Frame Relay Burden Compression
Cisco IOS software supports three options for burden compression on Frame Relay VCs: packetby-
packet, data-stream, and Frame Relay Forum Implementation Agreement 9 (FRF.9). FRF.9 is
the alone connected agreement of the three options. FRF.9 compression and data-stream compression
function basically the aforementioned way; the alone absolute aberration is that FRF.9 implies affinity with
non-Cisco devices.
All three FR compression options use LZS as the compression algorithm, but one key difference
relates to their use of compression dictionaries. LZS defines activating concordance entries that account a
binary cord from the aeroembolism data, and an associated abate cord that represents it during
transmission—thereby abbreviation the cardinal of $.25 acclimated to accelerate data. The table of abbreviate binary
codes, and their best associated cord of bytes, is alleged a dictionary. The packet-by-packet
compression adjustment additionally uses LZS, but the compression concordance is congenital for anniversary packet, then
discarded—hence the name packet-by-packet. The added two methods do not bright the dictionary
after anniversary packet. Table 15-4 lists the three FR compression options and their best important
distinguishing features.
FR Burden Compression Feature Comparison
Feature Packet-by-Packet FRF.9 Data-Stream
Uses LZS algorithm? Yes Yes Yes
Same concordance for all packets? No Yes Yes
Cisco-proprietary? Yes No Yes
FR burden compression agreement is configured per VC. The agreement varies depending
on whether point-to-point subinterfaces are used. On point-to-point subinterfaces, the frame-relay
payload-compress blazon subinterface command is used; otherwise, the frame-relay map command
must be configured forth with the payload-compress blazon option. Example 15-2 shows Frame
Relay compression configured in the same network as shown in Figure 15-4 and Example 15-1.
The VC from R1 to R3 (multipoint subinterface) uses data-stream compression, and the VC from
R1 to R4 uses FRF.9.
Frame Relay Data-Stream Compression
! Below, the configuration added to R1’s Example 15-1 configuration is shown.
! R3 uses a frame-relay map command as well, and R4 uses the same
! frame-relay payload-compress command.
interface Serial0/0/0.14 point-to-point
frame-relay payload-compress frf9 stac
!
interface Serial0/0/0.123 multipoint
frame-relay map ip 10.1.123.3 103 broadcast payload-compress data-stream stac
! Next, R1 sends 5000 200-byte pings to R4 to create traffic. R4 shows the pre- and
! post-compression stats in the show compress command.
R4# show compress
Serial0/0/0 - DLCI: 101
Software compression enabled
uncompressed bytes xmt/rcv 1021536/1021536
compressed bytes xmt/rcv 178090/177820
Compressed bytes sent: 178090 bytes 12 Kbits/sec ratio: 5.736
Compressed bytes recv: 177820 bytes 12 Kbits/sec ratio: 5.744
1 min avg ratio xmt/rcv 3.506/3.301
5 min avg ratio xmt/rcv 3.506/3.301
10 min avg ratio xmt/rcv 3.506/3.301
no bufs xmt 0 no bufs rcv 0
resyncs 0
Additional Stac Stats:
Transmit bytes: Uncompressed = 0 Compressed = 142922
Received bytes: Compressed = 142652 Uncompressed = 0