1. © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Ethernet Network Fundamentals – Chapter 9

2. ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Objectives  Identify the basic characteristics of network media used in Ethernet.  Describe the physical and data link features of Ethernet.  Describe the function and characteristics of the media access control method used by Ethernet protocol.  Explain the importance of Layer 2 addressing used for data transmission and determine how the different types of addressing impacts network operation and performance.  Compare and contrast the application and benefits of using Ethernet switches in a LAN as apposed to using hubs.  Explain the ARP process.

3. ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public History of Ethernet  The foundation for Ethernet technology was first established in 1970 with a program called Alohanet. Alohanet was a digital radio network designed to transmit information over a shared radio frequency between the Hawaiian Islands.  The first Ethernet standard was published in 1980 by a consortium of Digital Equipment Corporation, Intel, and Xerox (DIX).  In 1985, the Institute of Electrical and Electronics Engineers (IEEE) standards committee for Local and Metropolitan Networks published standards for LANs. These standards start with the number 802. The standard for Ethernet is 802.3.

4. ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Physical and Data Link Features of Ethernet  Standards and Implementation

5. ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Physical and Data Link Features of Ethernet  Ethernet Layer 1 and 2

6. ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Logic Link Control – Connecting the Upper Layers

7. ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public MAC-Getting data to the Medium  Media Access Control is implemented by hardware, typically in the computer Network Interface Card (NIC).  The Ethernet MAC sublayer has two primary responsibilities:  Data Encapsulation Data encapsulation provides three primary functions: Frame delimiting Addressing Error detection  Media Access Control The MAC sublayer controls the placement of frames on the media and the removal of frames from the media. This includes the initiation of frame transmission and recovery from transmission failure due to collisions.

8. ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public CSMA/CD

9. ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Conti…  Carrier Sense Multiple Access with Collision Detection

10. ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Conti…  Describe how a switch can eliminate collisions, backoffs and re- transmissions, the leading factors in reduced throughput on a hub-based Ethernet network

11. ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Physical Implementation of Ethernet The success of Ethernet is due to the following factors:  Simplicity and ease of maintenance  Ability to incorporate new technologies  Reliability  Low cost of installation and upgrade The introduction of Gigabit Ethernet has extended the original LAN technology to distances that make Ethernet a Metropolitan Area Network (MAN) and WAN standard

12. ITE PC v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Physical Implementation of Ethernet  The first version of Ethernet incorporated a media access method known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). CSMA/CD managed the problems that result when multiple devices attempt to communicate over a shared physical medium.

13. ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Ethernet Collision Management  Legacy Ethernet  Current Ethernet (moving to 1 Gbps and beyond

14. ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Conti…  Legacy Ethernet – Using Hubs

15. ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Conti…  Ethernet – Using Switches

16. ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Conti…  Ethernet Beyond the LAN The increased cabling distances enabled by the use of fiber-optic cable in Ethernet-based networks has resulted in a blurring of the distinction between LANs and WANs. Ethernet was initially limited to LAN cable systems within single buildings, and then extended to between buildings. It can now be applied across a city in what is known as a Metropolitan Area Network (MAN).

17. ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Encapsulating the Frame  The Ethernet frame structure adds headers and trailers around the Layer 3 PDU to encapsulate the message being sent.  The differences between framing styles are minimal. The most significant difference between the IEEE 802.3 (original) and the revised IEEE 802.3 is the addition of a Start Frame Delimiter (SFD) and a small change to the Type field to include the Length  Ethernet Frame Size The original Ethernet standard defined the minimum frame size as 64 bytes and the maximum as 1518 bytes. This includes all bytes from the Destination MAC Address field through the Frame Check Sequence (FCS) field. Type field describes which protocol is implemented.

18. ITE PC v4.0 Chapter 1 18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Encapsulating the Frame  Old Vs Revised Fields

19. ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Ethernet MAC Address  An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits  Ethernet MAC Address Structure Organizational Unique Identifier(24) and Vendor Assigned (24)

20. ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Numbering System  Hexadecimal Number system An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits  Representing Hexadecimal Values The technical representation of hexadecimal is preceded with "0x" (zero X).  Hexadecimal Conversions  Viewing the MAC Use a command “ipconfig/ all” on command prompt

21. ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layer 2 addressing and its Impact on Network Operation and Performance  Hexadecimal Numbering and Addressing

22. ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Another Layer of Addressing  The Network layer address enables the packet to be forwarded toward its destination.  The Data Link layer address enables the packet to be carried by the local media across each segment.

23. ITE PC v4.0 Chapter 1 23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Ethernet Unicast, Multicast and Broadcast

24. ITE PC v4.0 Chapter 1 24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Ethernet Timing  Bit Time For each different media speed, a period of time is required for a bit to be placed and sensed on the media  Interframe Spacing After a frame has been sent, all devices on a 10 Mbps Ethernet network are required to wait a minimum of 96 bit times (9.6 microseconds) before any device can transmit its next frame

25. ITE PC v4.0 Chapter 1 25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Switch Operation  To accomplish their purpose, Ethernet LAN switches use five basic operations:  Learning  Aging  Flooding  Selective Forwarding  Filtering

26. ITE PC v4.0 Chapter 1 26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Explain the Address Resolution Protocol (ARP) process.  Mapping IP to MAC Addresses

27. ITE PC v4.0 Chapter 1 27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Explain the Address Resolution Protocol (ARP) process.  The ARP protocol provides two basic functions:  Resolving IPv4 addresses to MAC addresses  Maintaining a cache of mappings

28. ITE PC v4.0 Chapter 1 28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Explain the Address Resolution Protocol (ARP) process.  ARP – Removing Address Mappings

29. ITE PC v4.0 Chapter 1 29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Explain the Address Resolution Protocol (ARP) process.  ARP Broadcasts - Issues

30. ITE PC v4.0 Chapter 1 30 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Proxy ARP  There are circumstances under which a host might send an ARP request seeking to map an IPv4 address outside of the range of the local network. In these cases, the device sends ARP requests for IPv4 addresses not on the local network instead of requesting the MAC address associated with the IPv4 address of the gateway.

31. ITE PC v4.0 Chapter 1 31 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary

32. ITE PC v4.0 Chapter 1 32 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public