Line timing from a synchronous port, such as a T1/E1 port or synchronous Ethernet port, provides the best synchronization performance through a synchronization distribution network. Line timing mode derives an 8 kHz clock from the framing of T1/E1, DS3/E3, and SONET/SDH signaling that can be used as an accurate reference between nodes in a network. Line timing mode is immune to any packet delay variation (PDV) occurring on Layer 2 or Layer 3 links.
On the 7705 SAR-M variants with T1/E1 ports, line timing is supported on the T1/E1 ports. Line timing is also supported on all RJ-45 Ethernet ports and SFP ports on the 7705 SAR-M and on the following 7705 SAR-M modules:
2-port 10GigE (Ethernet) module
6-port SAR-M Ethernet module
On the 7705 SAR-X, line timing is supported on T1/E1 ports and Ethernet ports.
On the 7705 SAR-H and 7705 SAR-Hc, line timing is supported on all Ethernet ports. Line timing is also supported on the following 7705 SAR-H modules:
4-port SAR-H Fast Ethernet module
T1/E1 ports of the 4-port T1/E1 and RS-232 Combination module
On the 7705 SAR-A variant with T1/E1 ports, line timing is supported on the T1/E1 ports. Line timing is also supported on all synchronous Ethernet ports on the 7705 SAR-A. Synchronous Ethernet is supported on the XOR ports (1 to 4), configured as either RJ-45 ports or SFP ports. Synchronous Ethernet is also supported on SFP ports 5 to 8. Ports 9 to 12 do not support synchronous Ethernet and therefore do not support line timing.
On the 7705 SAR-Ax, line timing is supported on all Ethernet ports.
On the 7705 SAR-Wx, line timing is supported on all Ethernet RJ-45 ports and SFP ports.
On the 7705 SAR-8 Shelf V2 and 7705 SAR-18, line timing is supported on the following adapter cards:
16-port T1/E1 ASAP Adapter card
32-port T1/E1 ASAP Adapter card
6-port Ethernet 10Gbps Adapter card
8-port Gigabit Ethernet Adapter card (dual-rate and copper SFPs do not support synchronous Ethernet)
2-port 10GigE (Ethernet) Adapter card
10-port 1GigE/1-port 10GigE X-Adapter card (supported on the 7705 SAR-18 only)
4-port DS3/E3 Adapter card
2-port OC3/STM1 Channelized Adapter card
4-port OC3/STM1 / 1-port OC12/STM4 Adapter card
4-port OC3/STM1 Clear Channel Adapter card
Packet Microwave Adapter card on ports that support synchronous Ethernet and on ports that support PCR