1Announcements• Homework 3 Due Today• Draft Term Paper Due Today• Minute Papers Returned• Survey HandedOut• Next Week Class: Strongly Encouraged to Attend NCITE Dinner(Handout) (Will return marked up Term Papers)• Homework 4 Handed Out at End of Class, Due April 27.• Two Weeks: Present Term Papers (In alphabetical order):– [ Joe Begnaud - Dustin Lang] on April 27, (Including Pavithra Kandadai-Parthasarathi)– [Fung Kit Lim - Ewa Zofka] on May 4.Email Presentations to Wenling Chen [email protected] in .ppt and .pdfformats with filenames CE5214-LastName.ppt and CE5214-LastName.pdf)by 6 pm April 22. Wenling will install them on laptop before class.CE5214: Lecture 9Network GrowthDavid LevinsonSurface TransportationNetwork Layers• 11 Places• 10 Trip Ends• 9 End to End Trip• 8 Driver/Passenger• 7 Service (Vehicle & Schedule)• 6 Signs and Signals• 5 Markings• 4 Pavement Surface• 3 Structure (Earth & Pavementand Bridges)• 2 Alignment (Vertical andHorizontal)• 1 Right-Of-Way• 0 Space• Each layer has rules ofbehavior:• some rules are physical andnever violated, others arephysical but probabilistic.,• some are legal rules orsocial norms which areoccassionally violatedCommunications: OSIReference Model• 7 Application!Layer - The Application Layer is the level of the protocol hierarchywhere user-accessed network processes reside.• 6 Presentation!Layer - For cooperating applications to exchange data, they mustagree about how data is represented. In OSI, this layer provides standard datapresentation routines.• 5 Session!Layer As with the Presentation Layer, the Session Layer is notidentifiable as a separate layer in the TCP/IP protocol hierarchy. The OSI SessionLayer manages the sessions (connection) between cooperating applications.• 4 Transport!Layer - Much of our discussion of TCP/IP is directed to the protocolsthat occur in the Transport Layer. The Transport Layer in the OSI reference modelguarantees that the receiver gets the data exactly as it was sent.• 3 Network!Layer The Network Layer manages connections across the network andisolates the upper layer protocols from the details of the underlying network. TheInternet Protocol (IP), which isolates the upper layers from the underlying networkand handles the addressing and delivery of data, is usually described as TCP/IP'sNetwork Layer.• 2 Data!Link!Layer The reliable delivery of data across the underlying physicalnetwork is handled by the Data Link Layer.• 1 Physical!Layer The Physical Layer defines the characteristics of the hardwareneeded to carry the data transmission signal. Features such as voltage levels, andthe number and location of interface pins, are defined in this layer.http://www.citap.com/documents/tcp-ip/tcpip006.htmWhere DoesIntelligence Lie• Smart Networks, Dumb Packets/Vehicles(Railroads, Telephone)• Smart Packets/Vehicles, DumbNetworks (Roads, Internet)• Important to resolve this in network designNetwork Design vs.Network Growth• Network Design Problem (NDP) tries todetermine “optimal” network according tosome criteria (Z). - Normative• E.g. Maximize Z, subject to someconstraints.• Network Growth Problem tries to predictactual network according to observed orhypothesized behaviors. - Positive2Questions• Why do networks expand and contract?• Do networks self-organize into hierarchies?• Are roads an emergent property?• Can investment rules predict location of network expansions andcontractions?• How can this improved knowledge help in planning transportationnetworks?• To what extent do changes in travel demand, population, income anddemographic drive changes in supply?• Can we model and predict the spatially specific decisions oninfrastructure improvements?Network Growth• Depends on existing and forecasttransportation demand• Depends on existing transportation supply• Network can be viewed as output of aproduction function: N = f( D, S)S-Curves00.10.20.30.40.50.60.70.80.911800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000YearProportion of Maximum ExtentCanalsRailTelegraphOil PipelinesSurfaced RoadsGas PipelinesS-Curve: Internet(Hypothesized)Internet Host Computers0100,000,000200,000,000300,000,000400,000,000500,000,000600,000,000Dec-66 Jun-72 Dec-77 May-83 Nov-88 May-94 Oct-99 Apr-05 Oct-10 Apr-16 Sep-21DatePredicted HostsLife Cycle Model€ f1− f= eat+ bWhere:f = fractional share oftechnology (technology’sshare of final marketshare)t = timea, b = model pa rametersMacroscopic ViewMiles of Road, Number of Vehicles in United States05001,0001,5002,0002,5003,0003,5004,0001900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000YearMiles of Road (1,000)050000100000150000200000Motor Vehicles(1,000)Miles of Road Motor Vehicles (1,000)Motor VehiclesRoad Miles3Networks in Motion• UK Turnpikes 1720-1790• UK Canals 1750-1950• Twin Cities 1920-2000• Twin Cities 1962-2000How networks changewith time• Nodes: Added, Deleted, Expanded,Contracted• Links: Added, Deleted, Expanded,Contracted• Flows: Increase, DecreaseThe NodeFormationProblemCityFeature in dominant cityNew York-Northern New Jersey-LongIsland, NY-NJ-CT-PAharborLos Angeles-Riverside-Orange County, CAharborChicago-Gary-Kenosha, IL-IN-WIharbor, river/canal connections toMississippiWashington-Baltimore, DC-MD-VA-WVharbor (Baltimore), capital (Washington)San Francisco-Oakland-San Jose, CAharborPhiladelphia-Wilmington-Atlantic City,PA-NJ-DE-MDharborBoston-Worcester-Lawrence, MA-NH-ME-CTharborDetroit-Ann Arbor-Flint, MIstrategic crossingDallas-Fort Worth, TXtrading post/crossing of Trinity RiverHouston-Galveston-Brazoria, TXharborAtlanta, GArail terminusMiami-Fort Lauderdale, FLrail terminus, resortSeattle-Tacoma-Bremerton, WAharborCleveland-Akron, OHriver/canal terminus, Great Lakes portMinneapolis-St. Paul, MN-WISt. Anthony Falls on Mississippi River,most northerly navigable locationPhoenix-Mesa, AZsite of an anc ient Native Americanirrigation system, Salt RiverSan Diego, CAharborSt. Louis, MO-ILconfluence of Missouri and M ississippiriversPittsburgh, PAconfluence of Allegheny and Monongahelarivers with Ohio riverDenver-Boulder-Greeley, COgold discovery at the confluence of CherryCreek and the South Platte River (resourceextraction)Christaller’s CentralPlace Theory (CPT)• How are urban settlements spaced, more specifically , what rules determine thesize, number and distribution of towns.• Christaller’s model made a