Subject: [Rserpool] Rserpool transport issues

From: Qiaobing Xie <[email-masked]>
Date: Tue, 21 Aug 2001 20:09:06 -0500

Hi, all:

Per Maureen's suggestion at this morning's conference call, I'd like to
invite the list to have some discussion on the transport issues of
Rserpool.

I think there are at least two sets of transport issues - Rserpool
internal transport and user application data transport. The former
includes the transportation of _Rserpool messages_ between PU/PE and
ENRP servers, and among ENRP servers. The latter refers to the
transportation of _user data_ between PU and PE.

For Rserpool internal transport, SCTP (plus some IP multicast/anycast
for discovery) seems to be a good choice. I don't see a convincing
argument to support multiple transports here.

However, for user data transport, this becomes a different story. There
may be a diversified set of user applications that may want to migrate
to Rserpool and those applications may have different requirements on
the transport:

1) Applications originally run over SCTP: we can simply move them to use
   ASAP/SCTP.

2) Applications originally run over TCP: we probably can move most of
   them to use ASAP/SCTP. For those die-hard TCP-based apps, we could
   do ASAP/TCP?

3) Application originally run over UDP: this is tricky since UDP does
   not have a way of monitoring the far-end reachability and thus does 
   not work well with ASAP (ASAP needs the far-end unreachable 
   notification from the lower layer to trigger its fail-over process). 

   However, ASAP/U-SCTP seems a very good candidate for this migration. 
   U-SCTP provides to the application the unreliable datagram service 
   similar to UDP but at the same time also provides the far-end 
   reachability monitoring to satisfy the ASAP layer fail-over.

   An Alternative may be to add reachability monitoring to UDP? 

4) Applications originally run over RTP (real-time apps): I'd like to
   hear your input on this one. ASAP/RTP+feedback? 

One thing seems clear - we will need to think about
ASAP/different-transport for user data transfer between PU and PE.

-Qiaobing

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