Table of Contents
Interoperability and Performance PlanningCompatible Standards
Specifications
Physical Network Planning
Parallel Links Between Adjacent Switches
Multiple Links Between Adjacent Peer Groups
Multiple Links to an External Network
Multiple Paths Between Network Nodes
Planning Guidelines for Hierarchical Networks
Interoperability and Performance Planning
This chapter describes the standards supported by the Cisco switches covered in this guide and provides performance specifications for these switches.
Compatible Standards
The Cisco switches described in this guide are designed to interoperate with switches that support the following standards:
Specifications
Table 2-1 lists PNNI network specifications for the PNNI switches covered in this guide.
Table 2-1 PNNI Networking Specifications
| Capabilities | BPX/SES 1.0 | BPX/SES 1.1 | MGX 8850 2.0 | MGX 8850 2.1 | MGX 8950 2.1 |
|---|---|---|---|---|---|
Physical Network Planning
The PNNI switches described in this guide can reroute connections and adjust to equipment or link failures only when the physical network has been designed to use redundant hardware and links. When designing a PNNI network, consider the following:
The following sections provide additional information on these guidelines.
Install Redundant Hardware in Switches
The switches described in this guide support redundant power supplies, Processor Switch Module (PXM) cards, line cards, and trunk cards. Although PNNI can reroute calls, using redundant hardware can improve network stability and performance by preventing reroutes caused by hardware failure.
Parallel Links Between Adjacent Switches
When parallel links are available between a pair of switches, PNNI can load balance calls across these links. If one link fails, the other is still available.
Multiple Links Between Adjacent Peer Groups
Communications between two peer groups takes place through two border nodes. Parallel links between two border nodes improves reliability. Adding additional border nodes to handle communications between two peer groups provides alternative routing paths and prevents network outages caused by a single node failure.
Multiple Links to an External Network
An external network connection is any non-PNNI network connection. External network connections include AINI and IISP connections. As with internal network links, consider using parallel links and additional border nodes to provide alternative paths to external networks. When you configure multiple static links to an external network, remember to duplicate the ATM address advertisement configuration on all redundant links.
Multiple Paths Between Network Nodes
It is good design practice to ensure that there are at least two different paths between any pair of nodes that will communicate with each other. A pair of redundant links is one path. If one switch site is damaged by fire or earthquake, there should be at least one other switch that can provide an alternative path between the source and destination switches.
Planning Guidelines for Individual Peer Groups
The first step in planning a PNNI topology is to determine if all network nodes will participate in one peer group or in hierarchical peer groups. The single and hierarchical peer group topologies are introduced in "Introduction to PNNI." When a network grows beyond the capabilities of a single peer group, you must use the hierarchical peer group topology.
The planning for a single peer group topology is the same as the planning for a single peer group within a hierarchical PNNI network. The difference between planning for a single peer group network and planning for a hierarchical network is that for hierarchical networks, you have to plan the communications between peer groups. The following list summarizes the capabilities and guidelines for a single peer groups:
- For networks with less than 100 nodes, Cisco Systems recommends using a single peer group topology.
- A single peer group supports up to 256 nodes as described in Table 2-1.
- All nodes within a single peer group must be adjacent to each other. If the only path between nodes A and B in a peer group is through another peer group, PNNI advertisements between nodes A and B will be blocked at the borders of the other peer group.
- PNNI can route calls through a maximum of 20 nodes within a single peer group. The structure of the peer group should be such that no node is more than 20 hops from any other node.
- As the number of nodes in a single peer group grows, the network and system resource requirements for each node grows.
- The level of PNNI processing required for your network is dependent on the service classes supported. For example, CBR and VBR calls consume more resources than ABR and UBR calls.
- Although the number of network nodes in your network might not dictate a hierarchical topology, other network requirements can. For example, if you want to take advantage of the individual peer group management capabilities in a split-border hierarchy, you must configure multiple peer groups.
- Consider future growth when planning peer groups. If the number of existing nodes is approaching the limit of a single peer group, consider using a hierarchical topology so that you do not have to reconfigure nodes later when the network size expands.
Planning Guidelines for Hierarchical Networks
When you have a plan for dividing your network into multiple peer groups, the next step is to plan communications between those peer groups. To enable communications between peer groups, you will need to identify a peer group leader for each peer group. The following sections provide planning guidelines for the peer group leaders and border nodes in a hierarchical network.
Planning Guidelines for Peer Group Leaders
Peer group leaders are the logical nodes that represent their peer group at the next higher level in the PNNI hierarchy. Peer group leaders are introduced in "Introduction to PNNI." The following are some planning guidelines for peer group leaders:
- For a peer group to communicate with another peer group, the peer group must have at least one node that is capable of acting as peer group leader.
- It is good design practice to configure multiple nodes within a peer group to serve as peer group leader. The peer group priority is a configurable parameter that determines which of the peer group leader candidates becomes peer group leader.
- To compensate for the additional processing requirements of peer group leaders, consider reducing the traffic load for the peer group leader switch and avoid using the same switch as both a peer group leader and a border node.
Planning Guidelines for Border Nodes
Border nodes are physical nodes that are members of one peer group and have connections to member nodes of other peer groups. Border nodes are introduced in "Introduction to PNNI." To compensate for the additional processing requirements of border nodes, consider reducing the intra-peer-group traffic load for the border node and avoid using the same switch as both a border node and a peer group leader.