Datasheet

1-2

PA-MC-T3 Port Adapter Installation and Configuration

OL-2695-05

Chapter 1 Overview

Multichannel T3 Overview

The PA-MC-T3 T3 link is channelized into 28 independent T1 data lines. Each T1 line can be

unchannelized or channelized for serial transmission of data.

Each of the T1 lines can use the whole T1 bandwidth, a portion of the T1 bandwidth, or the T1 bandwidth

in channelized form for data transmission. Usable bandwidths for each T1 line are n x 56 kbps or n x 64

kbps, where n is a number representing time slots 1 to 24. Channelized T1 allows up to 24 time slots

(56 kbps/64 kbps) per T1 line. The unused portion of the T1 bandwidth, when not running at full T 1

speeds, cannot be used and is filled with idle channel data. Aggregation of multiple T1 lines is not

supported. The PA-MC-T3 can support a maximum of 128 logical channels.

Note T1 lines on the PA-MC-T3 are numbered 1 to 28 instead of the more traditional zero-based scheme (0 to

27) used with other Cisco products. This is to ensure consistency with telco numbering schemes for T1

lines within channelized (multi-channel) T3 equipment.

The T3 section of the PA-MC-T3 supports the maintenance data link channel (when using c-bit parity)

as well as payload and network loopbacks. The T1 section of the PA-MC-T3 supports facilities data link

(FDL) in Extended Superframe (ESF) framing, as well as various loopbacks. Bit error rate (BER) testing

is supported on each of the T1 lines. Testing is typically done over an unframed T1 signal.

The PA-MC-T3 supports Cisco High-Level Data Link Control (HDLC), Frame Relay, PPP, and SMDS

Data Exchange Interface (DXI) encapsulations over each T1 link. For Switched Multimegabit Data

Service (SMDS) only, DXI is sent on the T1 line, so it needs to connect to an SMDS switch that has

direct DXI input.

Note The PA-MC-T3 does not support the aggregation of multiple T1 lines (called inverse multiplexing, or

bonding) for higher bandwidth data rates.

The physical T3 link on the PA-MC-T3 consists of two female BNC connectors, one for receive (RX)

and one for transmit (TX). You must use 75-ohm RG-59 coaxial interface cables with male BNC

connectors to connect the PA-MC-T3 interface with external T3 equipment. (For cable information, refer

to the “Cables, Connectors, and Pinouts” section on page 1-5.)

Any of the 28 T1 lines can be configured as channelized T1 lines. You can group the time slots in these

T1 lines into several individual logical channel groups, each of which carries data with different

data-link layer protocol encapsulations.

Each logical channel group can be composed of individual 56-kbps or 64-kbps time slots, or individual

time slots plus ranges of time slots; for example, a channel group might be composed of time slots 1, 9,

and 12–14. Each logical channel group can contain from 1 to 24 time slots maximum; the same time slot

cannot be used in more than one logical channel group. Any unused time slots are filled with

programmable idle-channel data.

Each T1 line contains onboard T1 bit error rate test (BERT) circuitry. With this, the port adapter software

can send and detect programmable patterns, and you can run a BERT on any T1 line or all of the 28 T1

lines simultaneously.

Note Onboard T3 BER testing is not supported.