Transcript Presentation: the internet layer, IP, the Internet Protocol

The internet layer
Skills: None
IT concepts: layered protocols, the internet
layer, IP protocol, router, dumb (“end-toend,” “neutral”) networks
This work is licensed under a Creative Commons Attribution-NoncommercialShare Alike 3.0 License.
Where does this topic fit?
• Internet concepts
– Applications
– Technology (Communication)
– Implications for
• Internet skills
– Application development
– Content creation
The initial vision: an IP address for every host
63.80.4.26
18.238.2.75
155.135.55.94
The TCP/IP protocol layers
There are two transport layer protocols, TCP and UDP. Web
applications use TCP because it checks for errors and controls speed.
Application
Get useful work done – retrieve Web pages, copy
files, send and receive email, etc.
Transport
Make client-server connections and optionally
control transmission speed, check for errors, etc.
Internet
Route packets between networks
Data link
Route data packets within the local area network
Physical
Specify what medium connects two nodes, how
binary ones and zeros are differentiated, etc,
The Internet consists of connected networks
Each network has a router at its edge
The router at the edge of our campus network
Campus
router
Firewall
CSU
router
AT&T
Data
center
Downtown LA
Responsibility of CSUDH
Links from
campus
buildings
1 gbps
A client has a packet to send to a server
The client and server are on different, Internet connected
networks, so the packet must be routed across the Internet.
It is sent across the LAN to the router
(using a data link protocol)
There are four possible outgoing routers.
The LAN router picks the “best” of the four
It uses information in local tables and makes a
new decision for each packet.
Each router does the same thing
The next “hop” ...
The packet reaches the destination network’s
router
And is delivered to the server
(using a data link protocol)
The complete route
What happens if something goes wrong?
Perhaps a router breaks or is over capacity or a cable
is cut
IP routes around the problem
By design, the Internet is dumb
The Internet
The telephone network
The telephone network is smart
The internet layer
Skills: None
IT concepts: layered protocols, the internet
layer, IP protocol, router, dumb (“end-toend,” “neutral”) networks
This work is licensed under a Creative Commons Attribution-NoncommercialShare Alike 3.0 License.
A few questions
• We asked what happens when something goes
wrong – what sorts of things might go wrong?
• Would the route from host A to B necessarily be
the same as the route from B to A?
• Might routes between two hosts change during
the day?
• Might the time to traverse a route vary during the
day?