BIP 123

BIP Classification

Deployed Type Process

Preamble

BIP: 123
Title: BIP Classification
Author: Eric Lombrozo
Status: Deployed
Type: Process
Assigned: 2015-08-26
License: CC0-1.0 OR FSFAP

Abstract

This document describes a classification scheme for BIPs.

BIPs are classified by system layers with lower numbered layers involving more intricate interoperability requirements.

The specification defines the layers and sets forth specific criteria for deciding to which layer a particular standards BIP belongs.

Copyright

This BIP is dual-licensed under the Creative Commons CC0 1.0 Universal and FSF All Permissive licenses.

Motivation

Bitcoin is a system involving a number of different standards. Some standards are absolute requirements for interoperability while others can be considered optional, giving implementers a choice of whether to support them.

In order to have a BIP process which more closely reflects the interoperability requirements, it is necessary to categorize BIPs accordingly. Lower layers present considerably greater challenges in getting standards accepted and deployed.

Specification

Standards BIPs are placed in one of four layers:

Consensus
Peer Services
API/RPC
Applications

Non-standards BIPs may be placed in these layers, or none at all.

1. Consensus Layer

The consensus layer defines cryptographic commitment structures. Its purpose is ensuring that anyone can locally evaluate whether a particular state and history is valid, providing settlement guarantees, and assuring eventual convergence.

The consensus layer is not concerned with how messages are propagated on a network.

Disagreements over the consensus layer can result in network partitioning, or forks, where different nodes might end up accepting different incompatible histories. We further subdivide consensus layer changes into soft forks and hard forks.

Soft Forks

In a soft fork, some structures that were valid under the old rules are no longer valid under the new rules. Structures that were invalid under the old rules continue to be invalid under the new rules.

Hard Forks

In a hard fork, structures that were invalid under the old rules become valid under the new rules.

2. Peer Services Layer

The peer services layer specifies how nodes find each other and propagate messages.

Only a subset of all specified peer services are required for basic node interoperability. Nodes can support further optional extensions.

It is always possible to add new services without breaking compatibility with existing services, then gradually deprecate older services. In this manner, the entire network can be upgraded without serious risks of service disruption.

3. API/RPC Layer

The API/RPC layer specifies higher level calls accessible to applications. Support for these BIPs is not required for basic network interoperability but might be expected by some client applications.

There's room at this layer to allow for competing standards without breaking basic network interoperability.

4. Applications Layer

The applications layer specifies high level structures, abstractions, and conventions that allow different applications to support similar features and share data.

