sendheaders message

The five-minute read

One action, walked through

1. Open BIP 130 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: Add a new message, "sendheaders", which indicates that a node prefers to receive new block announcements via a "headers" message rather than an "inv".
3. Name the object that changes: sendheaders message.
4. Ask what an old client, an old contract, or an offline counterparty does. If the document is silent, the silence is part of the design.

The argument, unpacked

What has to be true

• You are implementing BIP 130 at the status the text itself states: Deployed.
• The object that has to change is sendheaders message. A neighbouring document with a similar name is not this one.
• Measurements of delay in one year do not travel with the specification.

What happened after the paper

The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it. Later documents can narrow, replace, or ignore this one. Cite the number you mean.

What to check before you use the idea

• Which message does sendheaders message add, and which old peer must still be answered?
• What does a node do when the short form fails and the full object is required?
• Which names are normative: sendheaders message?

Terms

BIP 130

The public text titled sendheaders message.

Deployed

The document's own label for how finished the text is. It is not a market fact.

The problem the paper names

A node that cannot fetch, filter, or relay the data it is supposed to validate is not a peer of the network the paper describes.

What the design proposes

• Add a new message, "sendheaders", which indicates that a node prefers to receive new block announcements via a "headers" message rather than an "inv".
• Since the introduction of "headers-first" downloading of blocks in 0.10, blocks will not be processed unless they are able to connect to a (valid) headers chain.
• Consequently, block relay generally works as follows: # A node (N) announces the new tip with an "inv" message, containing the block hash # A peer (P) responds to the "inv" with a "getheaders" message (to request headers up to the new tip) and a "getdata" message for the new tip itself # N responds with a "headers" message (with the header for the new block along with any preceding headers unknown to P) and a "block" message containing the new block However, in the case where a new block is being announced that builds on the tip, it would be generally more efficient if the node N just announced the block header for the new block, rather than just the block hash, and saved the peer from generating and transmitting the getheaders message (and the required block locator).

How the mechanism is specified

• Taken from the specification, the next constraint is: Since the introduction of "headers-first" downloading of blocks in 0.10, blocks will not be processed unless they are able to connect to a (valid) headers chain.
• Locate sendheaders message in BIP 130 and apply it to one transaction or call.
• Then check the failure the class of rule always has: a node that did not upgrade, a reverted call, a replayed signature, or a peer that does not speak the message.

What this page does not treat as proven

• A peer protocol is not a consensus rule. A peer can disconnect. A block is still valid or not on its own.
• Measurements of delay in one year do not travel with the specification.
• The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it.

Why a venture studio still reads it

Use BIP 130 when a pitch says 'sendheaders message' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.