Re: Bridging

John G. Thompson (jgt10@livingston.com)
Wed, 21 May 1997 10:57:23 -0700

At 08:00 AM 5/21/97 -0500, Jake Messinger wrote:
>On Tue, 20 May 1997, Dale E. Reed Jr. wrote:
>
>> Now-a-days, switches and routers are abundant, and tunnelling non-routable
>> protocols through IP is common. Therefore bridging is not used in most
>> modern network topologies. The internet certainly doesn't bridge, but
>> Intranets still do it.
>
>You should say its not used in most NEW networks. There are MANY MANY
>older network infrastructures out there, quite large ones, that still use
>bridging and still want to buy NEW prodcuts that bridge.
>
>BUT, having said that... IP tunnelling may eventually do away with
>bridging all together. Encapsulation is the NEATEST THING!! If you have a
>packet your router doesnt understand, turn it into an IP packet. We even
>wrote software to do this about 5 years ago. It was pretty easy to tell
>you the truth once you realize the concept is easy.
>
>The drawbacks are that you have to have something on BOTH ends that will
>do the encapsulizaion and un-encapsulization, it introduces latency, and
>IP protocol is not as efficient as IPX for example. This is usually okay
>since your bottleneck (for use at least) is the physical connection.

Encapsulation IS a neat thing, when it is done correctly!

If you want to see it done incorrectly check out any user of the DirecPC
software from Hughes. The software encapsulates ALL IP traffic and routes
it to the Hughes NOC where the requests are proxied (I guess) and sent back
to the customer via satellite.

<RANT>

Only problem is that the Hughes encapsulation software doesn't create
rfc793 (or std7) ip headers. If you packet trace you see tcp header with
NEGATIVE byte counts. Okay, how does an unsigned number become negative?
You got it, it is a signed conversion of the unsigned number. BUT! WHY IS
THE NUMBER SOOOOOOO LARGE????

Don't know. Hughes won't talk to me anymore. The front line customer
support doesn't give last names, phone number of headquarters, case
numbers, etc.

</RANT>

JGT
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