51 lines
2.3 KiB
Markdown
51 lines
2.3 KiB
Markdown
---
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title: Understanding how Weave Net Works
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menu_order: 90
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---
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A Weave network consists of a number of 'peers' - Weave Net routers
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residing on different hosts. Each peer has a name, which tends to
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remain the same over restarts, a human friendly nickname for use in
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status and logging output and a unique identifier (UID) that is
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different each time it is run. These are opaque identifiers as far as
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the router is concerned, although the name defaults to a MAC address.
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Weave Net routers establish TCP connections with each other, over which they
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perform a protocol handshake and subsequently exchange
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[topology](/site/router-topology/network-topology.md) information.
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These connections are encrypted if
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so configured. Peers also establish UDP "connections", possibly
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encrypted, which carry encapsulated network packets. These
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"connections" are duplex and can traverse firewalls.
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Weave Net creates a network bridge on the host. Each container is
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connected to that bridge via a veth pair, the container side of which
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is given an IP address and netmask supplied either by the user or
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by Weave Net's IP address allocator.
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Weave Net routes packets between containers on different hosts via two
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methods: a [fast data path](/site/using-weave/fastdp.md) method, which operates
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entirely in kernel space, and a fallback `sleeve` method, in which
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packets destined for non-local containers are captured by the kernel
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and processed by the Weave Net router in user space, forwarded over
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UDP to weave router peers running on other hosts, and there injected
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back into the kernel which in turn passes them to local destination
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containers.
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Weave Net routers learn which peer host a particular MAC address resides
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on. They combine this knowledge with topology information in order to
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make routing decisions and thus avoid forwarding every packet to every
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peer. Weave Net can route packets in partially connected networks with
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changing topology. For example, in this network, peer 1 is connected
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directly to 2 and 3, but if 1 needs to send a packet to 4 or 5 it must
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first send it to peer 3:
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**See Also**
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* [Weave Router Sleeve Encapsulation](/site/how-it-works/router-encapsulation.md)
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* [How Weave Inteprets Network Topology](/site/how-it-works/network-topology.md)
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