[RFC] Vortex: A P2P File Transfer Protocol Based on TLV

[gaius-qi]

Overview

Vortex is a peer-to-peer (P2P) file transfer protocol that utilizes the TLV (Tag-Length-Value) format for efficient and flexible data transmission. This protocol is designed to provide reliable and scalable file sharing capabilities.

Protocol Fields

• Packet Identifier (8 bits): Uniquely identifies each packet.
• Tag (T, 7 bits): Specifies the type of data in the value field.
• Length (L, 30 bits): Indicates the length (in bytes) of the Value field, supporting up to 1GiB of data.
• Value (V, variable length): The actual data, up to 1GiB.

Tag Definitions

Tag	Name	Description
0	Piece Identifier	Composed of {Task ID}-{Piece ID}, where the Task ID is a 32-byte SHA-256 value and the Piece ID is a number.
1	Piece Content	The content of a piece, with a maximum size of 1 GiB per piece.
2-126	Reserved	Reserved for future use.
127	Error	Error message.

Packet Format

Packet ID (8 bits)	Tag (7 bits)	Length (30 bits)	Value (up to 1GiB)
8-bit	7-bit	30-bit	variable

• Packet ID: 8-bit unsigned integer.
• Tag: 7-bit field describing the content type.
• Length: 30-bit field specifying the size of the Value.
• Value: Actual data, size determined by Length.

Behavior

• Piece ID (Tag=0x00): Identifies the specific piece of the file.
• Piece Content (Tag=0x01): Raw piece data or piece fragments.
• Error (Tag=0x7F): Conveys error.
• Reserved Tags: May be allocated for metadata, compression, encryption, or future protocol extensions.

Example

• Packet ID: 0x12
• Tag: 0x00 (piece content)
• Length: 10 (indicating "HelloWorld" is 10 bytes)
• Value: "HelloWorld"

Conclusion

This TLV-based protocol, with an 8-bit Packet Identifier and support for up to 1GiB in the Value field, offers flexibility, simplicity, and room for future enhancements. By reserving Tags, it is scalable for evolving P2P file transfer requirements.

References

• https://en.wikipedia.org/wiki/Type%E2%80%93length%E2%80%93value
• https://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol
• https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol
• https://en.wikipedia.org/wiki/RADIUS