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ATM Service Networking. Transparent Transmission. Transparent transmission of ATM service. Multicast of ATM service, страница 4

The typical configurations of NE1, NE2, and NE3 are the same, as shown in Figure 5-4.

Figure 5-4 Typical configuration of NE1

The typical configuration of NE4 is shown in Figure 5-5.

Figure 5-5 Typical configuration of NE4

5.4  VP-Ring

VP-Ring is the protection for ATM service. It is realized through dual-fed signal selection. That is, the ATM processing module of the ATM processing board transmits services from both east and west side of the transmit end, and the ATM processing module of the ATM processing board at the receive end receives the services from one of the two directions. In transmitting direction, the ATM service accessed from the ATM optical interface is transmitted to A and B after passing the ATM processing module, as shown in Figure 5-6. Then, the SDH cross-connect module transmits the signal in both east and west directions. In receiving direction, the ATM processing module only processes one channel of signal from either A or B, and transmits the signal to the ATM optical interface.

Figure 5-6 Realization of VP-Ring

The VP-Ring protection may co-exist with SDH protection scheme. Two protection modes are preferable:

n  Bidirectional multiplex section ring and VR-Ring

In this case, you should set the switching delay time for VP-Ring protection. When the switching condition is satisfied, the SDH protection is enabled first and the VP-Ring is started only when the SDH protection fails, thus achieving the protection layer by layer.

n  Non-protection ring and VP-Ring

In this case, the switching delay time for VP-Ring protection should be set to zero. Then, VP-Ring is the first level protection.

Other protection modes of SDH may work together with the VP-Ring, but the configuration is complicated relatively and more bandwidth is occupied. Thus, it is not recommendable.

1.  Service Requirement

It is the same as what shown in section 5.3 “Statistical Multiplexing”.

ATM services adopt VP-Ring protection. There is no protection at SDH layer.

2.  Application

The network diagram is the same as what shown in section 5.3 “Statistical Multiplexing”.

3.  Implementation

Implementation

Statistical multiplexing: Multiplex the ATM services that NE2, NE3 and NE4 access from DSLAM into a VC-4, converge the VC-4 to a port of NE1 and transmit it to the upper ATM switch.

Hardware configuration

Configure an ADQ1 board at NE1 to converge ATM services of other nodes and transmit them to the upper ATM switch through a 155 Mbit/s port.

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

In NE4, configure ADQ1 and PL3 boards at NE4 to access 34 Mbit/s ATM services and share the bandwidth on the ring.

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.

NE1

NE2

NE3

NE4

PCR: 283020 cells/s

CDVT: 500ms

PCR: 23585 cells/s

CDVT: 500ms

PCR: 47170 cells/s

CDVT: 500ms

PCR: 47170 cells/s

CDVT: 500ms

PCR: 70755/s

CDVT: 500ms

Service route

NE1

NE2

NE3

NE4

ATM external port 1 (1–7,1) ïð ATM internal port 1 (1–7,1) ïð VC-4

10 Mbit/s service 1: ATM external port 1 (1,1) ïð ATM internal port 1 (1,1) ïð VC-4

Pass-through service: ATM internal port 1 (1–3,1) ïð ATM internal port 2 (1–3,1) ïð VC-4

Pass-through service: ATM internal port 1 (1–5,1) ïð ATM internal port 2 (1–5,1) ïðVC-4

10 Mbit/s service 2: ATM external port 2 (2,1) ïð ATM internal port 1 (2,1) ïð VC-4

10 Mbit/s service 3: ATM external port 3 (3,1) ïð ATM internal port 1 (3,1) ïð VC-4

-

20 Mbit/s service 1: ATM external port 1 (4,1) ïð ATM internal port 2 (4,1) ïð VC-4

-

20 Mbit/s service 2: ATM external port 2 (5,1) ïð ATM internal port 2 (5,1) ïð VC-4

Service route

-

-

20 Mbit/s service 1: PL3 interface ïð ATM external port 1 (6,1) ïð ATM internal port 2 (4,1) ïð VC-4

-

-

30 Mbit/s service 1: ATM external port 2 (7,1) ïð ATM internal port 2 (7,1) ïð VC-4

Note: The ATM external port 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.

Protection route

This example adopts VP-Ring at the ATM layer, and the switching time is no more than 50ms.

NE1

NE2

NE3

NE4

ATM external port 1 (1–7,1) ïð ATM internal port 2 (1–7,2) ïð VC-4

10 Mbit/s service 1: ATM external port 1(1,1) ïð ATM internal port 2 (1,2) ïð VC-4

-

-

10 Mbit/s service 2: ATM external port 2 (2,1) ïð ATM internal port 2 (2,2) ïð VC-4

-

-

10 Mbit/s service 3: ATM external port 3 (3,1) ïð ATM internal port 2 (3,2) ïð VC-4

-

-

Pass-through service: ATM internal port 3 (4–7,2) ïð ATM internal port 2 (4–7,2) ïð VC-4

20 Mbit/s service 1: ATM external port 1(4,1) ïð ATM internal port 3 (4,2) ïð VC-4

-

20 Mbit/s service 2: ATM external port 2 (5,1) ïð ATM internal port 3 (5,2) ïð VC-4

-

Protection route

Pass-through service: ATM internal port 4 (6–7,2) ïð ATM internal port 3 (6–7,2) ïð VC-4

20 Mbit/s service 1: PL3 interface ïð ATM external port 1 (6,1) ïðATM internal port 3 (4,2) ïðVC-4

30 Mbit/s service 1: ATM external port 2 (7,1) ïð ATM internal port 3 (7,2) ïð VC-4
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