Re: [OFF-PATH-BOF] SIP, naming, APIs and control

On Thu, 2006-07-13 at 15:38 -0400, Melinda Shore wrote:
> Maybe somebody should write up an informational document
> defining some of these terms so that we're at least all using the
> same language.

I'll draft up a proposal for the terms, but just so we are all on the
same page for mailing list discussion, my understanding of {on,off}path,
data{coupled,decoupled}, {in,out of}band, end-to-{end,middle}-signaling
are as follows.

   _----------S---------_
  /                      \
 /                        \
A --- N --Internet-- M --- B

If A and B are the two endpoints that want to communicate, the path that
data packets between the two will ultimately take is termed the
DATA-PATH. Data refers to some application data (not the signaling
packet).

OFF-PATH signaling, synonymous with DATA-DECOUPLED signaling, refers to
the case where signaling packets (at least the first signaling packet)
_necessarily_ take a path different than the DATA-PATH.

ON-PATH signaling, synonymous with DATA-COUPLED signaling, is when
signaling packets (even the first) do _not necessarily_ take a path
different from the DATA-PATH.

IN-BAND signaling is defined as a subset of ON-PATH signaling where the
signaling packets are piggy-backed on the data packets themselves i.e.
use the same 5-tuple as the data flow. OUT-OF-BAND signaling is a subset
of ON-PATH signaling where the signaling packets are not piggy-backed on
the data packets and use a different 5-tuple.

END-TO-END-SIG is where the signaling message sent by one end (A) MAY be
delivered to the other end (B).

END-TO-MIDDLE-SIG is where the signaling message sent by one end (A)
cannot be delivered to the other end.

Here is how I would classify some signaling protocols:
[Disclaimer: Some protocols can move between classification depending on
the mode they can be put in. Classification for other protocols may just
be entirely wrong. :-p]

OFF-PATH / DATA-DECOUPLED, END-TO-END-SIG
=====================================
SIP, XMPP (e.g. data is filetransfer), MPLS-LDP (END here is the LSR)

OFF-PATH / DATA-DECOUPLED, END-TO-MIDDLE-SIG
=====================================
DNS

ON-PATH / DATA-COUPLED, OUT-OF-BAND, END-TO-END-SIG
===================================
NSIS, RTCP, FTP control

ON-PATH / DATA-COUPLED, OUT-OF-BAND, END-TO-MIDDLE-SIG
===================================
UPnP, Midcom, SOCKS (for bind request), Remote-WinSock

ON-PATH / DATA-COUPLED, IN-BAND, END-TO-END-SIG
===================================
TCP SYN, TURN (note, TURN server may not be on the direct IP path, but
it is still on the DATA-PATH), BEEP

ON-PATH / DATA-COUPLED, IN-BAND, END-TO-MIDDLE-SIG
===================================
SOCKS (for connect request)

-- 
Saikat

Re: [OFF-PATH-BOF] SIP, naming, APIs and control

Attachment: signature.asc