Subject: RE: [Isms] Coming to consensus

From: "Fleischman, Eric" <[email-masked]>
Date: Fri, 1 Jul 2005 10:11:34 -0700

Juergen,

I'm sorry but I think that you will find (or, at least, this is what I
concluded after seeing many different studies over the years) that SNMP
performance results are heavily gated by the specific target
environment. Studies exist (e.g., see
http://www.ee.umd.edu/~dxj/IM2001.pdf#search='SNMP%20use%20of%20TCP')
concluding that SNMP performs much better over TCP for large bulk
transfers, for example. However, our experience is that SNMP performs
considerably worse using TCP within capacity limited environments and
also within wireless environments. The reason for this should be
obvious: in the former case (capacity limited environments) it is due to
UDP packets not being "good corporate citizens" and gobbling up all the
capacity they can, causing TCP transmissions to "back off"; in the
latter case (wireless) it is due to how TCP behaves in high signal
intermittence environments. In addition, TCP's misbehavior in high
latency environments (e.g., across geo-stationary satellites) is also
well-studied and well known, though I don't know of anyone who actually
used SNMP-over-TCP in that environment.

Regardless, I believe that the choice of which transport protocol to use
for SNMP is very much a function of where and how you want to use it.
Consequently, I believe that whatever session security we choose should
be able to support both SNMP transport alternatives.

If it is actually the case that SSH is only able to use reliable
transports, then it is not as viable an alternative as (D)TLS. If this
is indeed the case, then ISMS' determining the preferential protocol
should be a "no op" -- use the one that can handle both UDP and TCP
uses.

--Eric

-----Original Message-----
From: Juergen Schoenwaelder [mailto:[email-masked]] 
Sent: Friday, July 01, 2005 12:38 AM

> My own perspective (for whatever it is worth) is that SNMP has had 
> better performance in wireless and bandwidth constrained environments 
> using UDP than TCP.

Can you point me to the details of this study?

/js

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Isms mailing list
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https://www1.ietf.org/mailman/listinfo/isms

---

From: Donati Andrew-MGIA0477 <[email-masked]>
Date: Fri, 1 Jul 2005 14:55:42 -0400

Hi,

I heard of an observation from someone who noted that SNMP over TCP is not scalable with many devices. 
However, it would be interesting to hear about experiences using SNMP over TCP in the case where a table is read that contains over a thousand rows of data from one or a few devices.   
Perhaps the answer would be to use both UDP and TCP.  Use TCP to read large tables (from only a few devices at a time) and use UDP for all other cases.

Thanks,
Andy

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of David B Harrington
Sent: Friday, July 01, 2005 1:03 PM
To: 'Fleischman, Eric'; 'Tom Petch'; [email-masked]
Subject: RE: [Isms] Coming to consensus 

Hi,

> our experience is that SNMP behaves
> poorly using TCP within bandwidth limited environments. 

When you say "our experience", can you qualify "our"? Is that Boeing?
IETF?

Can you share the research that quantifies this assertion?
The debate about TCP or UDP for SNMP has raged for years.
I'd be interested in seeing some rigorous research on this.

David Harrington
[email-masked]

---

From: "Blumenthal, Uri" <[email-masked]>
Date: Fri, 1 Jul 2005 14:59:13 -0400

Clearly. If you need a lot of data from a few devices - TCP's the best.
If you need a few bits of data from a lot of devices - UDP's your best
friend. If you want a lot of data from a lot of devices - heavy
hierarchical infrastructure or pistol with one round is your only
choice.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Donati Andrew-MGIA0477
Sent: Friday, July 01, 2005 2:56 PM
To: [email-masked]; 'Fleischman, Eric'; 'Tom Petch'; [email-masked]
Subject: RE: [Isms] Coming to consensus 

Hi,

I heard of an observation from someone who noted that SNMP over TCP is
not scalable with many devices. 
However, it would be interesting to hear about experiences using SNMP
over TCP in the case where a table is read that contains over a thousand
rows of data from one or a few devices.   
Perhaps the answer would be to use both UDP and TCP.  Use TCP to read
large tables (from only a few devices at a time) and use UDP for all
other cases.

Thanks,
Andy

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of David B Harrington
Sent: Friday, July 01, 2005 1:03 PM
To: 'Fleischman, Eric'; 'Tom Petch'; [email-masked]
Subject: RE: [Isms] Coming to consensus 

Hi,

David Harrington
[email-masked]

---

From: Kaushik Narayan <[email-masked]>
Date: Fri, 01 Jul 2005 13:57:12 -0700

Hi Uri,

I am just stating that

1. Since we have already chose to go down the path of using an
encapsulated keying scheme for SNMPv3 security, we MUST not
get too hung up on SNMPoUDP. I think if there are applications for
SNMPoUDP, then they mostly like will use SNMPv3 USM.

2. We can definitely ease some of the "session establishment" pain
by making sure that we cross leverage across management protocols
since the managed end-points are the same. To that extent use of BEEP
is interesting since it can allow us to potentially share the BEEP session
(and the underlying TLS session) between NetConf, SNMPv3 and Syslog.

regards,
   kaushik!

At 01:22 PM 7/1/2005, Blumenthal, Uri wrote:
> >>......So depending on
> >>whether DTLS is used when a lot of short-lived sessions are created
>and
> >>destroyed, or when sessions are reasonably long-lived - you'd see it
> >>faring better than TCP, or not.
> >
> >That session establishment is what I am concerned about, I think the
> >assumption is that we would have long lived sessions between managers
> >and agents to reduce the initial session establishment cost. That could
> >be problematic since a single manager might be communicating with
> >10,000 agents on behalf of several users.
> >
> >That's a lot of state that needs to be maintained on the manager.
>
>In some foreign language there's a saying about an irreconcilable
>contradiction of the desire to both have sex and preserve the virginity.
>Obviously, something has to give.
>
>People cannot use session-oriented protocols (with session establishment
>cost) in the same way as "pure" UDP-based ones - with impunity.

---

From: "Blumenthal, Uri" <[email-masked]>
Date: Fri, 1 Jul 2005 17:37:26 -0400

> get too hung up on SNMPoUDP.

I do not see the logic of this. I.e. the conclusion doesn't follow...

> I think if there are applications for

I do not think this opinion has been accepted.

> (and the underlying TLS session) between NetConf, SNMPv3 and Syslog.

Hmm, fine... If that's the road the WG wants to follow.