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Configuring SAToP Emulation on Channelized T1 and E1 Interfaces

This configuration is the base configuration of SAToP on an ACX Series router as described in RFC 4553, Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP). When you configure SAToP on built-in channelized T1 and E1 interfaces, the configuration results in a pseudowire that acts as a transport mechanism for the T1 and E1 circuit signals across a packet-switched network.

The network between the customer edge (CE) routers appears transparent to the CE routers, making it seem that the CE routers are directly connected. With the SAToP configuration on the provider edge (PE) router’s T1 and E1 interfaces, the interworking function (IWF) forms a payload (frame) that contains the CE router’s T1 and E1 Layer 1 data and control word. This data is transported to the remote PE over the pseudowire. The remote PE removes all the Layer 2 and MPLS headers added in the network cloud and forwards the control word and the Layer 1 data to the remote IWF, which in turn forwards the data to the remote CE.

Figure 1: Pseudowire Encapsulation with SAToP

In Figure 1 the Provider Edge (PE) router represents the ACX Series router that is being configured in these steps. The result of these steps is the pseudowire from PE1 to PE2. Topics include:

Setting the T1/E1 Emulation Mode

Emulation is a mechanism that duplicates the essential attributes of a service (such as T1 or E1) over a packet-switched network. You set the emulation mode so that the built-in channelized T1 and E1 interfaces on the ACX Series router can be configured to work in either T1 or E1 mode. This configuration is at the PIC level, so all ports operate as either T1 interfaces or E1 interfaces. A mix of T1 and E1 interfaces is not supported. By default all the ports operate as T1 interfaces.

Configure the emulation mode:

[edit chassis fpc fpc-slot pic pic-slot]
user@host# set framing (t1 | e1)

For example:

[edit chassis fpc 0 pic 0]
user@host# set framing t1

After a PIC is brought online and depending on the framing option used (t1 or e1), on the ACX2000 router, 16 CT1 or 16 CE1 interfaces are created, and on the ACX1000 router, 8 CT1 or 8 CE1 interfaces are created.

The following output shows this configuration:

user@host# show chassis
fpc 0 {
    pic 0 {
        framing t1;
    }
}

The following output from the show interfaces terse command shows the 16 CT1 interfaces created with the framing configuration.

user@host# run show interfaces terse
Interface               Admin Link Proto    Local                 Remote
ct1-0/0/0               up    down
ct1-0/0/1               up    down
ct1-0/0/2               up    down
ct1-0/0/3               up    down
ct1-0/0/4               up    down
ct1-0/0/5               up    down
ct1-0/0/6               up    down
ct1-0/0/7               up    down
ct1-0/0/8               up    down
ct1-0/0/9               up    down
ct1-0/0/10              up    down
ct1-0/0/11              up    down
ct1-0/0/12              up    down
ct1-0/0/13              up    down
ct1-0/0/14              up    down
ct1-0/0/15              up    down

Note: If you set the framing option incorrectly for the PIC type, the commit operation fails.

If you change the mode, the router will reboot the built-in T1 and E1 interfaces.

Bit error rate test (BERT) patterns with all ones received by T1 and E1 interfaces configured for SAToP do not result in an alarm indication signal (AIS) defect. As a result, the T1 and E1 interfaces remain up.

Configuring One Full T1 or E1 Interface on Channelized T1 and E1 Interfaces

You must configure a child T1 or E1 interface on the built-in channelized T1 or E1 interface created because the channelized interface is not a configurable interface and SAToP encapsulation must be configured (in the next step) for the pseudowire to function. The following configuration creates one full T1 interface on the channelized ct1 interface. You can follow the same process to create one E1 interface on the channelized ce1 interface.

Configure one full T1/E1 interface:
[edit interfaces ct1-fpc/pic /port]
user@host# set no-partition interface-type (t1 | e1)
For example:
[edit interfaces ct1-0/0/0
user@host# set no-partition interface-type t1
The following output shows this configuration:
```
[edit]
user@host# show interfaces
ct1-0/0/0 {
    no-partition interface-type t1;
}
```

The preceding command creates the t1-0/0/0 interface on the channelized ct1-0/0/0 interface. Check the configuration with the show interfaces interface-name extensive command. Run the command to display output for the channelized interface and the newly created T1 or E1interface. The following output provides an example of the output for a CT1 interface and the T1 interface created from the preceding example configuration. Notice that ct1-0/0/0 is running at T1 speed and that the media is T1.

user@host> show interfaces ct1-0/0/0 extensive   
Physical interface: ct1-0/0/0, Enabled, Physical link is Up
  Interface index: 152, SNMP ifIndex: 780, Generation: 1294
  Link-level type: Controller, Clocking: Internal, Speed: T1, Loopback: None, Framing: ESF, Parent: None
  Device flags   : Present Running
  Interface flags: Point-To-Point SNMP-Traps Internal: 0x0
  Link flags     : None
  Hold-times     : Up 0 ms, Down 0 ms
  CoS queues     : 8 supported, 4 maximum usable queues
  Last flapped   : 2012-04-03 06:27:55 PDT (00:13:32 ago)
  Statistics last cleared: 2012-04-03 06:40:34 PDT (00:00:53 ago)
  DS1   alarms   : None
  DS1   defects  : None
  T1  media:            Seconds        Count  State
    SEF                          0            0  OK
    BEE                          0            0  OK
    AIS                          0            0  OK
    LOF                          0            0  OK
    LOS                          0            0  OK
    YELLOW                       0            0  OK
    CRC Major                    0            0  OK
    CRC Minor                    0            0  OK
    BPV                          0            0
    EXZ                          0            0
    LCV                          0            0
    PCV                          0            0
    CS                           0            0
    CRC                          0            0
    LES                          0
    ES                           0
    SES                          0
    SEFS                         0
    BES                          0
    UAS                          0
    Line encoding: B8ZS
    Buildout       : 0 to 132 feet
  DS1 BERT configuration:
    BERT time period: 10 seconds, Elapsed: 0 seconds
    Induced Error rate: 0, Algorithm: 2^15 - 1, O.151, Pseudorandom (9)
  Packet Forwarding Engine configuration:
    Destination slot: 0 (0x00)

