Hi

We are considering using a WLAN to run our VoIP telephone system between two sites 9 miles apart.

We were thinking of using two 3Com building to building 11mbps devices.

Are there any problems with VoIP & WLANS?

Thanks B

no problem with wireless.. Home many phones and how much data are you planning on moving?

wireless can cause delay. VOIP requires low latency.
Is your wireless device a router or bridge ? Huge difference in the answer to that question, as far as VOIP is concerned. How many users, what compression ? Any PC / what kind of traffic besides voice is there ? tom@rickenbackercommunications.com

Hi

I think i may have problems with the wireless connection as I am struggling to find line of sight.

I would use a bridge, with possibly up to 6 users but not always concurrent, we may put data down the connection two - mainly database access.

Thanks B

also don't forget that you have to allow for almost 200 kbps in each direction for voice traffic per call not to mention the overhead associated with the wlan standard in the first place. you will also need to have gear that can guarantee some quality of service on the phone lines to make the calls sound reasonable. ie pcf capable hardware

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

200kb per RTP stream?  you can due video for that?  What codec are you running lui?  Uncompressed PCM does not even run that high.

Bernie get the wirless link up and running and moving data with low latency/delay.  Then start running your VOIP over it.  You can do COS mapping on the port connected to your wireless bridge to give your VOIP traffic higher priority than all your data.  11mb/s is more than enough BW.  I doubt that you will actually achieve a speed that high but half of that is sufficient for small office/ med office.

with overhead its much higher than you think with wireless. i will get you the link

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

i am sorry 200 pps not 200 kbps per call. see this link


http://www.cisco.com/en/US/products/hw/phones/ps379/products_white_paper09186a00801ca827.shtml#number_phones

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

Ahhh ok...But he is going to use a PTP wireless bridge.  not shared BW AP.. most of the Doc seems to discuss shared Bw AP at 60 percent threshhold for voice.  great doc for AP design but I don't think it is relevent to PTP wireless technologies.

how voip calls have you been able to make over a 11 mb wireless bridged link?

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

we suuport a site with over 100 users over a cisco airo with the directional ant...

We allow 40 calls at one time to go through at G711 then another 20 at g729.  We have never had a problem with quality. What do you expect the issues to be lui3?

how many ip phones accross wireless link have you run?
how can you say his wireless solution will not work?

Oh, i don't think his solution will not work. I was just curious to what results you have had.

The problem with VOIP and data together is that even with CAC you can have weird things happen. Especially in shared environs. I like to play it safe with the lower bandwidth ranges especially with bridges. plus,  ,ore often than not people end up running linksys instead of cisco or some other brand and then end up putting more data on the line than expected. eventually results in overcrowding or screwy configurations. more often than not they don't use COS marking on the ports or TOS/DSCP marking or LLQ nor do they have a universal switch architecture in place with proper configuration to make things work properly. QOS is QOS people say but i disagree. People have gotten used to ciscos way of things working however thats not the case with all software. Different software platforms (ie cisco, linksys, cabletron, whoever) treat QOS differently. In a mixed environment its better to play it safe or at least be aware of the possible pitfalls of what you are trying to accomplish. I agree in a vendor homogenous environ, ie cisco, you can pretty much push everything to the limit however, i have not seen any mention of a vendor for the call manager (he did say he was using 3com for the bridges)  and to assume that this user will using cisco everywhere else could be a mistake. i would want to know more about the underlying hardware before making an assumption that cisco gear or whatever is in place to handle all of this.


i have never used 11 mbps for voice outside of aps. i have only used 1400s on bridged links and never in production. all cisco and no problems. no more than 10 users simultaneously.

are you using full cisco gear all over for your solution?

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

I Guess the confusion is this:  I don't agree with the WEIRD things happen analogy.  Predictable things happen, the only variable is if the solution is in our tech vocabulary or not.  An appropriate service policy with proper queueing mechanisms will work fine on any 11mbs connection.  The speed is the only thing that can be attributed to serialization delay wich in a PTP link is the real factor that will degrade you VOIP performance.  11 meg as a very acceptable serialazion delay.  The underlying L2 technology used is not relevant.  
I would do a few things on my access switches.  Not allow oversized frames for one. and implemented proper COS marking(prob not needed, we tend to skimp on LAN qos most of the time and as long as you seperate your Voice and data traffic vlan wise no issue most of time, (barring virus issues).  The most important issue is using a proper service policy that reserves enough BW for your VOIP traffic, and also using some sort of CAC to not exceed the reserved BW or SP.

IF these basic concepts are met the L2 technology used is not really relevant..

are you saying that you can guarantee the predictability of an environment that you have seen posted herein just based on the fact that the user is saying they are using 3com switching and voip. how do you know that they even have the gear to support proper marking/classify/queueing? you don't. that is my point. i agree with everything you are saying including the weird part. problem is in most situations, people don't know all the facts about the system. if they own it they have a better chance. i am not argueing over what strategies to take regarding voice quality i am just saying that i like to play it safe when dealing with the unknown parts of someone elses network. i have gotten burned when dealing out advice without knowing all the facts.

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

i also disagree with the underlying L2 tech in place not being a factor in success of the connection. i have networks in place that do not understand vlanning or do not mark packets to the extent that other gear does. that is not an issue of configuration or technology. that is an issue of hardware/software not supporting the necessary features. compatibility can be a real problem in the guarantee of proper QOS. cisco products do a great job of handling industry standards and then some other companies do not and it makes things difficult.

