Introduction cont. Network Core: Circuit Switching. Network Core: Packet Switching. Network Core: Packet Switching. Network Core: Packet Switching

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1 Intrductin cnt. Netwrk Cre: Circuit Switching Lecture gal: get cntext, verview, feel f netwrking mre depth, detail later in curse apprach: descriptive use Internet as example Overview: access net, media perfrmance: lss, delay prtcl layers, service mdels backbnes, NAPs, ISPs netwrk resurces (e.g., bandwidth) divided int pieces pieces allcated t calls resurce piece idle if nt used by wning call (n sharing) dividing bandwidth int pieces frequency divisin time divisin 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 1 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 2 Netwrk Cre: Packet Switching Netwrk Cre: Packet Switching each end-end stream divided int packets user A, B packets share netwrk resurces each packet uses full bandwidth resurces used as needed, Bandwidth divisin int pieces Dedicated allcatin Resurce reservatin resurce cntentin: aggregate resurce demand can exceed amunt available cngestin: packets queue, wait fr use stre and frward: packets mve ne hp at a time transmit ver wait turn at next A B 10 bs Ethernet queue f packets waiting fr utput statistical multiplexing 1.5 bs D Packet-switching versus circuit switching: human restaurant analgy C 45 bs E 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 3 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 4 Netwrk Cre: Packet Switching Packet-switching: stre and frward behavir Example 7.5 bit message 1.5 bps transmissin rate Kbit packets Packet switching versus circuit switching Packet switching allws mre users t use netwrk! 1 bit each user: 100Kbps when active active 10% f time circuit-switching: 10 users packet switching: with 35 users, prbability > 10 active less that.004 N users 1 bps 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 5 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 6 1

2 Packet switching versus circuit switching Packet-switched netwrks: ruting Is packet switching a slam dunk winner? Great fr bursty resurce sharing n call setup Excessive cngestin: packet delay and lss prtcls needed fr reliable transfer, cngestin cntrl Q: Hw t prvide circuit-like behavir? bandwidth guarantees needed fr audi/vide apps still an unslved prblem (chapter 6) Gal: mve packets amng ruters frm surce t destinatin we ll study several path selectin algrithms (chapter 4) gram netwrk: destinatin address determines next hp rutes may change during sessin analgy: driving, asking directins virtual circuit netwrk: each packet carries tag (virtual circuit ID), tag determines next hp fixed path determined at call setup time, remains fixed thru call ruters maintain per-call state 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 7 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 8 Access netwrks and media Q: Hw t cnnectin end systems t edge ruter? residential access nets institutinal access netwrks (schl, cmpany) mbile access netwrks Keep in mind: bandwidth (bits per secnd) f access netwrk? shared r dedicated? 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 9 Residential access: pint t pint access Dialup via mdem up t 56Kbps direct access t ruter (cnceptually) ISDN: intergrated services digital netwrk: 128Kbps alldigital cnnect t ruter ADSL: asymmetric digital subscriber line up t 1 bps hme-t-ruter up t 8 bps ruter-t-hme Ordinary PSTN 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 10 Residential access: cable mdems HFC: hybrid fiber cax asymmetric: up t 10bps upstream, 1 bps dwnstream netwrk f cable and fiber attaches hmes t ISP ruter shared access t ruter amng hme issues: cngestin, dimensining Institutinal access: lcal area netwrks cmpany/univ lcal area netwrk (LAN) cnnects end system t edge ruter Ethernet: shared r dedicated cable cnnects end system and ruter 10 bs, 100bps, Gigabit Ethernet LANs: chapter 5 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 11 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 12 2

3 Wireless access netwrks Physical edia shared wireless access netwrk cnnects end system t ruter wireless LANs: radi spectrum replaces wire e.g., Lucent Wavelan 10 bps wider-area wireless access GPRS (General Packet Radi Service) ruter base statin mbile hsts : transmitted bit prpagates acrss guided media: signals prpagate in slid media: cpper, fiber unguided media: signals prpagate freely e.g., radi Twisted Pair (TP) tw insulated cpper wires Categry 3: traditinal phne wires, 10 bps ethernet Categry 5 TP: 100bps ethernet 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 13 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 14 Physical edia: cax, fiber Physical media: radi Caxial cable: wire (signal carrier) within a wire (shield) baseband: single channel n cable bradband: multiple channel n cable bidirectinal cmmn use in 10bps Ethernet Fiber ptic cable: glass fiber carrying light pulses high-speed peratin: 100bps Ethernet high-speed pint-t-pint transmissin (e.g., 5 Gbps) lw errr rate signal carried in electrmagnetic spectrum n wire bidirectinal prpagatin envirnment effects: reflectin bstructin by bjects interference Radi types: micrwave e.g. up t 45 bps channels LAN (e.g., wavelan) 2bps, 11bps wide-area (e.g., cellular) e.g. GPRS, 10 s Kbps satellite up t 50bps channel (r multiple smaller channels) 270 msec end-end delay 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 15 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 16 Delay in packet-switched netwrks packets experience delay n end-t-end path fur surces f delay at each hp A B transmissin ndal prcessing ndal prcessing: 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 17 queuing prpagatin queuing check bit errrs determine utput time waiting at utput fr transmissin depends n cngestin level f ruter Delay in packet-switched netwrks Transmissin delay: R= bandwidth (bps) L=packet length (bits) time t send bits int = L/R A B transmissin ndal prcessing prpagatin queueing Prpagatin delay: d = length f s = prpagatin speed in medium (~2x10 8 m/sec) prpagatin delay = d/s Nte: s and R are very different quantities! 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 18 3

