Re: [TERNLI] Notes from tonight's ad hoc

[Wesley Eddy <[e-mail]>]

On Fri, Jul 28, 2006 at 08:56:08AM -0400, Mark Allman wrote:
> 
> I guess I see the signals as either ...
> 
>   + Giving the transport something it can directly use.  E.g., the
>     available bandwidth just increased from 2Mbps to 11Mbps.  E.g.,
>     the flow experienced congestion.  E.g., some probability of the
>     fraction of losses due to corruption.
> 
>     These are different from less-directly-useful information like
>     "switched to a new AP" or "am now using a different coding /
>     modulation scheme" which are much less directly applicable. 
> 
>   + Giving a generic signal that *something* has changed and it likely
>     matters and so the transport should re-init itself (e.g., forget the
>     SRTT, RTTVAR, cwnd, ssthresh, MTU value, etc.).

Is it possible to generalize this to say that signals should either
carry specific actionable information or request specific types of
actions?

This means:
"Modulation changed" is a bad signal to implement.

"Available capacity changed from X to Y, please probe" is a good signal
to implement, and could be generated in response to a change in
modulation or any number of other things.

"Registering a new Mobile IP CoA" is a bad signal to implement.

"Please reprobe path state" is a good signal to implement, and could be
generated in response to a MIP CoA update or several other events from
mobility or multihoming mechanisms.


I guess this might simplify our task into categorizing the actions that
each layer might implement, and defining a signal for each class of
actions (with optional additional data to accompany the signal such as X
and Y in a capacity change signal -- you could define specific
combinations of X and Y to mean "up", "down", and "I don't know", when
specific values aren't available).

-- 
Wesley M. Eddy
Verizon Federal Network Systems