RE: Here is the reference to 6.3.4 text that is ambigious text

["Hemant Singh (shemant)" <shemant at cisco.com>]

Title: Here is the reference to 6.3.4 text that is ambigious text

Since Thomas suggested some similar text, could folks please reply to this email from Josh.

 

Thanks.

 

Hemant

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From: Josh Littlefield (joshl)
Sent: Wednesday, December 05, 2007 2:08 PM
To: Hemant Singh (shemant)
Cc: Suresh Krishnan; bob.hinden at nokia.com; IETF IPv6 Mailing List
Subject: Re: Here is the reference to 6.3.4 text that is ambigious text

It is not crystal clear, but my impression is that this paragraph is saying:

Default sending behavior is send to default router.
Reception of L=1 signals on-link (can use ND to send directly)
Reception of L=0 is no-op.

Because L=0 is no-op, if one considered the prefix on-link due to prior L=1, then prefix is still on-link.
If one did not consider the prefix on-linke due to prior L=1, then retain default behavior.

It might be clearer to have said that default assumption is that all prefixes are off-link, and this means send to default router.  Only reception of L=1 can change that for any specific prefix.  A prefix with L=0 does not change off-link, or on-link status of prefix, and is the same as omitting the prefix entirely from the RA, from the point of view of on-link determination.

Hemant Singh (shemant) wrote:

The summary from this section snipped from 6.3.4 of RFC 4861 is saying no on-ink information does not mean off-link. So why is the text is red where is says, send traffic to default router being said because the text in red signals off-link behavior. Why is this paragraph not ambiguous?

Prefix Information options that have the "on-link" (L) flag set
   indicate a prefix identifying a range of addresses that should be
   considered on-link.  Note, however, that a Prefix Information option
   with the on-link flag set to zero conveys no information concerning
   on-link determination and MUST NOT be interpreted to mean that
   addresses covered by the prefix are off-link.  The only way to cancel
   a previous on-link indication is to advertise that prefix with the
   L-bit set and the Lifetime set to zero.  The default behavior (see
   Section 5.2) when sending a packet to an address for which no
   information is known about the on-link status of the address is to
   forward the packet to a default router; the reception of a Prefix
   Information option with the "on-link" (L) flag set to zero does not
   change this behavior.  The reasons for an address being treated as
   on-link is specified in the definition of "on-link" in Section 2.1.
   Prefixes with the on-link flag set to zero would normally have the
   autonomous flag set and be used by [ADDRCONF].

Hemant

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Josh Littlefield                                  Cisco Systems, Inc.
joshl at cisco.com                             1414 Massachusetts Avenue
tel: 978-936-1379  fax: 978-936-2226       Boxborough, MA  01719-2205

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