Autonegotiation; Figure 10-4 Autonegotiation - Cisco ONS 15600 Reference Manual

Chapter 10 Ethernet Operation
It is expected that the peer Ethernet interface stops sending new frames after receiving a PAUSE frame
for the amount of time as specified in the PAUSE_TIME. When an Ethernet interface is actively
generating PAUSE frames, it stops generating them when the ingress buffer passes below a certain level,
called the Low Water Mark. It is expected that the peer Ethernet interface starts sending new frames after
the PAUSE frames stop.
When an Ethernet interface is set to be capable of receiving PAUSE frames, it temporarily suspends
transmission of any new Ethernet frames upon reception of a PAUSE frame from its peer. Note that the
transmission of any Ethernet frames already begun are completed.
When an Ethernet interface has temporarily PAUSED transmission of Ethernet frames, it resumes
transmission of the frames when no new PAUSE frame is received within the PAUSE_TIME specified
in the last received PAUSE frame.
The High Water Mark and Low Water Mark values are both operator provisionable. Legal values are as
follows:
•
•
The Low Water Mark is always lower than the High Water Mark.
The ASAP line card utilizes tail drop when frames need to be dropped. This means that the last frames
received are the first to be dropped. This is implemented with a Last In First Out (LIFO) buffer.

10.6 Autonegotiation

The Ethernet interfaces on the ASAP card are capable of autonegotiating for full duplex (only) operation
as per IEEE 802.3z. The default provisioning is to autonegotiate the duplex mode and persists in
memory. Autonegotiation can be provisioned to be ON or OFF.
When flow control is turned on (and so is autonegotiation), the Ethernet interface autonegotiates and
advertises all modes that it supports. The mode used by the Ethernet interface is the one agreed to by the
Ethernet peers. If an agreement on the supported flow control mode cannot be reached, the transmitter
is turned off. Autonegotiation is depicted in
Figure 10-4
Router
Low Water Mark: from 10 kB to 74 kB
High Water Mark: from 11 kB to 75 kB
Autonegotiation
15xxx
Autonegotiation
Figure 10-4.
Ethernet links
15xxx
SONET network
Autonegotiation
10.6 Autonegotiation
Router
Cisco ONS 15600 Reference Manual, R8.0
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