1. ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Big Picture: Lab 3 Networks (OSI-view) physical data link network transport presentation application session physical data link network transport presentation application session physical data link network IP

2. 2 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Networking for Embedded Systems  Why we use networks.  Network abstractions, OSI.  Embedded Networks and TCP/IP.

3. 3 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Metcalfe’s Rule  Metcalfe: the “value” of a network is proportional to the square of the number of nodes adding a node benefits existing nodes the larger the network the larger the benefit

4. 4 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Networks in embedded systems  Internet-enabled embedded system: any embedded system that includes an Internet interface (e.g., burglar alarm system).  Internet appliance: embedded system designed for a particular Internet task (e.g. email). UMASS ECE SDP Internet-connected Refrigerator  Laser printer.  Home automation system.

5. 5 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Network abstractions  International Standards Organization (ISO) developed the Open Systems Interconnection (OSI) model to describe networks: 7-layer model.  Provides a standard way to classify network components and operations.  It is a conceptual model only.

6. 6 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 OSI model physical mechanical, electrical data link reliable data transport network end-to-end service transport connections presentation data format session application dialog control application end-user interface

7. 7 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Hardware network architectures Many different types of networks based on topology; scheduling of communication; and routing.

8. 8 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Point-to-point networks One source, one or more destinations: PE 1 PE 2 PE 3 link 1 link 2

9. 9 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Bus networks Common physical connection: PE 1PE 2PE 3PE 4 headeraddressdataECC packet format

10. 10 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Ethernet – a Physical Layer  Dominant non-telephone LAN.  Versions: 10 Mb/s, 100 Mb/s, 1 Gb/s, 10 Gb/s, 100Gb/s.  Goal: reliable communication over an unreliable medium.

11. 11 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Ethernet topology Bus-based system ABC

12. 12 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Ethernet performance  Carrier sense multiple access with collision detection (CSMA-CD) sense collisions; exponentially back off in time; retransmit.  Quality-of-service tends to non-linearly decrease at high load levels.  Can’t guarantee real-time deadlines. However, may provide very good service at proper load levels.

13. 13 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Internet Protocol – a Network Layer  Internet Protocol (IP) is basis for Internet.  Provides an internetworking standard: between two Ethernets, Ethernet and token ring, etc.  Higher-level services are built on top of IP.

14. 14 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 IP in communication physical data link network transport presentation application session physical data link network transport presentation application session physical data link network node A router node B IP

15. 15 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 IP packet  Includes: version, service type, length time to live, protocol source and destination address (IP addresses) data payload  Maximum data payload is 65,535 bytes.

16. 16 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 IP addresses  32 bits in early IP, 128 bits in IPv6.  Typically written in form xxx.xx.xx.xx.  Names (foo.baz.com) translated to IP address by domain name server (DNS).

17. 17 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 TCP/IP Basics : Data Encapsulation Application Data TCP Header IP Header Ethernet Header Application Data TCP Header IP HeaderEthernet Trailer Application Data App Header

18. 18 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Software Abstractions - Message-based  Transport layer provides message-based programming interface: send_msg(adrs,data1);  Data must be broken into packets at source, reassembled at destination.

19. 19 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 What’s next ?  Lab 3 details

20. 20 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Backup

21. 21 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Ethernet packet format preamble start frame source adrs dest adrs data payload lengthpaddingCRC

22. 22 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Embedding TCP/IP – The Advantages  Provides a universal, flexible, User Interface for the Device  UI can be exposed using a standard browser   Opens possibilities of remote diagnostics and software upgrade

23. 23 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Embedding TCP/IP – The issues  Resource Limitations – Code Size – Data Size – CPU Processing capacity  Operating System Services – Timer Services – Memory Management – Network Drivers  Processing Latency – Layer to layer buffering

24. 24 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 Bus arbitration Fixed: Same order of resolution every time. Fair: every PE has same access over long periods. round-robin: rotate top priority among PEs. A,B,C fixed round-robin ABCABC ABCABC

25. 25 ECE 354 Copyright ECE Department, some slides modified from W. Wolf, Computers as Components, Morgan Kaufmann, 2005 To Sum Up  TCP/IP is close to 20 years old, but it has outlasted more modern protocols and has become the de - facto standard for the internet  Proliferation of internet enabled devices is predicted in the next wave of the internet  As developers try to get their embedded devices on the net, they face the issue of the networking problem may exceed the application problem  Practical solutions are currently available to connect embedded devices to the internet