On Aug 19, 2010, at 3:07 PM, Thomas Narten wrote:

> Brian E Carpenter <[email protected]> writes:
> 
>> Jared,
> 
>> On 2010-08-16 13:06, Jared Mauch wrote:
>> ...
> 
>>> Is there a legitimate operational reason a host should not know
>>>    the subnet length it sits on?
> 
> A host should not be *required* to know the subnet length.  Very
> simple devices may have "simple" stacks. And indeed, for a simply
> host, all you need to know is a first hop router address. Redirects
> can do the rest.

If they can't handle to know an extra byte (mask) plus 128 bits for 'default'
gateway, I certainly understand small embedded solutions having limited space
but implementing the redirect codebase, aging, etc.. seems like a lot more
effort than knowing a mask and default gateway.

> This may not be the ideal situation, but it is one the architecure
> allows for.

Just because something is 'allowed' does not mean it should be encouraged.
I could announce vanity information in AS_PATH, but it's certainly not 
encouraged.

> It is also fine for more sophisticated implementations to know what
> the subnet length is.

- Jared
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