binaryfilestlv
How can I decode/encode a cable modem configuration file?
I'm currently looking into some of the inner workings of DOCSIS and related. One thing I'm struggling a bit with is how cable modem config files are made.
From what I've gathered:
- CM configs are binary files based on a TLV format.
- These configs are deployed using a TFTP server, hinted via DHCP to the modem itself when it boots.
I'm interested in knowing how these config files are structured. I have next to no knowledge of TLV aside from what I've read these past days.
- Is TLV just a generic method of stringing data together? It seems like TLV is used in both binary forms and json-like strings of clear text.
- Is the T and/or L parts of TLV a set size (in bytes)? How do I know where they separate?
- I think I read somewhere that CM configs use a subset of TLV called TLV-BER. If I'm not mistaken, this adds support for TLV nesting. How does this work?
I've heard that DOCSIS is well documented over at CableLabs, but I haven't been able to find this information yet. Helpful links are appreciated.
I have a binary config file in my possession that I've been able to decode using online tools, but assume I want to make my own tool for this purpose, how would I go about it?
Edit: Here's an excerpt of the first 64 bytes of the binary file, for reference.
03010112 01021916 08040668 51E00601 07070104 01020065 09040000 17C8181D
08040203 A0000904 00001F40 0E021F40 01020001 0F010207 01040601 07270101
Solution
03 01 01 ; 3 - Network access control: ON
12 01 02 ; 18 - Max Number of CPEs: 2
19 16 ; 25 - Downstream service flow
08 04 06 68 51 E0 ; 25.8 - Maximum Sustained Traffic Rate
06 01 07 ; 25.6 - Quality of Service Parameter Set Type: prov/adm/active
07 01 04 ; 25.7 - Traffic Priority: 4
01 02 00 65 ; 25.1 - Service Flow Reference or ASF Reference: 65
09 04 00 00 17 C8 ; 25.9 - Maximum Traffic Burst: 6,088
18 1D ; 24 - Upstream service flow
08 04 02 03 A0 00 ; 24.8 - Maximum Sustained Traffic Rate: 33,792,000
09 04 00 00 1F 40 ; 24.9 - Maximum Traffic Burst: 8,000
0E 02 1F 40 ; 24.14 - Maximum Concatenated Burst: 8,000
01 02 00 01 ; 24.1 - Service Flow Reference or ASF Reference: 1
0F 01 02 ; 24.15 - Service Flow Scheduling Type: 2
07 01 04 ; 24.7 - Traffic Priority: 4
06 01 07 ; 24.6 - QOS: 0x07 (prov|adm|active)
27 01 01 ; 39 - Enable 2.0 Mode: ON
Types
Type Description Spec Defined
======== ========================================================= ============
0 Pad DOCSIS 1.0
1 Downstream Frequency DOCSIS 1.0
2 Upstream Channel ID DOCSIS 1.0
3 Network Access Control Object DOCSIS 1.0
4 DOCSIS 1.0 Class of Service DOCSIS 1.0
5 Modem Capabilities Encoding DOCSIS 1.0
6 CM Message Integrity Check (MIC) DOCSIS 1.0
7 CMTS Message Integrity Check (MIC) DOCSIS 1.0
8 Vendor ID Encoding DOCSIS 1.0
9 SW Upgrade Filename DOCSIS 1.0
10 SNMP Write Access Control DOCSIS 1.0
11 SNMP MIB Object DOCSIS 1.0
12 Modem IP Address DOCSIS 1.0
13 Service(s) Not Available Response DOCSIS 1.0
14 CPE Ethernet MAC Address DOCSIS 1.0
15 Telephone Settings Option (deprecated) DOCSIS 1.0
17 Baseline Privacy (Security) DOCSIS 1.0
