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Telecommunication & Networking

Telecommunication & Networking. Lesson 7. Application Layer. telnet. ftp. SMTP. …. HTTP. TCP/UDP. IP. 10/100 Ethernet. Frame Relay. Gigabit Ethernet. FDDI. ATM. …. IEEE 802.3 CSMA/CD STP/UTP/Coax. Simpler HDLC Most media. Token Ring Fibre. Switching VPI Fibre,….

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Telecommunication & Networking

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  1. Telecommunication & Networking Lesson 7

  2. Application Layer telnet ftp SMTP … HTTP TCP/UDP IP 10/100 Ethernet Frame Relay Gigabit Ethernet FDDI ATM … • IEEE 802.3 • CSMA/CD • STP/UTP/Coax • Simpler HDLC • Most media • Token Ring • Fibre • Switching • VPI • Fibre,… T1: 1.544Mbps…

  3. Internet (TCP/IP) xDSL/Broadband ISP

  4. RFC’s • Published only with the approval of IESG (Internet Engineering Steering Group) of the IETF (Internet Engineering Task Force) • All Internet standards originated as RFC’s • Not all RFC’s are Internet standards • http://rs.interic.net/

  5. RFC Life Cycle Prototype Document + Working Model • Idea Experimental Others take it and implement IESG likes De facto standard Experimental RFC!

  6. Digital Subscriber Lines (DSLs) Asymmetric DSL (ADSL): upstream & downstrem transmission rates Rate Adaptive DSL (RADSL): transmission rate depends on distance and quality of line High Data Rate DSL (HDSL): T-1 speed/E-1 speed xDSLs

  7. Protocols • SNMP(v2) : Simple Network Management Protocol • SMTP : Simple Mail Transfer Protocol • MIME : Multipurpose Internet Mail Expansion • HTTP : Hyper Text Transfer Protocol

  8. SMTP • RFC 821/822 • Sends messages based on mailbox addresses • 7-bit character set • envelope (it attaches the path the message took) and content (it does not care what it is) • port 25

  9. POP3 (Post Office Protocol 3) • IMAP4 (Internet Message Access Protocol) • POP can be thought of as a "store-and-forward" service. IMAP can be thought of as a remote file server.

  10. MIME • Address limitations of SMTP • can’t transmit binary files • limited only to 7-bit characters • afriad of message size too big • ASCII - to - EBCDIC is not consistent : error in message • can’t interfact to X.400 (contains non-textual data) • other minor problems

  11. MIME • MultipurposeInternetMailExtensions (RFCs 2045 & 2046) • Open standard for sending information in various forms through Internet email • Supports almost a hundred predefined types of content • Content types are classified as a type and a subtype

  12. MIME • RFC 1521/1522 • Five header fields • MIME-version • Content-type: how to read this • Content-transfer-encoding: any encoding of message body? • Content-id • Content-description: audio track of the Beatles’ Yesterday

  13. MIME Content Type • Type/Subtype • Text/Plain • Multipart/Mixed:Parallel:Alternative/Digest • Message/rfc822:Partial:External-body • Image/jpeg:gif • Video/mpeg • Audio/Basic • Application/Postscript:octet-stream

  14. MIME Transfer Encodings • 7 bit • 8 bit • binary • quoted-printable : mostly ASCII text • base64 : mapping 6-bit blocks of input to 8-bit blocks of output, all of which are printable ASCII characters • x-token : A named non-standard encoding

  15. S/MIME(Network Security Essentials) • Signed data: “A digital signature is formed by taking themessage digest of the content to be signed and then encrypting that with the private key of the signer. The content plus signature are then encoded using base64 encoding. A signed data message can only be viewed by a recipient with S/MIME capability” • Clear-signed data: “only the digital signature is encoded…”

  16. HTTP • Standard for Web client and Web server - how connect and serve • MIME + HTML • MIME : encoded data as 7-bit ASCII transmitted over a serial line • Protocols: file, ftp, http, gopher, news, telnet, WAIS • SGML - early 1970’s by DOD (ISO 8879)

