Hello Robert,
Please see feedback inline [JL]

Any other comments from folks in the alias?

From: [email protected] [mailto:[email protected]] On Behalf Of Robert Raszuk
Sent: Tuesday, December 09, 2014 12:09 PM
To: Jose Liste (jliste)
Cc: [email protected]
Subject: Re: [bess] BESS - soliciting WG adoption - 
draft-keyupate-l2vpn-fat-pw-bgp

Hi Jose,

Great signature :)

One observations. The draft says:


"When the bit value is 1, the PE is requesting the ability

to send a Pseudowire packet that includes a flow label."



How can PE "request the ability" by setting a bit flag ?



[JL]During the PW signaling phase, the T/R bit flag values in the outgoing / 
incoming NLRIs will indeed allow a PE to determine whether it can use / expect 
flow labels on a given PW direction



I recommend if you want to keep it you replace the "requesting the ability" by 
"indicating the ability".



[JL] The T-bit indicates more than ability to transmit. It means desire to 
transmit (which of course requires it to be capable). For backwards 
compatibility, with T = 0, a non-capable (legacy) PE would transmit the same 
value as a capable one that does NOT wish to transmit FL

For consistency, please note that we are keeping the T/R bit definitions 
aligned with RFC6391



But is there any real use case for T flag at all ? What happens if node first 
advertised that it can not include flow label, but then sends packets to egress 
PEs with flow label ? Would you drop such packets?



[JL] Re-programming of data-plane after signaling and contradicting what was 
signaled should be treated as a defect in the PEs implementation. PWs must be 
re-signaled before making such change. Back to the hypothetical scenario, the 
egress PE is programmed NOT to expect flow labels. Any PW traffic arriving with 
“unexpected” FL will treat it (FL) as service delimiting (VC label). This will 
most likely translate to traffic being dropped (i.e. egress PE has no context 
for the label value) or in the worst case, could cause miss-merge



For completeness, see below a slide with the different states associated to T/R



Regards,

Jose



[cid:[email protected]]



Thx,

r.

On Tue, Dec 9, 2014 at 11:55 AM, Jose Liste (jliste) 
<[email protected]<mailto:[email protected]>> wrote:
Hi BESS WG,

Draft “draft-keyupate-l2vpn-fat-pw-bgp” proposes protocol extensions required 
to synchronize flow label states among PEs when using the BGP-based signaling 
procedures defined in RFC4761 / RFC6624
https://tools.ietf.org/html/draft-keyupate-l2vpn-fat-pw-bgp-03

We have presented this draft a couple of times in the L2VPN WG.

We would now like to solicit comments from the BESS WG. We believe that the 
draft is ready for WG adoption.

We request chairs and WG to consider adopting the draft as a WG document.

Best Regards,

[http://www.cisco.com/web/europe/images/email/signature/horizontal01.jpg]

Jose Liste
ENGINEER.TECHNICAL MARKETING
Corporate Development
[email protected]<mailto:[email protected]>
Phone: +1 408 527 3369<tel:%2B1%20408%20527%203369>


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