Question 9 - Switches and Switching Flashcards
At which point during the receipt of a frame does each of the switch types listed below start forwarding? What is the consequence for each type with respect to latency and errors?
(i) Store and forward
(ii) Fragment free
(iii) Fast forward
Store and forward switching has the highest latency as it starts forwarding only after the entire frame is received. This method ensures that all errors are detected.
Fragment free switching starts forwarding after receiving 64 bytes. This value is significant as it will include all collision fragments, which can then be discarded.
Fast forward switching has the lowest latency. Forwarding begins as soon as the destination address has been received. Any frames with errors will still be forwarded, which can lead to high traffic levels.
Explain the term ‘virtual local area network’ (VLAN), listing two benefits.
A VLAN is a logical broadcast domain that can cover multiple physical LAN segments. The benefits include easy administration, improved security and flexibility.
Explain the principles that underlie the operation of the STP (spanning tree protocol) and the consequences of not using such a protocol.
STP ensures that there is only one logical path between all destinations on the network by intentionally blocking redundant paths that could cause a loop. A port is considered blocked when network traffic is prevented from entering or leaving that port. This does not include bridge protocol data unit (BPDU) frames that are used by STP to prevent loops. Blocking the redundant paths is critical to preventing loops on the network. The physical paths still exist to provide redundancy, but these paths are disabled to prevent the loops from occurring. If the path is ever needed to compensate for a network cable or switch failure, STP recalculates the paths and unblocks the necessary ports to allow the redundant path to become active.
