Packet Switch

Why
Packet switches are important because they help packets reach their final destination correctly

Definition
Packet switches are devices that take an incoming packet and sends it off to the next switch or to its correct final destination

Store and Forward Transmission
Packet switches use the store and forward transmission technique which requires
 * The entire packet must be downloaded before pushing it through the outbound link

Example
Suppose we want to send a packet of $$L$$ bits through through $$N$$ links that supports $$R$$ bits per second, then sending this through the packet switch will take $${{NL} \over {R}}+ P$$ where $$P$$ is the propagation delay. If we did not follow store and forward transmission, then we would get $${{L} \over {R}} + P$$ because we don't have to wait for the other bits to arrive at our switch before we send bits out on our outbound link.

Output Buffers
Each packet switch has multiple outbound links and each outbound link has a output buffer. When this output buffer gets filled faster than it can be emptied, then we will experience queuing delays along our output link.

If the output buffer becomes full, then packet loss may even occur

Examples of Packet Switches
The two most common packet switches today are
 * Routers
 * Link-layer switches