EE122 Discussion Notes
September 5, 2007

Outline:

* Circuit Switching
* Packet Switching
* Socket programming (part 1) -- link to presentation slides on my course web site


=================
Circuit Switching
=================
For each link along the path from a source to a destination the link(s) must be reserved.
Bandwidth and other resources are determined using "deterministic multiplexing".  This basically
means that the resources alloted for each connection are statically allocated since all the resources
are equally partitioned.


   * Indivual links themselves need to be multiplexed (signals combined)

                        | Multiplex |
                        -------------- 
                              |
                    -------------------------
                   |                         |
                     |TDM|                  |FDM|
                       |                      |
                  Time divided            Link is divided into channels
                   into slots                that sum to total bandwidth


=================
Packet Switching
=================
Bandwidth and other resources are determined used "statistical multiplexing".  This basically
means that the resources are probabilistically designed to handle the average load on the network
with some room for occasional bursts in traffic.

   * Statistical averages/peak to determine resource allocation
   * Maximizes utilization but adds overhead to individual packets (source/destination information included in each packet)


=====================================================================================
Relationship between switching methods (packet and circuit) and TCP/UDP
=====================================================================================

              | Socket |
            -------------- 
                  |
        -----------------------
       |                       |

  |Stream (TCP)|         |Datagram (UDP)|
           |                |          
          ---------------------
                    |
                    |
       Both send packets for the network;
       The (inter)network is packet switched,
       so the routers/switches along the path to
       a destination read packet headers to
       route/forward packets.

**Note** There exist situation where virtual circuits are created in the network, but we will go into that
later in the semester.