Access Link Control Application Part (ALCAP)

ALCAP is the protocol used for control plane of transport layer UMTS in charge of managing and multiplexing users into ATM AAL2 virtual connections. ALCAP is specified for Iub, Iur and Iu (circuit switched domain) interfaces. This protocol is only used when these interfaces are ATM-based. The ITU-T Q.2630.2 standard, AAL type 2 signalling protocol - Capability Set 2, is chosen for ALCAP protocol.

History

For Iub and Iur interfaces, ALCAP is specified in 3GPP TS 25.426. For Iu interface, ALCAP is specified in 3GPP TS 25.414.

Protocol dependencies

Example traffic

Example of ALCAP (Q.2630) Establish request message decoded by Wireshark:

AAL type 2 signalling protocol (Q.2630)
    DSAID: 0x00000000
    Message Type: Establish request (ERQ) (5)
    Message Compatibility: 22
        .0.. .... = Pass-On SNI: Do Not Send Notification (0)
        ..10 .... = Pass-On II: Discard Message (2)
        .... .0.. = General SNI: Do Not Send Notification (0)
        .... ..10 = General II: Discard Message (2)
    Parameter: Originating signalling association identifier (OSAID) (6)
        Message Compatibility: 22
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..10 .... = Pass-On II: Discard Message (2)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..10 = General II: Discard Message (2)
        Length: 4
        OSAID: 0x02000044
    Parameter: Connection element identifier (CEID) (2)
        Message Compatibility: 22
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..10 .... = Pass-On II: Discard Message (2)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..10 = General II: Discard Message (2)
        Length: 5
        Path ID: 65
        CID: 127
    Parameter: Destination NSAP service endpoint address (DNSEA) (4)
        Message Compatibility: 22
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..10 .... = Pass-On II: Discard Message (2)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..10 = General II: Discard Message (2)
        Length: 20
        Address: 4556789ABCDEF0120F0000000000000000000000
        IDP = 4556789ABCDEF0120F
        X.213 Address Format Information ( AFI ): E.164 (0x45)
        IDI = 56789ABCDEF0120F
        Country Code: 56 Chile length 2
        DSP length 11(len 20 -9 )
        X.213 Address Format Information ( DSP ): 0000000000000000000000
    Parameter: Link characteristics (ALC) (5)
        Message Compatibility: 22
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..10 .... = Pass-On II: Discard Message (2)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..10 = General II: Discard Message (2)
        Length: 12
        Maximum Forward Bit Rate: 75
        Maximum Backwards Bit Rate: 81
        Average Forward Bit Rate: 75
        Average Backwards Bit Rate: 16
        .001 1000 = Maximum Forward CPS SDU Size: 24
        .001 1010 = Maximum Backwards CPS SDU Size: 26
        .001 1000 = Average Forward CPS SDU Size: 24
        .001 1010 = Average Backwards CPS SDU Size: 26
    Parameter: Served user generated reference (SUGR) (7)
        Message Compatibility: 22
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..10 .... = Pass-On II: Discard Message (2)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..10 = General II: Discard Message (2)
        Length: 4
        SUGR: 0F000000
    Parameter: Served user transport (SUT) (8)
        Message Compatibility: 11
            .0.. .... = Pass-On SNI: Do Not Send Notification (0)
            ..01 .... = Pass-On II: Discard Parameter (1)
            .... .0.. = General SNI: Do Not Send Notification (0)
            .... ..01 = General II: Discard Parameter (1)
        Length: 3
        SUT Length: 0x02
        SUT: 0204

Wireshark

The ALCAP dissector is fully functional however it can presently only be called by a user DLT (data link type) or called by name from another dissector. See FileFormatReference.

Preference Settings

(XXX add links to preference settings affecting how PROTO is dissected).

Example capture file

XXX - Add a simple example capture file to the SampleCaptures page and link from here (see below). Keep this file 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 ALCAP display filter fields can be found in the display filter reference

Capture Filter

Because ALCAP traces can only currently be read from existing trace files, there is no way to filter for ALCAP messages while capturing.

Discussion

ALCAP (last edited 2010-05-20 18:35:29 by BillMeier)