In the following output for the T1 interface, the parent interface is shown as ct1-0/0/0 and the link level type and encapsulation are TDM-CCC-SATOP.

user@host> show interfaces t1-0/0/0 extensive    
Physical interface: t1-0/0/0, Enabled, Physical link is Up
  Interface index: 160, SNMP ifIndex: 788, Generation: 1302
  Link-level type: TDM-CCC-SATOP, MTU: 1504, Speed: T1, Loopback: None, FCS: 16, Parent: ct1-0/0/0 Interface index 152
  Device flags   : Present Running
  Interface flags: Point-To-Point SNMP-Traps Internal: 0x0
  Link flags     : None
  Hold-times     : Up 0 ms, Down 0 ms
  CoS queues     : 8 supported, 4 maximum usable queues
  Last flapped   : 2012-04-03 06:28:43 PDT (00:01:16 ago)
  Statistics last cleared: 2012-04-03 06:29:58 PDT (00:00:01 ago)
  Egress queues: 8 supported, 4 in use
  Queue counters:       Queued packets  Transmitted packets      Dropped packets
    0 best-effort                    0                    0                    0
    1 expedited-fo                   0                    0                    0
    2 assured-forw                   0                    0                    0
    3 network-cont                   0                    0                    0
  Queue number:         Mapped forwarding classes
    0                   best-effort 
    1                   expedited-forwarding
    2                   assured-forwarding
    3                   network-control
  DS1   alarms   : None
  DS1   defects  : None
  SAToP configuration:
    Payload size: 192
    Idle pattern: 0xFF
    Octet aligned: Disabled
    Jitter buffer: packets: 8, latency: 7 ms, auto adjust: Disabled
    Excessive packet loss rate: sample period: 10000 ms, threshold: 30%
  Packet Forwarding Engine configuration:
    Destination slot: 0
  CoS information:
    Direction : Output 
    CoS transmit queue               Bandwidth               Buffer Priority   Limit
                              %            bps     %           usec
    0 best-effort            95        1459200    95              0      low    none
    3 network-control         5          76800     5              0      low    none

  Logical interface t1-0/0/0.0 (Index 308) (SNMP ifIndex 789) (Generation 11238)
    Flags: Point-To-Point SNMP-Traps Encapsulation: TDM-CCC-SATOP
  CE info               Packets        Bytes  Count
    CE Tx                     0            0
    CE Rx                     0            0
    CE Rx Forwarded                        0
    CE Strayed                0
    CE Lost                   0
    CE Malformed              0
    CE Misinserted            0
    CE AIS dropped            0
    CE Dropped                0            0
    CE Overrun Events                         0
    CE Underrun Events                        0
    Protocol ccc, MTU: 1504, Generation: 13130, Route table: 0

Setting the SAToP Encapsulation Mode

The built-in T1 and E1 interfaces must be configured with SAToP encapsulation at the PE router so that the interworking function (IWF) can segment and encapsulate TDM signals into SAToP packets, and in the reverse direction, to decapsulate the SAToP packets and reconstitute them into TDM signals.

On the PE router, configure SAToP encapsulation on the physical interface:
[edit interfaces (t1 | e1)–fpc/pic /port]
user@host# set encapsulation satop
For example:
[edit interfaces t1-0/0/0
user@host# set encapsulation satop
On the PE router, configure the logical interface:
[edit interfaces ]
user@host# set (t1 | e1)–fpc/pic/port unit logical-unit-number
For example:
[edit interfaces]
user@host# set t1-0/0/0 unit 0
It is not necessary to configure the circuit cross-connect (CCC) family because it is automatically created for the preceding encapsulation. The following output shows this configuration.
```
[edit interfaces]
user@R7# show t1-0/0/0 
encapsulation satop;
unit 0;
```

Configure the Layer 2 Circuit

When you configure the Layer 2 circuit, you designate the neighbor for the provider edge (PE) router. Each Layer 2 circuit is represented by the logical interface connecting the local PE router to the local customer edge (CE) router. All the Layer 2 circuits that use a particular remote PE router, designated for remote CE routers, are listed under the neighbor statement. Each neighbor is identified by its IP address and is usually the end-point destination for the label-switched path (LSP) tunnel that transports the Layer 2 circuit. Configure the Layer 2 circuit:

[edit protocols l2circuit neighbor address]
user@host# set interface interface-name virtual-circuit-id identifier
For example, for a T1 interface:
[edit protocols l2circuit neighbor 2.2.2.2
user@host# set interface t1-0/0/0.0 virtual-circuit-id 1
The preceding configuration is for a T1 interface. To configure an E1 interface, use the E1 interface parameters. The following output shows this configuration.
```
[edit protocols l2circuit]
user@R7# show neighbor 2.2.2.2 
interface t1-0/0/0.0 {
    virtual-circuit-id 1;
}
```