CSE 524 Lecture 3 Internet history Part 2

CSE 524: Lecture 3 Internet history (Part 2), Internet challenges, Physical layer 1

Administrative • Homework #1 due Wednesday, Oct. 3 rd • CSE 524 e-mail list created – E-mail TA if you have not received the introductory message 2

Last episode • Started on brief run-down of Internet history – TCP/IP deployment 3

LAN • Metcalfe – Invents Ethernet (Xerox PARC) 1973 • Proteon, IBM – Token Ring 1970 s • Proliferation of LANs leads to redefining IP space – Split space into 3 classes A, B, and C – C=LANs (large number of networks with small number of hosts – B=Regional scale networks – A=Large scale national networks 4

Application protocols • SMTP – Simple Mail Tranfer Protocol (Aug. 1982) Postel • http: //www. rfc-editor. org/rfc 821. txt • DNS – Hostnames server, SRI (Mar. 1982) Harrenstien • http: //www. rfc-editor. org/rfc 811. txt – Current hierarchical architecture (Aug. 1982) Su, Postel • http: //www. rfc-editor. org/rfc 819. txt – Domain Name System standard (Nov. 1983) Mockapetris • http: //www. rfc-editor. org/rfc/rfc 882. txt 5

Application protocols • Telnet – Telnet protocol (May 1983) Postel, Reynolds • http: //www. rfc-editor. org/rfc 854. txt • FTP – File transfer protocol (Oct. 1985) Postel, Reynolds • http: //www. rfc-editor. org/rfc 959. txt 6

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 AT&T: 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 7

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 985. 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 8

NSFNet • Structure – 6 nodes with 56 kbs 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, CO+RE backbone development 9

TCP/IP software • Berkeley – Unix TCP/IP available at no cost (Do. D) – 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 10

Privatization • Commercial interconnection – US Federal Networking Council (1988 -1989) – MCI Mail allowed • ARPANET decommissioned (1990) • NSFNet decommissioned (1995) – 21 nodes with multiple T 3 (45 Mbs) 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 11

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 (CPU+bandwidth) Allows rapid reconfiguration, robustness, scalability Distributes control (a bit) – Evolves into AS=Autonomous System • IGP ->Intra-AS routing (RIP/OSPF) • EGP -> Inter-AS routing (BGP) 12

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 13

IETF • Origins – DARPA • Cerf forms coordination bodies (late 1970 s) – 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) 14

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 15

WWW • CERN (European Organization for Nuclear Research) – Berners-Lee, Caillau work on WWW (1989) – First WWW client (browser-editor running under Ne. XTStep) – Defines URLs, HTTP, and HTML – Berners-Lee goes to MIT and LCS to start W 3 C • Responsible for evolving protocols and standards for the web – http: //www. w 3. org/People 16

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 17

Internet challenges • Not a complete list – Address depletion (IPv 4, IPv 6) – NAT and the loss of transparency – Routing infrastructure – Quality of service – Security – DNS scaling – Dealing with privatization – Interplanetary Internet 18

Address depletion • IPv 4: 32 -bit address (4. 3 billion identifiers) – 25% in use 960 million addresses (advertised in BGP tables) – http: //www. caida. org/outreach/resources/learn/ipv 4 spac e/ – Inactive IP addresses advertised as well – Estimated 86 million active (July 2000) – http: //www. netsizer. com/ – Do we need more addresses? • IPv 6: 128 -bit address 19

Current IP address allocation 20

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 21

NAT • What’s 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, P 2 P services and NAT – SIP, conferencing applications – Breaks IPsec – Man-in-the-middle attacks • What’s good about NAT? – Renumbering easy 22

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 23

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 24

Routing infrastructure 25

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 26

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 27

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 28

Routing Infrastructure • Other challenges – Policy-based routing, packet classification – Non-destination-based routing – Route-pinning for Qo. S 29

