Re: [core] CoAP for high throughput applications

Hi Zach, thanks for the pointer.

The problem with TCP is that you don't want one lost packet to block the train of (totally independent) LURK transactions — and as a consequence the bunch of pending TLS handshakes that are waiting on them for completion.

A UDP based transport would be better suited for the LURK use case.  One that minimise the wire overhead (e.g. by using CBOR/CoAP) would be even better.

Cheers, t

From: core <core-bounces@ietf.org<mailto:core-bounces@ietf.org>> on behalf of Zach Shelby <Zach.Shelby@arm.com<mailto:Zach.Shelby@arm.com>>
Date: Monday, 4 April 2016 19:45
To: Thomas Fossati <thomas.fossati@alcatel-lucent.com<mailto:thomas.fossati@alcatel-lucent.com>>
Cc: "core@ietf.org<mailto:core@ietf.org>" <core@ietf.org<mailto:core@ietf.org>>
Subject: Re: [core] CoAP for high throughput applications

Indeed, Matthias and I have done considerable work on the scalability of a single server talking to very large numbers of constrained endpoints [1], however each of those endpoints was NSTART=1. I have not seen any work done on high throughput between two endpoints, although my knee-jerk reaction would be that CoAP/TCP or some other TCP based protocol is more suitable.

[1] https://www.vs.inf.ethz.ch/publ/papers/mkovatsc-2014-iot-californium.pdf

Zach

On 04 Apr 2016, at 15:11, Fossati, Thomas (Nokia - GB) <thomas.fossati@nokia.com<mailto:thomas.fossati@nokia.com>> wrote:

Hi folks,

A slightly off-topic question -- though not too much, hopefully.

One of the LURK [0] proposals is draft-cairns-tls-session-key-interface [1].

In Section 7.1.2 [2] the authors propose to transport the LURK payloads over CBOR/CoAP (over DTLS/UDP, I guess).

Now, a single LURK box could have to handle lots of these requests, potentially in thousands per second, whereas CoAP's default congestion control algorithm parameters [3] are, by design, way too conservative to be suitable for high-throughput use cases.

Is there anyone that has played with CoAP for high-throughput applications who'd be willing to share his/her experience with the group and the wider IETF community?

Cheers, thanks very much,
t

[0] https://www.ietf.org/mail-archive/web/lurk/current/msg00083.html
[1] https://datatracker.ietf.org/doc/draft-cairns-tls-session-key-interface
[2] https://tools.ietf.org/html/draft-cairns-tls-session-key-interface-01#section-7.1.2
[3] https://tools.ietf.org/html/rfc7252#section-4.8

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