Need to prioritize port 5060 only - no DSCP

[jacob6000]

Hello

We are working to implement a voip solution. We are outsourcing our voip management. We basically have been given phones and the manager software resides at the provider's location.  The phones are using a standard data connection, ie: no trunking/802.1q, therefore no DSCP markings.

What is the easiest way to assure that all outbound traffic  to the internet on port 5060 gets the highest priority?

Thank you,

[cadet alain]

Hi,

The phones are using a standard data connection, ie: no trunking/802.1q, therefore no DSCP markings.

This is incorrect, no trunking means no COS but not no DSCP because DSCP is a L3 marking.

Regards.

Alain

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[jacob6000]

My apologies. No COS. Having said that, can you elaborate on the method to prioritize port 5060 traffic amongst all others?

[cadet alain]

Hi,

you can use an ACL to match traffic destined to  TCP/UDP port 5060 but this is control SIP traffic, you will also have to consider VoIP data traffic which is RTP( using UDP).You'll have to use LLQ and put the RTP traffic in the priority queue and

give some bandwidth for the call control packets( port 5060).

you'll find an example describing LLQ/CBWFQ here:http://netcerts.net/cbfq-and-llq-congestion-management-techniques/

Don't forget that this is QoS congestion management and so it comes into play only when there is congestion on the link.

Secondly in the Internet there is no QoS, everything is Best effort so unless you have a MPLS connection or are using a Tunnel you won't be able to maintain the priority of your packets from your side to the other side.

Regards.

Alain

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[Joseph W. Doherty]

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Posting

Secondly in the Internet there is no QoS, everything is Best effort so unless you have a MPLS connection or are using a Tunnel you won't be able to maintain the priority of your packets from your side to the other side.

To expand a little on Alain's comment.

Normally, Internet devices will not honor user set DSCP markings.  Also, Internet device might not pass user set DSCP markings (i.e. they might change the DSCP value).

Protecting original packets markings can be guaranteed if the packets are first encapsulated into another packet (tunneled) before sending them out to the Internet (as mentioned by Alain).

As  congestion is most likely on the links to/from the Internet, QoS can often be effective if packets are "QoS'ed" sequenced before sending them to the Internet and if both user sides manage and allow for only their traffic.  For example, if two different connections to the Internet only pass their traffic between themselves, you often can achieve QoS like performance similar to a dedicated p2p link.