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CENG 490/510 Network Programming Russell Deaton Rm. 324 501-575-5590 rdeaton@engr.uark.edu http://www.csce.uark.edu/~rdeaton/networkprog/
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Why Network Programming? New Economy Software for Network Applications Client/Server Architecture Platforms?
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Class Introduction Syllabus –Topics –Resources –Requirements –Grading Computer Accounts Introduction to the online resources ( http://engronline.ee.memphis.edu/ )
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Networks
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Common Xmit Media
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Shared Media Networks are a shared communication resource Only one user can access at a time
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Packet and Circuit Switched Circuit: Public Telephone Network Packet: Internet and US Mail Data divided into small units (packets) for transmission More efficient use of shared resource
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Time-Division Multiplexing
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Packets and Frames Packet: A small, self-contained parcel of data sent across a computer network. Each packet contains a header that identifies the sender and recipient, and data to be delivered. Frame: The form of a packet that the underlying hardware accepts and delivers.
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Frames Header and trailer indicates beginning and end of frame.
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Transmission Errors Error Detection and Error Correction Both require additional information beyond data, appended to end of frame Many Schemes Parity checking, Check Sum, CRC codes Error Correcting Codes: Hamming, Reed- Solomon, etc...
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Parity refers to the number of bits set to 1 in the data item Even parity - an even number of bits are 1 Odd parity - an odd number of bits are 1 A parity bit is an extra bit transmitted with a data item, chose to give the resulting bits even or odd parity Even parity - data: 10010011, parity bit 1 Odd parity - data: 10010111, parity bit 0
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Point-to-Point Networks
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LAN’s Reduce complexity and cost by sharing communication channel TDM Synchronization Effective because of locality of reference –Spatial –Temporal
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Topologies Star, Ring, Bus
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Ethernet Widely used LAN technology Invented at Xerox PARC (Palo Alto Research Center) in 1970s Defined in a standard by Xerox, Intel and Digital - DIX standard Standard now managed by IEEE - defines formats, voltages, cable lengths,... Uses bus topology Single coax cable - the ether Multiple computers connect One Ethernet cable is sometimes called a segment Limited to 500 meters in length Minimum separation between connections is 3 meters
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Originally 3 Mbs Currently, 10 Mbs Fast Ethernet, 100 Mbs One computer transmits at a time Signal is a modulated carrier which propagates from transmitter in both directions along length of segment
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Hardware Adresses Identify destination on shared channel Hardware or physical address Included in frame
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Ethernet Frame
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WAN Packet Switch: Moves complete packets from one connection to another
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Protocols and Layering A rule that specifies format and meaning of messages that computers exchange Protocols organized in layers, each of which solves specific aspect of communication problem.
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ISO 7 Layer Model
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Layer 7: Application Application-specific protocols such as FTP and SMTP (electronic mail) Layer 6: Presentation Common formats for representation of data Layer 5: Session Management of sessions such as login to a remote computer Layer 4: Transport Reliable delivery of data between computers Layer 3: Network Address assignment and data delivery across a physical network Layer 2: Data Link Format of data in frames and delivery of frames through network interface Layer 1: Physical Basic network hardware - such as RS-232 or Ethernet
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Nested Headers
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