CSE561: Graduate Computer
Networking
Venkat Padmanabhan
Microsoft Research
CSE561
Spring 2001
Venkat Padmanabhan
1
Prelimaries
Instructor: Venkat Padmanabhan
Email: padmanab@cs.washington.edu
Lectures: MF, 12:00-1:20 PM, EE1 003
Office hours: MF 1:30-2:00 PM, Sieg 226D
TA: Andrew Whitaker
Email: andrew@cs.washington.edu
Office hours: Th 2:30-3:30 PM, Sieg 433
Home page:
http://www.cs.washington.edu/education/cour
ses/561/01sp/
CSE561
Spring 2001
Venkat Padmanabhan
2
What’s this class about?
• Reading 25-30 papers spanning a wide
spectrum of the networking research
literature
• Learning how to critique networking
research
• Learning how to do networking research
through a hands-on project
CSE561
Spring 2001
Venkat Padmanabhan
3
Am I ready to take this class?
• If you have taken CSE 461 or an equivalent
undergraduate class elsewhere, then you’re all
set.
• If you haven’t but have at least some
background in computer systems, you can read
through a basic textbook (e.g., the book by
Peterson & Davie) without much effort.
• Minimal coverage of basic material in class
CSE561
Spring 2001
Venkat Padmanabhan
4
Syllabus
Focus on the Internet-related research
• Design philosophy and architecture
• Medium access control (Ethernet, wireless)
• Routing (BGP)
• Transport (TCP)
• Applications (Web/HTTP, audio/video)
• Novel paradigms (multicast, active networks)
• Novel networks (wireless, mobile)
• Security (protocol vulnerability, DoS attacks)
CSE561
Spring 2001
Venkat Padmanabhan
5
What you are expected to do
• Read and review research papers (20%)
• Actively participate in discussions in
class and on the mailing list (10%)
• Take midterm exam (20%)
• Define and work on a networking
research project (50%)
CSE561
Spring 2001
Venkat Padmanabhan
6
Literature Review
• 25-30 research papers
– all available online on the course home page
– only need to review papers marked as such
– “optional reading” need not be reviewed
• Review (one page max per paper)
– summarize paper in just a few sentences
– highlight contributions/lessons learned
– point out shortcomings in assumptions, approach,
data, etc. (ignore presentation problems!)
– bonus points for comparing and contrasting with
related literature (from reading list or elsewhere)
CSE561
Spring 2001
Venkat Padmanabhan
7
Literature Review (contd.)
• Reviews
– OK to discuss papers with others at any
time
– But you must write your own review!
– Hardcopy due at the start of each lecture
– You may choose to post your review on the
mailing list after the lecture period to get
some discussion going
CSE561
Spring 2001
Venkat Padmanabhan
8
Class Participation
• Read the papers before coming to class
• Actively participate in discussion in
class and on the mailing list
• Remember: there are few absolute
truths in networking. So don’t be afraid
to be a contrarian.
CSE561
Spring 2001
Venkat Padmanabhan
9
Mid-term Exam
• Scheduled for Friday, May 11
• Focus on understanding rather than the
knowledge of facts
CSE561
Spring 2001
Venkat Padmanabhan
10
Project
• Define and work on a research project that
– is interesting
– explores novel issues or approaches
– is doable in the available time
• Groups of 2-3 students (not a rule)
• You are encouraged to come up with ideas
– feel free to brainstorm on ideas with others
– aim high! The best projects could lead to papers at
the top conferences (SIGCOMM,Infocom,Mobicom)
– I’ll distribute a list of potential projects in class
next week
CSE561
Spring 2001
Venkat Padmanabhan
11
Project (contd.)
• Project scope
– implementation, simulation, measurement, analysis,
or some combination thereof
– this is not about doing a literature survey
• The process
– initial meeting (April 6)
– 1-2 page project proposal due April 13
• problem statement, specific goals, resources you
need, plan of attack, (anticipated) deliverables
• not a rigid document
CSE561
Spring 2001
Venkat Padmanabhan
12
Project (contd.)
• The process (contd.)
– checkpoint meetings after class on May 7
– project presentations and final report due
the first week of June (exact date TBD)
CSE561
Spring 2001
Venkat Padmanabhan
13
Elements of a Network
• Links carry information (bits)
– Wire, wireless, fiber optic, smoke signals …
• Switches move bits between links
– Routers, gateways, bridges, CATV headend,
PABXs, …
• Hosts are the communication endpoints
– PC, PDA, cell phone, toaster, …
CSE561
Spring 2001
Venkat Padmanabhan
14
Example – Local Area Network
Ethernet
Hub
Cable
Modem
Printer
Laptop
PC
• Your home network
– Ethernet is a broadcast-capable multi-access LAN
CSE561
Spring 2001
Venkat Padmanabhan
15
Example – An Internetwork
ISP 2
ISP 1
Local
Net 1
Local
Net 2
• Internetwork is a network of networks
• The Internet is a global internetwork in which
all participants speak a common language, IP.
