Cisco and DiffServ settings

[NYSTECH]

Just a quick question. I have been getting more and more into Ip phone installation with IP office and different routers/switches
Do you make it a pratice of changing the diffServe settings depending on the switch your connecting with or leave them default?

 

[tlpeter]

Most of the times it is like it should be.
Open the config and go to Lan 1 and you will find the values that the IPO and IP phones use.

BAZINGA!

I'm not insane, my mother had me tested!

 

[NYSTECH]

Wouldn't these settings be changed depending on the switch type connected to in order to do the proper tagging and QOS throught the network?

 

[CarGoSki]

Yes but QOS would be implemented at the router stage for ip trunk and at the switch port stage to prioritze queued traffic. The point is that you can change either the router and switch diffserve settings to match ipo or vice versa.

If qos for voip has not been implemented at the site then it is better to match the existing ipo settings.

 

[amriddle01]

Don't forget the default DSCP value is 46 which means EF (expedited forwarding) and is the most widepread setting on IP telephony for this (not just by Avaya) and will be honoured by most equipment by default

http://www.ipoffice.tel

 

[NYSTECH]

Thanks for the info and education.. Some of these settings I never touch until someone asks about them... The DSCP value for the Cisco that is connected is 26 and I have change the IP office to match that.. seems to be working fine..

 

[mattKnight]

>and will be honoured by most equipment by default

Most cisco switches will strip the DSCP settings, unless told otherwise

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[mattKnight]

Most cisco switches will strip the DSCP settings, unless told otherwise

If they have QoS enabled that is...

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[kholladay]

That is just plain wrong. DSCP 26 is AF (Assured Forwarding) with low drop probability but still qualifies for drop. Voice and video traffic should by definition always be marked as EF (Expedited Forwarding) aka DSCP 46.

Kyle Holladay / IPOfficeHelp.com
ACSS & APSS SME Communications
MCP/MCTS Exchange 2007
Adtran ATSA, Aruba ACMA

"I have one speed, I have one gear...GO!!!" - Charlie Sheen

"Thinking is the hardest work there is, which is the probable reason why so few engage in it." - Henry Ford

 

[mattKnight]

>Voice and video traffic should by definition always be marked as EF (Expedited Forwarding) aka DSCP 46.

I agree Voice should be marked as EF, but becuae of the bursty nature of Video, I'd mark that as AF31

A bit philosphical I know...

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[kholladay]

I would as well if I had both on the same network as voice is more important than video however when we do only video and no voice I mark it as EF to avoid the quality complaints.

Kyle Holladay / IPOfficeHelp.com
ACSS & APSS SME Communications
MCP/MCTS Exchange 2007
Adtran ATSA, Aruba ACMA

"I have one speed, I have one gear...GO!!!" - Charlie Sheen

"Thinking is the hardest work there is, which is the probable reason why so few engage in it." - Henry Ford

 

[mattKnight]

@kyle - fair point

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[CarGoSki]

26 appears to be for http.
You need 46 for voice quality
Perhaps the site net admin is more familiar with web traffic than voice traffic.

http://www.cisco.com/en/US/docs/ios/12_1t/12_1t5/feature/guide/dtdfsv.html

 

[NYSTECH]

I like a good discussion/education. So correct me if I am not right, But, basically if QOS is set on network I should just leave the IPO difserv setting at default..

 

[mattKnight]

>basically if QOS is set on network
>IPO difserv setting at default.

It depends on how the QoS is setup on the network...



Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[kholladay]

There are standards though. Voice wants low delay, low jitter and no drop rate. This is the definition of Expedited Forwarding (EF / DSCP 46). Sure you can use other things. Hell for that matter you can map Best Effort (BE) traffic to your high priority COS queue and really do something funky.

QoS on switches are usually handled in one of two ways. Either they recognize and act on the raw DSCP values or they map DiffServ to Class of Service (COS) queues and each vendor had different numbers of COS queues in their various switches for more granularity. It is usually the mapping of DiffServ to COS where things get screwed up.

Kyle Holladay / IPOfficeHelp.com
ACSS & APSS SME Communications
MCP/MCTS Exchange 2007
Adtran ATSA, Aruba ACMA

"I have one speed, I have one gear...GO!!!" - Charlie Sheen

"Thinking is the hardest work there is, which is the probable reason why so few engage in it." - Henry Ford

 

[NYSTECH]

Ok so this is what is set
DSCP is 46
DSCP mask is 63
sig dscp is 26.. This is what Cisco uses to tag packets correct/

sp it isn't the forwarding setting?