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Re: [RPRWG] Destination Address of RPR control messages


The original reason for differentiating them (as I recall
and I could be wrong). Was to provide different addresses
so that the type of control message (broadcast or hop by hop)
could be easily determined in terms of receiption rules. 
Checking for all ones or all zeros is very easy and from
a debugging perspective, makes it very easy to identify

Using a single "reserved" multicast for both hop by hop
and control defeats the purpose of making the reception
rules easy. 

Using two has the ugly semantics of a multicast address 
used to mark a unicast packet.


Anoop Ghanwani wrote:
> According to Clause 8 in D0.2, the destination address
> is set to "all zeros" for hop-by-hop control packets,
> and "all ones" for broadcast control packets.
> Other IEEE 802 MACs use reserved multicast addresses to
> identify MAC control frames.  For example, IEEE 802.3
> flow control frames are sent with a destination address
> of 01-80-C2-00-00-01.  These frames are only sent on
> full-duplex Ethernet links and must not be forwarded
> by the MAC.
> Is there any reason for deviating from the standard
> practice?
> -Anoop
> --
> Anoop Ghanwani - Lantern Communications - 408-521-6707

Michael Takefman              tak@xxxxxxxxx
Manager of Engineering,       Cisco Systems
Chair IEEE 802.17 Stds WG
2000 Innovation Dr, Ottawa, Canada, K2K 3E8
voice: 613-254-3399       fax: 613-254-4867