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Cisco ONS 15310-CL, ONS 15310-MA, and ONS 15310-MA SDH Ethernet Card Software Feature and Configuration Guide, R9.1 and R9.2
78-19415-01
Chapter 17 CE-Series Ethernet Cards
CE-100T-8 Ethernet Card
The CE-100T-8 card supports selective auto negotiation on the Ethernet ports. If selective auto
negotiation is enabled, the port attempts to auto negotiate only to a specific speed and duplex. The link
will come up if both the speed and duplex of the attached auto negotiating device matches that of the
port. You cannot enable selective auto negotiation if either the speed or duplex of the port is set to auto.
The CE-100T-8 card supports IEEE 802.3x flow control and frame buffering to reduce data traffic
congestion. Flow control is on by default.
To prevent over-subscription, buffer memory is available for each port. When the buffer memory on the
Ethernet port nears capacity, the CE-100T-8 card uses IEEE 802.3x flow control to transmit a pause
frame to the attached Ethernet device. Flow control and auto negotiation frames are local to the Fast
Ethernet interfaces and the attached Ethernet devices. These frames do not continue through the POS
ports.
The CE-100T-8 card has symmetric flow control and proposes symmetric flow control when auto
negotiating 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 17-2 illustrates pause
frames being sent and received by CE-100T-8 cards and attached switches.
Figure 17-2 Flow Control
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 17-3). 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.
115795
STS-N
SONET
Pause Frames
Ethernet
ONS 15310-CL ONS 15310-CL
Pause Frames
Ethernet