Chapter 16 CE-100T-8 Ethernet Operation
CE-100T-8 Ethernet Features
The CE-100T-8 card has symmetric flow control and proposes symmetric flow control when autonegotiating flow control with attached Ethernet devices. Symmetric flow control allows the CE-100T-8 cards to respond to pause frames sent from external devices and to send pause frames to external devices.
The pause frame instructs the source to stop sending packets for a specific period of time. The sending station waits the requested amount of time before sending more data. Figure 16-2illustrates pause frames being sent and received by CE-100T-8 cards and attached switches.
Figure 16-2 Flow Control | | |
ONS 15310-CL | | ONS 15310-CL |
Ethernet | STS-N | Ethernet |
|
| SONET | |
Pause Frames | | Pause Frames |
This flow-control mechanism matches the sending and receiving device throughput to that of the bandwidth of the STS circuit. For example, a router might transmit to the Ethernet port on the CE-100T-8 card. This particular data rate might occasionally exceed 51.84 Mbps, but the SONET circuit assigned to the CE-100T-8 port might be only STS-1 (51.84 Mbps). In this example, the CE-100T-8 sends out a pause frame and requests that the router delay its transmission for a certain period of time. With flow control and a substantial per-port buffering capability, a private line service provisioned at less than full line rate capacity (STS-1) is efficient because frame loss can be controlled to a large extent.
Ethernet Link Integrity Support
The CE-100T-8 supports end-to-end Ethernet link integrity (Figure 16-3). This capability is integral to providing an Ethernet private line service and correct operation of Layer 2 and Layer 3 protocols on the attached Ethernet devices.
End-to-end Ethernet link integrity means that if any part of the end-to-end path fails, the entire path fails. It disables the Ethernet port on the CE-100T-8 card if the remote Ethernet port is unable to transmit over the SONET network or if the remote Ethernet port is disabled.
Failure of the entire path is ensured by turning off the transmit pair at each end of the path. The attached Ethernet devices recognize the disabled transmit pair as a loss of carrier and consequently an inactive link or link fail.
Figure 16-3 End-to-End Ethernet Link Integrity Support
Ethernet port | | Ethernet port |
ONS 310 | STS-N | ONS 310 | |
Rx | | Rx | 115796 |
Tx | | Tx |
| |
SONET
Cisco ONS 15310-CL Ethernet Card Software Feature and Configuration Guide, R5.0
