help with SIP compatability

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aaron
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help with SIP compatability

Post by aaron » Thu Oct 13, 2011 8:31 pm

Hello, I am working for a telephone reseller (ESI) and I have a client that needs a specific 'secure' IP phone (TEO) and I want to make sure our comm server will talk to the phone via SIP/VoIP.

Is only one codec (G.711) needed, or do all need to match up between phone and server?
if both have 802.1q and DiffServ, do they also both need UDP and DHCP?
does 802.1p on the server side help or hinder a phone without that?

Thanks for the help, I know nothing about this type of protocall so please help me understand. :)

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paulej
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Re: help with SIP compatability

Post by paulej » Fri Oct 14, 2011 1:57 am

aaron wrote:Hello, I am working for a telephone reseller (ESI) and I have a client that needs a specific 'secure' IP phone (TEO) and I want to make sure our comm server will talk to the phone via SIP/VoIP.
I'm not sure what TEO is. A brand?
aaron wrote:Is only one codec (G.711) needed, or do all need to match up between phone and server?
One only needs one codec to match. However, many SIP devices will only offer one codec. The codecs usually chosen are G.711 or G.729, depending on available bandwidth to the phone. For the public Internet or bandwidth-contrained branch offices, use G.729. For communication over the LAN in an enterprise, use G.711. (If you have WAN links with plenty of bandwidth, use G.711. The audio quality is better.)
aaron wrote:if both have 802.1q and DiffServ, do they also both need UDP and DHCP?
This question does not make sense to me.
  • 802.1q is for VLAN support.
  • DiffServ is for indicating the class of service in an IP packet.
  • UDP is the protocol most commonly used to send media packets.
  • DHCP is a protocol for assigning dynamic IP addresses.
They all serve a different purpose.
aaron wrote:does 802.1p on the server side help or hinder a phone without that?
This is for indicating priority of packets at layer 2. So, I don't understand what you mean by having a server side.
aaron wrote:Thanks for the help, I know nothing about this type of protocall so please help me understand. :)
Folks on this board know this stuff, but I fully appreciate how overwhelmed you might be just getting into this area. It's definitely interesting to learn, but it will take a little time and it might be useful to get a book from Cisco on VoIP fundamentals. The information you might want to know is around the Internet, but having a good book with a lot of the background information would be helpful.

I'm happy to help answer questions, but it's hard to answer questions that are broadly scoped. If you were to ask me about specific messages or flows in H.323 or SIP, for example, that would be easier :-)

aaron
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Re: help with SIP compatability

Post by aaron » Fri Oct 14, 2011 12:33 pm

Thanks for the fast reply! This really helps clear up how the VoIP system will work. I think this will help make the sale.
Thanks again! :D

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