CSE524: Lecture 3

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CSE524 Lecture 3

• Internet history (Part 2), Internet challenges,
  Physical layer

2
Administrative

• Homework 1 due Wednesday, Oct. 3rd
• CSE524 e-mail list created
• E-mail TA if you have not received the
  introductory message

3
Last episode

• Started on brief run-down of Internet history
• TCP/IP deployment

4
LAN

• Metcalfe
• Invents Ethernet (Xerox PARC) 1973
• Proteon, IBM
• Token Ring 1970s
• Proliferation of LANs leads to redefining IP
  space
• Split space into 3 classes A, B, and C
• CLANs (large number of networks with small
  number of hosts
• BRegional scale networks
• ALarge scale national networks

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Application protocols

• SMTP
• Simple Mail Tranfer Protocol (Aug. 1982) Postel
• http//www.rfc-editor.org/rfc/rfc821.txt
• DNS
• Hostnames server, SRI (Mar. 1982) Harrenstien
• http//www.rfc-editor.org/rfc/rfc811.txt
• Current hierarchical architecture (Aug. 1982) Su,
  Postel
• http//www.rfc-editor.org/rfc/rfc819.txt
• Domain Name System standard (Nov. 1983)
  Mockapetris
• http//www.rfc-editor.org/rfc/rfc882.txt
• http//www.rfc-editor.org/rfc/rfc882.txt

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Application protocols

• Telnet
• Telnet protocol (May 1983) Postel, Reynolds
• http//www.rfc-editor.org/rfc/rfc854.txt
• FTP
• File transfer protocol (Oct. 1985) Postel,
  Reynolds
• http//www.rfc-editor.org/rfc/rfc959.txt

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Meanwhile, in a parallel universe

• Competing mostly inoperable networks from jealous
  government agencies and companies
• DOE MFENet (Magnetic Fusion Energy scientists)
• DOE HEPNet (High Energy Physicists)
• NASA SPAN (Space physicists)
• NSF CSNET (CS community)
• NSF NSFNet (Academic community) 1985
• ATT USENET with Unix, UUCP protocols
• Academic networks BITNET (Mainframe
  connectivity)
• Xerox XNS (Xerox Network System)
• IBM SNA (System Network Architecture)
• Digital DECNet
• UK JANET (Academic community in UK) 1984

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NSFNet

• NSF program led by Jennings, Wolff (1986-1995)
• Network for academic/research community
• Selects TCP/IP as mandatory for NSFNet
• Structures with DARPA Requirements for Internet
  Gateways to ensure interoperability
• http//www.rfc-editor.org/rfc/rfc985.txt
• Builds out wide area networking infrastructure
• Develops strategy for developing and handing it
  over eventually to commercial interests
• Historical note Al Gore helps win funding for
  NSFNet program

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NSFNet

• Structure
• 6 nodes with 56kbs links
• Jointly managed exchange points
• Statistical, non-metered peering agreements
• CSNET (Farber)
• Kahn (ARPANET)
• Cost-sharing of infrastructure
• Seek out commercial, non-academic customers
• Help pay for and expand regional academic
  facilities
• Economies of scale
• Prohibit commercial use of NSFNet to encourage
  commercial backbones
• Leads to PSINet, UUNET, ANS, CORE backbone
  development

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TCP/IP software

• Berkeley
• Unix TCP/IP available at no cost (DoD)
• Incorporates BBN TCP/IP implementation
• Later re-implements
• Large dispersal to community
• Critical mass (like the fax machine)
• PCs
• Low cost PC access (Wintel)
• Economies of scale

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Privatization

• Commercial interconnection
• US Federal Networking Council (1988-1989)
• MCI Mail allowed
• ARPANET decommissioned (1990)
• NSFNet decommissioned (1995)
• 21 nodes with multiple T3 (45Mbs) links
• Regional academic networks forced to buy national
  connectivity from private long haul networks
• TCP/IP supplants and marginalizes all others to
  become THE bearer service for the Internet
• Total cost of NSF program?

