I''d like to canvass thoughts on how big an IPv6 compatible NID
might be. We''d like to start anticipating changing to these NIDs
so that current development at least doesn''t dig us deeper into a
hole (e.g. on the nidtable entries sent over the wire in
imperative recovery). So here are some suggestions....
Current NID: 32 bit address-within LNET + 32 bit LNET number
64 bits / 8 bytes total
IPv6 compatible NID:
1. Minimum: 128 bit address-within-LNET + 32 bit LNET number.
160 bits / 20 bytes total.
2. Hedge a little by reserving an additional (say) 32 bits for
something we''ve not thought of yet and keeping the total a
multiple of 64 bits to simplify alignment.
192 bits / 24 bytes total.
3. Hedge a lot with a nice round number.
256 bits / 32 bytes total.
(2) gets my vote currently...
Cheers,
Eric
Eric Barton
CTO Whamcloud, Inc.
Tel: +44 (117) 330 1575
Mob: +44 (7920) 797 273
On Tue, 11 Oct 2011 14:20:44 +0100 "Eric Barton" <eeb at whamcloud.com> wrote:> 2. Hedge a little by reserving an additional (say) 32 bits for > something we''ve not thought of yet and keeping the total a > multiple of 64 bits to simplify alignment. > 192 bits / 24 bytes total. > > 3. Hedge a lot with a nice round number. > 256 bits / 32 bytes total.i would pick this. you never know what address size is coming in the future for any particular protocol. the infiniband link layer is 160 bits. so if someone implemented a ''native'' ib solution they would need 160 + 32 (192). of course, option 2 would work fine in this case. however, unless there is a pressing reason i would just pick 256 because we already have a case that could use up your ''hedge a little''.
On Oct 11, 2011, at 6:20 AM, Eric Barton wrote:> I''d like to canvass thoughts on how big an IPv6 compatible NID > might be. We''d like to start anticipating changing to these NIDs > so that current development at least doesn''t dig us deeper into a > hole (e.g. on the nidtable entries sent over the wire in > imperative recovery). So here are some suggestions.... > > Current NID: 32 bit address-within LNET + 32 bit LNET number > 64 bits / 8 bytes total > > IPv6 compatible NID: > > 1. Minimum: 128 bit address-within-LNET + 32 bit LNET number. > 160 bits / 20 bytes total. > > 2. Hedge a little by reserving an additional (say) 32 bits for > something we''ve not thought of yet and keeping the total a > multiple of 64 bits to simplify alignment. > 192 bits / 24 bytes total. > > 3. Hedge a lot with a nice round number. > 256 bits / 32 bytes total. > > (2) gets my vote currently...The cost of the bytes is so minor compared to the cost of revving the protocol, I vote for 3. BTW, Isaac is starting to look in to how much work it would be to rev the protocol for full IPv6 interoperability.______________________________________________________________________ This email may contain privileged or confidential information, which should only be used for the purpose for which it was sent by Xyratex. No further rights or licenses are granted to use such information. If you are not the intended recipient of this message, please notify the sender by return and delete it. You may not use, copy, disclose or rely on the information contained in it. Internet email is susceptible to data corruption, interception and unauthorised amendment for which Xyratex does not accept liability. While we have taken reasonable precautions to ensure that this email is free of viruses, Xyratex does not accept liability for the presence of any computer viruses in this email, nor for any losses caused as a result of viruses. Xyratex Technology Limited (03134912), Registered in England & Wales, Registered Office, Langstone Road, Havant, Hampshire, PO9 1SA. The Xyratex group of companies also includes, Xyratex Ltd, registered in Bermuda, Xyratex International Inc, registered in California, Xyratex (Malaysia) Sdn Bhd registered in Malaysia, Xyratex Technology (Wuxi) Co Ltd registered in The People''s Republic of China and Xyratex Japan Limited registered in Japan. ______________________________________________________________________
On Tue, Oct 11, 2011 at 02:20:44PM +0100, Eric Barton wrote:> ...... > IPv6 compatible NID: > > 1. Minimum: 128 bit address-within-LNET + 32 bit LNET number. > 160 bits / 20 bytes total.(1) might cause alignment problem somewhere. I remember that the PTLLND is picky on alignments, and there might be more such places.> 2. Hedge a little by reserving an additional (say) 32 bits for > something we''ve not thought of yet and keeping the total a > multiple of 64 bits to simplify alignment. > 192 bits / 24 bytes total. > > 3. Hedge a lot with a nice round number. > 256 bits / 32 bytes total. > > (2) gets my vote currently...I''d feel happy to pay the extra 8 bytes for the peace of mind that I wouldn''t have to handle this again. - Isaac ______________________________________________________________________ This email may contain privileged or confidential information, which should only be used for the purpose for which it was sent by Xyratex. No further rights or licenses are granted to use such information. If you are not the intended recipient of this message, please notify the sender by return and delete it. You may not use, copy, disclose or rely on the information contained in it. Internet email is susceptible to data corruption, interception and unauthorised amendment for which Xyratex does not accept liability. While we have taken reasonable precautions to ensure that this email is free of viruses, Xyratex does not accept liability for the presence of any computer viruses in this email, nor for any losses caused as a result of viruses. Xyratex Technology Limited (03134912), Registered in England & Wales, Registered Office, Langstone Road, Havant, Hampshire, PO9 1SA. The Xyratex group of companies also includes, Xyratex Ltd, registered in Bermuda, Xyratex International Inc, registered in California, Xyratex (Malaysia) Sdn Bhd registered in Malaysia, Xyratex Technology (Wuxi) Co Ltd registered in The People''s Republic of China and Xyratex Japan Limited registered in Japan. ______________________________________________________________________