network models data link control error detection and multiple access short notes

Topic Summary: ARP and Addressing Cheat Sheet

Flow Control Cheat Sheet

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Quick Reference: CRC and Hamming

Quick Reference: CRC and Hamming CRC Divisor: Degree r polynomial \to (r + 1) -bit divisor. Remainder is exactly r bits. CRC Arithmetic: XOR subtraction only (no borrows). Hamming Positions: Check bits at 1, 2, 4, 8, \dots . Data at 3, 5, 6, 7, 9, \dots . Hamming Syndrome: S = Recalculated Parities . Decimal value of S = exact error position. Error-Free Probability: (1 - p)^{n} for n independent bits with flip probability p .

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Network Models, Data Link Control, Error Detection and Multiple Access Short Notes for GATE CS

Network Models, Data Link Control, Error Detection and Multiple Access short notes for GATE CS: 4 study cards covering concepts, formulas, shortcuts and exam traps, plus solved practice questions.

Topic Summary: ARP and Addressing Cheat Sheet

Summary

Topic Summary: ARP and Addressing Cheat Sheet

1. ARP Mechanics

Purpose: Resolve IPv4 Address $\to$ MAC Address.
Request: Broadcast (FF:FF:FF:FF:FF:FF).
Reply: Unicast (To Requester's MAC).
Scope: Local LAN only (Routers block ARP).

2. Packet Traversal

IP Addresses: Constant (Source $\to$ Destination).
MAC Addresses: Change at every Hop (Source $\to$ Next Hop).

3. TCP Behavior

Piggybacking: Allowed. A segment can carry Data + ACK simultaneously.

4. OSI Layers

Network: Routing, Logical Addressing (IP).
Data Link: Framing, Physical Addressing (MAC), Error Detection.
Transport: End-to-End Reliability (TCP).

Flow Control Cheat Sheet

Summary

Quick Revision: Flow Control Formulas

Concept	Formula / Rule
Transmission Time ( $T_{t}$ )	$T_{t} = \frac{Frame Size (bits)}{Bandwidth (bps)}$
Propagation Delay ( $T_{p}$ )	$T_{p} = \frac{Distance}{Velocity}$
Ratio 'a'	$a = \frac{T _{p}}{T _{t}}$
Stop-and-Wait $U$	$U = \frac{1}{1 + 2 a}$
Sliding-Window $U$	$U = min (1, \frac{W}{1 + 2 a})$
Min Window for 100% $U$	$W_{min} = ⌈ 1 + 2 a ⌉$
Sequence Number Bits	$n = ⌈ lo g_{2} (W)⌉$ (Stop-and-Wait always needs 1 bit)

Quick Reference: CRC and Hamming

CRC Divisor: Degree $r$ polynomial $\to$ $(r + 1)$ -bit divisor. Remainder is exactly $r$ bits.
CRC Arithmetic: XOR subtraction only (no borrows).
Hamming Positions: Check bits at $1, 2, 4, 8, \dots$ . Data at $3, 5, 6, 7, 9, \dots$ .
Hamming Syndrome: $S = Recalculated Parities$ . Decimal value of $S$ = exact error position.
Error-Free Probability: $(1 - p)^{n}$ for $n$ independent bits with flip probability $p$ .

Quick Reference: Collision and Throughput

Pure ALOHA Throughput: $S = G e^{- 2 G}$ (Max $S \approx 0.184$ at $G = 1$ )
Slotted ALOHA Throughput: $S = G e^{- G}$ (Max $S \approx 0.368$ at $G = 1$ )
Normalized Load: $G = λ \times T_{f r}$
CSMA/CD Condition: $T_{t} \geq 2 \times T_{p}$
Minimum Frame Size: $L_{min} = B \times 2 \times (\frac{d}{v})$
Collision Window: The time interval $[0, 2 \times T_{p}]$ during which a collision can be detected by the sender.

network models data link control error detection and multiple access short notes

Topic Summary: ARP and Addressing Cheat Sheet

Topic Summary: ARP and Addressing Cheat Sheet

1. ARP Mechanics

2. Packet Traversal

3. TCP Behavior

4. OSI Layers

Flow Control Cheat Sheet

Quick Revision: Flow Control Formulas

Quick Reference: CRC and Hamming

Quick Reference: CRC and Hamming

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Network Models, Data Link Control, Error Detection and Multiple Access Short Notes for GATE CS

Topic Summary: ARP and Addressing Cheat Sheet

Topic Summary: ARP and Addressing Cheat Sheet

1. ARP Mechanics

2. Packet Traversal

3. TCP Behavior

4. OSI Layers

Flow Control Cheat Sheet

Quick Revision: Flow Control Formulas

Quick Reference: CRC and Hamming

Quick Reference: CRC and Hamming

Quick Reference: Collision and Throughput

Quick Reference: Collision and Throughput

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