VOIP phones and qos

Unanswered Question
Jan 29th, 2008

Hi all, when using say siemens voice phones, do they mark the dcsp or 802.1p tag ? and can switches nowadays read both ?

I have this problem too.
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mchin345 Mon, 02/04/2008 - 10:36

I think it depends upon your QOS setings and device implementaion. You can configure the switch to trust or override the traffic priority assigned by a IP phone.

carl_townshend Tue, 02/12/2008 - 09:50

ok, so does the switch look at the dscp header? does it treat this as a tagged packet as i believe tagged means 802.1q, whereas the dscp header is in the ip payload part of the packet, so would the switch still treat this as a tagged packet .

please explain

royalblues Mon, 02/18/2008 - 00:11

Yes.. the new range of L2 switches are capable of reading the DSCP bits

Phone by defualt can set both the DSCP as well as the 802.1p values. You can configure your port to trust either the Cos or DSCP

DSCP is preferred as it would be end to end while with COS you would require COS-DSCP mapping



b_ferguson Fri, 05/30/2008 - 18:15


Did you get your QoS setup properly for Siemens' phones. I have a customer with Siemens phones and can't seem to find documentation of the dscp values for the phones. Any help would be greatly appreciated.



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