and IBM 8260.

Table 25. TRS Capacity of the IBM 8285 Nways ATM Workgroup Switch and IBM 8260 Nways Multiprotocol Switching Hub

Description	Value
Maximum number of the ATM switches per a cluster	25
Maximum number of the ATM switch hops in a cluster	5

6.2.1.5 NNI Connection

The IBM 8285 implements static routing mechanism between ATM switches as well. It is called NNI and is fully-compliant with the IISP specification of The ATM Forum. The NNI connection may be established on a physical link (direct connection) or over a permanent VP (PVP) connection via the ATM WAN module. As of today, IISP is the only protocol that can be used to interconnect an IBM campus ATM switch to another vendor′s switch. On the NNI connection, the following capacity limitations should be considered:

•Maximum number of static route definitions

Chapter 6. IBM 8285 Planning and Installing 101