  17. HTTP • Not a protocol for transferring hypertext • But a protocol for transmitting information for making hypertext jumps easy • A stateless protocol • Builds commonly on top of TCP; but not required as long as the connection is reliable • Transaction oriented : TCP connection is established for each transaction and terminated at the end of the transaction (http 1.0); http 1.1 allows multiple requests/responses per connection

  18. content-coding = gzip | compress … • Media type media-type = type "/" subtype *( ";" parameter ) • “Media-type values are registered with the Internet Assigned Number Authority (IANA). The media type registration process is outlined in RFC 2048 [17]. Use of non-registered media types is discouraged.”

  19. Return-Path: <kell@runet.edu> Return-Receipt-To: "Kell" <kell@runet.edu> Reply-To: <kell@runet.edu> To: "'pipeline'" <pipe@runet.edu> Subject: ILOVEYOU Date: Thu, 4 May 2000 11:29:46 -0400 X-Priority: 3 (Normal) X-MSMail-Priority: Normal Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3612.1700 This is a multi-part message in MIME format. ------=_NextPart_000_003B_01BFB5BC.20384160 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit kindly check the attached LOVELETTER coming from me.

  20. ------=_NextPart_000_003B_01BFB5BC.20384160 Content-Type: application/octet-stream; name="LOVE-LETTER-FOR-YOU.TXT.vbs" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="LOVE-LETTER-FOR-YOU.TXT.vbs" rem barok -loveletter(vbe) <i hate go to school> rem by: spyder / ispyder@mail.com / @GRAMMERSoft Group / = Manila,Philippines On Error Resume Next dim fso,dirsystem,dirwin,dirtemp,eq,ctr,file,vbscopy,dow eq=3D"" ctr=3D0 Set fso =3D CreateObject("Scripting.FileSystemObject") set file =3D fso.OpenTextFile(WScript.ScriptFullname,1) vbscopy=3Dfile.ReadAll main() sub main()

  21. Content-Type: application/mac-binhex40; name="Chinnappan=ATCM'00=Paper_abs" Content-Disposition: attachment; filename="Chinnappan=ATCM'00=Paper_abs" (This file must be converted with BinHex 4.0) :(%0SD@jZBA"`B@i[394$65F`#p3BA"PFL"KBR!9cK#6Ne69d3"!!!$E!!!!!%H6&r3ca(JSE%Di3!!!!!!!!!!!!!!!!!!!!!q!!r[m*!!B!!!!!!!!!!!!!!!3!!!!f!!!!!!!!!!!3!!#J!3!!!3!!!2lrrrm!!!!!0`!!!$S!!!!l!!!!2!!2r

  22. HTTP Key Terms • Cache : stores cacheable responses to reduce same future references • Proxy : an intermediary program that acts on behalf of other clients • Tunnel : an intermediary program that acts as a blind relay between two connections • Connection : A transport layer virtual circuit between two programs

  23. Bluetooth? Cellular Network WAP Gateway Internet xDSL/Broadband Wireless ISP Security

  24. Ipsec(Network Security Essentials; chapter 6) • “A company can build a secure virtual private network over the Internet or over a public WAN.” • Connect to corporate intranet via an ISP if Ipsec is implemented in your client machine • Enhances e-commerce security • Enable secure communication with partners with authentication and confidentiality (along with key exchange mechanism).

  25. IPsec • IPSec Services (page 166) • Authentication and Encryption • AH (Authentication Header) and ESP (Encapsulating Security Payload (ESP) • Two modes: Transport and Tunnel • Tunnel Mode?

