Cisco Systems IGX 8400 manual Types of Connections on a UXM-E Trunk

Universal Switching Module Enhanced

Types of Connections on a UXM-E Trunk

This section introduces the connections that a UXM-E trunk supports. The context of each description is the trunk rather than the connection endpoints. The purpose of these descriptions is not only to inform but also help you plan the network. Some definitions overlap because a connection may qualify as more than one type.

•A Cell connection carries information that exists in ATM cell format throughout the path. On a UXM-E trunk, therefore, the only cell connections are those that have originated on a UXM-E port at one end and remain in cell format throughout the connection.

•A Gateway connection carries information that normally exists in ATM cell format but is translated to FastPacket format for some purpose at some point along the path. Reason for the translation could be that the connection terminates on a FastPacket-based card, is a network connection, or includes a FastPacket-based trunk card in the route.

•A Networking connection carries network messages between nodes and terminate as FastPackets (and therefore are also gateway connections).

•A User-connectionis a connection that a user has added at the current node. User-connections can be cell connections or gateway connections. User connections are mutually exclusive of via connections and network connections.

•A Via connection passes through a node and does not terminate on the node. You can neither view nor alter a via connection because the connection does not terminate on the node (the node that owns the connection has made the via node and trunk a part of the route).

•An Interworking connection is a service or network interworking connection in which one end terminates as ATM and the other as Frame Relay. Interworking connections are a subset of gateway connections.

Operating as a trunk, the UXM-E carries up to 8000 connections. A via connection can be either a cell-type or a gateway-type.

Because network messages use gateway channels, they subtract from the total number of available gateway connections. For each active port, the UXM-E reserves 270 gateway connections for networking regardless of the interface type. Therefore, with a fully-utilized 8-E1 or 8-T1 back card, the UXM-E reserves up to 2160 connections. Because these numbers potentially represent a very significant reduction in the number of gateway connections for user-data, switch software lets you specify a maximum number of active ports on the back card. The most applicable interfaces for this capability are the T1 and E1 ports, especially with Inverse Multiplexing Over ATM (IMA). See the section “Inverse Multiplexing over ATM on IGX Trunks” for the description of IMA.

You can specify the maximum number of logical trunks that can be active on a card through Cisco WAN Manager or the CLI. The applicable CLI command is cnftrkport. For example, if you intend an eight-port card to have two logical (IMA) trunks, you can use cnftrkport to specify a maximum number of two trunks. Software would therefore reserve 540 connections for network messages rather than the 2160 connections if you did not specify a maximum.

Inverse Multiplexing over ATM on IGX Trunks

Inverse Multiplexing over ATM (IMA) lets you group physical T1 or E1 lines to form a logical trunk. A logical trunk consisting of more than one T1 or E1 line supports connections with data rates that are much higher than the T1 or E1 rate. System software lets you specify IMA so that one or more physical lines within the logical trunk can serve as backup if a line fails.

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