[Rstplib-users] RE: operEdge: per Port or per MSTi in 802.1s ?

[Mick S. <mic...@ie...>]

Alex,

The port is either enabled for all MSTIs, and operEdge or not for all MSTIs
or not.

Pruning of VLANs is not done by the spanning tree, but by GVRP and the
associated controls that either feed into GVRP or manually substitute for
it.

If two bridges disagreed on MSTIs then, for one of them at least, the LAN
that connected them would be in a different region. That would mean frames
for all MSTIs would be delivered to this LAN by one or other of the Bridges.
It follows that a Bridge Port cannot be operEdge for some MSTIs and not for
others.

Mick

-----Original Message-----
From: own...@ma...
[mailto:own...@ma...]On Behalf Of Alex Ruzin
Sent: Thursday, December 13, 2001 4:56 AM
To: 'Tony Jeffree'
Cc: std...@ie...; rst...@li...
Subject: RE: operEdge: per Port or per MSTi in 802.1s ?



But all decision about Port Roles & Port states and
optimizations with Designated Port agreement handshake
we make "per MSTi", don't we ?

Another words: if in all VLANs, mapped to the MSTi,
there is no STP bridges,
connected to the Port, may we think, that operEdge
of this Port is TRUE *in this MSTi* ?

The similar considerations about portEnabled: may the port be
enabled in some MSTi (i.e. for all VLANs from this MSTi) and
disabled in another one ?

Best regards, Alex
---------------------
Open Source RSTP  https://sourceforge.net/projects/rstplib/
Optical Access Ltd. http://www.opticalaccess.com

> -----Original Message-----
> From: Tony Jeffree [mailto:to...@je...]
> Sent: Thursday, December 13, 2001 1:37 PM
> To: Ar...@op...
> Cc: std...@ie...; rst...@li...
> Subject: Re: operEdge: per Port or per MSTi in 802.1s ?
>
>
> The use of operEdge to signal an edge port allows the
> Spanning Tree state
> machines to make optimizations in transitions to Forwarding
> on such ports,
> based on the assumption that because the port is an edge port, there
> is   no bridge attached to the port (which, by definition,
> would mean that
> the port is not an edge port).
>
> Seeing *any* BPDU on a port that had been flagged as an edge
> port means
> that there is a bridge out there - and therefore, that the
> port is not at
> the edge of the bridged LAN, and therefore, any spanning tree
> optimizations
> that were based on the assumption that the port was an edge
> port are no
> longer valid.  Continuing to behave as an edge port in these
> circumstances
> would carry the risk of creating loops in one or more of the
> MSTIs and/or
> CIST. Hence, it is only necessary to have a single instance
> of the variable
> per port for it to do its job.
>
> Regards,
> Tony
>
> At 12:10 13/12/2001 +0200, Alex Ruzin wrote:
>
> >Hi,
> >
> >In 13.25 of 802.1s it is pointed, that the variable operEdge
> is  "single
> >per-Port instance
> >applies to the CIST and to all MSTIs."
> >
> >Why ?
> >If a Port had received BPDU with tag of some MSTi and had
> >not received any BPDU from another,
> >why we have to consider it as operEdge port in this second MSTi ?
> >
> >Best regards, Alex
> >---------------------
> >Open Source RSTP  https://sourceforge.net/projects/rstplib/
> >Optical Access Ltd. http://www.opticalaccess.com
>
>