BIP: 159 Layer: Peer Services Title: NODE_NETWORK_LIMITED service bits Author: Jonas Schnelli <[email protected]> Comments-Summary: No comments yet. Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0159 Status: Draft Type: Standards Track Created: 2017-05-11 License: BSD-2-Clause
Define service bits that allow pruned peers to signal their limited services
Pruned peers can offer the same services as traditional peer except of serving all historical blocks. Bitcoin right now only offers the NODE_NETWORK service bit which indicates that a peer can serve all historical blocks.
- Pruned peers can relay blocks, headers, transactions, addresses and can serve a limited number of historical blocks, thus they should have a way how to announce their service(s)
- Peers no longer in initial block download should consider connection some of its outbound connections to pruned peers to allow other peers to bootstrap from non-pruned peers
This BIP proposes two new service bits
| NODE_NETWORK_LIMITED_LOW | bit 10 (0x400) | If signaled, the peer MUST be capable of serving at least the last 288 blocks (~2 day / the current minimum limit for Bitcoin Core). |
| NODE_NETWORK_LIMITED_HIGH | bit 11 (0x800) | If signaled, the peer MUST be capable of serving at least the last 1152 blocks (~8 days) |
A safety buffer of additional 144 blocks to handle chain reorganizations SHOULD be taken into account when connecting to a peer signaling NODE_NETWORK_LIMITED_* service bits.
Full nodes following this BIP SHOULD relay address/services (addr message) from peers they would connect to (including peers signaling NODE_NETWORK_LIMITED_*).
Peers may have different prune depths (depending on the peers configuration, disk space, etc.) which can result in a fingerprinting weakness (finding the prune depth through getdata requests). NODE_NETWORK_LIMITED supporting peers SHOULD avoid leaking the prune depth and therefore not serve blocks deeper then the signaled NODE_NETWORK_LIMITED_* thresholds.
Pruned peers following this BIP may consume more outbound bandwidth.
Light clients (and such) who are not checking the nServiceFlags (service bits) from a relayed addr-message may unwillingly connect to a pruned peer and ask for (filtered) blocks at a depth below their pruned depth. Light clients should therefore check the service bits (and eventually connect to peers signaling NODE_NETWORK_LIMITED_* if they require [filtered] blocks around the tip). Light clients obtaining peer IPs though DNS seed should use the DNS filtering option.
This proposal is backward compatible.
This BIP is licensed under the 2-clause BSD license.