User Manual

Additional Remote Networking Bandwidth On Demand
5-5
5.3 Bandwidth On Demand
Note: Remote Node sites have a fixed bandwidth. The SCS cannot add or remote
bandwidth for Remote Node connections. This section discusses bandwidth for
LAN to LAN connections only.
The following sections outline the basic configuration needed to utilize SCS bandwidth on demand
functionality for LAN to LAN connections. For more detailed instructions on setting up both sides of a
bandwidth on demand connection, refer to Multilink PPP on page 7-4.
By default, sites will only attempt to bring up one port to a remote site in a LAN to LAN connection. If the
amount of incoming data on the Ethernet exceeds the current bandwidth of the serial port (and the SCS is
configured not to dial up additional bandwidth), congestion occurs and the extra data is discarded.
To avoid congestion, the SCS enables you to customize a site’s use of bandwidth. As it is needed, additional
bandwidth will be added. The SCS will assign more ports to the site until it has enough bandwidth or reaches
a certain threshold. When it is no longer needed, the extra bandwidth will be removed.
5.3.1 How Bandwidth is Controlled
A site’s use of bandwidth is controlled by the following factors:
◆ The initial and maximum bandwidth allotted to the site. These are static values.
◆ The threshold at which additional bandwidth should be added. This threshold is a percentage of the
currently-dialed bandwidth.
◆ The threshold at which unnecessary (unused) bandwidth should be removed. This threshold is a
percentage of the currently-dialed bandwidth.
◆ The period of time during which the current bandwidth usage is measured.
◆ The delay between bandwidth adjustments.
By default, additional bandwidth will not be added to a connection. In order for a connection to have flexible
bandwidth (bandwidth that is added and removed as necessary), the site’s maximum bandwidth must be
configured, as well as the thresholds at which bandwidth is added and removed.
Note: The initial bandwidth allotted to the site may also be configured. This is optional.
The threshold at which bandwidth is added and removed should have some room between them to regulate
how often bandwidth is added and removed. The “add bandwidth” threshold should be set to a percentage
between 80 and 100 percent; the “remove bandwidth” threshold should generally be set to less than 50%. If
the threshold values are set too close to one another, the connections will thrash; in other words, bandwidth
will be continuously added and dropped.
The order in which ports are selected to be added and removed is controlled by a priority setting; when SCS
bandwidth needs change, ports with the highest priority are the first to be added and the last to be removed.
Bandwidth is controlled by the host that initiates the call. If the SCS initiates a call, it controls the bandwidth
for each site. If the SCS receives an incoming call, the bandwidth is controlled by the remote host.