Day 2.1 lan segmentation
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Improving LAN performance can be done by segmenting the network using bridges, routers, or switches. Segmentation divides the network into smaller collision domains so fewer devices are sharing bandwidth. Bridges operate at the data link layer and learn segment locations by building MAC address tables, while routers use network layer addresses to forward packets between segments. Switches create microsegments to eliminate collisions altogether, allowing bandwidth utilization closer to 100%. Full duplex mode also improves bandwidth usage by allowing simultaneous transmission and reception between directly connected devices.
Day 2.1 lan segmentation
- 2. Improving LAN Performance • The performance of a network can be improved in a shared media LAN such as Ethernet by using one or more of the following solutions: • Segmenting the network using Bridges, Routers, or LAN Switches • Move to full duplex transmitting • Upgrade to the Fast Ethernet Standard
- 4. Why Segment LANs? A Cisco Segment • A network can be divided in smaller units called segments. Each segment uses the (CSMA/CD) protocol and maintains traffic between users on the segment. By using segments in a network less users/devices are sharing the same 10Mbps when communicating to one another within the segment. Each segment is considered its own collision domain.
- 6. Why Segment LANs? • In a segmented Ethernet LAN data passed between segments is transmitted on the backbone of the network using a bridge, switch, or router. • The backbone network is its own collision domain and uses CSMA/CD to provide a best effort delivery service between segments.
- 8. Segmentation with Bridges • Bridges are different than routers because they are Layer 2 devices, independent of Layer 3 protocols – they pass on data frames regardless of which Layer 3 protocol is being used and are transparent to the other devices on the network. • Bridges increase the latency (delay)in a network by 10-30%. • Why?
- 9. • A bridge is considered a store and forward device because it must examine the destination address (MAC) field in the frame and determine which interface to forward the frame. • If there is no match in the table, the frame is flooded out all other interfaces • Bridges "learn a network’s" segmentation by building address tables that contain the (MAC) address of each network device and which segment to use to reach that device. • Smaller collision domains are created, not broadcast domains.
- 11. Segmentation with LAN Switches • A switch segments a LAN into microsegments creating collision free domains from one larger collision domain, not broadcast domains. • With switched ethernet implementation the available bandwidth can reach closer to 100%.
- 12. Using Full Duplex • Node must – Be directly attached to a dedicated switched port – Have installed network interface card that supports full duplex Full Duplex Half Duplex HUB
- 13. Full-Duplex Ethernet Design • Standard Ethernet normally can only use 50-60% of the 10Mbps available bandwidth. • This is due to collisions and latency. • Full duplex Ethernet offers 100% of the bandwidth in both directions. • This produces a potential 20Mbps throughput – 10Mbps TX and 10Mbps RX.
- 16. • This virtual network circuit exists only when two nodes need to communicate. • This is why it is called a virtual circuit – it exists only when needed and is established within the switch. • Allows multiple users to communicate in parallel via these virtual circuits.
- 18. Source MAC address is used to build this table
- 20. How a LAN Switch Learns Addresses • This means that as new addresses are read they are learned and stored in Content Address Memory (CAM). • Each time an address is stored it is time stamped. • This allows addresses to be stored for a set period of time.
- 21. But more domains
- 23. Segmentation with Routers • Routers operate at the network layer and base all of their forwarding decisions between segments on the Layer 3 protocol address. • Because routers perform more functions than bridges they operate with a higher rate of latency. (Higher than other internetworking devices.)
- 24. Routers: • Segment broadcast domains • Forward packets based on destination network layer addresses • Segment collision domains
- 25. More collision domains, but more bandwidth for each user