Classification of existing BIPs

Number	Layer	Title	Owner	Type	Status
1		BIP Purpose and Guidelines	Amir Taaki	Process	Active
2		BIP process, revised	Luke Dashjr	Process	Draft
9		Version bits with timeout and delay	Pieter Wuille, Peter Todd, Greg Maxwell, Rusty Russell	Informational	Final
10	Applications	Multi-Sig Transaction Distribution	Alan Reiner	Informational	Withdrawn
11	Applications	M-of-N Standard Transactions	Gavin Andresen	Standard	Final
12	Consensus (soft fork)	OP_EVAL	Gavin Andresen	Standard	Withdrawn
13	Applications	Address Format for pay-to-script-hash	Gavin Andresen	Standard	Final
14	Peer Services	Protocol Version and User Agent	Amir Taaki, Patrick Strateman	Standard	Final
15	Applications	Aliases	Amir Taaki	Standard	Deferred
16	Consensus (soft fork)	Pay to Script Hash	Gavin Andresen	Standard	Final
17	Consensus (soft fork)	OP_CHECKHASHVERIFY (CHV)	Luke Dashjr	Standard	Withdrawn
18	Consensus (soft fork)	hashScriptCheck	Luke Dashjr	Standard	Accepted
19	Applications	M-of-N Standard Transactions (Low SigOp)	Luke Dashjr	Standard	Draft
20	Applications	URI Scheme	Luke Dashjr	Standard	Replaced
21	Applications	URI Scheme	Nils Schneider, Matt Corallo	Standard	Final
22	API/RPC	getblocktemplate - Fundamentals	Luke Dashjr	Standard	Final
23	API/RPC	getblocktemplate - Pooled Mining	Luke Dashjr	Standard	Final
30	Consensus (soft fork)	Duplicate transactions	Pieter Wuille	Standard	Final
31	Peer Services	Pong message	Mike Hearn	Standard	Final
32	Applications	Hierarchical Deterministic Wallets	Pieter Wuille	Informational	Final
33	Peer Services	Stratized Nodes	Amir Taaki	Standard	Draft
34	Consensus (soft fork)	Block v2, Height in Coinbase	Gavin Andresen	Standard	Final
35	Peer Services	mempool message	Jeff Garzik	Standard	Final
36	Peer Services	Custom Services	Stefan Thomas	Standard	Draft
37	Peer Services	Connection Bloom filtering	Mike Hearn, Matt Corallo	Standard	Final
38	Applications	Passphrase-protected private key	Mike Caldwell, Aaron Voisine	Standard	Draft
39	Applications	Mnemonic code for generating deterministic keys	Marek Palatinus, Pavol Rusnak, Aaron Voisine, Sean Bowe	Standard	Accepted
42	Consensus (soft fork)	A finite monetary supply for Bitcoin	Pieter Wuille	Standard	Draft
43	Applications	Purpose Field for Deterministic Wallets	Marek Palatinus, Pavol Rusnak	Informational	Draft
44	Applications	Multi-Account Hierarchy for Deterministic Wallets	Marek Palatinus, Pavol Rusnak	Standard	Accepted
45	Applications	Structure for Deterministic P2SH Multisignature Wallets	Manuel Araoz, Ryan X. Charles, Matias Alejo Garcia	Standard	Accepted
47	Applications	Reusable Payment Codes for Hierarchical Deterministic Wallets	Justus Ranvier	Informational	Draft
49	Applications	Derivation scheme for P2WPKH-nested-in-P2SH based accounts	Daniel Weigl	Informational	Draft
50		March 2013 Chain Fork Post-Mortem	Gavin Andresen	Informational	Final
60	Peer Services	Fixed Length "version" Message (Relay-Transactions Field)	Amir Taaki	Standard	Draft
61	Peer Services	Reject P2P message	Gavin Andresen	Standard	Final
62	Consensus (soft fork)	Dealing with malleability	Pieter Wuille	Standard	Withdrawn
64	Peer Services	getutxo message	Mike Hearn	Standard	Draft
65	Consensus (soft fork)	OP_CHECKLOCKTIMEVERIFY	Peter Todd	Standard	Final
66	Consensus (soft fork)	Strict DER signatures	Pieter Wuille	Standard	Final
67	Applications	Deterministic Pay-to-script-hash multi-signature addresses through public key sorting	Thomas Kerin, Jean-Pierre Rupp, Ruben de Vries	Standard	Accepted
68	Consensus (soft fork)	Relative lock-time using consensus-enforced sequence numbers	Mark Friedenbach, BtcDrak, Nicolas Dorier, kinoshitajona	Standard	Final
69	Applications	Lexicographical Indexing of Transaction Inputs and Outputs	Kristov Atlas	Informational	Accepted
70	Applications	Payment Protocol	Gavin Andresen, Mike Hearn	Standard	Final
71	Applications	Payment Protocol MIME types	Gavin Andresen	Standard	Final
72	Applications	bitcoin: uri extensions for Payment Protocol	Gavin Andresen	Standard	Final
