Re: STAC COMPRESSION

timmysyed · ‎02-16-2019

Hello

I have enabled STAC Compression on HDLC Serial Link. I choose 8192 Bytes ICMP to test the compression and got below results. I run it three times and got three different compression ratio .

FIRST TIME :

R2#ping 20.0.24.2 repeat 1 size 8192 timeout 2

Type escape sequence to abort.

Sending 1, 8192-byte ICMP Echos to 20.0.24.2, timeout is 2 seconds:

!

Success rate is 100 percent (1/1), round-trip min/avg/max = 40/40/40 ms

R2#show compress

Serial0/0

Software compression enabled

uncompressed bytes xmt/rcv 8452/8372

compressed bytes xmt/rcv 573/510

Compressed bytes sent: 573 bytes 0 Kbits/sec ratio: 14.750

Compressed bytes recv: 510 bytes 0 Kbits/sec ratio: 16.415

1 min avg ratio xmt/rcv 12.943/14.286

5 min avg ratio xmt/rcv 12.943/14.286

10 min avg ratio xmt/rcv 12.943/14.286

no bufs xmt 0 no bufs rcv 0

resyncs 0

Additional Stac Stats:

Transmit bytes: Uncompressed = 40 Compressed = 573

Received bytes: Compressed = 538 Uncompressed = 0

SECOND TIME:

R2#ping 20.0.24.2 repeat 1 size 8192 timeout 2

Type escape sequence to abort.

Sending 1, 8192-byte ICMP Echos to 20.0.24.2, timeout is 2 seconds:

!

Success rate is 100 percent (1/1), round-trip min/avg/max = 52/52/52 ms

R2#show compress

Serial0/0

Software compression enabled

uncompressed bytes xmt/rcv 8372/8452

compressed bytes xmt/rcv 507/574

Compressed bytes sent: 507 bytes 0 Kbits/sec ratio: 16.512

Compressed bytes recv: 574 bytes 0 Kbits/sec ratio: 14.724

1 min avg ratio xmt/rcv 14.976/13.415

5 min avg ratio xmt/rcv 14.976/13.415

10 min avg ratio xmt/rcv 14.976/13.415

no bufs xmt 0 no bufs rcv 0

resyncs 0

Additional Stac Stats:

Transmit bytes: Uncompressed = 20 Compressed = 507

Received bytes: Compressed = 606 Uncompressed = 0

Third Time :

Sending 1, 8192-byte ICMP Echos to 20.0.24.2, timeout is 2 seconds:

!

Success rate is 100 percent (1/1), round-trip min/avg/max = 84/84/84 ms

R2#show compress

Serial0/0

Software compression enabled

uncompressed bytes xmt/rcv 8850/8850

compressed bytes xmt/rcv 936/938

Compressed bytes sent: 936 bytes 0 Kbits/sec ratio: 9.455

Compressed bytes recv: 938 bytes 0 Kbits/sec ratio: 9.434

1 min avg ratio xmt/rcv 8.444/8.428

5 min avg ratio xmt/rcv 8.444/8.428

10 min avg ratio xmt/rcv 8.444/8.428

no bufs xmt 0 no bufs rcv 0

resyncs 0

Additional Stac Stats:

Transmit bytes: Uncompressed = 60 Compressed = 936

Received bytes: Compressed = 978 Uncompressed = 0

1. Three time three different ratio why it is so ? Am i missing anything to understand here ?

2. I see only difference in the field Additional Stac Stats: Transmit bytes: Uncompressed Field.

3. Is Transmit bytes : Uncompressed filed is Header field and this reason its not compressed ?

Thanks

TIM

Georg Pauwen · ‎02-16-2019

Hello,

as far as I recall, STAC is less predictable and consistent than Predictor. Your response times vary, that alone might cause the difference in compression rates. Do you get the same with 'compress predictor' ?

https://www.cisco.com/c/en/us/support/docs/wan/data-compression/14156-compress-overview.html

timmysyed · ‎02-16-2019

Thanks for the reply but i have not yet tried Predictor.

May be the its due to ICMP Packets ? where we dont know the randomness of payload. May be give more stable result when actually traffic pass through ?

Any update on my point 2 and Point 3 ?

2. I see only difference in the field Additional Stac Stats: Transmit bytes: Uncompressed Field.

3. Is Transmit bytes : Uncompressed filed is Header field and this reason its not compressed ?

I d