Media Gateway Control Protocol (MEGACO/H.248.1)

MEGACO/H.248 is used to control Media Gateways in a Multimedia systems. MEGACO can be Text or Binary (ASN.1) encoded. Sometimes it's also referred as GCP (Gateway Control Protocol).

A MediaGateway (MGw) as its name says is a system used as a Gateway for Media. Current uses are in telephony (Internet, Mobile and Wireline) and Video Broad and NarrowCasting. A MediaGateway is usually placed at the edge of two or more different Tranport Mediums (like: ATM (AAL1,AAL2,AAL5), IP, TDM, even two wire PSTN) and its main duty is to convert media (voice/video) between these domains. MediaGateways are often capable of playing and listening to DTMFs, playing tones (like busy tones), handling voice/video messaging and other similar tasks.


Regardless of the original intention to allow interoperability between systems. It has become an over-standarized protocol so that interoperability between machinery of different vendors (and even between different machines from the SAME vendor) it's almost impossible.

Protocol dependencies

  • MTP3: MEGACO can use MTP3 as its transport protocol; MEGACO is indicated in MTP3 by the service indicator 14.

  • SCTP: MEGACO can use 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

  • SSCOP: MEGACO can use SSCOP as its transport protocol. There's no standard VP/VC for MEGACO over SSCOP

Example traffic

H.248 over SCTP decoded by Ronnie Sahlberg's decoder in the 0.10.9-SVN-13213 build.


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, it now handles binary H248 ower M3UA and SCTP.

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 Wireshark can open gzipped files automatically.

Display Filter

A complete list of MEGACO display filter fields can be found in the display filter reference

A complete list of H.248 display filter fields can be found in the display filter reference

Show only the MEGACO based traffic:


Show only the H.248 based traffic:


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.

External links

  • RFC3015 Megaco Protocol Version 1.0

  • RFC3525 Gateway Control Protocol Version 1 (MEGACO version 2)

  • IANA Megaco assignments

  • ITU-T Recs. H.248.1 -> H.248.59 (the datum is from Sep-2007, you can bet that by the time you read this there'll be many more!)

  • ITU-T H.248.1 Gateway control protocol: Version 3


Given the fact that everyone extends the standard to make its implementation un-interoperable, was the standardization process really necessary???

Imported from on 2020-08-11 23:14:36 UTC