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IS3120 Network Communications Infrastructure Unit 2

IS3120 Network Communications Infrastructure Unit 2 IEEE 802.3 CSMA/CD and the Evolution of Ethernet Networking. Learning Objective. Differentiate between the Ethernet standards, specifications, and technologies that drive current LAN connectivity. Key Concepts.

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IS3120 Network Communications Infrastructure Unit 2

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  1. IS3120 Network Communications Infrastructure Unit 2 IEEE 802.3 CSMA/CD and the Evolution of Ethernet Networking

  2. Learning Objective • Differentiate between the Ethernet standards, specifications, and technologies that drive current LAN connectivity.

  3. Key Concepts • IEEE 802.3 CSMA/CD family of standards and specifications • IEEE 802.3 CSMA/CD versus Ethernet v2 frame formats • Data Link layer versus MAC layer 10/100/1000/10000 Ethernet networking • Single versus multiple broadcast domains

  4. EXPLORE: CONCEPTS

  5. Ethernet • Most common LAN technology • Data is transmitted in packets called frames • Standards include • Access and use • Physical hardware

  6. Access Method: CSMA/CD Carrier Sense Multiple Access with Collision Detection

  7. Ethernet Physical Layer Specifications • Deconstructing media type names [speed]Base[medium] • Speed is megabits per second (Mbit/s) • Medium describes the type of cabling or other transmission media • Example: 10Base-T = 10Mbit/s over twisted pair

  8. Specifications: Early • Speed: 10 Mbit/s • Mostly obsolete • Adopted 1983-1993

  9. Specifications: Fast Ethernet • Speed: 100 Mbit/s • Adopted 1995-1998 • Still widely in use *Collectively referred to as 100Base-T

  10. Specifications: Gigabit Ethernet • Speed: 1000 Mbit/s (1 Gbit/s) or 10 Gbit/s • Adopted 1998-Current

  11. Basic Wired Ethernet Topologies • Bus: All nodes are on the same wire • 10Base5, 10Base2 • Star: Nodes are wired to a central connection point • 10Base-T, Fast Ethernet, GigE • Hierarchical: Connected star networks

  12. Ethernet Frames • Ethernet-specific data packet • Besides data, contains elements required for routing to the proper endpoint and port • Most commonly used frames • Ethernet v2 (Ethernet II) • 802.3 (CSMA/CD) Ethernet IEEE 802.3 Standard Reference: http://standards.ieee.org/about/get/802/802.3.html

  13. Common Ethernet Frame Fields

  14. Ethernet v2 Frame • Aka DIX frame, Ethernet II frame • Existed prior to 802.3 Frame • Unique element EtherType identifies protocol • Examples: • 0x0800 – IPv4 • 0x0806 – Address Resolution Protocol (ARP) • 0x86DD – IPv6

  15. Ethernet 802.3 (CSMA/CD) Frame • Start of Frame Delimiter (SOFD) marks the end of the preamble • EtherType field replaced by Length field • Identifies length of Information field • Information field includes 8-byte LLC header containing EtherType field

  16. Compatibility • Ethernet v2 and 802.3 Ethernet are compatible • 802.3 Length field can contain length or EtherType

  17. EXPLORE: PROCESSES

  18. Working with Broadcast Domains

  19. Single Broadcast Domain with Switch

  20. Multiple Broadcast Domains with Router • Routers can segment network • Each segment has its own broadcast domain

  21. Multiple Broadcast Domains with VLANs • VLAN: Virtual LAN • Collection of ports on one or more switches configured into a single broadcast domain • Layer 3 device (e.g., router) is required to communicate between VLANs • Allows segmenting by business functional or security needs

  22. Multiple Broadcast Domains with VLAN

  23. Discussion Topics • What are the disadvantages of having many nodes in a single broadcast domain? • What are the advantages of creating multiple broadcast domains with VLANs instead of with routers? • How does segmentation of a large network using VLAN improve data security?

  24. EXPLORE: ROLES

  25. Role of CSMA/CD in Ethernet • CSMA/CD forces computers to listen to traffic on the Ethernet segment before sending • This makes sure that no other host on the wire is sending • Mitigates signal collision so that the transport media is not rendered unusable

  26. EXPLORE: CONTEXTS

  27. Seven Domains of a Typical IT Infrastructure

  28. IP Addressing Domains

  29. EXPLORE: RATIONALE

  30. Rationale • CSMA/CD protocols provide a more extensible network environment by allowing multiple computers to transmit data simultaneously on switched networks without requiring token-passing or deterministic enrollment for transmission control. • The Ethernet standard is found in many networks, from large extended enterprise environments to SOHO and home-scale.

  31. Summary • In this presentation, the following were covered: • Ethernet LAN Standards (IEEE 802.3) • Carrier sense multiple access with Collision Detection (CSMA/CD) • 802.3 Physical Specifications • Comparison of Ethernet v2 and 802.3 (CSMA/CD) frames • Working with broadcast domains

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