draft-ietf-6man-multi-homed-host - Routing packets from hosts in a multi-prefix network

[Brian E Carpenter <[e-mail]>]

Dusan,

As far as I know we are only changing the A=L=0 case. If A=0, the
prefix is not used for SLAAC at all, and if L=0 the prefix should not
be added to the on-link prefix list.

To be clear, L=0 doesn't mean the prefix is off-link. It just means
"I'm not telling you it's on-link".

So previously a host could simply ignore the PIO with A=L=0. But now it
will be a useful next-hop router signal to the host, if addresses in that
prefix have been assigned in another way, typically by DHCPv6.

Does that make sense?

   Brian

On 07/04/2016 07:40, Mudric, Dusan (Dusan) wrote:
> Hi Brian,
> 
> "Routing packets from hosts in a multi-prefix network" says:
>    A router
>    that advertises a prefix indicates that it is able to appropriately
>    route packets with source addresses within that prefix, regardless of
>    the setting of the L and A flags in the PIO.
> 
>    a host SHOULD NOT ignore a PIO simply because both L and
>    A flags are cleared; a router SHOULD be able to send such a PIO.
> 
>    A host SHOULD select
>    default routers for each prefix it is assigned an address in.
> 
> The prefix list is used to find out if the destination address is on-link. 
> 
> If the router can route the packets from a host with the source address using L=0 prefix, theoretically off-link prefix can be used for SLAAC address. The problem is that L=0 prefix might be used on other links and if the host creates SLAAC address using L=0 prefix, the host will not be able to detect if the address is in use (DAD does not work between different router links). For that reason looks like L=0 prefix should not be used for SLAAC. If L=0 prefix is not use for SLAAC, there will be no source address with L=0 prefix and L=0 prefixes will not help host to find the first hop router. Consequently, hosts can ignore L=0 prefixes.
> 
> Am I missing something about L=0 prefixes?
> 
> Thanks,
> Dusan.
> 
> -----Original Message-----
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> Subject: ipv6 Digest, Vol 142, Issue 35
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> Today's Topics:
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>    1. I-D Action: draft-ietf-6man-multi-homed-host-05.txt
>       ([e-mail])
>    2. I-D Action: draft-ietf-6man-multi-homed-host-06.txt
>       ([e-mail])
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 22 Feb 2016 10:32:52 -0800
> From: [e-mail]
> To: <[e-mail]>
> Cc: [e-mail]
> Subject: I-D Action: draft-ietf-6man-multi-homed-host-05.txt
> Message-ID: <[e-mail]>
> Content-Type: text/plain; charset="utf-8"
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the IPv6 Maintenance of the IETF.
> 
>         Title           : Routing packets from hosts in a multi-prefix network
>         Authors         : Fred Baker
>                           Brian Carpenter
> 	Filename        : draft-ietf-6man-multi-homed-host-05.txt
> 	Pages           : 13
> 	Date            : 2016-02-22
> 
> Abstract:
>    This document describes expected IPv6 host behavior in a network that
>    has more than one prefix, each allocated by an upstream network that
>    implements BCP 38 ingress filtering, when the host has multiple
>    routers to choose from.  It also applies to other scenarios such as
>    the usage of stateful firewalls that effectively act as address-based
>    filters.  This host behavior may interact with source address
>    selection in a given implementation, but logically follows it.  Given
>    that the network or host is, or appears to be, multihomed with
>    multiple provider-allocated addresses, that the host has elected to
>    use a source address in a given prefix, and that some but not all
>    neighboring routers are advertising that prefix in their Router
>    Advertisement Prefix Information Options, this document specifies to
>    which router a host should present its transmission.  It updates RFC
>    4861.
> 
> 
> The IETF datatracker status page for this draft is:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_draft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost_&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=PUqjeSn4pUOrtWVBsNjNailsRew5_ZvzDS1STFtTjDg&e= 
> 
> There's also a htmlized version available at:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost-2D05&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=Wqnr6PzhAWzCUOMlH0v2MPK87KyhpIfl1sDF96UNhP4&e= 
> 
> A diff from the previous version is available at:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ietf.org_rfcdiff-3Furl2-3Ddraft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost-2D05&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=vPYONcimyGIvGJFl1Th6RV-kSJv79qPXaULdoyeOHEo&e= 
> 
> 
> Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org.
> 
> Internet-Drafts are also available by anonymous FTP at:
> https://urldefense.proofpoint.com/v2/url?u=ftp-3A__ftp.ietf.org_internet-2Ddrafts_&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=DKDpwbqKxZRyMXqgSklNxE-zP1DZtdIAKnrO9nDBWis&e= 
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> 
> ------------------------------
> 
> Message: 2
> Date: Mon, 22 Feb 2016 10:55:30 -0800
> From: [e-mail]
> To: <[e-mail]>
> Cc: [e-mail]
> Subject: I-D Action: draft-ietf-6man-multi-homed-host-06.txt
> Message-ID: <[e-mail]>
> Content-Type: text/plain; charset="utf-8"
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the IPv6 Maintenance of the IETF.
> 
>         Title           : Routing packets from hosts in a multi-prefix network
>         Authors         : Fred Baker
>                           Brian Carpenter
> 	Filename        : draft-ietf-6man-multi-homed-host-06.txt
> 	Pages           : 13
> 	Date            : 2016-02-22
> 
> Abstract:
>    This document describes expected IPv6 host behavior in a network that
>    has more than one prefix, each allocated by an upstream network that
>    implements BCP 38 ingress filtering, when the host has multiple
>    routers to choose from.  It also applies to other scenarios such as
>    the usage of stateful firewalls that effectively act as address-based
>    filters.  This host behavior may interact with source address
>    selection in a given implementation, but logically follows it.  Given
>    that the network or host is, or appears to be, multihomed with
>    multiple provider-allocated addresses, that the host has elected to
>    use a source address in a given prefix, and that some but not all
>    neighboring routers are advertising that prefix in their Router
>    Advertisement Prefix Information Options, this document specifies to
>    which router a host should present its transmission.  It updates RFC
>    4861.
> 
> 
> The IETF datatracker status page for this draft is:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_draft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost_&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=PUqjeSn4pUOrtWVBsNjNailsRew5_ZvzDS1STFtTjDg&e= 
> 
> There's also a htmlized version available at:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost-2D06&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=lGfMGfWC7GV6V-rewMLkuXhmMv8qCGBHIxhCsFmkOnY&e= 
> 
> A diff from the previous version is available at:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ietf.org_rfcdiff-3Furl2-3Ddraft-2Dietf-2D6man-2Dmulti-2Dhomed-2Dhost-2D06&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=UFS97FbjEQDBE-DJBZaJF7J3umdmn66PA1Z4yc95xjU&e= 
> 
> 
> Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org.
> 
> Internet-Drafts are also available by anonymous FTP at:
> https://urldefense.proofpoint.com/v2/url?u=ftp-3A__ftp.ietf.org_internet-2Ddrafts_&d=BQICAg&c=BFpWQw8bsuKpl1SgiZH64Q&r=UT3Bk9cbLeaJxhf3iCrhIoUWB8YLZU23029sMQGQ2kY&m=lhfg8o3sQ_U0qWiAcIO67_OY6ltvVdPyRj2oQwwq530&s=DKDpwbqKxZRyMXqgSklNxE-zP1DZtdIAKnrO9nDBWis&e= 
> 
> 
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