Stream IDs describe direction
02The low two bits encode the initiator and whether the stream is bidirectional or unidirectional.
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Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAM§ 2.1 ↗
RFC 9000 · § 2.1EXAMPLE
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03
Allocate the next ID of a type.
Client-initiated bidirectional streams use IDs 0, 4, 8, and so on.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
IDs distinguish four stream types.
- Client-initiated IDs are even; server-initiated IDs are odd.
- The next-lowest bit distinguishes bidirectional from unidirectional streams.
- Successive IDs of one type increase by four; IDs are not reused within a connection.
Limits on how many streams may be opened are separate from a stream’s direction and ID.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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