Networking Overview
CPSC 330 - Spring 2004

communication

            communications
.--------.      medium      .----------.
| sender |----------------->| receiver |
`--------'                  `----------'

communication modes

communication protocols

network types -- by geography

These terms often describe distances but may also be used to indicate technologies and protocols. E.g., LAN is now often used as a term meaning a single broadcast domain that is not necessarily limited by physical distance.

Internet map
Internet growth

network types -- by topology

network types -- by technology

communications media

see also

example service providers

home network

standards

OSI layers - separation of concerns

  +-----------------------------+
  | 7 /data/ application layer  | - user applications
  +-----------------------------+
  | 6 /data/ presentation layer | - encryption, protocol translation
  +-----------------------------+
  | 5 /data/ session layer      | - open, maintain, close logical connections
  +-----------------------------+
  | 4 /segments/ transport layer| - end-to-end, reliable communication
  +-----------------------------+
  | 3 /packets/ network layer   | - routing of packets using logical addresses
  +-----------------------------+
  | 2 /frames/ data-link layer  | - final framing, synchronization, flow control
  +-----------------------------+
  | 1 /bits/ physical layer     | - wiring (connector size, # pins), signals
  +-----------------------------+

framing

               sender                                   receiver

             +---------+                               +---------+
             |  data   |                               |  data   |
             +---------+                               +---------+
    frame         V                           frame         ^
    +--------.---------.---------+            +--------.---------.---------+
    | header | payload | trailer | ---------> | header | payload | trailer |
    +--------^---------^---------+            +--------^---------^---------+

    each layer typically adds/removes another header field

IEEE 802 standard divides up data link layer into two sublayers

  +-----------------------------+
  | LLC (logical link control)  | - protocol between peer data link layers
  + - - - - - - - - - - - - - - +
  | MAC (medium access control) | - decides station access to shared medium
  +-----------------------------+     (1) RR (round-robin)
                                      (2) reservation
                                      (3) contention (e.g., CSMA/CD)
name of message unit

protocols vs. services

     services                                     services
      v   |                                        v   |
  +-----------+                                +-----------+
  | layer n-1 | <-- protocol for layer n-1 --> | layer n-1 |
  +-----------+                                +-----------+
      |   ^                                        |   ^
     services                                     services
      v   |                                        v   |
  +-----------+                                +-----------+
  |  layer n  | <--- protocol for layer n ---> |  layer n  |
  +-----------+                                +-----------+
      |   ^                                        |   ^
     services                                     services

performance

    |<---sender--->|<----transmission time---->|                            |
    |   overhead   | ` .                        ` .                         |
    |              |     ` .                        ` .                     |
    |              |         ` .                        ` .                 |
    |              |<--time of-->|<----transmission time---->|<--receiver-->|
    |              |   flight                                |   overhead   |
    |              |                                         |              |
    |              |<-----------transport latency----------->|              |
    |                                                                       |
    |<----------------------------total latency---------------------------->|

QoS (quality of service)

how stringent are various communication requirements across different applications?

                                               low    low jitter
                      reliability  bandwidth  delay   (variation
                                                       in delay)

          web access       ++          +         +         _
               email       ++          -         -         _
     video on demand        _         ++         _        ++
           telephony        _          -        ++        ++

                      ++ essential
                       + important
                       - desirable


extra info -- from RFC1122

[LL means link layer; note, however, that in common usage "frame" and "packet" are often used interchangeably]

  The terms frame, packet, datagram, message, and segment
  are illustrated by the following schematic diagrams:

 
    A. Transmission on connected network:
      _______________________________________________
     | LL hdr | IP hdr |         (data)              |
     |________|________|_____________________________|

      <---------- Frame ----------------------------->
               <----------Packet -------------------->


    B. Before IP fragmentation or after IP reassembly:
               ______________________________________
              | IP hdr | transport| Application Data |
              |________|____hdr___|__________________|

               <--------  Datagram ------------------>
                        <-------- Message ----------->

      or, for TCP:
               ______________________________________
              | IP hdr |  TCP hdr | Application Data |
              |________|__________|__________________|

               <--------  Datagram ------------------>
                        <-------- Segment ----------->


(see also what is a packet?)


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mark@cs.clemson.edu