4 Queuing delay (revisited) R= bandwidth (bps) L=packet length (bits) a=average packet arrival rate traffic intensity = La/R La/R ~ 0: average queuing delay small La/R -> 1: delays becme large La/R > 1: mre wrk arriving than can be serviced, average delay infinite! 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 19 Prtcl Layers Netwrks are cmplex! many pieces : hsts ruters s f varius media applicatins prtcls hardware, sftware Questin: Is there any hpe f rganizing structure f netwrk? Or at least ur discussin f netwrks? 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 20 Organizatin f air travel Organizatin f air travel: a different view ticket (purchase) ticket (cmplain) ticket (purchase) ticket (cmplain) baggage (check) baggage (claim) baggage (check) baggage (claim) gates (lad) gates (unlad) gates (lad) gates (unlad) runway takeff runway landing runway takeff runway landing airplane ruting airplane ruting airplane ruting airplane ruting airplane ruting airplane ruting a series f steps 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 21 Layers: each layer implements a service via its wn internal-layer actins relying n services prvided by layer belw 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 22 Layered air travel: services Distributed implementatin f layer functinality Cunter-t-cunter delivery f persn+bags baggage-claim-t-baggage-claim delivery peple transfer: lading gate t arrival gate runway-t-runway delivery f plane airplane ruting frm surce t destinatin Departing airprt ticket (purchase) baggage (check) gates (lad) runway takeff airplane ruting ticket (cmplain) baggage (claim) gates (unlad) runway landing airplane ruting arriving airprt intermediate air traffic sites airplane ruting airplane ruting 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 23 airplane ruting 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 24 4

5 Why layering? Dealing with cmplex systems: explicit structure allws identificatin, relatinship f cmplex system s pieces layered reference mdel fr discussin mdularizatin eases maintenance, updating f system change f implementatin f layer s service transparent t rest f system e.g., change in gate prcedure desn t affect rest f system layering cnsidered harmful? Internet prtcl stack applicatin: supprting netwrk applicatins ftp, smtp, http transprt: hst-hst transfer tcp, udp netwrk: ruting f grams frm surce t destinatin ip, ruting prtcls : transfer between neighbring netwrk elements ppp, ethernet : bits n the wire applicatin transprt netwrk 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 25 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 26 Layering: lgical cmmunicatin Each layer: distributed entities implement layer functins at each nde entities perfrm actins, exchange messages with peers applicatin transprt netwrk applicatin transprt netwrk applicatin transprt netwrk netwrk applicatin transprt netwrk Layering: lgical cmmunicatin E.g.: transprt take frm app add addressing, reliability check inf t frm gram send gram t peer wait fr peer t ack receipt analgy: pst ffice applicatin transprt netwrk applicatin transprt netwrk ack applicatin transprt netwrk netwrk applicatin transprt netwrk 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 27 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 28 Layering: cmmunicatin applicatin transprt netwrk applicatin transprt netwrk applicatin transprt netwrk netwrk applicatin transprt netwrk Prtcl layering and Each layer takes frm abve adds header infrmatin t create new unit passes new unit t layer belw Ht HnHt Hl HnHt surce applicatin transprt netwrk destinatin applicatin transprt netwrk Ht HnHt Hl HnHt message segment gram frame 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 29 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 30 5

6 ISO/OSI prtcl stack Internet structure: netwrk f netwrks End hst Applicatin Presentatin Sessin Transprt Netwrk Netwrk Netwrk Data Data Data Physical Physical Physical One r mre ndes within the netwrk ISO: Internatinal Standards Organisatin OSI: Open System Intercnnectin End hst Applicatin Presentatin Sessin Transprt Netwrk Data Physical rughly hierarchical natinal/internatinal backbne prviders (NBPs) e.g. BBN/GTE, Sprint, AT&T, IB, UUNet intercnnect (peer) with each ther privately, r at public Netwrk Access Pint (NAPs) reginal ISPs cnnect int NBPs lcal ISP, cmpany cnnect int reginal ISPs NAP reginal ISP lcal ISP NBP B NBP A lcal ISP reginal ISP NAP 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 31 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 32 SUNET NORDUnet 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 33 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 34 Summary Cvered a tn f material! Internet verview what s a prtcl? netwrk edge, cre, access netwrk perfrmance: lss, delay layering and service mdels backbnes, NAPs, ISPs Yu nw hpefully have: cntext, verview, feel f netwrking mre depth, detail later in curse 9/9-02 Datrkmmunikatin & Internet, Anders brberg, Umu - Intrductin 35 6