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EE- 6607 and/6607/ http: //w w w . csc. gatech. edu/~copel Pr of . John A . Copel and j ohn. copel and@ ece. gatech. edu 404 894- 5177 O f f i ce: GCA TT Bl dg 579 em ai l or cal l f or of f i ce vi si t,

  1. EE- 6607 and/6607/ http: //w w w . csc. gatech. edu/~copel Pr of . John A . Copel and j ohn. copel and@ ece. gatech. edu 404 894- 5177 O f f i ce: GCA TT Bl dg 579 em ai l or cal l f or of f i ce vi si t, or cal l Kathy Cheek, 404 894- 9496 Netw or k Sof tw ar e • Text: ks , 3r d Edi ti on Com puter N etw or by A ndr ew S. Tanenbaum Chap. 1, pp 16- 44 EE6607. 02

  2. OSI Ref erence M odel Fr om 1977 to 1983 the I nter nati onal Standar di zati on O r gani zati on (I SO ) devel oped a ar chi tectur al m odel that separ ated com puter com m uni cati on pr otocol f uncti ons i nto l ayer s. Thi s system i s know n as the O pen System s I nter connecti on (O SI ) Ref er ence M odel (I SO Standar d 7498). Thi s m odel i s al so know n as the "seven- l ayer " m odel . These l ayer s take outgoi ng data f r om the l evel above, per f or m cer tai n f uncti ons on i t, then pass the pr ocessed data dow n to the l ayer bel ow . They al so take r ecei ved data f r om the l ayer bel ow , per f or m (undo) the sam e f uncti ons, and pass the pr ocessed data up to the l ayer above.

  3. The Seven O SI Layer s 7. A ppl i cati on Layer 6. Pr esentati on Layer M anage- 5. Sessi on Layer m ent 4. Tr anspor t Layer Pl ane 3. Netw or k Layer 2. Data Li nk Layer 1. Physi cal Layer M em m oni c: A PeS Tr anspor t N etw or k Data Physi cal l y.

  4. Dat a Encapsulat ion Dat a Dat a Appl i cati on AH Dat a Appl i cati on Layer Layer TH AH Dat a Tr anspor t Tr anspor t Layer Layer NH TH AH Dat a Netw or k Netw or k Layer Layer DH NH TH AH Dat a Data Li nk Data Li nk Layer Layer Physi cal Bit s over Physical M edium Physi cal Layer Layer

  5. Application Process Process 5 Telnet , FTP, SM TP Application Layer I SO 7- Presenta- Transport Layer tion Layer 4 (TCP & UDP) M odel Session I EEE 802 Layers Layer Transport I nt ernet (I P) Logi cal Li nk Layer 3 Contr ol (LLC) Netw ork Layer Net w ork I nt erf ace M edi a Access 2 802 Data Contr ol (M AC) TCP/ I P has f our Link Layer concept ional layers Physi cal 802 Phys. 1 Layer Layer

  6. TCP/ I P - t he Prot ocol of t he I nt ernet While t he I nt ernet Prot ocol Suit e is generally know n as TCP/ I P, t here are a number of prot ocols at dif f erent layers t hat make t he I nt ernet w ork. Program (e.g., Brow ser) File Transf er Simple M ail Hyper- Text Telnet Prot ocol Transf er Transf er (Terminal) (FTP) (SM TP) Prot ocol (HTTP) User Dat agram Transmission Cont rol Prot ocol (TCP) Prot ocol (UDP) I nt ernet Prot ocol

  7. Pr otocol Layer Desi gn I ssues Data Di r ecti ons • Si m pl ex - one w ay onl y (f i r e al ar m ) • Hal f Dupl ex - one w ay at a ti m e (CB r adi o) • Dupl ex - Both w ays at once (tel ephone) Er r or Contr ol (Detecti on) • Retr ansm i ssi on (A CK, NA K, ti m e- out) • For w ar d er r or cor r ecti on Sequenci ng (SA R: Segm ent & Reassem bl e) M ul ti pl exi ng (m ul ti pl e sessi ons, 1 ci r cui t) Rever se M ul ti pl exi ng (1 sessi on, m ul ti - ci r cui ts)

  8. Service Access Point s I DU LAYER I CI + SDU SDU N+1 SAP LAYER N I CI SDU Node X Node Y I nt erf ace Dat a Unit PDU I nt erf ace Cont rol I nf o Service Dat a Unit Header + Prot ocol Dat a Unit SDU

