MUHAMMAD MU’IZUDDIN BIN MUHSINON

SN097083

SECTION 02A

Assignment

- Difference between Layer 2 & Layer 3 Switching

Layer 2 Switching

- Function

MAC addresses are learned from the incoming frames’ source addresses. A table of MAC addresses and their associated bridge and switch ports is built and

maintained. Broadcast and multicast frames are flooded out to all ports (except the one that

received the frame). Frames destined for unknown locations are flooded out to all ports (except the one

that received the frame). Bridges and switches communicate with each other using the Spanning Tree

Protocol to eliminate bridging loops. Performs essentially the same function as a transparent bridge. May have many ports and can perform hardware-based bridging. Frames are forwarded using specialized hardware, called application-specific

integrated circuits (ASIC).

One drawback to Layer 2 switching is that it cannot be scaled effectively. Switches must forward broadcast frames to all ports, causing large switched networks to become large broadcast domains. In addition, Spanning Tree Protocol (STP) can have a slow convergence time when the switch topology changes. STP also can block certain switch ports, preventing data transfer.

- Benefit

Hardware-based bridging (MAC) Wire speed High speed Low latency

Layer 3 Switching

Packets are forwarded at Layer 3, just as a router would do. Packets are switched using specialized hardware, ASIC, for high speed and low

latency. Packets can be forwarded with security control and quality of service (QoS) using

Layer 3 address information. Layer 3 switches are designed to examine and forward packets in high-speed LAN

environments. Whereas a router might impose a bottleneck to forwarding throughput, a Layer 3 switch can be placed anywhere in the network, with little or no performance penalty.

Determine paths based on logical addressing Run layer 3 checksums (on header only) Use Time to Live (TTL) Process and respond to any option information Update Simple Network Management Protocol (SNMP) managers with Management

Information Base (MIB) information Provide Security

- Benefit

Hardware-based packet forwarding High-performance packet switching High-speed scalability Low latency Lower per-port cost Flow accounting Quality of service (QoS)