Outputs¶

Logs¶

The srsRAN Project gNB application provides a highly configurable logging mechanism, with per-layer and per-component log levels.

Set the log file path and log levels in the gNB config file. See the for more details.

The format used for all log messages is as follows:

Timestamp [Layer] [Level] [TTI] message

Where the fields are:

Timestamp in YYYY-MM-DDTHH:MM:SS.UUUUUU format at which log message was generated

Layer can be one of MAC/RLC/PDCP/RRC/SDAP/NGAP/GTPU/RADIO/FAPI/F1U/DU/CU/LIB. PHY layers are specified as downlink or uplink and with executor number e.g. DL-PHY1.

Level can be one of E/W/I/D for error, warning, info and debug respectively.

TTI is only shown for PHY or MAC messages and is in the format SFN.sn where SFN is System Frame Number and sn is slot number.

An example log file excerpt can be seen below:

2023-03-15T18:29:25.142200 [MAC     ] [I] [  276.14] UL PDU rnti=0x4601 ue=0 subPDUs: [lcid=1: len=96, SBSR: lcg=0 bs=0, SE_PHR: total_len=3, PAD: len=424]
2023-03-15T18:29:25.142204 [RLC     ] [I] ue=0 SRB1 UL: RX PDU. pdu_len=96 dc=data p=1 si=full sn=0 so=0
2023-03-15T18:29:25.142226 [PDCP    ] [I] ue=0 SRB1 UL: RX PDU. type=data pdu_len=94 sn=0 count=0
2023-03-15T18:29:25.142228 [PDCP    ] [I] ue=0 SRB1 UL: RX SDU. count=0
2023-03-15T18:29:25.142245 [RRC     ] [D] ue=0 SRB1 - Rx DCCH UL rrcSetupComplete (88 B)
2023-03-15T18:29:25.142249 [RRC     ] [D] Content: [
  {
    "UL-DCCH-Message": {
      "message": {
        "c1": {
          "rrcSetupComplete": {
            "rrc-TransactionIdentifier": 0,
            "criticalExtensions": {
              "rrcSetupComplete": {
                "selectedPLMN-Identity": 1,
                "registeredAMF": {
                  "amf-Identifier": "000000100000000001000000"
                },
                "guami-Type": "native",
                "dedicatedNAS-Message": "7e01820be950137e004139000bf200f110020040e7000f272e04f070f0707100307e004139000bf200f110020040e7000f27100200402e04f070f0702f0201015200f11000000718010074000090530101"
              }
            }
          }
        }
      }
    }
  }
]
2023-03-15T18:29:25.142253 [RRC     ] [D] ue=0 "RRC Setup Procedure" finished successfully
2023-03-15T18:29:25.142263 [NGAP    ] [I] ue=0 Sending InitialUeMessage (ran_ue_id=0)

PCAPs¶

The srsRAN Project gNB application can output packet captures (PCAPs) at the MAC and NGAP layers. These PCAPs can be analyzed using Wireshark.

Enable PCAPs in the gNB config file. See the for more details.

MAC PCAPs¶

To analyze a MAC-layer PCAP using Wireshark, you will need to configure User DLT 149 for UDP and enable the mac_nr_udp protocol:

Go to Edit->Preferences->Protocols->DLT_USER->Edit and add an entry with DLT=149 and Payload protocol=udp.
Go to Analyze->Enabled Protocols->MAC-NR and enable mac_nr_udp

NGAP PCAPs¶

To analyze an NGAP-layer PCAP using Wireshark, you will need to configure User DLT 152 for NGAP and enable detection and decoding 5G-EA0 ciphered messages:

Go to Edit->Preferences->Protocols->DLT_USER->Edit and add an entry with DLT=152 and Payload protocol=ngap.
Go to Edit->Preferences->Protocols->NAS-5GS and enable “Try to detect and decode 5G-EA0 ciphered messages”.