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Configuring frame relay compression
Overview
Frame relay compression technique compresses frame relay packets to save network bandwidth,
reduces network load, and improves the data transfer efficiency on the frame relay network.
The device supports FRF.9 stac compression (called FRF.9) and FRF.20 IPHC (called FRF.20).
FRF.9
FRF.9 classifies packets into two types: control packets and data packets. Control packets are used
for status negotiation between the two ends of DLCI where the compression protocol has been
configured. FRF.9 data packets cannot be switched before the negotiation succeeds. If FRF.9 fails to
negotiate the state after ten FRF.9 control packets are sent, the negotiating parties stop negotiation
and the compression configuration does not take effect.
FRF.9 compresses only data packets and InARP packets; it does not compress LMI packets.
FRF.9 stac compression is suitable for low-speed links.
FRF.20
FRF.20 compresses the IP header (including the RTP/TCP header) of packets transmitted over
frame relay. For example, you can use it to compress voice packets (RTP packets) to save
bandwidth, decrease load, and improve transmission efficiency on a frame relay network.
FRF.20 classifies packets into control packets and data packets. Control packets are sent between
FRF.20-enabled interfaces to negotiate status information. The interfaces cannot exchange FRF.20
data packets before the negotiation succeeds. If FRF.20 fails to negotiate the state after ten control
packets are sent, the interfaces stop negotiation and their compression settings do not take effect.
FRF.20 compresses only RTP packets and TCP ACK packets.
Configuring FRF.9 compression
Frame relay main interface is a P2MP interface, and frame relay subinterface includes the following
types: P2P and P2MP. The configuration of frame relay FRF.9 compression varies by different
interface types. For a P2P subinterface, use the fr compression frf9 command to enable FRF.9
compression in subinterface view. For a P2MP frame relay interface or subinterface, the frame relay
compression is configured when creating static address mapping.
Configuration restrictions and guidelines
• To make FRF.9 compression take effect, enable it on both ends.
• The fr compression frf9 command is applicable to only P2P subinterfaces with IETF frame
relay enabled. Before configuring the fr compression frf9 command on a subinterface,
configure a DLCI on it first.
• After enabling or disabling FRF.9 compression on a subinterface, re-enable the subinterface
using the shutdown command and then the undo shutdown command to make the
configuration take effect.
• FRF.9 compression requires a synchronization procedure. If packets are out of order when
being compressed, the compression is prone to failure.
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