Introduction
great for bursty data
resource sharing
simpler, no call setup
excessive congestion possible:
packet delay and loss
protocols needed for reliable data transfer, congestion
control
Q:
How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video apps
still an unsolved problem (chapter 8)
Is packet switching a
“
slam dunk winner?
”
Packet switching versus circuit switching
1-1
Internet structure: network of networks
End systems connect to Internet via
access ISPs
(Internet
Service Providers)
Residential, company and university ISPs
Access ISPs in turn must be interconnected.
So that any two hosts can send packets to each other
Resulting network of networks is very complex
Evolution was driven by
economics
and
national policies
Let
’
s take a stepwise approach to describe current Internet
structure
Internet structure: network of networks
Question:
given
millions
of access ISPs, how to connect them
together?
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Internet structure: network of networks
Option:
connect each access ISP to every other access ISP?
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connecting each access ISP
to each other directly
doesn’t
scale:
O(
N
2
) connections.
