Each DS1, E1, DS3, or E3 circuit configured with DCR executes its own clock recovery from the packet stream. This allows each circuit to have an independent frequency.
Table: Supported Timestamp Frequencies for DCR-timed Circuits lists the supported timestamp frequencies for each platform and adapter card.
|
Timestamp Frequency (MHz) |
||||
|---|---|---|---|---|
|
103.68 |
77.76 |
25 |
19.44 |
|
|
16-port T1/E1 ASAP Adapter card |
✓ (default) |
✓ |
||
|
32-port T1/E1 ASAP Adapter card |
✓ (default) |
✓ |
||
|
4-port OC3/STM1 / 1-port OC12/STM4 Adapter card |
✓ (default) |
|||
|
4-port DS3/E3 Adapter card |
✓ (default) |
|||
|
7705 SAR-M |
✓ (default) |
✓ |
✓ |
✓ |
|
7705 SAR-A |
✓ (default) |
✓ |
✓ |
✓ |
|
4-port T1/E1 and RS-232 Combination module |
✓ (default) |
✓ |
✓ |
✓ |
|
7705 SAR-X |
✓ (default) |
✓ |
✓ |
✓ |
The timestamp frequency is configured at the adapter card level and is used by all DCR ports or channels on the supporting platforms and cards. Both ends of a TDM pseudowire using DCR must be running the same frequency. If a network contains different types of equipment using DCR, a common frequency must be selected that is supported by all equipment.
DCR complies with published jitter and wander specifications (G.823, G.824, and G.8261) for traffic interfaces under typical network conditions and for synchronous interfaces under specified packet network delay, loss, and delay variance (jitter) conditions.