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OptiX OSN 7500 Intelligent Optical Switching System. Technical Manual - part 6

VLAN 3

Traffic

Tunnel

VC

Destination

Port1+VLAN 2

200

200

Node 2

Port1+VLAN 3

300

300

Node 3

VLAN 4

Port1+VLAN 4

400

400

Node 4

GE

Node 1

FE

FE

VLAN 2

Node 2

Node 4

VLAN 4

Dual-ring

2.5 Gbit/s RPR

Node 3

FE

VLAN 3

Figure 6-14 EVPL service convergence

2. EVPLAN

The EVPLAN service supports traffic classification based on port or port + VLAN, and

encapsulates and forwards the traffic in the form of MPLS VMAN. The EVPLAN

service is realized by creating virtual bridge (VB) in the board. Each board may have

up to 32 VBs, each of which has 16 logic ports. VB supports source MAC address

learning and static MAC route configuration. Figure 6-15 shows an example of

EVPLAN service. The VB of each node determines the forward port of packets

through address learning, rpr1 is the port to access packets to the RPR. For node 1, if

the destination address is A1, the packet is forwarded through port 1; if the destination

is A2, the packet is forwarded through port 2. If the destination is B1, B2 or C1, the

packet is forwarded through port rpr1 to the RPR, added with a VMAN label being 100.

Node 2 forwards packets in the same way.

6-16

A2

MAC forwarding table of node 1

MAC

Port

VMAN

Port 1

Port 2

A1

port 1

none

A2

port 2

none

B1

rpr1

100

Node 1

B2

rpr1

100

B1

C1

rpr1

100

Dual-ring

2.5 Gbit/s RPR

Port 1

Node 2

Node 4

Port 2

B2

MAC forwarding table of node 2

Node 3

MAC

Port

VMAN

A1

rpr1

100

A2

rpr1

100

Port 1

B1

port 1

none

B2

port 2

none

C1

C1

rpr1

100

Figure 6-15 EVPLAN service

6.2.3 Protection

The RPR service of the OptiX OSN equipment takes the protection of several levels,

including:

„ Wrapping and Steering

„ Spanning tree and LCAS

„ Protection of optical transmission layer, such as MSP and SNCP

1. Wrapping

If an equipment or facility failure is detected, the traffic is wrapped back to the opposite

direction at the stations adjacent to the failure, connecting the outer ring with the inner

ring. The protection switching time is less than 50ms. Though featuring fast protection

switching, wrapping protection wastes bandwidth. As illustrated in Figure 6-16, traffic

is transferred from node 4 to node 1 through nodes 3 and 2. If there is a fiber cut

between node 2 and node 3, they will wrap the traffic and connect the two rings

together for protection.

6-17

Fiber cut

Traffic flow

X

Node 3

Node 1

Dual-ring

2.5 Gbit/s RPR

Node 6

Node 4

Node 5

Figure 6-16 Wrapping protection

2. Steering

For steering protection, a station shall not wrap a failed segment when a failure is

detected. Instead, the source node will send traffic to the destination through a route

avoiding the failed link. The protection switching time is less than 50ms. The steering

protection does not waste bandwidth, however, it needs longer switching time and

some data before setting up a route may be lost. Figure 6-17 illustrates an example of

steering protection. Node 4 sends traffic to node 1 on the outer ring through nodes 3

and 2. If there is a fiber cut between node 2 and node 3, the topology discovery

function can help the traffic be transferred to node 1 over the inner ring through nodes

5 and 6.

6-18

Fiber cut

Traffic flow before

switching

X

Dual-ring

Node 3

Node 1

2.5 Gbit/s RPR

Traffic flow

Node 6

Node 4

after switching

Node 5

Figure 6-17 Steering protection

3. Spanning Tree and LCAS

For details about spanning tree and LCAS, refer to “6.1 Ethernet”.

6.3 ATM Features

This section describes the ATM features of the OptiX OSN 7500 in terms of

functionality, application, and protection.

6.3.1 Functions

The OptiX OSN 7500 provides four different ATM processing boards: ADL4, ADQ1,

IDL4 and IDQ1. The IDL4 and the IDQ1 support inverse multiplexing for ATM (IMA).

An ADL4/IDL4 board can access and process one STM-4 ATM service and an

ADQ1/IDQ1 board can access and process four STM-1 ATM services. When working

with the PL3/PD3 board, the ADL4 board or ADQ1 board can access and process E3

ATM services. The functions of the four boards are listed in Table 6-4.