200 million from 1986-1995
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Growing pains

• Explosion of networks
• Routing initially flat, each node runs the same
  distributed routing algorithm
• Moved to hierarchical model
• IGP (interior gateway protocol) within a region
• EGP (exterior gateway protocol) to tie regions
  together
• Individual regions use their own IGP
• Saves on cost (CPUbandwidth)
• Allows rapid reconfiguration, robustness,
  scalability
• Distributes control (a bit)
• Evolves into ASAutonomous System
• IGP -gtIntra-AS routing (RIP/OSPF)
• EGP -gt Inter-AS routing (BGP)

13
Growing pains

• Each backbone router keeps global table of
  exponentially increasing network routes
• CIDR
• Classless Inter-Domain Routing
• Aggregate numerically adjacent routes going to
  the same AS
• Variable-length subnetting
• Saves space, but makes lookups harder
• Longest prefix match lookup

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IETF

• Origins
• DARPA
• Cerf forms coordination bodies (late 1970s)
• ICB (International Cooperation Board)
• ICCB (Internet Configuration Control Board)
• Leiner takes over Internet research program
  (1983)
• ICCB disbanded
• Forms structure of task forces
• Forms umbrella IAB (Internet Activities Board) to
  manage TFs
• IETF (Internet Engineering) is one task force
• Internet research program discontinued (1985)
• IAB becomes default leadership organization for
  the Internet
• IESG created (Internet Engineering Steering
  Group)
• IRTF created (Internet Research Task Force)

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IETF

• CNRI (Corporation for National Research
  Initiatives)
• Headed by Kahn (1991)
• Creates Internet Society to make process open and
  fair across research and commercial interests
• IAB reorganized to Internet Architecture Board
  under Internet society
• IAB, IESG, and IETF in place as they are now
• Process for arbitration and operation established

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WWW

• CERN (European Organization for Nuclear Research)
• Berners-Lee, Caillau work on WWW (1989)
• First WWW client (browser-editor running under
  NeXTStep)
• Defines URLs, HTTP, and HTML
• Berners-Lee goes to MIT and LCS to start W3C
• Responsible for evolving protocols and standards
  for the web
• http//www.w3.org/People

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WWW

• NCSA (National Center for Supercomputing
  Applications)
• Federally funded research center at University of
  Illinois at Urbana-Champaign
• Andreessen Mosaic and eventually Netscape (1994)
• http//www.dnai.com/thomst/marca.html

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Internet challenges

• Not a complete list
• Address depletion (IPv4, IPv6)
• NAT and the loss of transparency
• Routing infrastructure
• Quality of service
• Security
• DNS scaling
• Dealing with privatization
• Interplanetary Internet

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Address depletion

• IPv4 32-bit address (4.3 billion identifiers)
• 25 in use 960 million addresses (advertised in
  BGP tables)
• http//www.caida.org/outreach/resources/learn/ipv4
  space/
• Inactive IP addresses advertised as well
• Estimated 86 million active (July 2000)
• http//www.netsizer.com/
• Do we need more addresses?
• IPv6 128-bit address

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Current IP address allocation
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NAT

• Network address translation
• Source and destination IP addresses and
  (sometimes) ports rewritten by device
• Rewritten without knowledge of end-hosts
• Translation typically performed only on IP
  address portion of packet not on addresses within
  data
• Envelope analogy
• Return address on outside changed
• Return address on inside unchanged
• Application data must be rewritten to maintain
  consistency

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NAT

• Whats bad about NAT?
• Breaks transparency of IP
• Breaks hourglass and end-to-end principles
  (network must be changed for new applications to
  be deployed)
• FTP, servers, P2P services and NAT
• SIP, conferencing applications
• Breaks IPsec
• Man-in-the-middle attacks
• Whats good about NAT?
• Renumbering easy

