omcipcap is a professional GPON/XGS-PON OMCI Semantic Analysis Framework for ITU-T G.988 protocols. By implementing a table-driven semantic engine, it transforms raw pcap data into structured, human-readable insights—covering MIB state auditing, VLAN logic decoding, and T-CONT traffic hierarchy tracing.
The Master branch represents the latest evolution, shifting from a standalone tool to an analysis framework:
- For AI & Programmers: Full support for JSON IR (
-j / --json-output), making it easy to pipe MIB data into AI models or automation pipelines. - For Field Engineers: The legacy v0.2.x-lts branch remains available for on-site troubleshooting with traditional CLI outputs.
- Dual-Mode Output: Every command supports Rich Print (for human diagnosis) and JSON (for machine processing).
omcipcap is built to bridge the gap between complex raw protocol data and actionable engineering insights. It significantly reduces the time required for root-cause analysis in both lab and field environments.
Key Impact: Transform hour-long manual packet tracing into seconds of automated analysis, allowing engineers to focus on fixing bugs rather than finding them.
| Command | Description | Output Modes |
|---|---|---|
check |
Analyze RTT, TID duplicates, and ME failures | Table / JSON |
mibdb |
Dump the Semantic MIB Database | Table / JSON |
mibdb-diff (diff) |
Compare two MIBs with semantic decoding | Table / JSON |
vlan-tbl |
Analyze OMCI VLAN tagging logic (Table-driven) | Table / JSON |
tcont-flow |
Trace T-CONT → GEM → PQ traffic hierarchy | Table / JSON |
topology (graphic) |
Generate interactive topology HTML | Interactive HTML / JSON |
.
├── LICENSE # MIT License
├── README.md # Project documentation
├── examples # pcap and json samples
├── extensions # semantic extensions
├── omci # Core package
├── pyproject.toml # Build system & entry points
├── tests # Test suites
└── utils # pcap generators
pip install omcipcap
Get ready-to-run executables for your platform:
- Windows (64-bit): omcipcap.exe
- Linux (64-bit): omcipcap_linux
- macOS (ARM64): omcipcap_mac
No Python installation required!
# Windows
omcipcap.exe check your_file.pcap
# Linux
chmod +x omcipcap_linux
./omcipcap_linux check your_file.pcapAnalyze a pcap file to display a summary of all OMCI packets:
# print all vendor, failed, late and duplicates packets
omcipcap check omcicheck_example.pcap
# get JSON output of OMCI resp failed
omcipcap check --only-failed -j omcicheck_example.pcap
omcipcap check with --rtt-threshold argument
(venv) $ omcipcap check --rtt-threshold=1500 omcicheck_example.pcap
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
No. ID Action ME Class ME Instance Result RTT Status ME desc
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
38 19 MIB_UPLOAD_NEXT 241 0x0001 0 Reserved for vendor-specific managed entities
40 20 MIB_UPLOAD_NEXT 350 0x0001 0 Reserved for vendor-specific use
52 26 MIB_UPLOAD_NEXT 500 0x000a 0 Reserved for future standardization
58 29 CREATE 84 0x0001 Err: INSTANCE_EXISTS 0.000033 VLAN tagging filter data
59 30 SET 241 0x0001 0 Reserved for vendor-specific managed entities
60 30 SET 241 0x0001 Err: UNKNOWN_ME 0.000033 Reserved for vendor-specific managed entities
64 32 GET 257 0x0000 0 [TID_DUPLICATE] ONT2-G
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Summary: Found 2 failures, 5 Vendor packets, 1 duplicate packets, 0 late packetsMIB Database Dump
Dump all or filtered MIB instances from a pcap.