Table 6-4 Functions of the four ATM boards

Board

ADL4/IDL4

ADQ1/IDQ1

Function

Front panel interface

1 x STM-4

4 x STM-1

Optical interface index

S-4.1, L-4.1

I-1, S-1.1, L-1.1

Optical interface type

Hot swappable LC (SFP)

Hot swappable LC (SFP)

6-19

ADL4/IDL4

ADQ1/IDQ1

Function

E3 ATM interface

Access 12 x E3 services

Access 12 x E3 services

through the PD3/PL3 board

through the PD3/PL3 board

Maximum uplink

8 VC4s, or 12 VC3s + 4

8 VC4s, 12 VC3s + 4 VC4s

bandwidth

VC4s

ATM switching capability

1.25 Gbit/s

1.25 Gbit/s

Mapping mode

VC3, VC4, VC4-4c, or

VC3, VC4, VC4-4c,

VC4-Xv (X=1 - 4)

VC4-Xv (X=1 - 4)

Processable service types

CBR, rt-VBR, nrt-VBR and

CBR, rt-VBR, nrt-VBR and

UBR

UBR

Number of ATM

8000

8000

connections

Traffic type and QoS

IETF RFC2514

IETF RFC2514

Supportable ATM

Spatial multicast and logic

Spatial multicast and logic

multicast connections

multicast

multicast

ATM protection (ITU-T

Unidirectional/bidirectional

Unidirectional/bidirectional

I.630)

1+1/1:1 VPRing or VCRing

1+1/1:1 VPRing or VCRing

OAM function (ITU-T

AIS, RDI, LB (Loopback),

AIS, RDI, LB, CC

I.610)

CC (continuity check)

6-20

1. Supportable Services and Traffic Types

The OptiX OSN 7500 supports CBR, rt-VBR, nrt-VBR, and UBR services rather than

ABR services. CBR services apply to voice services, as well as video services and

circuit simulation services of a constant bit rate. These services require guaranteed

transmission bandwidth and latency. Rt-VBR services apply to audio and video

services of a variable bit rate. Nrt-VBR services are mainly used for data transmission.

UBR services are generally used for LAN simulation and file transmission. In terms of

the supported service and traffic types, the OptiX OSN 7500 meets IETF RFC2514,

ATM Forum TM 4.0 and ATM Forum UNI 3.1 recommendations, as shown in the Table

6-5..

Table 6-5 Supportable ATM service and traffic types of the OptiX OSN 7500

No.

Traffic type

Service type

Parameter

1

atmNoTrafficDescriptor

UBR

None

2

atmNoClpNoScr

UBR.1

Clp01Pcr

CBR

Clp01Pcr

3

atmClpNoTaggingNoScr

CBR

Clp01Pcr, Clp0Pcr

4

atmClpTaggingNoScr

CBR

Clp01Pcr, Clp0Pcr

5

atmNoClpScr

nrt-VBR.1

Clp01Pcr, Clp01Scr, Mbs

6

atmClpNoTaggingScr

nrt-VBR.2

Clp01Pcr, Clp0Scr, Mbs

7

atmClpTaggingScr

nrt-VBR.3

Clp01Pcr, Clp0Scr, Mbs

8

atmClpNoTaggingMcr

ABR

Clp01Pcr, Cdvt, Mcr

9

atmClpTransparentNoScr

CBR.1

Clp01Pcr, Cdvt

10

atmClpTransparentScr

rt-VBR.1

Clp01Pcr, Clp01Scr, Mbs,

Cdvt

11

atmNoClpTaggingNoScr

UBR.2

Clp01Pcr, Cdvt

12

atmNoClpNoScrCdvt

UBR

Clp01Pcr, Cdvt

CBR

Clp01Pcr, Cdvt

13

atmNoClpScrCdvt

rt-VBR.1

Clp01Pcr, Clp01Scr, Mbs,

Cdvt

14

atmClpNoTaggingScrCdvt

rt-VBR.2

Clp01Pcr, Clp0Scr, Mbs, Cdvt

15

atmClpTaggingScrCdvt

rt-VBR.3

Clp01Pcr, Clp0Scr, Mbs, Cdvt

6-21

2. Application of Band Exclusive ATM Services

When the bandwidth is not shared, ATM services at the source and sink NEs are only

processed at the ATM layer through the ATM service process board. On intermediate

NEs, only SDH timeslot pass-through is performed, without ATM layer processing. In

this case, each ATM service has the whole VC3/VC4 channel to itself. The ATM

services are converged at the central node and then multiplexed to an STM-1 or

STM-4 optical port for output. As shown in the Figure 6-18, the 34 Mbit/s ATM services

of NE1 and NE3 each occupy a VC3 bandwidth. The 155 Mbit/s ATM service of NE2

occupies a VC4 bandwidth alone. SDH timeslot pass-through is only performed at

NE3. After they reach the central site NE4, they are converged through the ATM board

and output through the 622 Mbit/s optical interface.

