From: Church, Chuck (cchurch@netcogov.com)
Date: Wed Jun 01 2005 - 00:59:38 GMT-3
What your traffic is really has a bearing on how you choose to compress
it. Keep in mind a few things:
CRTP will only work on RTP traffic. If you have little or no RTP
traffic, it really won't help. Won't work on payload, but RTP is
already compressed.
TCP Header compression. Savings similar to CRTP, but works on all TCP
traffic. Won't work on payload either.
L2 compression - Stac, FRF.9, etc compress everything. Higher CPU than
the above two, since everything is compressed. Pretty useless if all
your traffic is web browsing where most things like embedded images are
already compressed, or for RTP traffic. But if your traffic is
compressible stuff - Netbios, database traffic, telnet, etc; you may see
some impressive gains. Traffic that uses ACKs will be improved also,
because ACKs are typically mostly padded packets with much of the data
the same.
With the link being only a 256kb, compression at layer 2 is probably ok
to use.
Chuck Church
Lead Design Engineer
CCIE #8776, MCNE, MCSE
Netco Government Services - Design & Implementation Team
1210 N. Parker Rd.
Greenville, SC 29609
Home office: 864-335-9473
Cell: 703-819-3495
cchurch@netcogov.com
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x4371A48D
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: Tuesday, May 31, 2005 4:01 PM
To: Ralph Sherry; Quetta Walla; ccielab@groupstudy.com
Subject: RE: Compression on low band link
Hi Ralph,
Yes you could use cRTP, however this will only achieve compression on
certain types of traffic, basically real time protocol traffic. It is a
header compression algorithm, whereas stac is compressing everything,
cRTP will compress the IP/UDP/RTP header down to around 2 to 4 bytes,
however the payload remains uncompressed. RTP is usually used in the
tranport of Voice.
HTH
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Ralph
Sherry
Sent: 31 May 2005 19:45
To: simon hart; Quetta Walla; ccielab@groupstudy.com
Subject: RE: Compression on low band link
I think you could also use CRTP.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/q
os_c
/qcpart6/qcrtphc.htm
I am unfamiliar with when you would want to use stac over CRTP though.
Would anybody like the explain when you would use one over the other?
simon hart <simon.hart@btinternet.com> wrote:
The only compression algorithm you can use on an HDLC link is stac (the
Lempel-Ziv compression algorithm).
Enter the command compression stac directly on the interface at both
ends of
the link.
The stac algorithm is heavy on the CPU, therefore if you are using a lot
of
CPU already, use with caution. If this is the case, then you can change
the
link encapsulation to PPP and then use predictor. The trade off here is
that you will not use so much CPU, but will have to have enough memory.
HTH
Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Quetta Walla
Sent: 30 May 2005 10:49
To: ccielab@groupstudy.com
Subject: Compression on low band link
Hey,
What compression method is recommended on say 256k hdlc link?
And why?
Thanks
--
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