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VOIP limits

Posted: Wed Jun 27, 2007 11:48 pm
by DirectWireless
On a 5ghz Mikrotik system @20mhz channels, what is the most number of simultaneous voice calls anyone has achieved without a significant quality loss?

Thanks

Re: VOIP limits

Posted: Thu Jun 28, 2007 12:29 am
by Superdust
Each voice call with good quality would take about 64Kbps full duplex, so about 125 calls I would guess.

Re: VOIP limits

Posted: Thu Jun 28, 2007 12:40 am
by DirectWireless
But 125 calls, theoretically, sounds good, but I mean from real experience. I'm thinking with and without NStreme, any #s on that?

Re: VOIP limits

Posted: Fri Jun 29, 2007 4:17 pm
by nick52
Each voice call with good quality would take about 64Kbps full duplex, so about 125 calls I would guess.
You should consider the switching performance of the RouterBoard (in terms of packets per second, pps), not only the the throughput.

Usually the payload of the VoIP packet is from 20 up 60 bytes long, whom you have to add the IP+UDP+RTP header = 40 bytes, so the total lenght of the VoIP packet is about 70 bytes (equal to 560 bits).

The pps number concerning a 64 Kbps flow of lenght 560 bits, is:

64 Kb/s / 560 b/packet = 114 pps

As we tested that a RB532 can switch about 8000 pps of any lenght, we can state that it can manage a numbebr of 8000 / 114 = 70 calls (35 in the case of full duplex calls).

It seems to me very distant from the 125 calls!!

nick52

Re: VOIP limits

Posted: Fri Jun 29, 2007 4:23 pm
by Superdust
Thank you for clearing that up Nick.

I didn`t concider that :shock:

Re: VOIP limits

Posted: Fri Jun 29, 2007 4:45 pm
by Superdust
Does this mean that using RB532 as backbone link also has the same limitations?

Re: VOIP limits

Posted: Fri Jun 29, 2007 4:58 pm
by nick52
Does this mean that using RB532 as backbone link also has the same limitations?
Yes! for me it is so!

nick52

Re: VOIP limits

Posted: Fri Jun 29, 2007 5:00 pm
by Superdust
Ok, wakeupcall :shock:

Is there any other routerboard with more performance?
Or you have to go with pc hardware?

Re: VOIP limits

Posted: Fri Jun 29, 2007 5:12 pm
by Superdust
He is saying mutch more, witch is right?
http://forum.mikrotik.com/viewtopic.php ... &hilit=pps

Re: VOIP limits

Posted: Sat Jun 30, 2007 12:32 am
by Diganet
He is saying mutch more, witch is right?
http://forum.mikrotik.com/viewtopic.php ... &hilit=pps
Both are right. It all depends on which interfaces we are talking about

/Henrik

Re: VOIP limits

Posted: Sat Jun 30, 2007 1:43 am
by Superdust
Ok, so using RB532 as P2P WDS transparent bridge, you can only push 8000pps?
Any better board for P2P use?

Re: VOIP limits

Posted: Sun Jul 01, 2007 11:21 am
by ivaring
For Mikrotik products 100 simultaneous calls on a routerboard it would be a good limit.

Regards.

Re: VOIP limits

Posted: Sun Jul 01, 2007 1:12 pm
by Superdust
For Mikrotik products 100 simultaneous calls on a routerboard it would be a good limit.

Regards.
Is this wired or wireless, witch routerboard?
Does this mean that you would get 22000-23000PPS?

I`m asking this because I was planing to use MT for backbone also, but if it can only handle 8000PPS wireless with the best routerboard available it`s not an option.

Re: VOIP limits

Posted: Mon Jul 02, 2007 2:24 am
by Diganet
Ok, so using RB532 as P2P WDS transparent bridge, you can only push 8000pps?
Any better board for P2P use?
It's not the board but the Radio. You should use Nstreme for P2P links, this will make PPS much better by putting small packets into bigger wireless frames but will also cause jitter if traffic isn't high enough for these "jumbo frames" to flow because Nstreme can "hold back" packages until frame is filled up.. Also your links need to be perfect before running Nstreme.. One dropped Nstreme frame will mean a lot of dropped VOIP packages..

