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Revision 11 as of 2004-10-31 20:12:58
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 * You can change the PORTS on which MEGACO is dissected for UDP/TCP
 * Raw text output can be selected
 * Wether to display tree dissection or not.
 * You can change the ports on which MEGACO is dissected for UDP/TCP
 * You can specify whether the raw text of MEGACO packets is to be displayed
 * You can specify whether a detailed dissection of MEGACO packets is to be displayed

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; MEGACO is indicated in M3UA by a Protocol user id of 14.
  • ["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 2944; 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 2944

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
  • You can specify whether the raw text of MEGACO packets is to be displayed
  • You can specify whether a detailed dissection of MEGACO packets is to be displayed

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.

Discussion

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