NDN packet format

View NDN packet in Wireshark

Open Wireshark from Terminal:

wireshark -X lua_script:ndn.lua

The file ndn.lua was previously hosted at /montimage/mmt-test/scripts/ndn.lua but is no longer in this repository.

Understand NDN data format

Each NDN packet is encoded in a Type-Length-Value (TLV) format. You can check Type-Length-Value (TLV) Encoding and Type value assignment

Interest packet

We will parse an interest packet:

05:3b:07:2b:08:08:6c:6f:63:61:6c:68:6f:70:08:0c:6e:64:6e:2d:61:75:74:6f:63:6f:6e:66:08:11:72:6f:75:74:61:62:6c:65:2d:70:72:65:66:69:78:65:73:09:02:12:00:0a:04:2c:f3:00:6e:0c:02:03:e8

Analysis

Packet type

T-05: interest packet
L-3b: 59 (decimal value) -> The NDN packet len is 59 octets, the value after this
V- Common fields
- T-07: Name
- L-2b: 43 -> The name of NDN packet has the lenght 43 octets, the value after this
- V-
  - T-08: NameComponent
  - L-08: 8 -> The length of NameComponent is 8 octets
  - V-6c:6f:63:61:6c:68:6f:70: localhop
  - T-08: NameComponent
  - L-0c: 12 -> The length of NameComponent is 12 octets
  - V-6e:64:6e:2d:61:75:74:6f:63:6f:6e:66: ndn-autoconf
  - T-08: NameComponent
  - L-11: 17 -> The length of NameComponent is 17 octets
  - V-72:6f:75:74:61:62:6c:65:2d:70:72:65:66:69:78:65:73: routable-prefixes
Interest packet
- T-09: Selectors
- L-02: 2 -> The length of Selectors is 2 octets
- V-
  - T-12: MustBeFresh
  - L-00: 0 -> The length of this field is 0 octet
- T-0a: Nonce
- L-04: 4-> The length of this field is 4 octets
- V-**2c:f3:00:6e:754122862
- T-0c: InterestLifetime
- L-02: 2 -> The length of this field is 2 octets
- V-03:e8: 1000 seconds

Data packet

We will parse a NDN data packet:

06:fd:01:f4:07:45:08:03:6e:64:6e:08:09:62:72:6f:61:64:63:61:73:74:08:0a:43:68:72:6f:6e:6f:43:68:61:74:08:05:74:65:73:74:31:08:20:e3:b0:c4:42:98:fc:1c:14:9a:fb:f4:c8:99:6f:b9:24:27:ae:41:e4:64:9b:93:4c:a4:95:99:1b:78:52:b8:55:14:04:19:02:03:e8:15:62:80:60:81:5e:07:59:08:07:70:72:69:76:61:74:65:08:05:6c:6f:63:61:6c:08:02:f0:2e:08:17:63:68:72:6f:6e:6f:63:68:61:74:2d:74:6d:70:2d:69:64:65:6e:74:69:74:79:08:08:36:65:36:65:30:63:64:65:08:0f:43:48:52:4f:4e:4f:43:48:41:54:2d:44:41:54:41:08:05:74:65:73:74:31:08:08:00:00:01:4a:ed:bf:e5:04:82:01:01:16:3d:1b:01:01:1c:38:07:36:08:09:6c:6f:63:61:6c:68:6f:73:74:08:08:6f:70:65:72:61:74:6f:72:08:03:4b:45:59:08:11:6b:73:6b:2d:31:34:32:31:31:34:30:31:37:30:37:33:34:08:07:49:44:2d:43:45:52:54:17:fd:01:00:5b:d6:58:71:e2:3c:3c:3f:0d:4d:ba:4b:7c:87:b6:21:3b:eb:9f:51:c8:85:2a:89:dd:fc:8a:8c:71:fb:aa:ff:26:f8:4f:34:f0:f8:44:6c:86:e5:d8:89:7d:4e:23:59:22:70:d0:3f:62:e0:ec:9e:05:98:3e:fe:98:ff:58:90:78:59:a6:c1:16:d6:90:3c:01:16:d8:15:1f:23:0a:bc:fa:c6:5c:bf:cf:9f:d4:83:0f:fe:a6:71:57:29:ad:ed:fb:eb:0c:91:8c:53:be:67:38:5b:50:ea:63:0d:2f:68:77:fc:b4:ae:03:d5:a8:57:02:4a:06:21:fa:48:24:82:41:9e:a7:d7:ea:96:c4:d9:76:d0:b2:fa:4b:08:39:d9:9c:a2:dc:ff:96:dd:91:be:b8:da:61:84:97:dc:0d:a0:3b:24:e2:4e:73:4c:cf:35:9a:cb:b9:6e:93:d6:cf:3f:72:79:85:23:41:26:95:03:fe:15:f3:9b:31:c9:d3:fa:9a:d4:cb:bd:3f:9c:60:bd:d0:fd:1d:f7:85:f4:41:fe:14:75:f8:55:d9:23:30:43:77:c0:ff:2f:09:c5:43:3f:8c:dd:6b:ad:7a:0e:2e:63:14:ba:df:d2:a2:1b:49:de:6c:c9:bc:9a:c1:7e:a6:a9:0e:f8:0a:fd:ae:a3:d7:5d

Analysis

Packet type

T-06: data packet
L-fd: 253 (decimal value) -> 2 octets (see why?)

