Karl,
>The FOLLOW-UP question is:
>Is there experience with tcp spoofing, increasing the throughput
>from the sender over the wired network towards the gateway, and
>removing slow-start (and possibly modifying congestion avoidance)
>(by the gateway) towards the mobile terminal behind the (long delay
>
>and fully controlled) wireless link ?
>tcp sender -- (network) -- gateway -- (wireless link) -- mobile receiver
>
>(no modifications on sender/receiver, low bandwidth and long dely on
>the wireless link, many small tcp connections as typically in http /
>www-traffic)
>
What you are looking for seems to be an entity that be
can dropped in at the interface between your wireless
links and their interconnection to the/a relatively
"uncontrolled" internet (intranet); Via deployment of
this magic box you'd like:
a. To garner as much bandwidth over the tethered
network path as if your mobile client were
co-located with this entity
b. To maximize the data throughput over the tetherless
path > In The Direction Toward The Mobile Device <
c. To leave as unmodified the protocol stacks (and
any other configuration specific parameters) on
both the mobile device and the random data sources
from which the mobile wishes to extract data/content
Since you state that the tetherless portion of your
network path is "fully controlled", the magic box you
seem to desire should (keyed to the above):
a. Act as a transparent proxy for the mobile device
(either at the application layer or a the transport
layer); All associated distastefulness and pitfalls
acknowledged[*] by you and related to your users/subscribers
(right?)
b. Pace the data (in the form of proper TCP segments)
toward the mobile device at a rate prescribed by
your "fully controlled" wireless link's configuration
parameters.
c. The above pacing should be *reliable*, making use
of (and properly interpreting) the well defined TCP
semantics - as the mobile device is going to be
utilizing an unmodified TCP.
d. Bonus: Retransmit any segments lost over the
tethered network (for whatever reason) without
requiring them to be retransmitted over the
tetherless path (improving both power utilization
and responsiveness)
If I have gotten the above correct, then to answer your question:
Yes, we do have experience doing precisely this;
Yes, it works very well (but also introduces all
the risks associated with the violence of shoving
something in the middle of a TCP connection)
Since the mailing lists are not places for advertising
or plugs (shameless of otherwise), I've previously sent
you appropriate pointers/contact information for a
TCP Tranquility (SCPS-TP) gateway implementation.
Remember as you go down this path:
since you are accreting transport state at the
interface of the wireless/wired regions, you are
going to have to have some mechanism(s) (outside
the scope of your transport protocol/spoofing
techniques) for handing off this state (these
transport connections) as your mobile roams.
Eric
([email protected])
[*] unfortunately for those who choose to live
an honest life, there are no free lunches.
This archive was generated by hypermail 2b29 : Tue Apr 16 2002 - 20:38:56 EDT