73	Applications	Use "Accept" header for response type negotiation with Payment Request URLs	Stephen Pair	Standard	Final
74	Applications	Allow zero value OP_RETURN in Payment Protocol	Toby Padilla	Standard	Draft
75	Applications	Out of Band Address Exchange using Payment Protocol Encryption	Justin Newton, Matt David, Aaron Voisine, James MacWhyte	Standard	Draft
80		Hierarchy for Non-Colored Voting Pool Deterministic Multisig Wallets	Justus Ranvier, Jimmy Song	Informational	Deferred
81		Hierarchy for Colored Voting Pool Deterministic Multisig Wallets	Justus Ranvier, Jimmy Song	Informational	Deferred
83	Applications	Dynamic Hierarchical Deterministic Key Trees	Eric Lombrozo	Standard	Draft
99		Motivation and deployment of consensus rule changes ([soft/hard]forks)	Jorge Timón	Informational	Draft
101	Consensus (hard fork)	Increase maximum block size	Gavin Andresen	Standard	Withdrawn
102	Consensus (hard fork)	Block size increase to 2MB	Jeff Garzik	Standard	Draft
103	Consensus (hard fork)	Block size following technological growth	Pieter Wuille	Standard	Draft
105	Consensus (hard fork)	Consensus based block size retargeting algorithm	BtcDrak	Standard	Draft
106	Consensus (hard fork)	Dynamically Controlled Bitcoin Block Size Max Cap	Upal Chakraborty	Standard	Draft
107	Consensus (hard fork)	Dynamic limit on the block size	Washington Y. Sanchez	Standard	Draft
109	Consensus (hard fork)	Two million byte size limit with sigop and sighash limits	Gavin Andresen	Standard	Draft
111	Peer Services	NODE_BLOOM service bit	Matt Corallo, Peter Todd	Standard	Accepted
112	Consensus (soft fork)	CHECKSEQUENCEVERIFY	BtcDrak, Mark Friedenbach, Eric Lombrozo	Standard	Final
113	Consensus (soft fork)	Median time-past as endpoint for lock-time calculations	Thomas Kerin, Mark Friedenbach	Standard	Final
114	Consensus (soft fork)	Merkelized Abstract Syntax Tree	Johnson Lau	Standard	Draft
120	Applications	Proof of Payment	Kalle Rosenbaum	Standard	Draft
121	Applications	Proof of Payment URI scheme	Kalle Rosenbaum	Standard	Draft
122	Applications	URI scheme for Blockchain references / exploration	Marco Pontello	Standard	Draft
123		BIP Classification	Eric Lombrozo	Process	Draft
124	Applications	Hierarchical Deterministic Script Templates	Eric Lombrozo, William Swanson	Informational	Draft
125	Applications	Opt-in Full Replace-by-Fee Signaling	David A. Harding, Peter Todd	Standard	Accepted
126		Best Practices for Heterogeneous Input Script Transactions	Kristov Atlas	Informational	Draft
130	Peer Services	sendheaders message	Suhas Daftuar	Standard	Accepted
131	Consensus (hard fork)	"Coalescing Transaction" Specification (wildcard inputs)	Chris Priest	Standard	Draft
132		Committee-based BIP Acceptance Process	Andy Chase	Process	Withdrawn
133	Peer Services	feefilter message	Alex Morcos	Standard	Draft
134	Consensus (hard fork)	Flexible Transactions	Tom Zander	Standard	Draft
140	Consensus (soft fork)	Normalized TXID	Christian Decker	Standard	Draft
141	Consensus (soft fork)	Segregated Witness (Consensus layer)	Eric Lombrozo, Johnson Lau, Pieter Wuille	Standard	Draft
142	Applications	Address Format for Segregated Witness	Johnson Lau	Standard	Deferred
143	Consensus (soft fork)	Transaction Signature Verification for Version 0 Witness Program	Johnson Lau, Pieter Wuille	Standard	Draft
144	Peer Services	Segregated Witness (Peer Services)	Eric Lombrozo, Pieter Wuille	Standard	Draft
145	API/RPC	getblocktemplate Updates for Segregated Witness	Luke Dashjr	Standard	Draft
146	Consensus (soft fork)	Dealing with signature encoding malleability	Johnson Lau, Pieter Wuille	Standard	Draft
147	Consensus (soft fork)	Dealing with dummy stack element malleability	Johnson Lau	Standard	Draft
150	Peer Services	Peer Authentication	Jonas Schnelli	Standard	Draft
151	Peer Services	Peer-to-Peer Communication Encryption	Jonas Schnelli	Standard	Draft
152	Peer Services	Compact Block Relay	Matt Corallo	Standard	Draft

# Abstract

# Copyright

# Motivation

# Specification

# 1. Consensus Layer