RE: CORRECTION Re: [EFM] EFM Requirements
Junmei-
802.3ac doesn't do anything about priorities anywhere within 802.3.
The ONLY normative thing that 802.3ac does within 802.3 is to
change:
maxFrameSize 1518
octets
to
maxUntaggedFrameSize 1518
octets
and
Add
provision to include:
QTag
Prefix
4 octets
This results in a maximum frame size of 1522 octets
The first 2 octets of the QTag Prefix constitute a normal EtherType
assignment
to call out a specific Ethernet protocol. The contents and behavior of
any such protocol (with the exception of MAC Control) is outside the
scope of 802.3
There is some "informative" information that indicates what use
802.1Q makes of some of the bits. That information is not normative to
802.3. It is part of 802.1Q.
As I said earlier, there is no priority mechanism within 802.3.
There are priority mechanisms in some Ethernet typed protocols. The
operation of those mechanisms is outside the scope of IEEE Std.
802.3.
Geoff
At 08:57 AM 8/21/01 -0500, Junmei Wang wrote:
How
about 802.3ac?
Junmei
- -----Original Message-----
- From: Geoff Thompson
[mailto:gthompso@xxxxxxxxxxxxxxxxxx]
- Sent: Monday, August 20, 2001 8:31 PM
- To: Harry Hvostov; mattsquire@xxxxxxx
- Cc: stds-802-3-efm
- Subject: CORRECTION Re: [EFM] EFM Requirements
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