Packet Data Convergence Protocol (PDCP) for LTE

This protocol sits between the RLC and RRC layers in the LTE air interface (connecting an LTE UE with an eNodeB).

Protocol dependencies

The dissection of RRC and IP payloads are controlled by preference settings. This dissector may be called by the RLC-LTE dissector for signalling plane messages (if preference settings are enabled).

A UDP framing format for PDCP-LTE has been defined (described in packet-pdcp-lte.h, purely for use with Wireshark)

Example traffic

pdcp-rtp-rohc.png

Wireshark

The PDCP-LTE dissector is mostly functional. It can decode the PDCP-LTE headers but has limited support for ROHC payloads. Deciphering of EEA2 (AES) messages is supported where Wireshark is built with libgcrypt. There is support for reading PDCP-LTE frames from:

  • RLC-LTE SDUs, which may have been reassembled from multiple segments, OR

  • DCT2000 log files, OR

  • using the UDP format defined in packet-pdcp-lte.h. This (BSD-licensed) program gives an example of how you might send PDCP-LTE frames in this format.

Preference Settings

  • Show User-Plane uncompessed data as IP. Default is Off.
  • Show unciphered Signalling-Plane data as RRC. Default if Off.
  • Attempt to decode ROHC data. Default is Off.
  • Try Heuristic LTE-PDCP over UDP framing. Default is Off. Starting from Wireshark 2.0, heuristic activation is moved to Enabled Protocols window.
  • Which layer info to show in Info column. Default is RLC.
  • PDCP UE security keys. A table of (UEId, RRCKey, UPKeys) entries.
  • Attempt to decipher Signalling (RRC) SDUs. Default is Off.
  • Attempt to decipher User-plane (IP) SDUs. Default is Off.

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 PDCP-LTE display filter fields can be found in the display filter reference

Show only the PDCP-LTE based traffic:

 pdcp-lte 

Capture Filter

You cannot directly filter PDCP-LTE protocols while capturing.

External links

  • 3GPP TS 36.323 Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification

  • RFC 3095 RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed

  • Example program that generates and sends frames using the supported UDP framing format

Discussion

It is recommended that you use current sources or a recent automated build for this and other LTE dissectors.


Imported from https://wiki.wireshark.org/PDCP-LTE on 2020-08-11 23:17:51 UTC