Week 39: Link Layer
This was a fairly difficult week as we get closer to the end of this course. This week we had our final which was definitely hard, but the final project has been harder mainly because I never got around to resolving issues in the chat app. As for the reading material, this weeks content focused on the Link layer.
My main takeaways for Link Layer are:
- Link layer provides services such as framing, link access, and reliable delivery between adjacent nodes, flow control, error detection, error correction, and half/full duplex transmission.
- The link layer is implemented in a combination of hardware and software.
- Some techniques used for error detection and correction are: Parity checking(single or 2d), internet checksum, CRC(cyclic redundancy check.
- there are two types on links used: Point to point or broadcast
- Multiple access protocols utilize distributed algorithm to determine how nodes share channels and when nodes can transmit
Multiple access: - TDMA :time division multiple access - access to channel in rounds, fixed length slot
- FDMA: Frequency division multiple access - channel spectrum divided into bands (This is how ISP and cable providers send TV and internet over coax)
Random access protocols: - Slotted ALOHA,
- CSMA: Carrier sense multiple access - listen before transmitting
- CSMA/CD: Carrier sensing collisions are detected within short time colliding transmissions are aborted.