Antminer X9
Monero ASIC Miner
1000KH
HASHRATE
2.47W/KH
EFFICIENCY
2470W
POWER
£861.31
EST. MONTHLY
205
DAYS
EST. ROI
This guide explains BIP 155 addrv2 message in plain English. It covers the problem behind the BIP, why it matters and whether the proposal is part of Bitcoin today.
TL;DR
- What it is: BIP 155 defines the deployed addrv2 peer-to-peer message for relaying network endpoints too large or varied for legacy addr. It adds a network identifier and variable-length address, uses CompactSize for service flags and negotiates support with sendaddrv2.
- Why it matters: BIP 155 gives Bitcoin address gossip an extensible typed format. Correct implementations negotiate at the right handshake point, enforce small bounded inputs and follow current network-specific validity rules.
- Current position: Require a second reviewer and explicit rollback or expiry, and pause payments, signing or network-dependent services until post-change evidence is complete.
BIP 155 addrv2 message in simple English
BIP 155 addrv2 message: sendaddrv2 means a peer prefers addrv2 and may be sent only after its version message and before verack.
Simple example
A node operator is checking BIP 155 addrv2 message. Enforce limits before allocating memory and rate-limit unsolicited address churn. Peers without it continue receiving legacy addr and cannot receive newer address types.
Key terms in plain English
- BIP:
- Bitcoin Improvement Proposal: a document describing a proposed rule, standard or process. Its status must be checked separately.
- Bitcoin Core:
- Widely used software that validates Bitcoin and can provide wallet, network and operator tools.
- Node:
- A computer running Bitcoin software that checks data and communicates with other peers.
Why addrv2 exists
Legacy addr allocated 16 bytes and represented old onion services through OnionCat. Tor v3 and I2P use 32-byte identifiers, so a typed variable-length field was needed to gossip them without disguising them as IPv6.
Record format
Each entry carries timestamp, CompactSize services, one-byte network ID, variable address bytes and big-endian port. Parse widths independently and reject non-canonical CompactSize or truncated data.
Networks and lengths
IPv4 uses four bytes, IPv6 sixteen, Tor v3 and I2P thirty-two, while other assigned overlays have fixed lengths. Known IDs with wrong lengths are meaningless and must be rejected.
Hard limits
One message permits at most 1,000 addresses and each address field at most 512 bytes. Enforce limits before allocating memory and rate-limit unsolicited address churn.
Negotiation
sendaddrv2 means a peer prefers addrv2 and may be sent only after its version message and before verack. Peers without it continue receiving legacy addr and cannot receive newer address types.
Privacy and unknown networks
Relaying known networks can hide local transport preference, but unknown networks should not be gossiped because the receiver cannot validate them. Address tables reveal topology and require restricted diagnostics.
How specialists test it
Developers test the proposal with made-up data on an isolated test network. They check normal cases and deliberately invalid cases. Different implementations should reach the same result before anyone relies on the proposal.
Frequently asked questions
What is the main point of BIP 155 addrv2 message?
BIP 155 addrv2 message: sendaddrv2 means a peer prefers addrv2 and may be sent only after its version message and before verack.
For BIP 155 addrv2 message, why addrv2 exists?
Legacy addr allocated 16 bytes and represented old onion services through OnionCat.
For BIP 155 addrv2 message, what should a beginner know about record format?
Each entry carries timestamp, CompactSize services, one-byte network ID, variable address bytes and big-endian port.
For BIP 155 addrv2 message, what should a beginner know about networks and lengths?
IPv4 uses four bytes, IPv6 sixteen, Tor v3 and I2P thirty-two, while other assigned overlays have fixed lengths.
Conclusion
BIP 155 gives Bitcoin address gossip an extensible typed format. Correct implementations negotiate at the right handshake point, enforce small bounded inputs and follow current network-specific validity rules.
Primary sources
Check the current specification status and the documentation for the exact implementation you operate before moving production funds or changing a mining node.
Join the ASIC Mining Discussion
Members can read and join the discussion
Log in to read comments from other miners. Create a free account if you would like to ask a question or share your experience.
Membership helps us protect the discussion from spam and keep answers useful.