Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Computer Networks and the Internet
IMT2431 - Data Communication and Network Security
Erik Hjelm˚
as
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Introduction to IMT2431
•
Teachers are Lasse Øverlier and Erik Hjelm˚
as
http://www.hig.no/~erikh
•
Lectures and Lab in A126/A115
•
Course webpage
http://www.hig.no/imt/in/emnesider/imt2431
•
Course mailinglist [email protected]
[email protected] to join
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Introduction to IMT2431
•
10 credits ∼ 15 hrs per week
•
Evaluation based on:
•
Mid-term exam
•
Project
•
Final exam
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Internet: Nuts and Bolts view
•
millions of connected computing devices:
hosts
=
end systems
•
running network apps
•
communication links
•
fiber, copper, radio, satellite
•
transmission rate =
bandwidth
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Internet: Nuts and Bolts view
•
Protocols control sending, receiving of msgs
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e.g., TCP, IP, HTTP, FTP, ARP
•
Internet: ”network of networks”
•
loosely hierarchical
•
public Internet versus private intranet
•
Internet standards
•
IETF: Internet Engineering Task Force
•
RFC: Request for comments
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Internet: Service view
•
communication infrastructure enables distributed
applications:
•
Web, email, games, e-commerce, file sharing
•
communication services provided to apps:
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Protocols
•
all communication activity in Internet governed by
protocols:
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Structure
•
Network edge
•
applications and hosts
•
Network core
•
routers/switches
•
network of networks
•
Access networks, physical media
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Edge
•
End systems with distributed applications
•
Client/Server model
•
server listens, clients make initial request
•
e.g. www, email, dns
•
Peer-peer (P2P) model
•
end systems are both clients and servers
•
minimal (or no) use of dedicated servers
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Edge: Two Services
•
Distributed applications use one of two services for
data
transfer between end systems
•
Connectionless
•
UDP - User Datagram protocol (RFC768)
•
unreliable, no state information or handshake
•
no flow control
•
no congestion control
•
but possibly fast!
•
Connection-oriented
•
TCP - Transmission Control Protocol (RFC793)
•
reliable, in-order bytestream
•
flow control
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Core
•
Mesh of interconnected routers
•
How is data transferred through networks?
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Core: Circuit Switching
•
Dedicated resources: no sharing
•
Circuit-like (guaranteed) performance
•
Call setup required
•
Resource ’piece’ idle if not used by owning call (no sharing)
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Network Core: Packet Switching
•
Each end-end data stream divided into packets
•
Users’ packets share network resources
•
Each packet uses full link bandwidth
•
Resources used as needed
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Packet-switched Networks:
Forwarding
•
Move packets through routers from source to destination
(Chp 4)
•
Datagram network
•
destination address in packet determines next hop
•
routes may change during session
•
Virtual circuit network
•
each packet carries tag (virtual circuit ID), tag determines
next hop
•
fixed path determined at call setup time, remains fixed
thru call
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Access Networks
•
Residential access networks
•
Dialup via modem
•
ISDN
•
xDSL
•
Cable (HFC)
•
Institutional access networks
•
Ethernet
•
Mobile access networks (Note:
Prof. Tan’s course
IMT4751 Wireless Communication Security
)
•
wireless LANs: 802.11
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Physical Media
•
Bit: propagates between transmitter/rcvr pairs
•
Physical link: what lies between transmitter and receiver
•
guided media: signals propagate in solid media
•
copper
•
fiber
•
coax
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Internet Structure and ISPs
•
Tier 1 ISPs are
Internet backbone
networks
•
POP (Points of Presence) are the ISP’s routers where
customers (possibly other ISPs) connect
•
ISPs interconnect through private peering points or
NAPs/IXPs (Network Access Points/Internet Exchange
Points)
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Types of Delay
•
Processing
•
Queuing
•
Transmission
•
Propagation
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Queuing Delay and Packet Loss
•
R = link bandwidth (bps)
•
L = packet length (bits)
•
a = average packet arrival rate
•
traffic intensity =
La
R
•
Packet loss
•
queue (aka buffer) has finite capacity
•
when packet arrives to full queue, packet is dropped
•
lost packet may be retransmitted by previous node, by
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Traceroute
•
Prints the route packets take to network host
•
Provides three delay measurements
> traceroute rtfm.mit.edu
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Networks are Complex!
•
Is there any hope of organizing structure of network?
•
Or at least our discussion of networks?
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Networks under Attack
•
Malware
•
(D)DoS
•
Packet sniffing
•
Masquarading/spoofing
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week
Very Brief History
•
1961-1972: Early packet-switching principles
•
1972-1980: Internetworking, new and proprietary nets
•
1980-1990: The Internet as we know it
Erik Hjelm˚as Introduction to IMT2431 What is the Internet? Network Edge Network Core Access Networks and Physical Media Internet Structure and ISPs Delay and Loss Protocol Layers Attacks History Next Week