What is thread local state
A stream is a sequence of packets from a source to a specific destination (it can be a unicast, multicast, or broadcast destination if the network protocol supports it) at a specific point in time. The details depend on the context, especially the network and transport protocols. For example, for TCP and IP, a specific flow protocol is identified by the protocol (TCP), source and destination port numbers, and source and destination IP addresses. If security is applied (for example, IPSec), this can complicate the task, as it can introduce, for example, tunnels, which mainly create flows within a stream.
What you are talking about about the flow state on a router means that the router stores this data (usually for a certain amount of time) in order to be able to identify packet flows. A router usually does this, for example. monitor connections or make filtering decisions (for example, rejecting incoming packets that do not belong to a stream set by a computer on the internal network).
So, for example, when I open a new browser window and type www.google.com
in it, it will create a new thread with the following parameters:
- transport protocol:
TCP
- source port: source TCP port allocated for web browser eg.
12345
- port of destination:
80
- Source IP: IP address of the computer, for example.
1.2.3.4
- Destination IP: IP address has
www.google.com
been resolved eg.173.194.44.17
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for example, a voice call consists of many consecutive packets, all parts of the same message. We call this sequence of packets a stream. More specifically: Stream: A collection of datagrams belonging to the same end-to-end connection, for example. TCP connection.
for flow state is not supported by routers / switches, they just route packets separately. they treat each packet uniquely, although they may go to the same destination, hence no flow state is maintained
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