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Computer Networks (CS3623)

Computer Networks (CS3623). # 20 | Data Transformation. What is this?.

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Computer Networks (CS3623)

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  1. Computer Networks(CS3623) #20 | Data Transformation

  2. What is this? • 1011010100101000010101011110100100100100010001001101010010010010100101010010101001010100111101011001100011010111010100110001100111111010100101001001000010100101010100100101001010100101001010100110101001010100111101011001100011010111010100110001100111111010100101001001000010100101010100100 ……….

  3. Issues • The two sides agreeing to a message format, often called the presentation format • The efficiency of the encoding (data compression)

  4. Presentation format

  5. Encoding & Decoding Data • Exp: Big / Little Endian

  6. Argument marshalling • converting, packing, and linearizing

  7. Taxonomy • Data types • base, flat, complex • Conversion strategies • canonical intermediate form, receiver-makes-right • Tags • Tagged, untagged • Stub • interpreted., compiled

  8. Tagged: example • A 32-bit integer

  9. Stub

  10. Popular network data representations • XDR (External Data Representation) SunRPC • ASN.1 (Abstract Syntax Notation One)  ISO • NDR (Network Data Representation)  DCE • XML (Extensible Markup Language)

  11. XDR: example

  12. ASN.1 • (tag, length, value)

  13. XML: example

  14. XML Schema Definition (XSD)

  15. Data compression

  16. Classes • Lossless • Run length encoding (RLE) • differential pulse code modulation (DPCM) • Dictionary-Based Methods: Lempel-Ziv & its variants • Lossy • JPEG • MPEG • MP3

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