  26. Application Layer SMTP ftp HTTP TLS TCP/UDP IP/IPSec 10/100 Ethernet Frame Relay Gigabit Ethernet FDDI ATM … • IEEE 802.3 • CSMA/CD • STP/UTP/Coax • Simpler HDLC • Most media • Token Ring • Fibre • Switching • VPI • Fibre,… T1: 1.544Mbps…

  27. Internet Intranet Do we need this? Mobile Terminal

  28. Land Lines versus Wireless • Fixed costs: stations where you need it versus wires/cables • Marginal costs: a handset versus NIC (given that you have a PC)

  29. IEEE 802.11 • Through the MAC layer, supports communications using electromagnetic waves via through the air • Supports stationary, movable stations and stations travel at pedestrian or vehicular speed • Basic Service Area (BSA): station to station communication within the same area • Extended Service Area (ESA): station to other stations through some distribution system

  30. Spread Spectrum • Frequency Hopping: • 79 nonoverlapping frequency channels with 1MHz channel spacing • Up to 26 collocated networks • Resistent to “multipath fading through the inherent frequency diversity mechanism” • Minimum hop distance of 3 channels

  31. Portals Portals Internet Wireless Network Fixed Network

  32. Advanced Mobile telePhone System (AMPS) • 1983 • Time Division Multiple Access (TDMA) • 1988 (3 fold increase) • Code Division Multiple Access (CDMA) • Shortly, Qualcomm (10 fold or more increase) • Adopted 1993 by CTIA (Cellular Telephone Industry Association) • PCS (Personal Communications System) • GSM (Global System for Mobile Communications) in Europe • CDPD (Cellular Digital Packet Data)

  33. WAP • Open standard for access using a mobile device • WAP Forum: History • With the limited mobile environment in mind • Small screens • Limited memory on device • Limited bandwidth • Limited battery life • … • HTTP/XML/XHTML

  34. Competitions? • Wireless Knowledge: Microsoft (Windows CE) & Qualcomm; BT (Europe), NTT (Japan) and Nextel (USA) • Palm VII: Mobitex wireless modem; Palm.net • I-mode: Spring 1999 • Aethersystems/Riverbed Technologies

  35. Wireless Application Protocol Application Layer (WAE) XHTML/Javascript Session Layer (WSP) HTTP Transaction Layer (WTP) Security Layer (WTLS) TLS (SSL) WDP (Transport Layer) TCP/UDP IP SMS, USSD, CSD, IS-136, CDMA, GPRS,…

  36. Statistics? • By 2004, close to 95% of all (?) users with WAP-enabled phones will have WAP subscriptions • By 2004, 36% doing WAP-based financial services; of this, 50% is served by a WAP gateway belonged to financial institutions

  37. WAP Specification • Programming model based on WWW programming model (WAE) • WML: XML, HTML, HDML • WMLScript: ECMA (European Computer Manufacturers Association) • Microbrowser • Integration of telephone and microbrowser function

  38. WAP 1.2 • PUSH functions • Wireless telephony applications • End-to-end solutions? • WAP 2.0

  39. CDMA (Code Division Multiple Access): A spread-spectrum approach to digital transmission. With CDMA, each conversation is digitized and then tagged with a code. The mobile phone is then instructed to decipher only a particular code to pluck the right conversation off the air. The process can be compared in some ways to an English-speaking person picking out in a crowded room of French speakers the only other person who is speaking English. • CDPD (Cellular Digital Packet Data): Technology that allows data files to be broken into a number of 'packets' and sent along idle channels of existing cellular voice networks. • GPRS (General Packet Radio Service): An extension to the GSM standard to include packet data services. It is expected to be launched in 2000.

  40. Code Division Multiple Access, a cellular technology also known as IS-95 (800 MHz), that competes with GSM technology for dominance in the cellular world. • Developed by Qualcomm; enhanced by Ericsson • Adopted by the Telecommunications Industry Association (TIA) in 1993 • Universal Mobile Telephone Standard - the next generation of global cellular which should be in place by 2004. Proposed data rates of <2Mbps, using combination TDMA and W-CDMA. Operates at around 2GHz

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