Quality of service • Predictable performance • “Weak-link” phenomenon • Requires – ISP agreements – Global support for Qo. S • Applications • OS • All devices in the network (routing failures, updates, queuing) – Packet sizes and unpredictable media 30

Security • Anonymity of IP – Sender fills in its address – Connectivity over security • Spoofing and DDo. S • IP traceback – http: //www. acm. org/sigs/sigcomm 20 01/p 1. html • Ingress filtering – http: //www. ietf. org/rfc 2827. txt 31

Security • DNS centralized – 13 root name servers – Limited due to packet size constraints • Routing decentralized – Rogue source sending updates – Convergence problems • L 0 pht – May 1998: 30 min to shut down Internet 32

DNS scaling • • • Relatively flat structure 13 centralized TLD name servers. com servers overloaded DNS used as a directory service Internet directory service? – Real. Names – AOL Keywords 33

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 34

Interplanetary Internet • Extremely long round-trip times • Protocols designed with terrestrial timeout parameters 35

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 36

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 37

PL: Good URLs • Get ‘em while they last…. – ftp: //rtfm. mit. edu/pub/usenet-byhierarchy/comp/answers/LANs/cabling-faq – http: //fcit. coedu. usf. edu/network/ 38

PL: Common Cabling • Copper – Twisted Pair • Unshielded (UTP) – CAT-1, CAT-2, CAT-3, CAT-4, CAT-5 e • Shielded (STP) – Coaxial Cable • Fiber – Single-mode – Multi-mode 39

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 40

PL: Twisted pair • 5 categories – Category 1 • Voice only (telephone wire) – Category 2 • Data to 4 Mbs (Local. Talk) – Category 3 • Data to 10 Mbs (Ethernet) – Category 4 • Data to 20 Mbs (16 Mbs Token Ring) – Category 5 (100 MHz) • Data to 100 Mbs (Fast Ethernet) – Category 5 e (350 MHz) • Data to 1000 Mbs (Gigabit Ethernet) 41

PL: Twisted Pair • Common connectors for Twisted Pair – RJ 11 (6 pairs) – RJ 45 (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) 42

PL: UTP • Unshielded Twisted Pair – Limited amount of protection from interference – Commonly used for voice and ethernet • Voice: multipair 100 -ohm UTP 43

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) 44

PL: Coaxial cable • Single copper conductor at center • Plastic insulation layer • Highly resistant to interference – Braided metal shield – Support longer connectivity distances over UTP 45

PL: Coaxial cable • Thick (10 Base 5) – Large diameter 50 -ohm cable – N connectors • Thin (10 Base 2) cables – Small diameter 50 -ohm cable – BNC, RJ-58 connector • Video cable – 75 -ohm cable – BNC, RJ-59 connector – Not compatible with RJ-58 46

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 47

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 48

PL: Fiber connectors • ESCON • Duplex SC • ST • MT-RJ (multimode) • Duplex LC 49

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 50

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PL: What runs on them? Protocol Summary Protocol Cable Speed Topology Ethernet Twisted Pair, Coaxial, Fiber 10 Mbps Linear Bus, Star, Tree Fast Ethernet Twisted Pair, Fiber 100 Mbps Star Local. Talk Twisted Pair . 23 Mbps Linear Bus or Star Token Ring Twisted Pair 4 Mbps - 16 Mbps Star-Wired Ring FDDI Fiber 100 Mbps Dual ring ATM Twisted Pair, Fiber 155 -2488 Mbps Linear Bus, Star, Tree 52

PL: Bandwidth lingo • Specifies capacities over physical media • Electronic – T 1/DS 1=1. 54 Mbps – T 3/DS 3=45 Mbps • Optical (OC=optical carrier) – – – OC 1=52 Mbps OC 3/STM 1=156 Mbps OC 12=622 Mbps OC 48=2488 Mbps OC 192=10 Gbps OC 768=40 Gbps 53

Next class • Data-link layer (Chapter 5) 54