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NAT

• Application writing before NAT
• New applications require no changes to be
  deployed on the Internet
• New applications require no changes in the
  Internet to be deployed
• Application writing after NAT
• All new applications must be written with
  explicit knowledge of intermediate devices which
  rewrite network and application information

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Routing infrastructure

• http//www.telstra.net/ops/bgptable.html
• Backbone routers must keep table of all routes
  (75000 entries)
• Growth of table size
• Alleviated with CIDR aggregation and NAT
• Potentially exacerbated if portable addressing
  used
• Routing instability
• Frequency of updates increases with size
• Update damping occuring already
• Potential for breakdown in connectivity

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Routing infrastructure
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Routing infrastructure

• Reducing state in the network
• Global state at every backbone router
• Other non-global approaches?
• Ambulance routing
• Airplane routing
• Landmark routing
• Chess games
• Limited-distance look-ahead
• Better scaling properties

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Routing infrastructure

• Non-adaptive routing on backbone
• Opt-out early routing
• Tier 1 ISPs route traffic solely on whether
  destination is within network
• Limited alternative paths
• Limited robustness and poor performance

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Routing Infrastructure

• Increasing routing performance
• Lambda switching, MPLS
• DWDM requires extremely fast forwarding
• At edges, map traffic based on IP address to
  wavelength or other non-IP label
• Wavelength or label switch across multiple hops
  to other edge
• Eliminate intermediate IP route lookups
• Faster IP lookups
• Data structures and algorithms for fast lookups

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Routing Infrastructure

• Other challenges
• Policy-based routing, packet classification
• Non-destination-based routing
• Route-pinning for QoS

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Quality of service

• Predictable performance
• Weak-link phenomenon
• Requires
• ISP agreements
• Global support for QoS
• Applications
• OS
• All devices in the network (routing failures,
  updates, queuing)
• Packet sizes and unpredictable media

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Security

• Anonymity of IP
• Sender fills in its address
• Connectivity over security
• Spoofing and DDoS
• IP traceback
• http//www.acm.org/sigs/sigcomm/sigcomm2001/p1.htm
  l
• Ingress filtering
• http//www.ietf.org/rfc/rfc2827.txt

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Security

• DNS centralized
• 13 root name servers
• Limited due to packet size constraints
• Routing decentralized
• Rogue source sending updates
• Convergence problems
• L0pht
• May 1998 30min to shut down Internet

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DNS scaling

• Relatively flat structure
• 13 centralized TLD name servers
• .com servers overloaded
• DNS used as a directory service
• Internet directory service?
• RealNames
• AOL Keywords

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Dealing with Privatization

• Improving routing instability, traffic
  characterization, security, etc. difficult
• Finding sources of disruption (software,
  hardware, users) difficult
• Problems are hidden not shared
• Open standards in the face of commercial
  interests
• Patents on protocols
• Closed protocols
• ICQ, AIM, Hotmail
• Potential for closed networks
• Cable network consolidation, ISP consolidation

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Interplanetary Internet

• Extremely long round-trip times
• Protocols designed with terrestrial timeout
  parameters

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The rest of the course

• From birds-eye view, we will now focus on
  specific components
• Review Lectures 1, 2, and 3 for perspective when
  looking at the parts
• Mostly classical material with some references to
  newer technologies

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Physical Layer

• Plethora of physical media
• Fiber, copper, air
• Specifies the characteristics of transmission
  media
• Too many to cover in detail, not the focus of the
  course
• Many data-link layer protocols (i.e. Ethernet,
  Token-Ring, FDDI. ATM run across multiple
  physical layers)
• Physical characteristics dictate suitability of
  data-link layer protocol and bandwidth limits

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PL Good URLs

• Get em while they last.
• ftp//rtfm.mit.edu/pub/usenet-by-hierarchy/comp/an
  swers/LANs/cabling-faq
• http//fcit.coedu.usf.edu/network/

