| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
Chao.
Just back from the holidays ...
A bit of context is in order.
SAS (Spatially Aware Sublayer) is a sublayer of the RPR (802.17) MAC. It is not a (bridge) client of the MAC. SAS (amongst other things) will improve the spatial awareness (i.e., improve the bandwidth utilization) of traffic of the RPR media when bridge clients (as defined by IEEE 802.1) are involved.
Persistent flooding that may occur in a bridged network is an artifact of (IEEE 802.1) Bridge clients behavior/operation. Consequently, the issue of persistent flooding and SAS is a bit orthogonal.
That being said, the 802.17-2004 specifications attempted to deal with the potential persistent flooding issues. The RPR MAC will essentially flood frames being transmitted by a Bridged client over the RPR media in order to mitigate the resulting persistent flooding within the bridged network containing RPR. The obvious side-effect of this solution is that the bandwidth utilization over the RPR media is impacted in order to preserve the integrity of the network (by eliminating the potential persistent network flooding). What SAS will do is address the persistent flooding over the RPR media.
To re-iterate, there are two things to consider:
1) Persistent flooding within a bridged network (containing RPR), and
2) Persistent flooding over the RPR media.
The 802.17-2004 specifications address the first issue. The SAS will address the second issue while maintaining the solution for the first issue.
Regarding your second point ...
The package that you referenced is one of the options currently being considered. The three options being considered are summarized by: http://www.ieee802.org/17/documents/presentations/nov2004/MH_SAS_interworking_options_01.pdf
The groups current position is that when SAS capable RPR MACs interact with non-SAS capable RPR MACs, the functional behavior will degenerate to no spatial aware improvements.
Persistent flooding over the RPR media does NOT occur when two SAS capable RPR MACs are involved in frame transmissions and receptions for a given session. A flood over the RPR media (i.e., undirected Tx) does occur for the first transmission, however once the RPR MAC "proxy" providing an attachment interface to the end client address is learnt, directed transmissions (i.e., unicast transmissions) over the RPR media will persistently occur. Consequently, persistent flooding over the RPR media does not exist between two SAS capable RPR stations.
In general, I think we need to clearly delineate the persistent flooding issues. One is over the RPR media, and the other is within a bridged network containing RPR. SAS addresses the former issue, while the 802.17-2004 MAC addresses the latter.
Marc Holness
-----Original Message-----
From: owner-stds-802-17@LISTSERV.IEEE.ORG [mailto:owner-stds-802-17@LISTSERV.IEEE.ORG] On Behalf Of Wang Chao (SW)
Sent: Wednesday, January 05, 2005 4:27 AM
To: STDS-802-17@LISTSERV.IEEE.ORG
Subject: [RPRWG] Concerns about 802.17b ideas.
Hi all,
I have read the recent 802.17 group meeting presentations about 802.17b.
Here I bring out two concerns.
(1) How dos SAS layer solve the persistent flooding at bridged 802.3 network problem, which is specified by 802.17-2004 standard's annex F.1.4.2.1?
The recent presentations seemed not care about it, except for http://www.ieee802.org/17/documents/presentations/oct2004/ng_SR_01.pdf page 4. I think the incomplete learning issue is the same as persistent flooding issue.
(2) Why SAS aware station can not do SAB update(learning) for remote frames sent by non-SAS station?
Alough http://www.ieee802.org/17/documents/presentations/nov2004/rc_SASehb_01.pdf page 3 gave an example for why, but I think this example is not convincing.
Because the persistent flooding is also exist when do learning between two SAS aware stations.
Would any experts be kind to make clear explaination about these two issues?
Best Regards,
Chao Wang
Photonic Bridges.
86-21-61101124