# print all MIB infomation
omcipcap mibdb examples/omci.pcap
# print all MIB for class 84 and 171
omcipcap mibdb --class-id 84,171 examples/omci.pcap
# print JSON of MIB snapshots (MIB uploads)
omcipcap mibdb -j --only-upload examples/omci.pcapCustomize attribute decoding with specific semantics
omcipcap mibdb --semantic-dir ./extensions --class-id 134 input.pcaptry:
from omci.omcisemantic import OMCISemantic
except ImportError:
pass
def ip_host_mode(value):
if value & 0x1:
return "DHCP"
return "Static"
OMCISemantic.register(134, "IP options", ip_host_mode)Analyze two pcap files to identify differences in MIB provisioning
# Compare MIB snapshots between two pcaps, only compare MIB upload MIBs by default
omcipcap mibdb-diff mib_vendor_v1.pcap mib_vendor_v2.pcap
# Compare MIB snapshots between two pcaps with user defined MIB
omcipcap mibdb-diff mib_vendor_v1.pcap mib_vendor_v2.pcap --mib-json examples/vendor_355.json
# Compare Full provision MIB between two pcaps
omcipcap mibdb-diff --full ont1.pcap ont2.pcap
# Compare full MIB provisioning between two PCAPs for Class 84 and 171, and output JSON
omcipcap diff -j --full --class-id=84,171 ont1.pcap ont2.pcapExample Output When comparing a vendor-specific configuration (Class 355), omcidiff provides a clear view of the state change:
(venv) $ omcipcap mibdb-diff mib_vendor_v1.pcap mib_vendor_v2.pcap --mib-json examples/vendor_355.json
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Status ME Name (ID) Inst Attribute Pcap 1 Pcap 2
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
MODIFIED Reserved for vendor-specific use (355) 0x0 CPE mode HGU SFU
MODIFIED Reserved for vendor-specific use (355) 0x0 Support VOIP 0x1 0x0
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Summary: Added: 0, Removed: 0, Modified: 2
Advanced: Custom ME JSON Format To define your own Vendor MEs for the --mib-json flag, use the following structure:
{
"355": ["HWTC 355 ME", [
["CPE mode", 3, "str", False],
["Support VOIP", 1, "u8", False]
]]
}omcipcap topology omci.pcap -o example.html
omcipcap vlan-tbl omci.pcap
List All ME 171 instances and detail of VLAN table
omcipcap tcont-flow single_unit_1_tont_2_gem.pcap
Traces the complete upstream traffic hierarchy from T-CONT → GEM Port → Priority Queue and displays bandwidth/scheduling parameters in a tree view.
Example Output:
(venv) $ omcipcap tcont-flow single_unit_1_tont_2_gem.pcap
GPON T-CONT Flow Analysis
├── T-CONT 32768 (alloc-id=1000)
│ ├── GEM 1001
│ │ ├── [US] PQ 32775 → up:CIR=0.128Mbps/PIR=9953.28Mbps
│ │ └── [DS] PQ 0 → Priority 0 dn:Unrestricted
│ └── GEM 1002
│ ├── [US] PQ 32768 → up:CIR=0.128Mbps/PIR=100Mbps
│ └── [DS] PQ 6 → Priority 6 dn:Unrestricted
└── T-CONT 32769 (Unassigned)
(venv) $
Each T-CONT entry shows:
- alloc-id: The Alloc-ID assigned by the OLT;
Unassignedmeans the T-CONT has not been activated (Alloc-ID = 0xFFFF). - GEM ports: All GEM Port Network CTPs bound to this T-CONT.
- [US] PQ: Upstream Priority Queue with CIR/PIR bandwidth limits.
- [DS] PQ: Downstream Priority Queue with scheduling priority.
this software is for educational and network debugging purposes only. The author (daneshih1125) provides this software "as is" without warranty of any kind.
- The users are solely responsible for ensuring that they have the legal right and proper authorization to capture, process, and analyze any network packets (pcap/log) used with this tool.
- The author shall not be held liable for any data breaches, compliance violations (such as GDPR, PDPA), leakage of trade secrets, or security incidents caused by the users processing sensitive or production network data with this tool or exporting data to third-party AI models.
Copyright (c) 2026 Dong-Yuan Shih daneshih1125@gmail.com Licensed under the MIT License.