Ethereum Source (05): Network Service analysis

Http://mp.weixin.qq.com/s/yJAwLYbrD9AHLqmlZvy_WA

Directory

1 network layering ..... ..... ..... ........................ ..... ..... ..... ..... .............. ........... 4

2 Session layer ..... ..... .... ..... ..... ...................... ..... ..... ..... ..... ..... .............. .......... 4

2.1 Peer Introduction ...... ..... ......................... ....... ..... .................. ......... 5

2.2 Peer management ...... ..... ........................ ....... ..... .................. ......... 5

2.2.1 Peer Dynamic Add delete process ..... ..... ... ..... .... ..... ..... ..... ..... ..... ..................... 5

2.2.2 Peer handshake mechanism ..... ..... .................... ............................. 6

3 Presentation layer: RLP encoding ...... ..... ..... ................ ........ ................... ....... 6

4 Application layer: Eth protocol ...... ..... ..... ................ ........ ................... ....... 6

1 Network tiering

Ethereum all network functions are shown in the following diagram: All network functions are built on the Ethernet transport layer, TCP and UDP are used.

2 Session Layer

The session layer mainly includes peer management, nodetable Management and RPC protocol, this article focuses on peer management, nodetable please refer to the peer-network and neighbor node discovery mechanism. Key code that involves the session layer:

2.1 Peer Introduction

Peer refers to a neighbor node that passes the communication handshake, and only the neighbor node becomes a peer, and only the nodes in the peer list can communicate properly.

2.2 Peer Management

Peers exists in the code as a map structure, created by the server Run method run, and added and removed in the Run method. Pees maximum default number is (Node/defaults.go defined)

2.2.1 Peer Dynamic Add Delete process

Peer addition is divided into two types: passive and active Add. 1) Passive add refers to the other node initiates the handshake, the process is as follows:

2) Whenever there is a change in the current peers, such as adding, deleting, or once the Dial task is completed, an active handshake process is performed, where the nodes to be Dial (dial-up, i.e. handshake communication) are composed of the following parts:

Static node, configuration file write at system startup

Random selection in nodetable (One-second of the current needdyndials, needdyndials value (s.maxpeer+1)/2=13)

Node in Loobbuf (Neighbor node in discovery Task)

When the number of nodes in the LOOKBUF is insufficient, a nodetable flush is forced, and the node written to Lookbuf is flushed.

3) Peer Deletion has three ways: RPC command deletion, one application layer of communication complete automatic deletion, communication process read-write error.

2.2.2 Peer handshake Mechanism

Refer to "Ethereum Bottom technology research: Peer handshake mechanism"

3 Presentation layer: RLP encoding

Ethereum is related to the data sent on the network x follow the RLP code, reference "RLP mechanism analysis"

4 Application layer: Eth protocol

After the Peer handshake succeeds, the application layer communication can be performed, and the Eth protocol packet is shown in the following table:

The ETH protocol application layer includes the following commands:

This article is organized by the core chain team.