Cisco Systems IGX 8400 manual Cable Redundancy for the NTM, NTM Status, Network Trunk Module

Network Trunk Module

Network Trunk Module

The network trunk module (NTM) enables FastPacket transmission on a trunk. NTM functions include the following:

•Takes FastPackets off the cellbus and places them in queues before transmission to the trunk

•Arbitrates access to the trunk for the traffic type

•Monitors the age of each timestamped FastPacket, updates the timestamp for FastPackets at intermediate nodes, and discards FastPackets that exceed age limit

•

•

•

•

Receives and checks FastPackets from the trunk and queues them for transmission to the cellbus

Provides packet alignment based on the CRC in the FastPacket header

Extracts clocking from the trunk that can be used as a clock source on the node or as a clock path

Collects trunk usage statistics

Note The NTM card exists in two forms. One uses an ACM1 adaptor, and the other is a single-card or “native” version. They are functionally identical, but their firmware is not interchangeable. The native NTM requires revision F or later firmware.

An NTM can occupy any available front service card slot in the range 3 to 32. The choice of back card depends on the trunk interface type.

For fractional T1 trunk lines, the NTM and BC-T1 card set can provide the interface. A fractional trunk interface uses a group of 64-Kbps channels to create a partial T1 trunk. For example, a

512-Kbps fractional T1 trunk might use every third channel among channels 1 to 24. The user makes the channel assignments. For the clock rate, fractional trunks use the basic trunk frequency (such as 1.544 Mbps for T1).

Fractional E1 is the same as fractional T1 except that the channels are 1 to 15 and 17 to 31 (0 and 16 reserved), and the clock rate is 2.048 Mbps.

The NTM supports subrate trunks if a BC-SR back card and appropriate local bus are present. Subrate trunks interface to the transmission facility at rates in the range 64 Kbps to 2.048 Mbps. Three interface connections are possible: EIA/TIA-449, X.21, and V.35.

Y-Cable Redundancy for the NTM

You can configure the NTM for 1:1 redundancy by using a second, identical, card group in an adjacent slot and a Y-cable to connect the card sets. All NTM back cards support redundancy.

NTM Status

The faceplate of the NTM has four LEDs. The first two in the following list apply to the NTM front card. Each of the other two LEDs is a summary alarm for the back cards. Their significance is:

•The green Active LED indicates the NTM is active and functioning normally.

•The red Fail LED indicates an NTM card failure was detected.

•The yellow Minor LED indicates non-service-interrupting faults or statistical errors that have exceeded a preset threshold.

•The red Major LED indicates a service-affecting failure was detected.

Trunk Cards 4-37