3300 series and Voice over IP?

[TomMonger]

Are 3COM 3300 switches compatible with Voice over IP systems? I want to set up a Nortel 9150, MCK or ITG system over an existing data T1 connection between 2 of our buildings. There are already routers in place for the data, and our corporate people won't allow me to tamper with these routers. I understand I may be able to use the ITG card plugged directly into a LAN switch on the near side. There will only be 4 users on the far side.

Thanks,
-Tom in Scranton, PA

 

[ADB100]

Yes, or sort of depending on what QoS you expect to set up.......
The 3300 can only understand Layer-2 QoS (802.1p information in 802.1q VLAN tagged frames). I have looked at the documentation but there is no explicit control or viewing of how the 802.1p queues are handled. You would need to ensure that your Nortel kit was tagging frames with 802.1q headers (obviously make sure the VLAN tags match etc) and also that they were setting an 802.1p value, as to what value I can only guess, but probably 5. As to the clients these would need to do the same.
I would suggest if you need to deploy QoS then upgrade the 3300's for more inteligent switches that can handle QoS better - Cisco Catalyst 2950, 3550, 2970, 3750.

Andy

 

[TomMonger]

Thank you, Andy. I'll check into this further.

-Tom

 

[awj]

Create a seperate vlan for your voice traffic and let an intelligent L3 device sort out the QoS.

An alternative to the cisco products mentioned, would be the 3com 4400 series or 42xx/38xx series they also have QoS built into the hardware and are probably a lot cheaper.

 

[TimRegester]

The 3300 has only two queues, it can understand dscp priority and move VOIP packets into a higher queue, but this is not configurable and only really works for native NBX voip systems.

The 4400 is a better choice as it gives the increased functionality you need to configure prioritisation of packets.

That said if your network is not under heavy load it may not need prioritisation anyway, the 3300 works well in networks with VOIP when traffic levels are what I call normal i.e. peaks of 10Mbps per PC. I would try it and if it fails use either layer 3 QOS via a core switch or router or upgrade to the 4400. All of which are a damned sight cheaper than the cisco options mentioned and without the cost of ownership of Cisco kit.

The best implemenations of VOIP use dedicated switched networks or at the minimum dedicated VLANs (essential for DSCP anyway). But if you have a good network management and traffic stats moving

if you are making the investment in VOIP some form of RMON network management would help you keep tabs on your network performance and head off problems at pass.

 

[ADB100]

Tim

Where did you find the information on the 3300 and its support for DSCP????? I looked and could only see a vague comment about the switch recognising the 802.1p priority field in 802.1q packets, I saw nothing about DSCP or the number of queues etc. If you have alink to this information I would be grateful

Andy

 

[TimRegester]

I was privy to internal 3Com information. Most partners also have this information. Have you checked the knowledgebase and release notes for the 3300. There is a wealth of information in there that is not in the specs etc.

I will have a look for you when I get the chance.

 

[ADB100]

I have downloaded various documents from 3Coms website along with the release notes, I have also done some searching on the knowledgebase but I have never found anything. As I said the only thing I can find is a section in a manual in Acrobat format titled 'Traffic Prioritization' - it states 'If you use IEEE 802.1p traffic prioritization, we recommend that all relevant ports on your Switch are placed in one or more Virtual LANs(VLANs) using 802.1Q tagging. For a brief explanation of VLANs, see “Virtual LANs” on page 26. For a detailed explanation of VLANs and 802.1Q tagging, see “Virtual LANs (VLANs)” on page 163.'

and that is it.

Andy