Subject: [TLS] CoAP, TLS and ALPN

From: Hannes Tschofenig <[email-masked]>
Date: Wed, 30 Aug 2017 10:07:02 +0200

Hi all,

I would need your deployment experience with the use of ALPN.

Here is the background: With the CoAP over TCP/TLS described in
https://tools.ietf.org/html/draft-ietf-core-coap-tcp-tls-09
we are defining how to run CoAP over TCP and TLS. CoAP is a protocol
typically used in the Internet of Things environment, which was
initially designed to operate over UDP.

To ensure proper multiplexing we offer two approaches, namely one using
ALPN and the other one is to use a dedicated port.

The suggestion was made to only use ALPN (see
https://github.com/core-wg/coap-tcp-tls/issues/155).

This is may be fine since many stacks implement ALPN already (including
embedded TLS stacks).

What is the situation on the TLS loadbalancer/concentrator side? Do
these boxes also forward the ALPN information to the application server?
Has someone run into operational issues with ALPN on the server-side?

Ciao
Hannes