NDNLP-TLV » History » Revision 3
Revision 2 (Alex Afanasyev, 01/20/2014 08:00 PM) → Revision 3/8 (Alex Afanasyev, 01/21/2014 04:44 PM)
# NDNLP TLV packet format NDN packet format is shifting from CCNB to [NDN-TLV](http://named-data.net/doc/ndn-tlv/). In this format, every packet, and every field within a packet, is represented by a tuple of Type-Length-Value. [NDNLP: A Link Protocol for NDN](http://named-data.net/publications/techreports/trlinkprotocol/) provides two services to enable NDN communication directly on Ethernet: * Fragmentation and Reassembly * Acknowledgement and Retransmission NDNLP is initially designed to work with CCNx, and therefore adopts a CCNB-based packet format. Although it's possible to enclose NDN-TLV packets in CCNB-based NDNLP packets, this is awkward. Therefore, a TLV-based packet format should be defined for NDNLP. This document defines the TLV-based packet format for NDNLP. In operation reality, acknowledgement and retransmission is rarely used. This version only defines packet type and fields necessary for fragmentation and reassembly. Basic [protocol operations](http://named-data.net/publications/techreports/trlinkprotocol/) are unchanged. Fragmentation and reassembly operations are [extended to multicast](https://github.com/NDN-Routing/NDNFD/blob/80c3e009106d7e16db85ee8afd647ba85b5b7c2d/docs/NDNLP.md). ## Link Data Packet A Link Data packet carries a NDN-TLV packet or a fragment of it as the payload. It has the following format: NdnlpData ::= NDNLP-DATA-TYPE TLV-LENGTH NdnlpSequence NdnlpFragIndex? NdnlpFragCount? NdnlpPayload These elements MUST appear in the given order. All elements are required unless otherwise stated. ### sequence number NdnlpSequence ::= NDNLP-SEQUENCE-TYPE TLV-LENGTH nonNegativeInteger A unique sequence number for each packet. ### fragment index NdnlpFragIndex ::= NDNLP-FRAG-INDEX-TYPE TLV-LENGTH nonNegativeInteger The 0-based index of current fragment within the network layer packet. Optional. Default to '0' if not present. ### fragment count NdnlpFragCount ::= NDNLP-FRAG-COUNT-TYPE TLV-LENGTH nonNegativeInteger Total number of fragments of the network layer packet. Optional. Default to '1' if not present. ### payload NdnlpPayload ::= NDNLP-PAYLOAD-TYPE TLV-LENGTH Interest or Data The payload. ## TLV-TYPE assignments NDNLP-TLV temporarily adopts its [original DTAGs](http://redmine.ccnx.org/issues/100710) as TLV-TYPE numbers. 20653248,NdnlpData 20653249,NdnlpSequence 20653251,NdnlpFragIndex 20653252,NdnlpFragCount 20653253,NdnlpPayload Type | Assigned value | Assigned value (hex) ------------------------------------------- | ----------------- | -------------------- NdnlpData | 20653248 | NdnlpSequence | 20653249 | NdnlpFragIndex | 20653251 | NdnlpFragCount | 20653252 | NdnlpFragCount | 20653253 | `NdnlpData` should be assigned a 1-byte TLV-TYPE number that does not conflict with NDN-TLV, so that it can be efficiently used on the same connection with NDN-TLV. There is no uniqueness requirements on the TLV-TYPE numbers for other elements.