[relp] RELP over udp

[chris mr]

My car anaglogy is: UDP is to Drum Brakes as TCP is to Disc Brakes.
Drum brakes will take longer to stop in a critical situation but they don't need as much maintenance; disc brakes are more reliable and effective but you have to change them more often.  The driver in both cars is still the same (RELP).



----- Original Message ----
From: Rainer Gerhards <rgerhards at hq.adiscon.com>
To: Matt Hellman <mattjhell at gmail.com>; chris mr <chris.misztur at yahoo.com>
Cc: relp at lists.adiscon.com
Sent: Saturday, August 2, 2008 1:54:28 PM
Subject: RE: [relp] RELP over udp

> I'm not sure I understand your point. HTTP is conceptually a two way
> conversation. syslog is not.

... but RELP is ;) RELP is NOT syslog, it just transports syslog
messages (and it could transport many other things...). That's a big
difference. The problem with the syslog protocol is that it is simplex
communication, thus it can not be reliable. RELP goes great lengths to
solve this issue. To do so, it needs two-way conversations. As a side
note, RELP involves much more peer-to-peer c2-way ommunication than
HTTP. 

If you have not yet see it, I suggest to have a look at this blog post:

http://blog.gerhards.net/2008/04/on-unreliability-of-plain-tcp-syslog.ht
ml

Rainer

> 
> On 01/08/2008, chris mr <chris.misztur at yahoo.com> wrote:
> > I would sum it up that you can't run HTTP over UDP.
> >
> >
> >
> > ----- Original Message ----
> > From: Rainer Gerhards <rgerhards at hq.adiscon.com>
> > To: Matt Hellman <mattjhell at gmail.com>
> > Cc: relp at lists.adiscon.com
> > Sent: Friday, August 1, 2008 12:50:28 AM
> > Subject: Re: [relp] RELP over udp
> >
> > Well, this saves us the hassle of doing our own timeouts for lost
> > frames. It also simplifies a lot of use cases, like we know 
> we get an
> > ordered stream of events, so we also do not need to 
> reassemble frames
> > from the packets we receive. We also inherit congestion 
> control at all
> > from TCP. It of course would be possible to extend RELP to 
> run over UDP,
> > but it would require substantial work and the re-invention 
> of most parts
> > of TCP. IMHO this is not useful work.
> >
> > I hope that explains, but different views are always appreciated ;)
> >
> > Rainer
> >
> >> -----Original Message-----
> >> From: relp-bounces at lists.adiscon.com [mailto:relp-
> >> bounces at lists.adiscon.com] On Behalf Of Matt Hellman
> >> Sent: Friday, August 01, 2008 12:25 AM
> >> To: relp at lists.adiscon.com
> >> Subject: [relp] RELP over udp
> >>
> >> Just reading some of the documentation and I have a conceptual
> >> question...why the requirement for TCP if RELP has app level acks?
> >> Seems like there would be advantages to using UDP in high volume
> >> environments.
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