Hardware for STM-1 (upto 63 E1)

System Hardware

Chasis

The VCL100MC-1 (upto 63 E1) is a 19" wide, 5.25" high 3 tributary-slot chassis, in a half-depth rack allowing back-to-back arrangement for VCL100MC-1s. This chassis can be installed in both 19" and 23" rack with suitable adapters.

Line sketch of the chassis

Faceplate layout

Hardware components

Chasis

The base chassis houses the following:

STM-1 interfaces: 1 or 2 STM-1 optical / electrical interfaces depending on Terminal multiplexer or Add-Drop Multiplexer configuration.

Cross Connect : A cross-connect fabric for 4x4 STM-1 with granularity of VC-12 (i.e 252x252) and VC-3 (i.e. 12x12) is built into the base chassis.

Management interfaces: This is provided through the 10/100 Mbps NMS (Ethernet) port or an RS232C craft port.

Timing Interfaces: External 2Mbps or 2.048 MHz timing signal inputs are provided for synchronizing the equipment.

Order-wire: This is provided through the analog 2-wire interface. The EOW bytes are software selectable to E1 or E2.

Alarms: These provide dry contacts for extending the alarms. Five such potential free outputs are provided that are tied to alarms for Critical, Major, Minor, Order Wire and Power. Two potential free inputs are provided for environmental alarms like "Power or Air-conditioning failure", " equipment room door open" etc.

Auxiliary Ethernet interface: A single Ethernet interface is available to carry Ethernet data traffic over SDH. This is mapped to a single VC-12 on the aggregate side. This interface is optional.

Power supply and Management Interfaces:

28xE1/DS3 Tributary Card
Up to three 28 E1/DS1 tributary cards are supported in a single VCL100MC-1 chassis, the maximum in a single chassis being 63 E1 (maximum number for E1s) or 84 DS1 (maximum number for DS1) interfaces.

1xE3/DS3 Tributary Card
Up to three 1xE3/DS3 tributary cards are supported in a VCL100MC-1 chassis. E3 traffic is carried in an AU4 mode.

1/2xSTM-1optical / electrical, 140 Mbps Tributary Card
Can support one 1-port STM-1 optical or electrical card. All STM-1 interfaces need to be configured in the same mapping mode viz., AU3 or AU4, as the case maybe. STM-1e and 140 Mbps interfaces are software configurable.

8-Port 10/100 Mbps Ethernet Tributary Card
The 8-port Ethernet Tributary Card maps 10/100 Mbps Ethernet data on to VC-12's with a rate adaptation granularity of 2 Mbps. Each port's bandwidth is configurable in increments of 2Mbps, based on per port user demand. The aggregate bandwidth from each ETC card is at most STM-1 line rate (63 VC-12 worth of traffic). It also supports auto-negotiation and auto-sensing with full rate 10/100 Mbps Ethernet service. Ingress Ethernet traffic is shaped using flow control as per the standard IEEE 802.3x by using PAUSE control frames. This card is compliant to ITU-T X.86 and supports Virtual Concatenation.

Power Supply Unit
Power to all the cards in the chassis is distributed from this unit accessible from the rear. This is a hot-insertible, hot stand-by current sharing power supply, running off a -36V to -60V DC supply. This would supply power to all the cards. This can be configured to be redundant.

Synchronization

VCL100MC-1 can derive its clock from a variety of sources. VCL100MC-1 could be line-timed, externally timed or could derive its clock from its own internal Stratum-3 source. In a line-timed mode, it derives its clock from any one of the E1 tributaries or STM-1 signals. In an externally timed mode, an external 2048 KHz or 2 Mbps signal could be used as the clock source. If none of these sources are available, VCL100MC-1 goes into a holdover mode when it uses the stored timing data to control the output frequency for a short duration (of around 24 hrs). Beyond this it uses its own internal oscillator in a free-running mode.

VCL100MC-1 also supports Synchronization Status Messaging (SSM) as per ITU-T standards. This is a messaging technique, which enables a SDH equipment to determine the derivation of timing source. It uses overhead bytes contained within the SDH overhead (S1) for transmitting these messages. Thus when a failure occurs, elements communicate timing reconfiguration information across the network.

A 2.048 M BITS clock output is available from the system, which can be set to either a 2.048 MHz clock or a framed E1 data at 2.048 Mbps.

Related Links

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