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PL Common Cabling

• Copper
• Twisted Pair
• Unshielded (UTP)
• CAT-1, CAT-2, CAT-3, CAT-4, CAT-5, CAT-5e
• Shielded (STP)
• Coaxial Cable
• Fiber
• Single-mode
• Multi-mode

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PL Twisted Pair

• Most common LAN interconnection
• Multiple pairs of twisted wires
• Twisting to eliminate interference More twisting
  Higher bandwidth, cost
• Standards specify twisting, resistance, and
  maximum cable length for use with particular
  data-link layer

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PL Twisted pair

• 5 categories
• Category 1
• Voice only (telephone wire)
• Category 2
• Data to 4Mbs (LocalTalk)
• Category 3
• Data to 10Mbs (Ethernet)
• Category 4
• Data to 20Mbs (16Mbs Token Ring)
• Category 5 (100 MHz)
• Data to 100Mbs (Fast Ethernet)
• Category 5e (350 MHz)
• Data to 1000Mbs (Gigabit Ethernet)

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PL Twisted Pair

• Common connectors for Twisted Pair
• RJ11 (6 pairs)
• RJ45 (8 pairs)
• Allows both data and phone connections
• (1,2) and (3,6) for data, (4,5) for voice
• Crossover cables for NIC-NIC, Hub-Hub connection
  (Data pairs swapped)

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PL UTP

• Unshielded Twisted Pair
• Limited amount of protection from interference
• Commonly used for voice and ethernet
• Voice multipair 100-ohm UTP

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PL STP

• Shielded Twisted Pair
• Not as common at UTP
• UTP susceptible to radio and electrical
  interference
• Extra shielding material added
• Cables heavier, bulkier, and more costly
• Often used in token ring topologies
• 150 ohm STP two pair (IEEE 802.5 Token Ring)

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PL Coaxial cable

• Single copper conductor at center
• Plastic insulation layer
• Highly resistant to interference
• Braided metal shield
• Support longer connectivity distances over UTP

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PL Coaxial cable

• Thick (10Base5)
• Large diameter 50-ohm cable
• N connectors
• Thin (10Base2) cables
• Small diameter 50-ohm cable
• BNC, RJ-58 connector
• Video cable
• 75-ohm cable
• BNC, RJ-59 connector
• Not compatible with RJ-58

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PL Fiber

• Center core made of glass or plastic fiber
• Transmit light versus electronic signals
• Protects from electronic interference, moisture
• Plastic coating to cushion core
• Kevlar fiber for strength
• Teflon or PVC outer insulating jacket

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PL Fiber

• Single-mode fiber
• Smaller diameter (12.5 microns)
• One mode only
• Preserves signal better over longer distances
• Typically used for SONET or SDH
• Lasers used to signal
• More expensive
• Multi-mode fiber
• Larger diameter (62.5 microns)
• Multiple modes
• LEDs used to signal
• WDM and DWDM
• Photodiodes at receivers

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PL Fiber connectors

• ESCON
• Duplex SC
• ST
• MT-RJ (multimode)
• Duplex LC

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PL Wireless

• Entire spectrum of transmission frequency ranges
• Radio
• Infrared
• Lasers
• Cellular telephone
• Microwave
• Satellite
• Acoustic (see ESE sensors)
• Ultra-wide band
• http//www.ntia.doc.gov/osmhome/allochrt.html

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(No Transcript)
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PL What runs on them?
Protocol Summary
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PL Bandwidth lingo

• Specifies capacities over physical media
• Electronic
• T1/DS11.54 Mbps
• T3/DS345Mbps
• Optical (OCoptical carrier)
• OC152 Mbps
• OC3/STM1156 Mbps
• OC12622 Mbps
• OC482488 Mbps
• OC19210 Gbps
• OC76840 Gbps

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Next class

• Data-link layer (Chapter 5)