Architectural Model

1
Architectural Model

• Chapter 3

2
Introduction

• A scheme that allows us to collect the diverse
  network technologies into a coordinated whole
• High-level abstraction

3
Application-Level

• Hiding details, handling heterogeneity
• Early approach
• Application gateways
• An application-level program executing on each
  computer understands the details of the network
  connection
• Application programs forward email!
• What happened as the number of applications
  increased?

4
Network-Level

• Network-level interconnection
• Deliver small packets of data
• Maps directly onto the hardware making it
  extremely efficient
• Separates data communication from application
  programs
• Allows intermediate hosts to forward data without
  understanding the application
• New technology? Modify or add a single piece of
  software. App programs dont change.

5
Network-Level

• No single network technology can satisfy all
  constraints
• Users desire universal interconnection

6
Properties of the Internet

• Application programs should not understand
  details
• Want to mandate a network interconnection
  topology
• Adding a new network should not mean connecting
  to a centralized switching point or adding direct
  connections to all existing networks
• We want a universal set of host identifiers

7
Internet Architecture

• Connect two networks with a machine that is
  connected to each of them
• Router or gateway
• Routers use the destination network, not the
  destination host, when forwarding a packet
• The amount of information a router needs to keep
  is proportional to the number of NETWORKS, not
  hosts

8
The Users View

• The internet is a single, virtual network to
  which all machines attach
• Isnt it amazing how much information we have at
  Calvin!
• Application programs are independent of internet
  software. It is possible to optimize the internal
  structure of the internet by altering physical
  connections while applications are running.

9
All Networks are Equal

• A LAN, a WAN used as a backbone, or a
  point-to-point link each count as one network
• http//www.calvin.edu/lave/figure-3.3.pdf

10
The Unanswered Questions

• What is the exact form of an internet address?
• What happens if packets arrive too fast?
• How do multiple applications communicating with
  different destinations not interfere with each
  other?