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Bandwidth Question

Hello guyz! need some expertise advice

I have 2 routers setup

connected via s0/3/0

ospf running

1 cipc phone on R1

Analogue phone R2

dial peers setup all fine

Codec = g711a

Bandwidth = 128

DCE = 128000

No QoS

Very basic setup...

Theory 1 G711a phone call = 95.2 kbps (Correct me if I'm wrong)

I call R2 from R1, one voice call and I get quality problems

I have setup IP SLA to monitor the values

MOS = 2.03

I have checked cables, changed cables, used different routers and they all give me the same MOS value 1.97 - 2.08

What can be the problem? because there's still 25% available bandwidth (95.2/128 = 74%)- MOS values should still be higher than 2

Please help!

Thanks in advance


Re: Bandwidth Question

Hi, check that you have enabled this commands on your routers:

1. check connectivity first

2. configure "h323-gateway voip bind srcaddr ip address" on the interface

3. configure "voice rtp send-recv"



New Member

Re: Bandwidth Question

Hi David,

Connectivity is ok

the 2 commands, what do they do (in short?)

I will try those 2 commands out later

Just puzzled how 1 g711 call will cause jitter, packet loss etc on a 128 kbps serial link... =[

Hall of Fame Super Gold

Re: Bandwidth Question

If you click the "?" twice button on IPCP, does it show packet loss ?

New Member

Re: Bandwidth Question

Hi p.bevilacqua,

Sorry if I sound 'noob' like...

What is ICPC?

Only ? I know of is checking syntax or command in cisco CLI

Hall of Fame Super Gold

Re: Bandwidth Question

The cipc.

New Member

Re: Bandwidth Question

yes it does, packet loss increases by ~30 every sec

I repeated the test with:

2 g711a calls - average mos ~ 1.86
3 g711a calls - average mos ~ 1.76
4 g711a calls - average mos ~ 1.67

Over 128kbps bandwidth

Still i find these results strange

New Member

Re: Bandwidth Question

Ok guyz I found the problem...

I left IP SLA config as default

ip sla 1
udp-jitter 2222 codec g711a

freq 5
tos 184

With some help from a techy, looked into the config and bandwidth...

sh ip sla conf (Cisco default config of other parameters)

no of packets 1000

packet size 172

So 1 g711 call = 95 kbps + this ip sla traffic, will defo mess up my results!!!

every 5 sec sending 1000 packets size of 172 bytes!

I'm not sure how to work out the ip sla traffic badwidth, unless u guyz can explain!

But yes i changed the no of packets to 100

and size to 100

I get the result!

2nd Q.

What parameters does the Industry use? If left at default its going to screw up the results

Too low the packets will get through no problem!

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