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

Lui..
What does L2 technology have to do with capability of his gear.  First off.. This is a wan connection and needs to be treated as such.. NO matter what L2 technology he chooses he is going to need a prioritization and marking mechanism in place.  I am assuming if price was not an issue he would just purchase a 10 meg ATM pipe.  Would you argue that Voice would not work fine over this connection?
Assuming his gear can do 11mb he has more bandwidth and less delay in the wireless solution by over 30 percent!!!
Just cause L2 changes you still need to manage your voice network properly. All the arguments you are making apply to any WAN solution he implements.  Wich I think is great advice.  But bottom line the WIRELESS link can handle this fine.

"are you saying that you can guarantee the predictability of an environment that you have seen posted herein just based on the fact that the user is saying they are using 3com switching and voip. how do you know that they even have the gear to support proper marking/classify/queueing? you don't. that is my point."
  DOES THIS CHANGE IF HE USES ATM OR FRAME?  

"i also disagree with the underlying L2 tech in place not being a factor in success of the connection. i have networks in place that do not understand vlanning or do not mark packets to the extent that other gear does"
This has nothing to do with the WAN  framing method he chooses.  It is a problem with any solution he decides to implement!!! Are you saying don't run VOIP over the WAN?

Ohh And yes I agree he viability of using the 3com here is pretty slim.. he will probably need to go to a differnt vendor to cover his 9 miles.

When i say layer 2 technology, i am not speaking of ATM or frame but of the capabilities of the equipment implementing that technology. That is my point. I am sorry that this has become so confusing and off topic.

It looks like your experience with wireless and VOIP far exceeds my own. Thanks for your input.

Good luck with the project, bernie321.

Lui3
CCNP,CCDA,A+/Net+
Cisco Wireless Specialization

Well, we're not going 9 miles, but we are going 3.8 miles.  Across lake superior.  With boats crossing the path.  And our VOIP and network are running FANTASTIC; we're using a 5Ghz link, and pushing about 30MB across.  We're using NEC DTerm series I VOIP phones, and so far nobody has had a single lag/poor quality complaint.

I'm on that link as I type this.  :)

Just my $0.02

"In order to start solving a problem, one must first identify its owner." --Me
--Greg

HI Guys

Sorry for the lack of response, i have had loads of trouble logging into this thread.

We are going to start by just using a DSL link and experimenting with Wireless - until we are happy with our knowlege of the technology.

Thanks to everyone that has posted

If you use DSL, make sure you have a equal Download and Upload.  What state are you in Bernie?  Like ccmuser, said...get the link up, than try your VoIP.  If it only for VoIP, no real biggy.  If other data is going over the stream you will want to do some kind of packet shaping and prioritize the VoIP data.

In the future everything will work...

We are doing the same thing, except our sites are 2 miles apart.  We are using wireless radio and we get a whopping throughput of 45Mbps.

All of our phone lines are at one location and we are using data and voice over the same wireless connection.

We use 3COM NBX 100 phones.  Now I just need to figure out the IP on the Fly feature so I can add a remote user accessing the server current via a vpn.

Bernie321 your wireless WLAN very doable as was mentioned/tossed around with 3Com wares previously.

The Layer 2/3 good idea for the 3Com solution but since ccmuser is bent on Cisco and Cisco is the only thing he has an answer with and IP--well, forget it.

Bernie321 get your info from 3Com- they initially ran an 11MBPS WLAN in Upper Marlboro just not the 40 simultaneous calls and as mentioned, weird things do happen regardless of what IP solution you adopt and bandwidth and how the channels are hopped and interleaved among the bazillion other effects that wireless tech incurs will make your head spin.  Is it 100 percent PERFECTED- no, of course not.  Is it viable ? Yes.  Anyway, regarding 3C0m and their site: This was several years ago (4-5) and the Ghz solutions today are definitely amiable and the hopping in and out is improved in all the wares as is the added space to operate in unlicensed...but check the h/w out first.

9 Miles isn't all that far- there are some other options to look at and inspite of the IP- think about more bandwidth for the WLAN as there are some good campus sites that are using WLAN successfully (L2/L3).  If itz a 3Com solution you want then it's very viable.  IF it's Cisco, then it's their way or the highway.

lui3 - good info ! Layer 2 has a lot to do with his gear if he's L2 on his IP setup of his phones.  If he's Layer 3 then he can do some software tricks if his equipment and software support it.

gbaughma - good solution, good product.

pnabby - awesome, ain't it ?  If you are need of 3Com NBX info and configs IPOTF and other info:

view: http://www.tek-tips.com/threadminder.cfm?pid=1230

and visit: http://www.nbxgroup.com and their forums too at: http://www.nbxgroup.com/nbxcommunityservices/index...

The older I get, the less I know

And to add - the WEIRDNESS that was suggested is there and the whole reason behind 802.16d is to:

Fix things not covered by 802.11c, (which is the standard for developing access points)

The older I get, the less I know

Can someone please post part numbers and approx prices for a 9 mile NLos solution of all current 3com part numbers?

oh yes.. and not 802.11 please..

and BTW. I would use the  Proxim Tsunami bridges myself.

I didn't say 3Com manufactures a solution for NLOS- you read more into it...I referred to "the Ghz solutions today..."

As for the 3Com solution talking about is their NBX, SS3 and vcx product line as was discussed by 'pnabby'

As for 802.16d the reference is to FIX weirdness (that you have issue with) in 802.11c

It ain't all 3Com and it's definitely not ALL Cisco.

To the edge and back, makes a difference.

Last one pondering point ccmuser- that's what's nice and LIKEABLE about 3Com products and solutions- they involve other product lines from other manufacturers !

The older I get, the less I know

BTW..  Just cause My screen name is CCMuser,  That does not mean I ONLY use CISCO!!!!!