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Internetworking
Lecture 10
October 23, 2000
Introduction to Internetworking
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So far, we’ve discussed about how a single
network functions.
Internetworking is how multiple networks are
connected.
All material from here relates to “the big
picture.”
Why Internetworking?
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Each network has its own specific task.
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LAN functionality
WAN functionality
Internetworking is a culmination of multiple,
independent networks being developed.
In another light, internetworking is the glue
behind the Internet.
Universal Service
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Universal Service is the concept that any
device on any network can communicate with
any arbitrary device on another network.
The Internet is a heterogeneous environment,
with multiple, independent network topologies.
In LANs, we have seen that heterogeneous
technologies cannot interconnect without the
help of a device to translate from one medium
to another.
Internetworking
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The interconnects between different networks
are a combination of hardware and software
elements.
Routers provide the proper hardware/software
translation to connect two different networks
together.
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LAN routers
WAN routers
The Router
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The router is very similar to a bridge.
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Memory
CPU
Separate I/O ports for each network topology
The Router (cont.)
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The router can perform multiple tasks
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LAN / LAN routing
WAN / WAN routing
LAN / WAN routing
The clouds in each picture can represent a
different network topology (FDDI, Ethernet),
address scheme (IP, IPX), or both!
Internet Architecture
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The book likes to use the cloud diagram:
I Like This Diagram
Why the Later is Realistic
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Rarely do you have a “linear” network!
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Inefficient transport
Bandwidth limitations in the “middle”
A Universal Service goal not only dictates if
you can talk to another machine, but how fast!
Reliability
Capacity
Cost
Internet as a Virtual Network
Internetworking and TCP/IP
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ARPANet
NSFNet
TCP/IP
TCP/IP Layers
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These are not hard and
fast rules. Many different
models exist.
Layer 1: Physical
Layer 2: Network
Interface
Layer 3: Internet
Layer 4: Transport
Layer 5: Application
TCP/IP & ISO Model
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Application (Layers 6
and 7 in ISO model)
Transport (Layer 4 in
ISO model)
Internet (Layer 3 in ISO)
Network Interface (Layer
2 in ISO)
Physical (Layer 1 in ISO)