News and Notes 4/20

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News and Notes 4/20

• Thursdays class will be a course review
• will make comments about relative importance of
  topics for final
• Thursdays class will also have formal course
  evaluation
• very important!
• Several people have requested more time for HW4
• Our final deal
• all present in Thursdays class have until Tue
  4/27 to submit HW4
• will pass around attendance sheet
• those not at Thursdays class must meet original
  HW4 deadline
• which, of course, is Thursday

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Game Theory and the Internet

• Networked Life
• CSE 112
• Spring 2004
• Prof. Michael Kearns

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The Internet What is It?

• The Internet is a massive network of connected
  but decentralized computers
• Began as an experimental research NW of the DoD
  (ARPAnet) in the 1970s
• All aspects (protocols, services, hardware,
  software) evolved over many years
• Many individuals and organizations contributed
• Designed to be open, flexible, and general from
  the start
• Completely unlike prior centralized, managed NWs
• e.g. the ATT telephone switching network

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Internet Basics

• Can divide all computers on the Internet into two
  types
• computers and devices at the edge
• your desktop and laptop machines
• big compute servers like Eniac
• your web-browsing cell phone, your
  Internet-enabled toaster, etc.
• computers in the core
• these are called routers
• they are very fast and highly specialized
  basically are big switches
• Every machine has a unique Internet (IP) address
• IP Internet Protocol
• like phone numbers and physical addresses, IP
  addresses of nearby computers are often very
  similar
• IP addresses are how everything finds everything
  else!
• Note the Internet and the Web are not the same!
• the Web is one of many services that run on the
  Internet

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Internet Packet Routing

• At the lowest level, all data is transmitted as
  packets
• small units of data with addressing and other
  important info
• if you have large amounts of data to send (e.g. a
  web page with lots of graphics), it must be
  broken into many small packets
• somebody will have to reassemble them at the
  other end
• All routers do is receive and forward packets
• forward packet to the next router on path to
  destination
• they only forward to routers they are physically
  connected to
• how do they know which neighboring router is
  next?
• Routing tables
• giant look-up tables
• for each possible IP address, indicates which
  router is next
• e.g. route addresses of form 128.8.. to
  neighbor router A
• route 128.7.2. to neighbor router B, etc.
• need to make use of subnet addressing (similar to
  zip codes)
• distributed maintenance of table consistency is
  complex
• must avoid (e.g.) cycles in routing
• requires distributed communication/coordination
  among routers
• Two handy programs traceroute and nslookup

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The IP (Internet Protocol)

• There are many possible conventions or protocols
  routers could use to address issues such as
• what to do if a router is down?
• who worries about lost packets?
• what if someone wants their packets to move
  faster?
• However, they all use a single, simple protocol
  IP
• IP offers only one service packet delivery
• with no guarantee of delivery
• with no levels of service
• with no notification of lost or delayed packets
• knows nothing about the applications
  generating/receiving packets
• this simplicity is its great strength provides
  robustness and speed
• Higher-level protocols are layered on top of IP
• TCP for building connections, resending lost
  packets, etc.
• http for the sending and receiving of web pages
• ssh for remote access to edge computers
• etc. etc. etc.

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Competition in the Internet

• You and I both want to download the Starr report
• Id like to get the material as quickly as
  possible so would you
• connectivity to the hosting server is a finite
  resource
• were in competition
• I want to watch The Matrix in streaming
  high-res video
• you just want to read your email
• real-time arrival of packets is important to me
  not to you
• I might be willing to pay more for priority
  service packet delivery
• Many of us want to watch The Matrix (multicast)
• those of near each other (e.g. Penn) might
  share costs
• share common route from source until final hop
• some parties might be more isolated
• e.g. lone Wyoming Tech grad student
• his route has little overlap with anyone else
• how should we pay?

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Case Study Selfish Routing

• Standard Internet routing
• route your traffic follows entirely determined by
  routing tables
• out of your control
• generally based on shortest paths, not current
  congestion!
• Source routing
• you specify in the packet header the exact
  sequence of routers
• better be a legitimate path!
• in principle, can choose path to avoid congested
  routers
• Source routing as a game
• traffic desiring to go from A to B (a flow)
  viewed as a player
• number of players number of flows (huge)
• actions available to a flow all the possible
  routes through the NW
• number of actions number of routes (huge)
• penalty to a flow following a particular route
  latency in delivery
• rationality if flow can get lower latency on a
  different route, it will!
• Lets look at T. Roughgardens excellent slides
  on the topic
• we will examine the material in pages 1-23

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Case Study QoS

• QoS Quality of Service
• many varying services and demands on the Internet
• email real-time delivery not critical
• chat near real-time delivery critical
  low-bandwidth
• voice over IP real-time delivery critical
  low-bandwidth
• teleconferencing/streaming video real-time
  critical high-bandwidth
• varying QoS guarantees required
• email not much more than IP required must
  retransmit lost packets
• chat/VoIP two-way connection required
• telecon/streaming high-bandwidth two-way
  connections
• Must somehow be built on top of IP
• Whose going to pay for all of this? How much?
• presumably companies offering the services
• costs passed on to their customers
• What should the protocols/mechanism look like?
• There are many elaborate answers to these
  questions

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Brief Aside Differential Pricing

• Suppose party P produces a research report at
  cost 1000
• Only two possible customers, A and B
• A values the report at 400, B at 900
• If P charges 400 both A and B buy, P makes 800
  lt 1000
• If P charges 900, only B buys, P makes 900 lt
  1000
• Solution charge each their valuation, P makes
  1300
• Fairness questions
• Differential pricing?
• first class vs. coach airfaire and other
  premium services

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QoS and the Paris Metro

• Paris Metro (until recently)
• two classes of service first (expensive) and
  coach (cheaper)
• exact same cars, speed, destinations, etc.
• people pay for first class
• because it is less crowded
• because the type of person willing/able to pay
  first class is there
• etc.
• self-regulating
• if too many people are in first class, it will be
  come less attractive
• Andrew Odlyzkos PMP protocol for QoS
• divide the Internet into a small number of
  identical virtual NWs
• simply charge different prices for each
• an entirely economic solution
• California toll roads