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---
layout: post
slug: understanding-bittorrent
status: draft
sitemap: false
title: Understanding BitTorrent
description: From the network perspective
categories:
tags:
- p2p
- distributed system
---
In this blog post, we will only review the core of BitTorrent.
We are not interested in its extensions, its optimizations, how it manages spam, etc.
Compared to the specifications, we will focus our analysis on the importance of parameters and the emerging behaviours that arise when many BitTorrent clients communicate together.
Moreover, as this (hopefully series of) article will be written in a goal to evaluate Peertube planned implementation of "webstream" (live-streaming over webtorrent), we will use the webtorrent implementation as reference for everything outside specifications.
We will also try to connect BitTorrent design to some academic papers to put things in perspective.
## A problem well stated is a problem half solved
**Discover content**
**Discover peers**
**Discover peers' content**
**Induce a desirable emerging behavior**
## The .torrent file
Describes the content of the file to download.
Multiplexing.
## The role of the tracker
Discovering peers.
What property it must enforce.
Random sample of the network
You will have some neighbors.
## Discovering the chunks known by your neighbors
introduce some Xerox Taxonomy {% cite DBLP:journals/sigops/DemersGHILSSST88 %}.
"bitfield" puis "have" -> le push sur l'anti entropy
If it's done symmetrically, we are in a push+pull model.
## Downloading the data
The importance of Local Rarest First {% cite DBLP:conf/infocom/BharambeHP06 %}
## Conclusion
BitTorrent is efficient as it multiplexes chunks.
## References
{% bibliography --cited %}