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Merge pull request bitcoin#592 from jonasschnelli/node_network_limited
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Remove second service bit from NODE_NETWORK_LIMITED/BIP159
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luke-jr authored Sep 23, 2017
2 parents e49aa21 + 8b971ea commit 7fccc60
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2 changes: 1 addition & 1 deletion README.mediawiki
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|-
| [[bip-0159.mediawiki|159]]
| Peer Services
| NODE_NETWORK_LIMITED service bits
| NODE_NETWORK_LIMITED service bit
| Jonas Schnelli
| Standard
| Draft
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22 changes: 10 additions & 12 deletions bip-0159.mediawiki
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<pre>
BIP: 159
Layer: Peer Services
Title: NODE_NETWORK_LIMITED service bits
Title: NODE_NETWORK_LIMITED service bit
Author: Jonas Schnelli <[email protected]>
Comments-Summary: No comments yet.
Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0159
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== Abstract ==

Define service bits that allow pruned peers to signal their limited services
Define a service bit that allow pruned peers to signal their limited services

==Motivation==

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
# Peers no longer in initial block download should consider connecting some of its outbound connections to pruned peers to allow other peers to bootstrap from non-pruned peers
== Specification ==

=== New service bits ===
=== New service bit ===

This BIP proposes two new service bits
This BIP proposes a new service bit

{|class="wikitable"
|-
| NODE_NETWORK_LIMITED_LOW || bit 10 (0x400) || If signaled, the peer <I>MUST</I> 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 <I>MUST</i> be capable of serving at least the last 1152 blocks (~8 days)
| NODE_NETWORK_LIMITED || bit 10 (0x400) || If signaled, the peer <I>MUST</I> be capable of serving at least the last 288 blocks (~2 day / the current minimum limit for Bitcoin Core).
|}

A safety buffer of additional 144 blocks to handle chain reorganizations <I>SHOULD</I> be taken into account when connecting to a peer signaling <code>NODE_NETWORK_LIMITED_*</code> service bits.
A safety buffer of additional 144 blocks to handle chain reorganizations <I>SHOULD</I> be taken into account when connecting to a peer signaling the <code>NODE_NETWORK_LIMITED</code> service bit.

=== Address relay ===

Full nodes following this BIP <I>SHOULD</I> relay address/services (<code>addr</code> message) from peers they would connect to (including peers signaling <code>NODE_NETWORK_LIMITED_*</code>).
Full nodes following this BIP <I>SHOULD</I> relay address/services (<code>addr</code> message) from peers they would connect to (including peers signaling <code>NODE_NETWORK_LIMITED</code>).

=== Counter-measures for peer fingerprinting ===

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 <I>SHOULD</I> avoid leaking the prune depth and therefore not serve blocks deeper then the signaled <code>NODE_NETWORK_LIMITED_*</code> thresholds.
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 <I>SHOULD</I> avoid leaking the prune depth and therefore not serve blocks deeper then the signaled <code>NODE_NETWORK_LIMITED</code> thresholds.

=== Risks ===

Pruned peers following this BIP may consume more outbound bandwidth.

Light clients (and such) who are not checking the <code>nServiceFlags</code> (service bits) from a relayed <code>addr</code>-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 <code>NODE_NETWORK_LIMITED_*</code> if they require [filtered] blocks around the tip). Light clients obtaining peer IPs though DNS seed should use the DNS filtering option.
Light clients (and such) who are not checking the <code>nServiceFlags</code> (service bits) from a relayed <code>addr</code>-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 <code>NODE_NETWORK_LIMITED</code> if they require [filtered] blocks around the tip). Light clients obtaining peer IPs though DNS seed should use the DNS filtering option.

== Compatibility ==

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