Re: [Roll] [roll] #89: Spec is limited to single interface intermediate routers

["roll issue tracker" <[e-mail]>]

#89: Spec is limited to single interface intermediate routers

Changes (by jpv@…):

 * status:  new => closed
 * resolution:   => fixed


Comment:

 #89: Spec is limited to single interface intermediate routers

 Problem
 ------------------------------
 The spec does not allow for routers with multiple interfaces. It expects
 that an address is usable downwards and upwards.

 Resolution:
 -----------------------------
 Add the following text to the Applicability section:

 "The participation in a P2P-RPL route discovery is currently limited to
 the routers with IPv6 addresses that are reachable in both forward and
 backward directions, which it quite typical in usual LLN routers with a
 single radio"

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

 [Pascal]
 "When an
 intermediate router adds itself to a route, it MUST ensure that the
 IPv6 address added to the route is reachable in both forward and  backward
 directions."
 This is written with the vision that the router has a single interface
 and acts as a repeater.
 But really a router could have 2 interfaces on a same subnet in which
 case that clause does not fly.

 [Mukul]
 All I mean is that the accumulated route MUST NOT have an address that
 cannot be accessed in one of the directions. If the address cannot be
 accessed in the backward direction, then the DRO would not be able to
 travel to the origin.

 [Pascal2] Then you're preventing a router with 2 interfaces. That's sad.
 I'm fine for an experimental draft   but for standard track that will
 have to be changed.

 [Mukul2] OK, I am keeping it the way it is.

 [Pascal3] This also need to be logged as a last call issue and its
 proposed resolution. Nothing wrong with having limitations, yet I think
 we must have specific text to indicate that the spec so far is limited  to
 devices with a single interface. When we make the Standard Track  version,
 I expect we'll have to go beyond that limitation. The drawback  is for
 experimental  implementations that may not be interoperable with  the
 final solution.

 [Mukul3] Could you please explain how does the requirement regarding
 addresses to be accessible in both forward and backward directions  limits
 P2P-RPL to only single interface devices? I think this  requirement means
 that P2P-RPL cannot be used across link layers. Is  that what you mean? I
 think allowing operation across link layers would  require P2P-RDO to
 accumulate additional information (backward address  to be used for
 forward addresses not accessible in backward direction).
 I think at the moment we want to avoid this complexity.

 [Pascal4] Because an IP address is associated to an interface. If you
 have 2 interfaces, even in a same subnet, there should be 2 addresses.

 [Mukul4] But, why would the two IP addresses the device has on the same
 subnet wont be accessible in both forward and backward directions?

 [Mukul5]
 I propose the following text to be placed inside the Applicability
 section:

 "The participation in a P2P-RPL route discovery is currently limited to
 the routers with IPv6 addresses that are reachable in both incoming and
 outgoing directions, which it quite typical in usual LLN routers with a
 single radio"

 Can we close this ticket?

 [Pascal5]

 I'd prefer to use upward and downward which are the terms that RPL
 traditionally uses....

 Is that OK with you? Otherwise yes, this text addresses my issue.

 [Mukul6]
 Should we use forward and backward terms? I already define them in the
 draft.

 [Pascal6]
 Yes, that would be perfect


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

Ticket URL: <http://trac.tools.ietf.org/wg/roll/trac/ticket/89#comment:1>
roll <http://tools.ietf.org/wg/roll/>