Payload Compression Configuration

Payload compression requires little configuration. You must enable compression on both ends of a point-to-point serial link, or on both ends of a Frame Relay VC for Frame Relay. The compress command enables compression on point-to-point links, with the frame-relay payload-compression command enabling compression over Frame Relay.

Table 7-5 lists the various configuration and show commands used with payload compression, followed by example configurations.

Table 7-5 Configuration Command Reference for Payload Compression

Table 7-5 lists the various configuration and show commands used with payload compression, followed by example configurations.

Table 7-5 Configuration Command Reference for Payload Compression

Command

Mode and Function

compress predictor

Interface configuration mode; enables Predictor compression on one end of the link.

compress stac

Interface configuration mode; enables Stacker compression on one end of the link.

compress mppc [ignore-pfc]

Interface configuration mode; enables MPPC compression on one end of the link.

compress stac [distributed | software]

Interface configuration mode; on 7500s with VIPs, allows specification of whether the compression algorithm is executed in software on the VIP.

compress {predictor | stac [csa slot | software]}

Interface configuration mode; On 7200s, allows specification of Predictor or Stacker compression on a compression service adapter (CSA).

compress stac caim element-number

Interface configuration mode; enables Stacker compression using the specified compression AIM.

frame-relay payload-compress {packet-by-packet | frf9 stac [hardware-options] | data-stream stac [hardware-options]}

Interface configuration mode; enables FRF. 9 or data-stream style compression on one end of a Frame Relay link. Hardware-options field includes the following options: software, distributed (for use w/VIPs), and CSA (7200s only).

You can use the show compress command to verify that compression has been enabled on the interface and to display statistics about the compression behavior.

The first example uses the network described in Figure 7-3, with a PPP link between R1 and R3. The example uses the same familiar web browsing sessions, each of which downloads two JPGs. An FTP get transfers a file from the server to the client, and two voice calls between R1 and R4 are used.

Figure 7-3 The Network Used in PPP Payload Compression Examples Note: All IP Addresses Begin 192.168.

Client1

1.251 12.251

R1 s0/1

11.100

Server1

3.100

1001 1002

3.254 f

R4 I

SjJj

3001 3002

Example 7-1 shows the Stacker compression between R1 and R3.

Example 7-1 Stacker Payload Compression Between R1 and R3 (Output from R3)

R3#show running-config

Building configuration...

! Lines omitted for brevity interface Serial0/1 bandwidth 128

ip address 192.168.12.253 255.255.255.0 encapsulation ppp compress stacker clockrate 128000

! Portions omitted for brevity r3#show compress

Serial0/1

Software compression enabled uncompressed bytes xmt/rcv 323994/5494 compressed bytes xmt/rcv 0/0

1 min avg ratio

xmt/rcv 1.023/1

422

5 min avg ratio

xmt/rcv 1.023/1

422

10 min avg ratio

xmt/rcv 1.023/1

422

no bufs xmt 0 no

bufs rcv 0

resyncs 2

The configuration requires only one interface subcommand, compress stacker. You must enter this command on both ends of the serial link before compression will work. The show compress command lists statistics about how well compression is working. For instance, the 1-, 5-, and 10-minute compression ratios for both transmitted and received traffic are listed, which gives you a good idea of how much less bandwidth is being used because of compression.

You can easily configure the other two payload compression tools. Instead of the compress stacker command as in Example 7-1, just use the compress mppc or compress predictor command.

Example 7-2 shows FRF.9 payload compression. The configuration uses a point-to-point subinterface and the familiar network used on most of the other configuration examples in the book, as shown in Figure 7-4.

Figure 7-4 The Network Used in FRF.9 Payload Compression Example Note: All IP Addresses Begin 192.168.

Figure 7-4 The Network Used in FRF.9 Payload Compression Example Note: All IP Addresses Begin 192.168.

Example 7-2 FRF.9 Payload Compression Between R1 andR3 (Output from R3)

R3#show running-config

Building configuration...

! Lines omitted for brevity interface Serial0/0 description Single PVC to R1. no ip address encapsulation frame-relay IETF no ip mroute-cache load-interval 30 clockrate 128000

Example 7-2 FRF.9 Payload Compression Between R1 andR3 (Output from R3) (Continued)

interface Serial0/0.1 point-to-point

description point-point subint global DLCI 103

connected via

PVC to DLCI 101 (R1)

ip address 192.168.2.253 255.255.255.0

no ip mroute-cache

frame-relay interface-dlci 101 IETF

frame-relay payload-compression FRF9 stac

! Portions omitted for brevity !

R3#show compress

Serial0/0 - DLCI: 101

Software compression enabled

uncompressed bytes xmt/rcv 6480/1892637

compressed bytes xmt/rcv 1537/1384881

1 min avg ratio xmt/rcv 0.021/1.352

5 min avg ratio xmt/rcv 0.097/1.543

10 min avg ratio xmt/rcv 0.097/1.543

no bufs xmt 0 no bufs rcv 0

resyncs 1

Additional Stacker Stats:

Transmit bytes: Uncompressed = 0

Compressed =

584

Received bytes: Compressed = 959636

Uncompressed =

0

Frame Relay payload compression takes a little more thought, although it may not be apparent from the example. On point-to-point subinterfaces, the frame-relay payload-compression FRF9 stac command enables FRF.9 compression on the VC associated with the subinterface. If a multipoint subinterface is used, or if no subinterfaces are used, however, you must enable compression as parameters on the frame-relay map command.

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