18 Max Number of CPEs DOCSIS 1.0
19 TFTP Server Timestamp DOCSIS 1.0
20 TFTP Server Provisioned Modem IPv4 Address DOCSIS 1.0
21 SW Upgrade IPv4 TFTP Server DOCSIS 1.0
22 Upstream Packet Classification DOCSIS 1.1
23 Downstream Packet Classification DOCSIS 1.1
24 Upstream SF DOCSIS 1.1
25 Downstream SF (11.4) DOCSIS 1.1
26 Payload Header Suppression DOCSIS 1.1
27 HMAC-Digest DOCSIS 3.1
28 Maximum Number of Classifiers DOCSIS 1.1
29 Privacy Enable DOCSIS 1.1
30 Authorization Block DOCSIS 1.1
31 Key Sequence Number DOCSIS 1.1
32 Manufacturer Code Verification Certificate DOCSIS 1.1
33 Co-Signer Code Verification Certificate DOCSIS 1.1
34 SNMPv3 Kickstart Value DOCSIS 1.1
35 Subscriber Mgmt Control DOCSIS 1.1
36 Subscriber Mgmt CPE IPv4 List DOCSIS 1.1
37 Subscriber Mgmt Filter Groups DOCSIS 1.1
38 SNMPv3 Notification Receiver DOCSIS 1.1
39 Enable 2.0 Mode DOCSIS 2.0
40 Enable Test Modes DOCSIS 2.0
41 Downstream Channel List DOCSIS 2.0
42 Static Multicast MAC Address DOCSIS 2.0
43 DOCSIS Extension Field DOCSIS 1.0
44 Vendor Specific Capabilities DOCSIS 1.0
45 Downstream Unencrypted Traffic (DUT) Filtering DOCSIS 2.0
46 Transmit Channel Configuration (TCC) DOCSIS 3.0
47 Service Flow SID Cluster Assignment DOCSIS 3.0
48 Receive Channel Profile DOCSIS 3.0
49 Receive Channel Configuration DOCSIS 3.0
50 DSID Encodings DOCSIS 3.0
51 Security Association Encoding DOCSIS 3.0
52 Initializing Channel Timeout DOCSIS 3.0
53 SNMPv1v2c Coexistence DOCSIS 3.0
54 SNMPv3 Access View Configuration DOCSIS 3.0
55 SNMP CPE Access Control DOCSIS 3.0
56 Channel Assignment Configuration Settings DOCSIS 3.0
57 CM Initialization Reason DOCSIS 3.0
58 SW Upgrade IPv6 TFTP Server DOCSIS 3.0
59 TFTP Server Provisioned Modem IPv6 Address DOCSIS 3.0
60 Upstream Drop Packet Classification DOCSIS 3.0
61 Subscriber Mgmt CPE IPv6 Prefix List DOCSIS 3.0
62 Upstream Drop Classifier Group ID DOCSIS 3.0
63 Subscriber Mgmt Control Max CPE IPv6 Prefix DOCSIS 3.0
64 CMTS Static Multicast Session Encoding DOCSIS 3.0
65 L2VPN MAC Aging Encoding DOCSIS 2.0
66 Management Event Control Encoding DOCSIS 3.0
67 Subscriber Mgmt CPE IPv6 Prefix List DOCSIS 3.0
68 Default Upstream Target Buffer Configuration DOCSIS 3.0
69 MAC Address Learning Control Encoding DOCSIS 3.0
70 Upstream Aggregate Service Flow Encodings DPoE 2.0
71 Downstream Aggregate Service Flow Encodings DPoE 2.0
72 Metro Ethernet Service Profile DPoE 2.0
73 Network Timing Profile DPoE 2.0
74 Energy Management Parameter Encoding DOCSIS 3.0
75 Energy Mgt. Mode Indicator DOCSIS 3.1
76 Energy Mgt. Identifier List for CM DOCSIS 3.1
77 DOCSIS Time Protocol Enable DOCSIS 3.1
78 AQM Disable DOCSIS 3.1
79 UNI Control Encoding DOCSIS 3.0
80 Energy Management – DOCSIS Light Sleep Encodings DOCSIS 3.1
81 Manufacturer CVC Chain DOCSIS 3.1
82 Co-signer CVC Chain DOCSIS 3.1
83 L2CP Management DPoE 2.0
201-231 eCM eSAFE Configuration File TLVs
201 ePS
202 eRouter eRouter
203-215 Reserved
216 eMTA PacketCable 1.x
217 eSTB DSG
218 Reserved
219 eTEA TEI
220 eDVA PacketCable 2.0
221 eSG SMA gateway
222-231 Reserved
255 End-of-Data DOCSIS 1.0