01-05-2004 05:09 AM - edited 03-02-2019 12:40 PM
hi,
i configured the following on my router:
!
interface Serial0/0
description Int S0/0 - Verbdg. zum BR-LinzLand
bandwidth 512
no ip address
max-reserved-bandwidth 95
encapsulation frame-relay IETF
load-interval 30
no snmp trap link-status
frame-relay traffic-shaping
frame-relay lmi-type q933a
!
interface Serial0/0.1 point-to-point
description Serial0/0.1: Verbindg. zum BR-LinzLand
ip address 10.20.255.2 255.255.255.252
no cdp enable
frame-relay class 512k_voice
frame-relay interface-dlci 16 CISCO
frame-relay ip rtp header-compression
!
fact is that i can not see any compressed rtp-packets - but i have voice-traffic!
is there anything wrong in the config (must i also turn on compression on the physical int ??)
r-traun1#sh ip rtp header-compression
RTP/UDP/IP header compression statistics:
DLCI 16 Link/Destination info: point-to-point dlci
Interface Serial0/0:
Rcvd: 0 total, 0 compressed, 0 errors, 0 status msgs
0 dropped, 0 buffer copies, 0 buffer failures
Sent: 0 total, 0 compressed, 0 status msgs
0 bytes saved, 0 bytes sent
Connect: 256 rx slots, 256 tx slots,
0 long searches, 0 misses 0 collisions, 0 negative cache hits
r-traun1#
01-05-2004 12:17 PM
CRTP feature used not to work under IETF encapsulation, not sure whether it does currently,
you might need to change it to cisco ecapsulation.
01-06-2004 11:56 PM
hi,
thanks for answer - but:
i have enc cisco for dlci 16 which is the one where the branch is connected.
or do you mean that i have to change the enc to cisco on the maininterface ?
01-07-2004 08:55 AM
That's true, I didn't notice that. So as long as both are set for cisco encapsulation, this should not be an issue. I suppose if there is no compression, there must be something else going on.
Hmm, do you know that the RTP stream conforms to the cRTP requirements ? Here's the link for what's required on those streams:
01-09-2004 02:07 AM
hi thanks for the url.
it seems that in fact my rtp-stream is in a range which does cisco not compress (by default?).
i sniffered some phone-connection and saw that our
siemens-voip shelfs use udp port 4512 - 4600 for example.
do you know if there is a possibility to change the routers udp - ports for compressing ??
thanks
01-09-2004 08:43 AM
As far as I know, no, there is no way to change the way packets are considered for compression with cRTP.
However, you might be able to just use a simple header compression. Your compression ratio will not be as great as instead of compressing 40 bytes like in cRTP you will be only compressing 28 bytes. But, at least you still have an option. You'd need to use
'ip rtp header-compression iphc-format' under the serial interface or modular QOS cli, here is an example:
class-map match-any identify-voip
mathc ip address 180
policy-map compress-voip
class identify-voip
compress header ip rtp
access-list 180 permit udp any any range 4512 4600
Unfortunately, this might not work under frame-relay, unless you use ppp over frame-relay. I remember it being supported under PPP and HDLC only. Also, the statistics for rtp compression will not show anything being compressed, as no RTP was identified. I know it doesn't look like this should work, but that's how it is. You are still able to compress the header, but it's not an RTP compression no more.
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