Subject: [v6ops] comments about draft-townsley-troan-ipv6-ce-transitioning-02

From: Tassos Chatzithomaoglou <[email-masked]>
Date: Thu, 29 Mar 2012 14:40:57 +0200

Hi,

I had a quick look at this draft and i wanted to make some comments.

First, i believe it would be good to have some examples of the 
Information Bases (their structure) used under the Terminology paragraph.

>    SRIB                      A Source Address Routing Information Base
>                               containing an entry per delegated prefix.
>                               Each entry points to one or more
>                               Destination Address Routing Tables (DRIB).
Replace "Destination Address Routing Tables" with "Destination Address 
Routing Information Base (DRIB) tables "?

> MH-1:  An IPv6 CE router MUST create a separate DRIB for each WAN
>            interface (real or virtual) and installs a route for the
>            associated delegated prefix, default route and more specific
>            routes.

What kind of route is installed in the DRIB  (pointing to the WAN?) for 
the associated delegated prefix?
Or does this refer to a route pointing to a LAN interface?

> MH-2:  An IPv6 CE router MUST create an SRIB containing entries for
>            associated delegated prefixes.  Each entry points to one or
>            more DRIBs.  An entry points to multiple DRIBs only in the
>            case where an identical delegated prefix is associated with
>            multiple WAN interfaces.

I guess the last paragraph refers to when having two or more connections 
to the same ISP.
Can't the same DRIB be used in that case, especially if the NH is the same?
There is also the following reference under 3, which forbids it, but 
there could be a pointer from each WAN interface to the DRIB(s).

> The CE
>     router has a single SRIB, and one DRIB associated with each WAN
>     Interface.

> This is important not only
>     in order to choose the best path, but also because the networks that
>     the CE are connected to typically employ source address verification
>     mechanisms.

Replace "verification" with "validation" in order to be in accordance 
with savi?

>   MH-3:  When forwarding a packet from a LAN interface, the CE router
>            MUST do a longest matching lookup based on the packet's Source
>            Address in the SRIB.  A Destination Address lookup is then
>            performed in the corresponding DRIB or DRIBs.  When there are
>            multiple equal matches, the route with the lowest cost is
>            chosen.

Who defines the cost and what exactly is it?
Is this different from the following under 4.2?
> If more than one
>     interface is selected (which will be the case when more than one
>     active WAN interface programs a default route in the RIB), then
>     packets are sent via the interface with the highest configured
>     preference.  If the preference is the same, packets may be load-
>     balanced.

>   6RDS-2:  By default, the 6rd virtual interface MUST be assigned a
>              higher routing cost than a native IPv6 interface.

Is this the same as above too?
If i'm not mistaken, in your draft routes have costs/metrics (lower is 
better) and interfaces have preferences (higher is better), but it would 
be good to clarify that.

> As entries in
>     the NPIB table naturally time out, or if the Native interface is
>     deactivated, the CGN within the DS-Lite AFTR takes over the NAPT
>     state of the CE router.
Replace "state" with "functionality"?
One might think that the current state is "transferred" as it is.

> The following table indicates a basic ordering
>     (least to most preferred) for some of the known IPv4 extension and
>     IPv6 transition mechanisms under development today.

Since "Native IPv4" (which is neither IPv4 extension, nor IPv6 
transition) is also included in the table, maybe the above should be 
rephrased.

Also, i didn't notice any reference to the packets (or traffic in 
general) originating from or terminating to the CER itself. Shouldn't 
that be included too?

-- 
Tassos