Message Transfer Part Layer 2 (MTP2)

MTP2 is the Data Link layer used with in SS7; it is used to carry MTP3 traffic from point to point.

History

XXX - add a brief description of MTP2 history

Protocol dependencies

• MTP2 is carried by MTP Level 1 which is equivalent to the OSI Physical Layer. It defines the physical, electrical, and functional characteristics of the digital signaling link. Physical interfaces defined include:

  • E-1 (2048 kb/s: 32 64 kb/s channels)
  • DS-1 (1544 kb/s: 24 64kb/s channels)
  • V.35 (64 kb/s)
  • DS-0 (64 kb/s)
  • DS-0A (56 kb/s)

• MTP2 carries MTP3.

In IP networks MTP2 is logically replaced by the SIGTRAN protocols:

• M2PA

• M2UA

Example traffic

XXX - Add example decoded traffic for this protocol here (as plain text or Wireshark screenshot).

Wireshark

The MTP2 dissector is fully functional.

Preference Settings

The MTP2 dissector can dissect messages from either traditional (channelized) speed links (64k,56k) or high speed links (unchannelized E1/T1 from Q.703, Annex A), based on the dissector's preference setting. The difference between the two is the size of the sequence numbers.

Example capture file

• SampleCaptures/ansi_tcap_over_itu_sccp_over_mtp3_over_mtp2.pcap This capture contains a single MTP2 frame carrying ITU MTP3/SCCP which is carrying an ANSI TCAP message.

Display Filter

A complete list of MTP2 display filter fields can be found in the display filter reference

Show only the MTP2 based traffic:

 mtp2

Capture Filter

You cannot directly filter MTP2 while capturing.

External links

• The ITU specifications of MTP2 are available for free on the web:

  • Q.701 gives an introduction to MTP (layers 1, 2, and 3)

  • Q.702

  • Q.703

Discussion

Imported from https://wiki.wireshark.org/MTP2 on 2020-08-11 23:17:00 UTC