The internet layer Skills: None IT concepts: layered protocols, the internet layer, IP protocol,...
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Transcript of The internet layer Skills: None IT concepts: layered protocols, the internet layer, IP protocol,...
The internet layer
Skills: None
IT concepts: layered protocols, the internet layer, IP protocol, router, dumb (“end-to-end,” “neutral”) networks
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
• Internet concepts– Applications– Technology (Communication)– Implications for
• Internet skills– Application development – Content creation
Where does this topic fit?
The initial vision: an IP address for every host
18.238.2.75
155.135.55.94
63.80.4.26
direct, end-to-end connection
The TCP/IP protocol layers
Application
Transport
Internet
Data link
Physical
Get useful work done – retrieve Web pages, copy files, send and receive email, etc.
Make client-server connections and optionally control transmission speed, check for errors, etc.
Route packets between networks
Route data packets within the local area network
Specify what medium connects two nodes, how binary ones and zeros are differentiated, etc,
There are two transport layer protocols, TCP and UDP. Web applications use TCP because it checks for errors and controls speed.
The Internet consists of connected networks
Each network has a router at its edge
Datacenter
Campusrouter
The router at the edge of our campus network
FirewallCSUrouter
Responsibility of CSUDH
1 gbps
AT&T
Links from campus buildings
Downtown LA
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.
It uses information in local tables and makes a new decision for each packet.
The LAN router picks the “best” of the four
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-to-end,” “neutral”) networks
This work is licensed under a Creative Commons Attribution-Noncommercial-Share 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?