Backlog Protection

Every WAN connection has a maximum capacity. Routing daemons cannot exceed this physical limitation. When the volume of routed data is greater than WAN capacity, rvrd buffers the outbound data.

Data backlog can occur in several scenarios; for example:

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An unexpected burst of data exceeds WAN capacity.

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A temporary problem with the WAN sharply decreases its capacity.

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WAN capacity is insufficient for the required volume of data.

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WAN capacity is generally sufficient, but rvrd is misconfigured to route more data than expected. The total data volume exceeds WAN capacity.

The Connected Neighbors page displays the peak backlog for each neighbor; see Connected Neighbors.

Maximum Backlog

An extremely large backlog can cause severe problems for rvrd and its host computer. Administrators can configure rvrd to protect against this possibility.

When enabling this feature, the administrator specifies the maximum permissible backlog (in kilobytes). When an outbound backlog of this size accumulates for any neighbor connection, rvrd automatically disconnects from that neighbor, clears the corresponding outbound data buffer, and attempts to reconnect to the neighbor.

To obtain a reasonable estimate for the threshold value that triggers this action, calculate the process storage available to rvrd, divided by the number of neighbor connections it serves.

You can configure this feature separately for each routing table entry. The router applies that maximum to all of its neighbor connections.

To configure this feature, see Routers.

Warning

Notice that enabling this feature represents a deliberate decision to discard data in certain extreme circumstances. When this feature is disabled (the default), the routing daemon does not protect against backlog. The decision to use this feature must be based on the business requirements of the enterprise.