  9. Connecti on O r i ented Ser vi ce • Li ke Tel ephone System • Packets ar r i ve i n or der Connecti onl ess Ser vi ce • Li ke Post O f f i ce w i th m ul ti pl e l etter s • Packets can be out of sequence V ar i abl e del ay • Q ual i ty of Ser vi ce • Rel i abl e - never l oses data (A CKed) • Unr el i abl e - m ay l ose data

  10. Service Primit ives M essages Bet w een Layers LAYER N+1 Request Response Service User LAYER N Service I ndicat ion Conf irm Provider Node X Node Y Node X

  11. Novel l Netw ar e Layer A ppl i cati on: Ser vi ce A dver ti si ng Pr otocol , Fi l e Ser ver Tr anspor t: NCP (f i l es) SPX (Lotus Notes) Netw or k: I PX Datal i nk: Ether net Token Ri ng A RCnet Physi cal : Ether net Token Ri ng A RCnet

  12. I nter net (TCP/I P) Layer A ppl i cati on: M ai l , Ter m i nal (Tel net), W eb, Fi l e Tr ansf er (FTP) Tr anspor t: TCP (r el i abl e) UDP (datagr am ) Netw or k: I P (I nter net Pr otocol ) Datal i nk: Ether net, Token Ri ng, FDDI , DO CSI S (CA TV ), A TM , . . . Physi cal : Ether net, Token Ri ng, FDDI , DO CSI S (CA TV ), A TM , . . .

  13. A RPA net - by A dvanced Resear ch Pr oj ects A gency • 1960' s, used I nter f ace M essage Pr ocessor s • Bui l t by BBN, har d to connect to other netw or ks • 1980' s - Dom ai n Nam i ng System (DNS) devel oped NSFnet Desi gned f or uni ver si ty r esear ch gr oups (1984) • • NSF f unded backbone and r egi onal netw or ks • A NS (I BM , M CI et al ) com m er ci al i zed i n 1994, sol d to A m er i ca O nl i ne i n 1995. NREN (3 Gbps netw or k) author i zed by Congr ess i n 1991 • • NSF f unded NA P' s i n San Fr an. , NYC, Chi cago, W ash. DC • I nter net - m any m or e . com ' s than . edu' s, . gov' s today. Based on TCP/I P Pr otocol s, def i ned by RFC.

  14. At lant a M ap of t he I nt ernet - Primary and Secondary Backbone Rout es

  15. Gi gabi t Testbeds (1996) • A ur or a - M I T, U. Penn. , W atson, Bel l cor e • Bl anca - A T& T Bel l Labs, Ber kel ey, U. W i sconsi n • CA SA - Los A l am os, Cal Tech, JPL, San Di ego S. C. Nectar - M A N f r om Pi ttsbur gh SC to CM U • • V I STA net - UNC, NCSU, M CNC (Res. Tr i angl e Par k) m ost used 622 M bps (gover nm ent Gi gabi t) • l l cl osed now , except: • vBNS - V er y hi gh- speed Backbone Netw or k (622M bps)

  16. Com m er ci al Data Com m uni cati on Ser vi ces X. 25 - pl us X. 3, X. 28, & X. 29 f or dum b ter m i nal s • vi r tual ci r cui ts over 56 kbps l i nes Fr am e Rel ay ski ps er r or checki ng at i nter m edi ate nodes • • connecti on- or i ented (vi r tual l eased l i nes) SM DS - Sw i tched M ul ti m egabi t Data Ser vi ce • Packet ser vi ce, connecti onl ess, LA N i nter connects • Usual l y DS- 3 (45 M bps) I SO NET - Constant bi t- r ate, channel i zed or not I SDN - BRI (2x64 kbps di al up) & PRI (24x64kbps) B- I SDN - A TM sw i tches and SO NET

  17. Standar ds O r gani zati ons I TU - I nter nati onal Tel ecom m uni cati ons Uni on • W or l dw i de (CCI TT unti l 1993 nam e change) I SO - I nter nati onal Standar ds O r gani zati on • O SI (O pen System s I nter connect) M odel I A B - I nter net A r chi tectur e (A cti vi ti es) Boar d set up by DO D i n 1060' s • • has I ETF - I nter net Engi neer i ng Task For ce • gener ates RFC' s - r equests f or com m ents. • >70 w or ki ng com m i ttees I nter net Soci ety - i nter est gr oup cr eated, Tr ustees now appoi nt I A B m em ber s. U. S. - NI ST (gov), ANSI (i ndust r y), I EEE (pr of essi onal )

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