DSLAM

34M ATM

Traffic

Service

Convergence

NE 1

155M ATM

2.5 Gbit/s SDH

622M ATM

Traffic

Ring

Traffic

NE 2

NE 4

Router

DSLAM

NE 3

34M ATM

Traffic

DSLAM

Figure 6-18 Application of Band exclusive ATM Services

3. Application of Band-Shared ATM Services

In shared rings VR-Ring and VC-Ring, the ATM services share the same bandwidth

and are multiplexed statistically. The ATM services on each NE share the same VC

(VC3, VC4, or VC-Xv) and are all processed on ATM layer. As shown in the Figure

6-19, NE1 accesses E3 ATM traffic through the tributary board and sends it to the ATM

board for ATM switching and protection (1+1/1:1) configuration. Then the traffic is

encapsulated into VC4-Xv and sent to the line through the cross-connect board. NE2

6-22

switching and protection configuration. The ATM traffic from NE1 is also dropped at

NE2 for ATM layer processing. Then the locally accessed traffic and that from NE1 are

encapsulated into the same VC4-Xv and sent to the next NE. The same goes at NE3

and NE4. A single VP/VC-Ring can have a maximum bandwidth of 300 Mbit/s.

The ATM traffic from NE1

DSLAM

is droped to the NE2, then

send to VP/VC-Ring after

34M ATM

converged with local

Traffic

NE 1

service.

155M ATM

Traffic

NE 4

Router

VC4-Xv

VP/VC-Ring

622M ATM

DSLAM

NE 2

Traffic

NE 3

34M ATM

Traffic

DSLAM

Figure 6-19 VP/VC-Ring

6.3.3 Protection

The ATM service of the OptiX OSN equipment is protected on many layers, including:

„ Protection on the ATM layer

„ Protection on the optical transmission layer, such as MSP, and SNCP.

1. Protection on the ATM Layer

Compliant with ITU-T Recommendation I.630, protection on the ATM layer can be

classified into many types according to different classification method, as shown in the

Table 6-6. You can select the configuration as required, for example, 1+1 bidirectional

non-revertive protection”.

Table 6-6 Classification of ATM protection

Classification mode

1+1 protection

1:1 protection

Switching direction

Unidirectional protection

Bidirectional protection

Connection level

VPC protection

VCC protection

6-23

aturesOSN 7500

Technical Manual - System Description

7 Intelligent Features

preconfigured route; support span protection and end-to-end service protection,

improving the scalability of the network.

7.1 SLA Service

1. Classification of SLA Service

The SLA service can be classified into multiple levels in terms of protection (high level

service, medium level service, reroute service, unprotected service and extra service,

and so on). Charges vary with the service levels and thus demands of different users

can be satisfied flexibly. The principle for classifying services is as follows:

„ High level service: Provided with 1+1 protection or alike, with the switch-ing time of

0-50ms.

„ Medium level service: Provided with M:N protection or alike (for example, two-fiber

MSP), with the switching time of 0-50ms.

„ Reroute service: Recalculate the path in real time, with the switching time from

100ms to several seconds.

„ Unprotected service: Provided with no protection in the case of any fault.

„ Extra service: Pre-empted by services with higher priorities when the network

resource is insufficient.

2. SLA-Based Protection at Different Service Levels

With the SLA service provided, the OptiX OSN 7500 enables the operators to win

more customers in a differentiated market with better service and lower cost.

Table 7-1 Differential protection for service at different levels

Service level

Protection level

Service quality

Diamond

High level protection

The QoS increases higher from

bottom up

Gold

Medium level protection

Silver

Rerouting protection

Copper

Non-protection

Iron

Preemptive

Diamond level service is to meet demands of users such as banks, securities,

important government offices, and so on. Gold level service is to satisfy the demands

for speech, multimedia and video. Silver level service is applicable to common data

service transmission. Services of copper and iron levels are suitable for applications

such as family network access

7-2

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