[9fans] Network design question

[9fans] Network design question

[dantes]

Hello everyone,

I'm currently writing a batch of presentations about distributed 
systems, and I was of course having a look at Plan 9, especially on its 
network and communication implementation. I've been through the papers, 
and here is what I understood.

Just to be sure I don't include erroneous data, could you please confirm 
(or oppose, but then please explain :) those assertions:

- from the OSI point of view, the layers 4, 5 and 6 have a custom 
protocol implementation: 9P.

- 9P offers an interface at layer 5 (messages, local)

- 9P offers an interface at layer 6 (RPC, local)

- a service does translation from 9P to TCP for external communication 
(at level 4?).

Where does IL fit in all this?

Hmm, still a bit confused.

Sorry if the question seem a bit lousy, and thanks a lot for any help!
Best regards
Jef

Re: [9fans] Network design question

[vdharani]

> - from the OSI point of view, the layers 4, 5 and 6 have a custom
> protocol implementation: 9P.
9p is similar to nfs protocol. the main difference is nfs is designed to
serve regular data files and so it treats data in terms of blocks. 9p
additionally takes care of device files and the data is treated as
messages of variable size (max is 8192). and 9p messages are not cached.

> - 9P offers an interface at layer 5 (messages, local)
>
> - 9P offers an interface at layer 6 (RPC, local)
i am not sure if 9p can be treated like this. i guess it is pretty much
the 4 layer tcp/ip with 9p sitting on top of tcp/ip. 9p is like nfs
protocol and uses rpc mechanism.

> - a service does translation from 9P to TCP for external communication
> (at level 4?).
>
> Where does IL fit in all this?
il is pretty much similar to tcp except that while tcp works in
byte-stream mode, il wrok in message-mode.

thanks
dharani

Re: [9fans] Network design question

[dantes]

vdharani@infernopark.com wrote:
>>- from the OSI point of view, the layers 4, 5 and 6 have a custom
>>protocol implementation: 9P.
> 
> 9p is similar to nfs protocol. the main difference is nfs is designed to
> serve regular data files and so it treats data in terms of blocks. 9p
> additionally takes care of device files and the data is treated as
> messages of variable size (max is 8192). and 9p messages are not cached.

Isn't it a bit more than NFS? From "The Organisation of Networks in Plan 
9", it seems it can also *do* messages and RPC, while AFAIK NFS is 
*using* messages and SUN RPC... Maybe I'm just plain wrong.

>>- 9P offers an interface at layer 5 (messages, local)
>>
>>- 9P offers an interface at layer 6 (RPC, local)
> 
> i am not sure if 9p can be treated like this. i guess it is pretty much
> the 4 layer tcp/ip with 9p sitting on top of tcp/ip. 9p is like nfs
> protocol and uses rpc mechanism.

Considering from your next answer that IL is a transfer protocol, can 9P 
be fully used on top of IL? (ie does it rely exclusively on TCP and its 
stream orientation?)

>>- a service does translation from 9P to TCP for external communication
>>(at level 4?).
>>
>>Where does IL fit in all this?
> 
> il is pretty much similar to tcp except that while tcp works in
> byte-stream mode, il wrok in message-mode.

OK, thanks for this input.

> thanks
> dharani

Thanks a lot
Jef