/Henrik

Re: VOIP limits

Posted: Mon Jul 02, 2007 10:28 am
by Superdust
Ok, this is R52 limitations, or all compatible radio cards?

Re: VOIP limits

Posted: Mon Jul 02, 2007 12:39 pm
by ivaring
For Mikrotik products 100 simultaneous calls on a routerboard it would be a good limit.

Regards.
Is this wired or wireless, witch routerboard?
Does this mean that you would get 22000-23000PPS?

I`m asking this because I was planing to use MT for backbone also, but if it can only handle 8000PPS wireless with the best routerboard available it`s not an option.
Well, according 2 me, 532 is a really good card, if u want to do something with 13x, mmmmm.
This limit is a little theoric, anyway, it will depend on your network, of course.

Regards.

Re: VOIP limits

Posted: Mon Jul 02, 2007 12:47 pm
by Diganet
Ok, this is R52 limitations, or all compatible radio cards?
This is radios in general i think. You have a certain limit within the 802.x protocols. This is why Nstreme is so handy. SIP is always a problem because of the small packets and unless you have some wireless gear that can do small packets you have to go with Nstreme if you want to move a lot of SIP. I use Nstreme on our backbone links and it works great. I have no exact number on amount of simultaneous calls though.

/Henrik

Re: VOIP limits

Posted: Tue Jul 03, 2007 10:19 am
by nick52
My tests result using a RouterBoard532 and two Ethernet interfaces (NOT Wireless interfaces) are, for different packet lenghts:

L=64 bytes BW=3.90 Mbps switching performace=7500 pps
L=250 bytes BW=15.5 Mbps switching performace=7700 pps
L=550 bytes BW=36 Mbps switching performace=8100 pps
L=1470 bytes BW=85 Mbps switching performace=7200 pps

As you can see, independently on packet lenght, the switching performance of RouterBoard 532 is always about 8000 pps.

nick52

Re: VOIP limits

Posted: Tue Jul 10, 2007 12:28 am
by aaronm
So it looks like the 8000pps ceiling is really a limitation of the Routerboard itself, not the wireless card. I'd be curious to see how a decent x86 box would do.

Re: VOIP limits

Posted: Thu Jul 19, 2007 12:44 pm
by ricrc
Quick update,

I had issues with a Customer who had an old RB112-RB112 Wireless link, Wds/Bridge Config.

They started out with just a few VoIP clients and everything worked out perfect.

Now they have 16 VoIP clients installed on they're remote office, no idea how many concurrent calls they were making but compaints started coming trough.

i recently switched the RB'ds to 532's @ 400Mhz and have had 0 complaints.

So, from what experience i got from the fileld, i'd say the 175Mhz processor could probably handle around 10 VoIP Calls?

Im guessing the RB532 would probalby handle somewhere in the 20's calls, the 35 calls sounds about right as an optimal value.
I agree the limitation is in the PPS.

RRC

Re: VOIP limits

Posted: Thu Jul 19, 2007 9:22 pm
by Superdust
Thank you for the info on this

This means I`ll still be using Alvarion B100 in backbone, or MT with X86?

Re: VOIP limits

Posted: Fri Jul 20, 2007 4:19 pm
by stephenpatrick
IMHO, Use a decent x86 system with MT.
AFAIK a 1GHz CPU would remove that PPS bottleneck, which is limited by the CPU.
MT is much more flexible than Alvarion, I don't think there's much comparison.

Regards

CableFree Solutions

Re: VOIP limits

Posted: Fri Jul 20, 2007 10:35 pm
by Superdust
Maybye the new boards will be some improvements to 8)
It`s not always so good using x86 systems on all locations.....