←Back to Subject
Notes
Notes
Study material and explanations
Diagrams
Diagrams
Visualize concepts easily
Mnemonics
Mnemonics
Tricks to remember faster
One Night Prep
One Night Prep
Short and focused revision
Revision
Revision
Quick summary and key points
Important Questions
Important Questions
Practice most relevant questions
Notes

Channel Allocation Problem & Terminal Handling Architecture

Study material and explanations for Unit 3

Channel Allocation Problem and Terminal Handling in Networks

When multiple computers share a single common communication wire or radio frequency, a critical question arises: How do we decide which computer gets to transmit right now?

This fundamental challenge is called the Channel Allocation Problem.

1. Static Channel Allocation (FDM & TDM)

In Static Channel Allocation, the total channel capacity is divided into fixed slices (frequency bands or time slots) and assigned permanently to each user:

  • How it Works: If there are N users, the bandwidth is split into N equal portions (e.g., using FDM).
  • The Major Problem (Burstiness of Data): Computer data is bursty—a student types for 5 seconds, then reads for 2 minutes. During those 2 minutes of reading, their allocated channel sits completely empty and wasted, while other students waiting to download files suffer long delays!
  • Conclusion: Static allocation works fine for traditional voice calls, but is terribly inefficient for computer data networks.

2. Dynamic Channel Allocation (On-Demand)

In Dynamic Channel Allocation, the channel is not assigned permanently to anyone. Time slots or bandwidth are allocated dynamically on-demand only when a station actually has data to send!

5 Key Assumptions of Dynamic Channel Allocation
1. Station Model
N independent computers generate frames at random times
2. Single Channel
One shared wire or radio frequency for all transmissions
3. Collision Event
If two machines send at the same time, signals collide and garble
4. Continuous / Slotted Time
Transmissions can begin anytime or only at discrete clock ticks
5. Carrier Sensing
Stations can listen to the wire before talking to avoid collisions

3. Terminal Handling in Networks

In traditional computing, “dumb terminals” (screens with keyboards but no CPU) connected to a central mainframe computer.

  • Character-Mode Terminals: Every single keystroke typed was immediately sent across the network to the server. Highly inefficient.
  • Block-Mode Terminals: The user fills in an entire on-screen form locally; pressing the “Submit” key sends the entire block of data across the network in one efficient packet.

💡 DAVV Exam Tip

Question (5 Marks): “Explain the Channel Allocation Problem in computer networks. Differentiate between Static and Dynamic allocation.”

  • Explain why static allocation (FDM/TDM) wastes bandwidth due to the bursty nature of computer traffic.
  • List the 5 assumptions of Dynamic Channel Allocation.