[Asterisk-Users] 802.1p , precedence and TOS

[SCollins]

I Don't know if this is a solution that is not better suited for your  
Linux Distro, using vconfig and a 802.1q/1p aware NIC, on the * Server, to  
create and prioitize the Ingress and Egress Voice VLAN traffic.

Would you not agree?

Sean












  On Wed, 20 Apr 2005 21:14:17 +0200, Eugenio De Vena <edevena at gsy.it>  
wrote:

> Thanks for your kind help, I understand ip precedence and that's ok. I  
> also
> found on Snom phones how to mark 802.1p ( which is what I need now ). On
> the 3Com 3300 802.1p is enabled and correctly priorized . The only thing  
> I miss
> is how to tell asterisk to originate rtp packet marked with 802.1p tag  
> ( at layer 2 )
> Any idea?
>
> ----- Original Message ----- From: "SCollins" <smjjscollins at comcast.net>
> To: "Asterisk Users Mailing List - Non-Commercial Discussion"  
> <asterisk-users at lists.digium.com>
> Sent: Tuesday, April 19, 2005 8:45 PM
> Subject: Re: [Asterisk-Users] 802.1p , precedence and TOS
>
>
>> Questions:
>> 1) How can I set the 802.1p precedence field from Snom and asterisk?
>>
>> 2) Which is the differences between the IP Precedence field and TOS
>>  field?
>>
>> IP Precednce and ToS are synonymous. There is a 3-bit ToS field in the  
>> IP header that allows for 8 levels of classification of IP traffic -  
>> these are known as the IP precedence bits.
>>
>> 802.1p or CoS (Class of Service) is a Layer 2 Prioitization protocol.  
>> 802.1p uses a 3-bit prioitization field, in an 802.1q TAG,to define 8  
>> priority levels.  To obtain the correct Layer 2 CoS on your 3300 I  
>> believe you need to set the prioritization on the IP phone, using  
>> 802.1q and then setting the prioritization, and then configure the  
>> clasifiers and profiles on the 3Com 3300 so that it will remark the  
>> packets on ingress.  The CoS traffic classification will need to be  
>> configured on ALL Switches in your network for the 802.1p prioritzation  
>> of the Voice traffic.
>>
>> Most layer 3 Switches support both ToS and CoS and will re-mark the  
>> 802.1p Prioritization into the ToS field in the IP header, so that if  
>> the traffic is being routed, between VLANs for example, the traffic  
>> will maintain it's priority.
>>
>>
>> Hope this helps.
>>
>> Sean
>>
>>
>> On Tue, 19 Apr 2005 15:28:43 +0200, Eugenio De Vena <edevena at gsy.it>  
>> wrote:
>>
>>> Hello everyone, I have some doubt on the QoS matter and I hope that  
>>> someone
>>> could
>>> bring me some light.
>>> I see my 3Com 3300 switch supports 802.1p priorization ,
>>> I see through Microsoft network monitor that the packet coming from my  
>>> SIP
>>> phones
>>> have in IP header  a field which is marked "Precedence" and when the  
>>> packet
>>> is sent from
>>> phone to asterisk the value is "CRITICAL/EXP" , when the packet is  
>>> sent back
>>> from asterisk
>>> to phone the value is "Normal". To correct this I set the value "Tos"  
>>> in
>>> sip.conf to 160 and now
>>> the packet sent back from asterisk to phone is marked "CRITICAL/EXP"  
>>> too.
>>> Fine.
>>> Under the field "Precedence" there is a value called "Type of Service"  
>>> (
>>> TOS ) and the values is
>>> "Normal" both ways.
>>>
>>> Googling around I see that 802.1p is a Layer2 and not Layer3  
>>> specification
>>> so it must work at MAC level,
>>> so I think that these field which are contained into the IP header are  
>>> not
>>> considered  by my switch and are just ignored.
>>> The Ip precedence field I think would be considered when routed by a  
>>> QoS
>>> router ( which is not my case ).
>>>
>>> Questions:
>>> 1) How can I set the 802.1p precedence field from Snom and asterisk?
>>> 2) Which is the differences between the IP Precedence field and TOS  
>>> field?
>>>
>>> Thanks Everyone
>>> Eugenio
>>>
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>>
>>
>>
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>>
>>
>>
>
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