NDNLP-TLV » History » Version 8
Davide Pesavento, 01/03/2023 02:22 AM
| 1 | 8 | Davide Pesavento | # NDNLPv1 TLV packet format (obsolete) |
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| 2 | 1 | Junxiao Shi | |
| 3 | 8 | Davide Pesavento | NDN packet format is shifting from CCNB to [NDN-TLV](https://named-data.net/doc/NDN-packet-spec/current/). |
| 4 | 1 | Junxiao Shi | In this format, every packet, and every field within a packet, is represented by a tuple of Type-Length-Value. |
| 5 | |||
| 6 | [NDNLP: A Link Protocol for NDN](http://named-data.net/publications/techreports/trlinkprotocol/) provides two services to enable NDN communication directly on Ethernet: |
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| 7 | |||
| 8 | * Fragmentation and Reassembly |
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| 9 | * Acknowledgement and Retransmission |
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| 10 | |||
| 11 | NDNLP is initially designed to work with CCNx, and therefore adopts a CCNB-based packet format. |
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| 12 | Although it's possible to enclose NDN-TLV packets in CCNB-based NDNLP packets, this is awkward. |
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| 13 | Therefore, a TLV-based packet format should be defined for NDNLP. |
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| 14 | |||
| 15 | This document defines the TLV-based packet format for NDNLP. |
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| 16 | 4 | Junxiao Shi | In operation reality, acknowledgement and retransmission is rarely used. **This version only defines packet type and fields necessary for fragmentation and reassembly**. |
| 17 | 1 | Junxiao Shi | |
| 18 | Basic [protocol operations](http://named-data.net/publications/techreports/trlinkprotocol/) are unchanged. |
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| 19 | Fragmentation and reassembly operations are [extended to multicast](https://github.com/NDN-Routing/NDNFD/blob/80c3e009106d7e16db85ee8afd647ba85b5b7c2d/docs/NDNLP.md). |
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| 21 | |||
| 22 | ## Link Data Packet |
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| 23 | |||
| 24 | A Link Data packet carries a NDN-TLV packet or a fragment of it as the payload. |
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| 25 | It has the following format: |
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| 26 | |||
| 27 | 4 | Junxiao Shi | NdnlpData ::= NDNLP-DATA-TYPE TLV-LENGTH |
| 28 | 7 | Junxiao Shi | NdnlpSequence |
| 29 | NdnlpFragIndex? |
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| 30 | NdnlpFragCount? |
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| 31 | NdnlpPayload |
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| 32 | 1 | Junxiao Shi | |
| 33 | ### sequence number |
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| 34 | |||
| 35 | 7 | Junxiao Shi | NdnlpSequence ::= NDNLP-SEQUENCE-TYPE TLV-LENGTH(=8) |
| 36 | BYTE+ |
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| 37 | 4 | Junxiao Shi | |
| 38 | 7 | Junxiao Shi | A sequence number for each packet. |
| 39 | 1 | Junxiao Shi | |
| 40 | 7 | Junxiao Shi | This sequence number is unique for recent packets. It can wrap around ultimately. |
| 41 | |||
| 42 | 1 | Junxiao Shi | ### fragment index |
| 43 | |||
| 44 | 7 | Junxiao Shi | NdnlpFragIndex ::= NDNLP-FRAG-INDEX-TYPE TLV-LENGTH |
| 45 | nonNegativeNumber |
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| 46 | 1 | Junxiao Shi | |
| 47 | The 0-based index of current fragment within the network layer packet. |
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| 48 | |||
| 49 | Optional. Default to '0' if not present. |
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| 50 | |||
| 51 | ### fragment count |
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| 52 | |||
| 53 | 7 | Junxiao Shi | NdnlpFragCount ::= NDNLP-FRAG-COUNT-TYPE TLV-LENGTH |
| 54 | nonNegativeNumber |
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| 55 | 1 | Junxiao Shi | |
| 56 | Total number of fragments of the network layer packet. |
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| 57 | |||
| 58 | Optional. Default to '1' if not present. |
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| 59 | |||
| 60 | ### payload |
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| 61 | |||
| 62 | 7 | Junxiao Shi | NdnlpPayload ::= NDNLP-PAYLOAD-TYPE TLV-LENGTH |
| 63 | BYTE+ |
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| 64 | 1 | Junxiao Shi | |
| 65 | 7 | Junxiao Shi | The payload, which is a fragment of network layer packet. |
| 66 | 3 | Alex Afanasyev | |
| 67 | ## TLV-TYPE assignments |
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| 68 | |||
| 69 | Type | Assigned value | Assigned value (hex) |
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| 70 | ------------------------------------------- | ----------------- | -------------------- |
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| 71 | 6 | Junxiao Shi | NdnlpData | 80 | 0x50 |
| 72 | NdnlpSequence | 81 | 0x51 |
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| 73 | NdnlpFragIndex | 82 | 0x52 |
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| 74 | NdnlpFragCount | 83 | 0x53 |
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| 75 | NdnlpPayload | 84 | 0x54 |