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ATM Service Networking. Transparent Transmission. Transparent transmission of ATM service. Multicast of ATM service, страница 2

Multicast services are carried over SDH directly. Each service occupies a bandwidth, and thus the bandwidth utilization is low.

1.  Service Requirement

City 1 needs to broadcast unidirectional ATM services (TV program) to city 2, city 3 and city 4. The ATM services are accessed from the ATM switch over a 50 Mbit/s bandwidth.

The ATM switch in city 1 provides an external 155 Mbit/s optical interface with the service type of CBR.

2.  Application

The ATM service processing board in the OptiX OSN 3500 can broadcast ATM services unidirectionally. Figure 5-2 shows the networking diagram.

NE1 (central node in city 1) adopts the OptiX OSN 3500 to access ATM services from the ATM switch, and then broadcast the services to NE2 (city 2), NE3 (city 3), and NE4 (city 4).

NE2, NE3, and NE4 (end offices) adopt the OptiX OSN 3500 to receive ATM services from NE1.

Figure 5-2 Multicast of ATM service

3.  Implementation

Implementation

Point-to-multipoint transmission

The ATM services accessed from the ATM switch are duplicated on the OptiX OSN 3500 and then transmitted to NE2, NE3, and NE4.

Hardware configuration

Configure an ADQ1 board at NE1 to access the 155 Mbit/s ATM service from the ATM switch.

Configure an ADQ1 board at NE2, NE3, and NE4 respectively to access the broadcast service from NE1.

For slots of the ADQ1 board, refer to “Appendix A Network Configuration Requirements”.

Traffic control

In this example, the type of ATM service is CBR and the traffic parameters PCR and CDVT should be set. The traffic parameters of each ATM service connection are the same.

PCR: 117925 cells/s

CDVT: 500ms

Service route

NE1

NE2

NE3

NE4

Root connection: ATM external port 1 (1,1) ð ATM internal port 1 (1,1) ð VC-4 (No.1)

p2p connection: VC-4 (No.1) ð ATM internal port 1 (1,1) ð ATM external port 1 (1,1)

-

-

Leaf connection: ATM external port 1 (1,1) ð ATM internal port 2 (2,1) ð VC-4 (No.2)

VC-4 pass-through

p2p connection: VC-4 (No.2) ð ATM internal port 1 (2,1) ð ATM external port 1 (2,1)

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Leaf connection: ATM external port 1 (1,1) ðATM internal port 2 (3,1) ðVC-4 (No.3)

-

-

p2p connection: VC-4 (No.3) ð ATM internal port 1 (3,1) ð ATM external port 1 (3,1)

Note:

1. The ATM external port of ADQ1 is the external optical port used to access ATM services, while the ATM internal port refers to the logical port used to connect the ATM processing module and the SDH cross-connect module.

2. The service received by NE2, NE3 and NE4 are duplicated in the central node NE1. Therefore, it is necessary to create a root connection and two unidirectional leaf connections. The service over the leaf connection is duplicated from the root connection.

Protection

The service can be protected by the protection scheme of SDH equipment networking.

5.3  Statistical Multiplexing

The statistical multiplexing feature of the ATM service is widely used to multiplex ATM services accessed from different stations into one VC-4. Then converge it to a port of the central node to transmit to the ATM switch at the upper layer. This feature can save bandwidth and port resources.

1.  Service Requirement

A city needs to construct a new communication network among four NEs. Services accessed from DSLAM (ATM equipment) are to be transmitted to the ATM switch in the central node - NE1. The ATM switch in NE1 provides a 155 Mbit/s optical interface to access ATM services from other NEs.

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