Re: Will Cisco routers help my VoIP issue...
- From: bod43 <Bod43@xxxxxxxxxxxxx>
- Date: Mon, 13 Apr 2009 18:53:31 -0700 (PDT)
On 13 Apr, 15:51, "Default User" <nospam38...@xxxxxxxxx> wrote:
Hi,
What I have is two office phone systems (2 locations) and 5 IP phones. The
two office systems communicate with each other over IP and so do the 5 IP
phones. We have a T1 at each office. The 5 IP phones are at branch offices
that have DSL.
We are not current using Cisco routers and have in place some SonicWall
routers. We are experiencing voice quality issues and are thinking about
switching to Cisco routers because of this.
I have enabled QoS on the SonicWall routers as well as outgoing bandwdith
management to limit the amount of bandwidth consumed by non-voice traffic..
This made a huge improvement in voice quality although we are still not
where we want to be.
I have an IP phone and I can always hear people just fine. This would mean
that outgoing traffic from our main office to me works great and that the
outgoing bandwidth limiting of non-voice traffic is doing its job. The
problem is that people are unable to hear my voice going back to that
location. I have a theory on this which is that people at that location are
consuming the incoming bandwidth and there isn't enough leftover for the
incoming voice traffic.
The question is - how do you limit incoming bandwidth? The SonicWall does
have a feature to do this, but it makes the problem worse rather than
better. I don't really see how you can throttle what is sent to you because
once you have it, it has already been received.
I guess there must be some sort of technique for throttling outgoing
requests that can throttle the incoming packets for that type of traffic.
Does Cisco utilize some sort of techniques like this?
Questions:
1. Do you think replacing our routers with Cisco routers would solve this
problem? In other worse, does Cisco have some sort of technique for
properly sharing voice and data on the same WAN connection in such a way
that the data traffic will not cause problems for the voice traffic?
2. I thought about putting the voice on its on dedicated WAN connection,
but this will complicate the network configuration as well as have a service
cost to it.
3. I found something called a "traffic shaping bridge". Would this be a
possible solution worth looking at?
You obviously cannot influence the incoming internet traffic
unless the ISP and all ISPs between the locations honour
the QoS bits *AND* they are prepared to do QoS
on your traffic. As far as I know there are no ISPs that
do this but I am not sure.
There is however one trick that you might consider
for controlling incoming traffic from the internet.
Most internet traffic is TCP and TCP self regulates its
use of bandwidth if there is a restriction in the path. So if
you say have a 2M DSL you could in principle
restrict the incoming non-voice to 1.5M leaving
512k for voice which might be enough for two
simultaneous calls. You need to check the
exact values yourself.
If you are doing other UDP (peer to peer systems
seem to like UDP but will also use TCP) then this
may not work so well but all web browsing is TCP.
It does not matter whether you restrict the non-voice
traffic heading into the router from the outside
or heading to the inside from the router.
This *does* work. I have implemented it myself.
Of course you lose the 512k for non-voice traffic
but that is something that you may be able to
live with.
Cisco routers have the tools to implement the
above scheme.
.
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