-> L-01:f4 500 -> The NDN packet len is 500 octets, the value after this
V- Common fields
- T-07: Name
- L-45: 69 -> The name of NDN packet has the lenght 69 octets, the value after this
- V-
  - T-08: NameComponent
  - L-03: 3 -> The length of NameComponent is 3 octets
  - V-6e:64:6e: ndn
  - T-08: NameComponent
  - L-09: 9 -> The length of NameComponent is 9 octets
  - V-62:72:6f:61:64:63:61:73:74: broadcast
  - T-08: NameComponent
  - L-0a: 10 -> The length of NameComponent is 10 octets
  - V-43:68:72:6f:6e:6f:43:68:61:74: ChronoChat
  - T-08: NameComponent
  - L-05: 5 -> The length of NameComponent is 5 octets
  - V-74:65:73:74:31: test1
  - T-08: NameComponent
  - L-20: 32 -> The length of NameComponent is 32 octets
  - V-e3:b0:c4:42:98:fc:1c:14:9a:fb:f4:c8:99:6f:b9:24:27:ae:41:e4:64:9b:93:4c:a4:95:99:1b:78:52:b8:55: ã°ÄBüûôÈo¹$’®AädL¤xR¸U
Data packet
- T-14: MetaInfo
- L-04: 4 octets
- V-
  - T-19: FreshnessPeriod
  - L-02: 2 octets
  - V-03:e8: 1000 seconds
- T-15: Content
- L-62: 98 octets
- V-: 80:60:81:5e:07:59:08:07:70:72:69:76:61:74:65:08:05:6c:6f:63:61:6c:08:02:f0:2e:08:17:63:68:72:6f:6e:6f:63:68:61:74:2d:74:6d:70:2d:69:64:65:6e:74:69:74:79:08:08:36:65:36:65:30:63:64:65:08:0f:43:48:52:4f:4e:4f:43:48:41:54:2d:44:41:54:41:08:05:74:65:73:74:31:08:08:00:00:01:4a:ed:bf:e5:04:82:01:01 -> ^Yprivatelocalð.chronochat-tmp-identity6e6e0cdeCHRONOCHAT-DATAtest1Jí¿å
- T-16: SignatureInfo
- L-3d: 61 octets
- V-
  - T-1b: SignatureType
  - L-01: 1 octet
  - V-01: SignatureSha256WithRsa (see why)
  - T-1c: KeyLocator
  - L-38: 56 octets
  - V-:07:36:08:09:6c:6f:63:61:6c:68:6f:73:74:08:08:6f:70:65:72:61:74:6f:72:08:03:4b:45:59:08:11:6b:73:6b:2d:31:34:32:31:31:34:30:31:37:30:37:33:34:08:07:49:44:2d:43:45:52:54 -> 6 localhostoperatorKEYksk-1421140170734ID-CERT
- T-17: SignatureValue
- L-fd: 253 -> 2 octets for length-> L-01:00: 256 octets
- V-:5b:d6:58:71:e2:3c:3c:3f:0d:4d:ba:4b:7c:87:b6:21:3b:eb:9f:51:c8:85:2a:89:dd:fc:8a:8c:71:fb:aa:ff:26:f8:4f:34:f0:f8:44:6c:86:e5:d8:89:7d:4e:23:59:22:70:d0:3f:62:e0:ec:9e:05:98:3e:fe:98:ff:58:90:78:59:a6:c1:16:d6:90:3c:01:16:d8:15:1f:23:0a:bc:fa:c6:5c:bf:cf:9f:d4:83:0f:fe:a6:71:57:29:ad:ed:fb:eb:0c:91:8c:53:be:67:38:5b:50:ea:63:0d:2f:68:77:fc:b4:ae:03:d5:a8:57:02:4a:06:21:fa:48:24:82:41:9e:a7:d7:ea:96:c4:d9:76:d0:b2:fa:4b:08:39:d9:9c:a2:dc:ff:96:dd:91:be:b8:da:61:84:97:dc:0d:a0:3b:24:e2:4e:73:4c:cf:35:9a:cb:b9:6e:93:d6:cf:3f:72:79:85:23:41:26:95:03:fe:15:f3:9b:31:c9:d3:fa:9a:d4:cb:bd:3f:9c:60:bd:d0:fd:1d:f7:85:f4:41:fe:14:75:f8:55:d9:23:30:43:77:c0:ff:2f:09:c5:43:3f:8c:dd:6b:ad:7a:0e:2e:63:14:ba:df:d2:a2:1b:49:de:6c:c9:bc:9a:c1:7e:a6:a9:0e:f8:0a:fd:ae:a3:d7:5d -> …

How to classify NDN packet?

C1: Start with 05 or 06
C2: Assume that the packet is satisfied C1, calculate the length of packet(follow T-L-V format) and compare with the total length of packet.
C3:(Considering…) Check the mask: T-V-07:…. -> The NDN packet must have the common field.

There could be two ways to classify:

Solution 1: Uss MMT_NDN_BITS_MASK to check:

Interest packet:

M1: 0000 0101 xxxx xxxx 0000 0111 (<253)
M2: 0000 0101 1111 1101 xxxx xxxx xxxx xxxx 0000 0111 (=253)
M3: 0000 0101 1111 1110 xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 0000 0111 (=254)
M4: 0000 0101 1111 1111 xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 0000 0111 (=255)

Data packet:

M1: 0000 0110 xxxx xxxx 0000 0111 (<253: ex: )
M2: 0000 0110 1111 1101 xxxx xxxx xxxx xxxx 0000 0111 (=253)
M3: 0000 0110 1111 1110 xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 0000 0111 (=254)
M4: 0000 0110 1111 1111 xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 0000 0111 (=255)

Solution 2: Parse the packet data:

Check first condition C1
If C1 is satified then check C2
If C1, C2 is satified then check C3