CSE561
Spring 2001
Venkat Padmanabhan
16
Key Features of the Internet
• Distributed
– decentralized operation, global reach
• Large-scale
– 110 million hosts (Jan 2001) and growing
• Heterogeneous
– links, end-points
• Intelligent end-points
– supercomputers, PCs, PDAs
• Multi-purpose
– Web, audio/video conferencing, telnet
CSE561
Spring 2001
Venkat Padmanabhan
17
Growth of the Internet
CSE561
Spring 2001
Venkat Padmanabhan
18
Network Components
Say you want download a file from host A
onto host B.
What problems do you need to solve?
CSE561
Spring 2001
Venkat Padmanabhan
19
Host Discovery
Locating the remote host
• The “naming” problem
– provides a level of indirection between
names and addresses
• Domain Name System (DNS)
– the “telephone directory” of the Internet
CSE561
Spring 2001
Venkat Padmanabhan
20
Medium Access Control
Putting bits on the wire
• The network carries packets, not bits
– framing to create packets out of bits
• Physical medium may be shared
– example: Ethernet, wireless
– medium access control (MAC) to arbitrate amongst
several contenders
• Actually, the network only carries electrical or
optical signals
– modulation to convert digital data into analog signals
CSE561
Spring 2001
Venkat Padmanabhan
21
Routing
How do a packet find its way through the
network?
• Internet is distributed
– no central “brain”
– routing happens in a decentralized manner
• Internet is not owned by any one
organization
– hierarchical routing architecture
– intra-domain and inter-domain
CSE561
Spring 2001
Venkat Padmanabhan
22
Transport Protocol
How do you ensure reliable transmission of the
file over an unreliable network?
• Links and routers are a shared resource
– a packet may be dropped when the resource is overutilized (or even otherwise!)
– resources need to be apportioned “fairly”
• Need to perform loss recovery and congestion
control
• Transmission Control Protocol (TCP)
– responsible the vast majority of Internet traffic
CSE561
Spring 2001
Venkat Padmanabhan
23
Interaction of Transport
Protocols with Applications
One size doesn’t fit all
• Transfer size
– a protocol designed for large file transfers
may be too heavyweight for exchanging
short messages
• Reliability
– necessary for ordinary file transfer
– not necessary for live streaming audio
CSE561
Spring 2001
Venkat Padmanabhan
24
Multicast
Several clients may want to download a file at
the same time
• Repeated unicast would be inefficient
• Need to multicast the file
– avoid sending a packet over a link repeatedly
• Multicast makes existing problems harder,
especially because of heterogeneity
– routing
– loss recovery
– congestion control
CSE561
Spring 2001
Venkat Padmanabhan
25
Resource Discovery
Say you have a choice of where to
download the file from
• Best to download it from “nearest”
source
– this is exactly the goal of content
distribution networks (e.g., Akamai)
• But Internet “distance” is not a static
metric and is hard to measure
CSE561
Spring 2001
Venkat Padmanabhan
26
Security
It ain’t a friendly world out there!
• Eavesdropping on conversations
• Masquerading as another entity
– man-in-the-middle attack
• Non-compliance with the protocols
• Deliberate overconsumption of
resources
– denial of service attack
CSE561
Spring 2001
Venkat Padmanabhan
27
Mobility
Hosts and/or networks may be mobile
• Examples:
– a person carrying a laptop from work to home
– a planeload of people
• Maintaining Internet connectivity in the face
of mobility
– mobility impacts most of the other components
(discovery, routing, transport, applications,
security)
CSE561
Spring 2001
Venkat Padmanabhan
28
Lecture Roadmap
1.
2.
3.
4.
5.
6.
Internet design principles and architecture
Medium Access Control
Internet routing
Router architectures
Transport protocols: congestion control
Transport protocols: interaction with
applications
7. Router support for congestion control
8. Multicast routing
CSE561
Spring 2001
Venkat Padmanabhan
29
Lecture Roadmap (contd.)
9.
10.
11.
12.
13.
14.
15.
16.
Multicast transport and applications
Naming
Resource discovery and selection
Host and network mobility
Wireless networks (medium access control)
Wireless networks (TCP interactions)
Network and protocol vulnerability
Active networks
CSE561
Spring 2001
Venkat Padmanabhan
30
Topics Not Covered
•
•
•
•
•
Quality of service
Real-time communication
Traffic measurement and analysis
Ad-hoc networks
… and many others
CSE561
Spring 2001
Venkat Padmanabhan
31
Next Lecture: Internet Design
Principles and Architecture
• History and evolution of the Internet
• Current architecture
• Defining principles:
–
–
–
–
–
layering
datagram service
statistical multiplexing
decentralized architecture
end-to-end principle
CSE561
Spring 2001
Venkat Padmanabhan
32
Next Lecture (contd.)
• Papers to read
– D. Clark, The Design Philosophy of the
DARPA Internet Protocols, ACM SIGCOMM
1988
– .H. Saltzer, D.P. Reed, D.D. Clark, End-toEnd Arguments in System Design, ACM
TOCS, November 1984
• The optional papers are also classics!
• No reviews due
CSE561
Spring 2001
Venkat Padmanabhan
33