Installation Guide

Table Of Contents
Task 2: Configuring IP and Ethernet interfaces
Attribute Meaning
Timer Type
Keep Alive is the default timer type. This timer will enable a
keepalive that will check the status of the link periodically.
The user can set a keepalive period. If no data is seen from
the PPPoE server for that period, the link is taken down and a
reconnection attempt is started. For marginal links, the keep
alive timer can be useful so that the session will stay alive
over periodic dropouts. The keepalive timer must be set such
that the session can outlast any session drop. Some PPPoE
servers will have a session check timer of their own so that
the timeouts of the server and the SM are in sync, to ensure
one side does not drop the session prematurely.
Idle Timeout enables an idle timer that checks the usage of
the link from the customer side. If there is no data seen from
the customer for the idle timeout period, the PPPoE session is
dropped. Once data starts flowing from the customer again,
the session is started up again. This timer is useful for users
who may not be using the connection frequently. If the
session is idle for long periods of time, this timer will allow the
resources used by the session to be returned to the server.
Once the connection is used again by the customer, the link is
reestablished automatically.
Timer Period The length in seconds of the PPPoE keepalive timer.
TCP MSS
Clamping
If this is enabled, then the SM will alter TCP SYN and SYN-
ACK packets by changing the Maximum Segment Size to be
compatible with the current MTU of the PPPoE link. This way,
the user does not have to worry about MTU on the client side
for TCP packets. The MSS is set to the current MTU 40 (20
bytes for IP headers and 20 bytes for TCP headers). This will
cause the application on the client side to not send any TCP
packets larger than the MTU. If the network is exhibiting
large packet loss, try enabling this option. This may not be an
option on the PPPoE server itself. The SM will NOT
reassemble IP fragments, so if the MTUs are incorrect on the
end stations, then MSS clamping will solve the problem for
TCP connections.
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pmp-0957 (April 2015)