Re: [core] #394 (coap-tcp-tls): Ping/pong

["core issue tracker" <[e-mail]>]

#394: Ping/pong


Comment (by [e-mail]):

 Here is the story for adding keep-alive functionality to the CoAP over TCP
 document.

 After reaching out to folks measuring TCP usage I was told that the use of
 TCP keepalive messages is often unreliable since network operators deploy
 middleboxes, which suppress these messages.

 For this reason we are suggesting to add a ping/pong message to the CoAP
 over TCP document. Here is how this could look like.

 First, we define a new CoAP Method Codes (for the request) and CoAP
 Response Codes (for the responses). Let us give them new numbers, such as
 7.01 (for PING) and 7.02 (for PONG).

 Here is an example message exchange:
 {{{
                         Client              Server
                            |                  |
                            | <--- TCP --->    |
                            | Connection Setup |
                            |                  |
                            |   NON            |
                            | GET /temperature |
                            |   (Token 0x74)   |
                            +----------------->|
                            |                  |
                            |   NON [0x23bc]   |
                            |   2.05 Content   |
                            |   (Token 0x74)   |
                            |     "22.5 C"     |
                            |<-----------------+
                            |                  |
                            |      ......      |
                            |   time passes    |
                            |      ......      |
                            |                  |
                            |7.03 Ping         |
                            |(Token 0x7f)      |
                            +----------------->|
                            |                  |
                            |7.02 Pong         |
                            |(Token 0x7f)      |
                            |<-----------------+
                            |                  |
                            |  <--- TCP --->   |
                            |  Conn. Teadown   |
 }}}

 The PING packet would look as follows:

 {{{
     0                   1                   2
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      0x01     |      0xe1     |      0x7f     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Len   =    0 ------>  0x01
     TKL   =    1 ___/
     Code  =  7.01     --> 0xe1
     Token =               0x7f

            Figure: PING Encoding Example.
 }}}

 The PONG packet has the following structure:

 {{{
     0                   1                   2
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      0x01     |      0xe2     |      0x7f     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Len   =    0 ------>  0x01
     TKL   =    1 ___/
     Code  =  7.02     --> 0xe2
     Token =               0x7f

            Figure: PONG Encoding Example.
 }}}

-- 
-------------------------+-------------------------------------------------
 Reporter:               |       Owner:  draft-ietf-core-coap-tcp-
  [e-mail]         |  [e-mail]
     Type:  protocol     |      Status:  new
  enhancement            |   Milestone:
 Priority:  minor        |     Version:
Component:  coap-tcp-    |  Resolution:
  tls                    |
 Severity:  Active WG    |
  Document               |
 Keywords:               |
-------------------------+-------------------------------------------------

Ticket URL: <https://trac.tools.ietf.org/wg/core/trac/ticket/394#comment:1>
core <https://tools.ietf.org/core/>