RE: CORRECTION Re: [EFM] EFM Requirements
How
about 802.3ac?
Junmei
Harry/Matt
At 08:09 PM 8/20/01 -0400,
Matt Squire wrote:
Harry Hvostov wrote:
>
>
Matt,
>
> For the record, the actual stream transport for VoIP
is done via RTP/RTCP -
> application
> layer protocols. Needless
to say, these protocols would rely on the QoS
> mechanisms supported
at L2/L3. For an example of mapping the MGCP session
> descriptions
into L2 QoS parameter
> sets please see PacketCable 1.0 Dynamic QoS
specification at
> www.packetcable.com. The spec is publicly
available.
>
So what. At the Ethernet level a packet has
priority.
For the record: At the Ethernet level, a packet has
NO priority.
There is no mechanism to manipulate or order Priorities
anywhere in 802.3
There is a field allocated in the 802.1Q VLAN TAG that
allows "user priority" information to be transported across Ethernet in an
agreed upon location within a packet within a particular Ethernet protocol
(802.1QTagType: 0x81-00)
This information location of not normative in
802.3
This information acted upon anywhere in 802.3
This priority
information is a feature of 802.1Q, not 802.3
There are many other Ethernet
protocols,each with their own identifying Type number. More than a few of them
have a field for priority information. We (802.3) treat those protocols in
exactly the same way that we treat packets of the 802.1Q protocol type, that
is, we send them and receive them between the MAC Client and the medium on a
first-in, first-out basis. That's all.
Geoff