Differences between revisions 7 and 8
Revision 7 as of 2004-10-28 17:01:21
Size: 2149
Editor: GuyHarris
Comment: Punctuation, PROTO->MEGACO, note that you can capture-filter the SCTP port.
Revision 8 as of 2004-10-28 17:04:38
Size: 2179
Editor: GuyHarris
Comment: Note how MEGACO is indicated in SCTP.
Deletions are marked like this. Additions are marked like this.
Line 10: Line 10:
 * ["SCTP"]: Typically(?) MEGACO uses ["SCTP"] as its transport protocol, MEGACO is indicated in SCTP.  * ["SCTP"]: Typically(?) MEGACO uses ["SCTP"] as its transport protocol; MEGACO is indicated in SCTP by a payload protocol ID of 7.

Media Gateway Control Protocol (MEGACO/H.248.1)

MEGACO is used to control a Media Gateway in a VoIP system. MEGACO can be Text or Binary (ASN.1) encoded.

History

Protocol dependencies

  • ["M3UA"]: MEGACO can use ["M3UA"] as its transport protocol; if M3UA is used there is an indication in the M3UA part that this is MEGACO.
  • ["SCTP"]: Typically(?) MEGACO uses ["SCTP"] as its transport protocol; MEGACO is indicated in SCTP by a payload protocol ID of 7.
  • ["TCP"]: MEGACO can use ["TCP"] as its transport protocol. The well known TCP port for MEGACO traffic is xx; if TCP is used, a TPKT header must be included.
  • ["UDP"]: MEGACO can use ["UDP"] as its transport protocol. The well known UDP port for MEGACO traffic is xx

Example traffic

XXX - Add example traffic here (as plain text or Ethereal screenshot).

Ethereal

The MEGACO dissector works for TEXT encoding of the protocol if EOL is used as SEParator. Dissection of binary encoding has recently been added (2004-10-25) as a separate dissector, but is currently only working if M3UA is used as transport.

  • If TCP is used there may be issues with desegmentation; such traces would be valuable.

Preference Settings

  • You can change the PORTS on which MEGACO is dissected for UDP/TCP
  • Raw text output can be selected
  • Something else

Example capture file

XXX - Add a simple example capture file to the SampleCaptures page and link from here. Keep it short, it's also a good idea to gzip it to make it even smaller, as Ethereal can open gzipped files automatically.

Display Filter

A complete list of MEGACO display filter fields can be found in the [http://www.ethereal.com/docs/dfref/MEGACO/MEGACO.html display filter reference]

  • Show only the MEGACO based traffic:

     MEGACO 

Capture Filter

You cannot directly filter MEGACO protocols while capturing. However, if you know the ["TCP"] or ["SCTP"] port used (see above), you can filter on that one.

  • add link to MGCP specification and where to find additional info on the web about MGCP

Discussion

H248/MEGACO (last edited 2010-05-24 19:34:29 by BillMeier)