Re: [Roll] [roll] #90: use of transient instance ID

[Mukul Goyal <[e-mail]>]

Hi Pascal

Please see inline.

Thanks
Mukul

[Pascal] Also, when there are no routing states in intermediate routers, an indication from upper layers can be used in the end points to consider that all states for an instanceID are now cleaned up.

[Mukul] Not sure what you mean. 

[Pascal2] Let me reword:  if HbH routin gis not used, the only states with any persistence are on the origin and target(s). The upper layer protocol (ULP) in origin and target may know when they are done with their need for the routes. If they are done before (config option) lifetime is up, they can tear down the states. This requires a new cross layer interaction triggered by ULP, similar to IPv6 ND in DELAY state.

[Mukul2]
You think P2P-RPL needs to define this cross-layer interaction? This is simply the upper layer telling the network layer to chuck a source route. Isn't it? The upper/lower layers dont even need to remember that this route was discovered using P2P-RPL. Also, the origin (or the target) can use a source route as long as it wants. Why should the lifetime in config option dictate how long this route can be used?

----- Original Message -----
From: "Pascal Thubert (pthubert)" <[e-mail]>
To: "Mukul Goyal" <[e-mail]>, [e-mail]
Sent: Tuesday, April 10, 2012 4:52:50 AM
Subject: RE: [Roll] [roll] #90: use of transient instance ID

Mukul:

I meant a suggestion, not a capitalized word. I prefer the suggestion but I'm still OK with your proposal. If we get in agreement on the lifetime of the states (issue #85), then you can indicate that lifetime is one way to determine when all stale states can be considered gone. Also, when there are no routing states in intermediate routers, an indication from upper layers can be used in the end points to consider that all states for an instanceID are now cleaned up.

Cheers,

Pascal


-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Mukul Goyal
Sent: dimanche 8 avril 2012 18:09
To: [e-mail]
Subject: Re: [Roll] [roll] #90: use of transient instance ID

Hi Pascal

Re-read your proposed resolution text. I am not sure that the draft should suggest rotating the instance ids. My proposed resolution is to simply suggest not using instance id that might be in use.

" [Mukul2] Makes sense. I think it is sufficient to caution (with a SHOULD
 NOT) against reusing instance ids for which the stale state might exist  in the nodes."

Thanks
Mukul

----- Original Message -----
From: "roll issue tracker" <[e-mail]>
To: [e-mail], [e-mail]
Cc: [e-mail]
Sent: Wednesday, April 4, 2012 8:11:44 AM
Subject: [roll] #90: use of transient instance ID

#90: use of transient instance ID

 Problem (resolution agreed upon)
 ------------------------------
 P2P creates temporary states in the transient DAG with a transient  instance ID. The protocol must ensure that if the instance ID is reused  then the new operation it is not confused with states resulting from the  previous use of the same instance ID. Suggestion is to propose a  rotation.

 Discussion
 -------------

 [Pascal]
 "RPLInstanceID: RPLInstanceID MUST be a local value as described in  Section 5.1 of [I-D.ietf-roll-rpl]. The origin MUST NOT use the same  RPLInstanceID in two or more concurrent route discoveries."

 I'd suggest that you enforce a round robin or an opaque circulation so  that the new instanceID is the least recently used one out of the 64  possible.

 [Mukul]
 I think we should leave it to the origin to decide which value it wants  to use for RPLInstanceID. I know some implementations are planning to  use a fixed RPLInstanceID value for all route discoveries.

 [Pascal2] Changing the instance ID will help debug the network and avoid  conflicts with stale states. What's really up to the device is the  initial sequence. Leaving it up to the origin may help the origin defeat  some attacks to some degree. OTOH, after all the instances have been  played, LRU forces to replay the same sequence again so the shield  drops. My preferred approach would be a SHOULD that would say that the  next instance ID SHOULD NOT be one of the (16?) most recently used and  MUST NOT be one for which states might still exist in the network. IOW  either the states deletion was acknowledged, or all pending lifetimes  are exhausted.

 [Mukul2] Makes sense. I think it is sufficient to caution (with a SHOULD
 NOT) against reusing instance ids for which the stale state might exist  in the nodes. Using a "MUST NOT" may not be OK since a node may never be  100% sure about non-existence of stale state with a particular instance  id (thus, all possible instance id values will become suspect and hence  unusable after a while).

 [Pascal3] Agreed. Note that a circulation is a bonus to defeat replays.
 And now we're back to the issue above. How does the device know that  there is no state left? A lifetime definition would be very useful. That  lifetime is different from the DAG's one in RDO. I think we have an open  issue here.

 [Mukul3] As I mentioned above, the life time parameters inside the DODAG  configuration option specify the life time of the hop-by-hop routing  state for the routes discovered using P2P-RPL.

 [Pascal4] This boils down to the thread above. Only one issue really,  which lifetime is which? So IMHO no need to log anything for this  thread.

 [Mukul4] OK.

 Pascal

-- 
-----------------------------------+---------------------
 Reporter:  jpv@…                  |      Owner:  mukul@…
     Type:  defect                 |     Status:  new
 Priority:  major                  |  Milestone:
Component:  p2p-rpl                |    Version:
 Severity:  Submitted WG Document  |   Keywords:
-----------------------------------+---------------------

Ticket URL: <https://svn.tools.ietf.org/wg/roll/trac/ticket/90>
roll <http://tools.ietf.org/wg/roll/>

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