Re: [Mip6] [issue94] fixing encapsulation mechanism in IPv4 network

[Keiichi SHIMA <keiichi at iijlab.net>]

Hello,

On 2007/03/21, at 2:25, Hesham Soliman wrote:

> We will have a formal concensus call on this but let's here a few  
> opinions
> first. My opinion below:

OK, thanks.


> > New submission from Keiichi SHIMA <keiichi at iijlab.net>:
> >
> > The current DSMIPv6 draft specifies two encapsulation
> > formats, one is the IPv4 encap format, the other is
> > UDPv4 encap format.  The default encapsulation format is the
> > IPv4 format, and if the HA explicitly
> > specifies to change the encapsulation format to the UDPv4
> > format if there is a NAT box between the HA
> > and the MN.  Because of this specification, HA and MN have
> > to support both encapsulation formats and
> > have to change the format dynamically, that may increase the
> > hurdle for implementors and may cause
> > complexity in interoperability.
> >
> > Isn't it possible to fix the encapsulation format to one of
> > these mechanisms described in the draft?
>
> => So basically you're asking for UDP-only tunnelling. As I  
> mentioned in a
> previous email, this a tradeoff between reducing the implementer's  
> work and
> reducing redundant bits on the wire. I think it makes more sense to  
> reduce
> additional bits on the wire. The UDP tunnel is redundant if no NAT  
> were
> detected. So your suggestion amounts to removing NAT detection and  
> always
> using UDP tunnels. I think this is inefficient, especially when the  
> cost of

About the possibility of using the UDP encap mechanism, please refer  
my mail replied to Vijay's mail.


> switching between the UDP tunnel and IP n IP is very small (from an
> implementation point of view).

I may not agree on the above point.  Since UDP is a transport  
protocol, encapsulating something in it cannot be handled by a  
*normal* packet decapsulation flow, while IPv4-in-IPv4 can be fit to  
the natural flow.  So switching from IPv4 encapsulation to UDP  
encapsulation may not be so easy as you say, especially for MIP  
stacks that are implemented in user space.

I would like to hear opinions from who have already implemented DSMIPv4.

---
Keiichi SHIMA
IIJ Research Laboratory <keiichi at iijlab.net>
WIDE Project <shima at wide.ad.jp>

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