Re: [RE] Grand master identifier
Hugh and John
Actually there is a well know and inexpensive way for provisioning
admission control. It is called a MAC.
A gig capable bridge with multi-speed ports can restrict admission of a
requesting service to 10, 100 or Gig.
If it always keeps ports in a default state of 10 then they can make
service requests for the port to reboot to a higher speed.
Geoff
At 07:22 AM 5/6/2005 -0700, Hugh Barrass wrote:
>John,
>
>It depends on how you measure cost.
>
>I assume that any RE device will support IP- in fact, I would recommend
>against any networked device ignoring that requirement. This means that
>the devices will also support DHCP and DNS. Furthermore I would recommend
>that most devices will also support either TCP or UDP and that any key
>device will support HTTP. Given those assumptions, incremental requirement
>to support RSVP will be no more than 10's of kbytes of codespace. A
>reasonably implemented and appropriately scaled device (whether end
>station or hub) should be able to support a standard method for
>provisioning at NO INCREMENTAL COST. I would like to see an analysis
>disproving this that also demonstrates why a new standard would not incur
>equivalent overheads. Remember that the argument that nobody builds it
>today is equally applicable to anything new that is proposed.
>
>Regarding your comments - it is absolutely true that no mechanism exists
>in 802.3 for either of those requirements. This is because both of those
>requirements are met (or otherwise) by the bridge and the system behavior.
>Nothing in the definition of a PHY or a fullduplex MAC will help to meet
>those requirements (with the exception of PHY latency that is under
>discussion in 10GBASE-T). It is entirely specious to suggest that anything
>defined at a higher layer (than 802.3) will be too expensive or not
>interoperable. There are many things that are very cheap indeed and
>interoperate perfectly that are not defined by 802.3 - although I would
>recommend against any physical layer network interface defined by anyone
>else :-)
>
>Hugh (speaking for myself, and not representative of the views of ITU-T :-)
>
>John Gildred wrote:
>
>>Hi Hugh:
>>
>>I am not aware of any low cost standardized methods for provisioning,
>>admission control, policing and QoS which work together to satisfy
>>the requirements of RE. The consumer electronics definition of low
>>cost is NO INCREMENTAL COST.
>>
>>My understanding of the 2 most basic RE requirements:
>>1. We need a low cost way to ensure that the traffic for one
>>application does not interfere with the timely delivery of all
>>traffic for another application.
>>2. We need a low cost way to ensure a very low max latency (250 usec
>>per hop) for all traffic of a specific application.
>>
>>My comments on current mechanisms for this in 802.3:
>>A. There is no mechanism in 802.3 to ensure requirement #2 will be
>>met in every case, across various implementations.
>> -Overprovisioning cannot provide such a guarantee as more
>>applications are added to the network.
>> -There is no admission control system for 802.1D priorities.
>>Of course, higher layer protocols (Layer 3+) could be used for
>>admission control, but at considerable cost and added risk to
>>interoperability.
>>B. There is no mechanism in 802.3 to ensure requirement #2 will be
>>met in every case, across various implementations.
>>