1 CCNA 3 v3.1 Module 4 Switching Concepts Claes Larsen, CCAI

222 Objectives

LAN Development

444 Bridges

LAN Development: Today’s LANs

666 Devices Function at Layers

777 Factors that Impact Network Performance Network traffic (congestion). Multitasking desktop operating systems (Windows, UNIX, and Mac) allow simultaneous network transactions. Faster desktop operating systems (Windows, UNIX, and Mac) can initiate faster network activity. Increased number of client/server applications using shared network data.

888 Typical Causes of Network Congestion

999 Ethernet Performance of a shared-medium Ethernet/802.3 LANs is negatively affected by factors such as the following: The broadcast delivery nature of Ethernet. Carrier sense multiple access collision detect (CSMA/CD) access method allows only one host to transmit at a time. Multimedia applications with higher bandwidth demand such as video and the Internet. The latency of additional devices added by the extension of LANs by using repeaters. The distance added by using Layer 1 repeaters.

10 Half-Duplex Ethernet Design

11 Network Congestion

12 Network Latency Latency, or delay, is the time a frame or a packet takes to travel from the source station to the final destination.

13 Ethernet 10BASE-T Transmission Times Bit time (or slot time) — The basic unit of time in which 1 bit can be sent. For electronic or optical devices to recognize a binary 1 or 0, there is a minimum duration during which the bit is "on" or "off. " Transmission time — equals the number of bits to be sent times the bit time for a given technology. Another way to think about transmission time is the interval between the start and end of a frame transmission, or between the start of a frame transmission and a collision. Small frames take a shorter amount of time. Large frames take a longer amount of time.

14 Benefits of Using Repeaters

15 Full-Duplex Transmitting

16 LAN Segmentation Segmentation allows network congestion to be significantly reduced within each segment.

17 LAN Segmentation with Bridges

18 LAN Segmentation with Routers

19 LAN Segmentation with Switches

20 LAN Switching Basics

21 LAN Switch Operation

22 Ethernet Switch Latency

23 Layer 2 Switching

24 Layer 3 Switching

25 Symmetric Switching

26 Asymmetric Switching

27 Memory Buffering Port-based memory buffering Packets are stored in queues that are linked to specific incoming ports. It is possible for a single packet to block all other packets because its destination port is busy (even if the other packets could be delivered). Shared-memory buffering All packets use a common memory buffer. Packets in the buffer are then linked (mapped) dynamically to the appropriate destination port. Helps balance between 10- and 100-Mbps ports.

28 Two Switching Methods

29 Store-and-forward

30 Cut-through

31 Functions of Ethernet Switches

32 Frame Transmission Modes

33 Network Switch Using CAM

34 How Switches and Bridges Filter Frames

35 Microsegmentation of the Network A switch employs “microsegmentation” to reduce the collision domain on a LAN. The switch does this by creating dedicated network segments, or point-to-point connections.

36 Switches and Collision Domains The network area where frames originate and collide is called the collision domain. All shared media environments are collision domains.

37 Three Methods of Communication

38 Switches and Broadcast Domains Broadcasting is when one transmitter tries to reach all the receivers in the network. The server station sends out one message, and everyone on that segment receives the message.

39 Communication Between Switches and Workstations

40 Summary