1. 1 2004.5.20.  Last Class  Finish Chapter 6  This Class  Chapter 7

2. 2 End-to-End Data  So far we have studied  how to frame/deframe a packet  how to route a packet point-to-point or in an inter-network  how to send packets “reliably” receiver capability (flow control) network resourc sharing (congestion control) efficiency (window-based than stop-and-wait)  Sending rate? proportional to (1/RTT x sqrt(loss rate))

3. 3 Format of Data?  Presentation Format  Need argument “marshalling”  Data Compression

4. 4 Presentation Formatting  Data Types  base types: integers, floating-point nos, char  flat types: structures and arrays  complex types: use pointers  Conversion Strategy  canonical intermediate form  receiver-makes-right

5. 5 Example Data Presentation Formats  XDR  External Data Representation used with SunRPC  ASN.1  Abstract Syntax Notation  ISO standard   NDR  Network Data Representation used in DCE  XML

6. 6 XML  Extensible Markup Language  defines syntax for describing data that applications might share on the Internet

7. 7 Sample XML Sue Moon Assistant Professor 777 1 August 2003

8. 8 XML  Extensible Markup Language  defines syntax for describing data that applications might share on the Internet  XML Schema  specifies how to interpret a collection of data

9. 9 Sample XML Schema <xs:schema xmlns:xs=“http://xxx/XMLSchema”http://xxx/XMLSchema targetNamespace=“http://xxx”http://xxx xmlns=http://xxxhttp://xxx elementFormDefault=“qualified”>...

10. 10 How is XML different from HTML?

11. 11 Data Representation in TCP?

12. 12 TCP/IP Header

13. 13 Socket Library  ntohs(), ntohl(), htons(), htonl()  convert 16-bit and 32-bit integers from host to network byte order and vice versa

14. 14 Data Compression  Lossless compression  Lossy compression

15. 15 Lossless Compression Algorithms  Run Length Encoding  Differential PCM  Dictionary-Based Methods  Lempel-Ziv compression  GIF (Graphical Interchange Format) Extract 256 colors out of 2 24 colors

16. 16 Lossy Compression  JPEG  MPEG  I/B/P frames  forward and bidirectional predictions  MP3

17. 17 Next Class