M1: Computer Network (Network Transmission Mode and Network Latency)

Computer Network Network Transmission Mode and Network Latency) (ET: 1.5 Hours)

Video Tutorial: Network Transmission Mode and Network Latency

Transmission Mode and Network Performance

- 1
  Transmission Modes
  Transmission Mode refers to the way data is transmitted from one device to another. There are three main types: Simplex, Half-Duplex and Full-Duplex.
  1. Simplex: Communication occurs in only one direction. A device can either send or receive data, but cannot do both. Examples: Keyboard, Monitor, Radio and Television.
  2. Half-Duplex: Communication occurs in both directions, but not at the same time. One device sends while the other receives, and then they can switch roles. Example: Walkie-Talkie.
  3. Full-Duplex: Communication occurs in both directions simultaneously. Devices can send and receive data at the same time. Examples: Telephone/Mobile Communication and Ethernet connections.
  Remember: Simplex = One-Way, Half-Duplex = Two-Way but One at a Time, Full-Duplex = Two-Way at the Same Time.
  
  Transmission Mode হলো একটি Device থেকে অন্য Device-এ Data কীভাবে Transmit হয় তার পদ্ধতি। Transmission Mode প্রধানত তিন ধরনের: Simplex, Half-Duplex এবং Full-Duplex।
  ১. Simplex: Communication শুধুমাত্র একদিকে হয়। একটি Device হয় Data Send করতে পারে অথবা Receive করতে পারে, কিন্তু একই সাথে উভয়টি করতে পারে না। উদাহরণ: Keyboard, Monitor, Radio ও Television।
  ২. Half-Duplex: Communication উভয় দিকে হতে পারে, তবে একই সময়ে নয়। এক Device Data Send করার সময় অন্যটি Receive করে এবং পরে তারা ভূমিকা পরিবর্তন করতে পারে। উদাহরণ: Walkie-Talkie।
  ৩. Full-Duplex: Communication একই সময়ে উভয় দিকে হতে পারে। অর্থাৎ Device একই সময়ে Data Send এবং Receive করতে পারে। উদাহরণ: Telephone/Mobile Communication ও Ethernet Connection।
  মনে রাখুন: Simplex = One-Way, Half-Duplex = Two-Way but One at a Time, Full-Duplex = Two-Way at the Same Time।
- 2
  Network Performancce
  Network Performance refers to how efficiently and effectively a computer network can transmit data from one point to another. It is an important aspect of networking because it determines how fast, reliably, and efficiently data can be communicated.
  Network performance is mainly measured using three fundamental factors: Bandwidth, Throughput, and Latency (Delay).
  1. Bandwidth: Bandwidth is the maximum amount of data that a network link can transmit in a given period of time. It represents the capacity of a network. For example, a link with a bandwidth of 1 Gbps has the capacity to transmit up to 1 gigabit of data per second under ideal conditions. In digital communication, bandwidth is commonly expressed in bits per second (bps).
  2. Throughput: Throughput is the actual amount of data successfully transmitted through a network in a given period of time. It represents the real performance of the network. Throughput is usually lower than the available bandwidth because of congestion, protocol overhead, device limitations, and other network conditions. For example, a link may have a bandwidth of 1 Mbps, but its actual throughput may be only 200 Kbps.
  3. Latency (Delay): Latency is the amount of time required for data to travel from the source to the destination. Lower latency means faster communication. Total network latency consists mainly of four components: Transmission Delay, Propagation Delay, Queuing Delay, and Processing Delay.
  In short: Bandwidth = Capacity, Throughput = Actual Data Transfer Rate, and Latency = Time Taken for Data to Reach the Destination.
  
  Network Performance বলতে একটি Computer Network কতটা দক্ষতার সাথে এবং কার্যকরভাবে এক স্থান থেকে অন্য স্থানে Data Transmit করতে পারে তাকে বোঝায়। Network কত দ্রুত, নির্ভরযোগ্য এবং কার্যকরভাবে Data Communication করতে পারে তা Network Performance-এর মাধ্যমে বোঝা যায়।
  Network Performance প্রধানত তিনটি গুরুত্বপূর্ণ বিষয়ের মাধ্যমে পরিমাপ করা হয়: Bandwidth, Throughput এবং Latency (Delay)।
  ১. Bandwidth: Bandwidth হলো একটি নির্দিষ্ট সময়ে Network Link সর্বোচ্চ কত পরিমাণ Data Transmit করতে পারে। এটি Network-এর Capacity নির্দেশ করে। যেমন, কোনো Link-এর Bandwidth যদি 1 Gbps হয়, তাহলে আদর্শ অবস্থায় এটি প্রতি সেকেন্ডে সর্বোচ্চ 1 Gigabit Data Transmit করতে পারে। Digital Communication-এ Bandwidth সাধারণত Bits per Second (bps)-এ প্রকাশ করা হয়।
  ২. Throughput: Throughput হলো নির্দিষ্ট সময়ে Network-এর মাধ্যমে বাস্তবে কত পরিমাণ Data সফলভাবে Transmit হয়েছে। এটি Network-এর Actual Performance নির্দেশ করে। Network Congestion, Protocol Overhead, Device Limitation এবং অন্যান্য কারণে Throughput সাধারণত Available Bandwidth-এর চেয়ে কম হয়। যেমন, কোনো Link-এর Bandwidth 1 Mbps হলেও এর Actual Throughput মাত্র 200 Kbps হতে পারে।
  ৩. Latency (Delay): Latency হলো Source থেকে Destination-এ Data পৌঁছাতে যে সময় লাগে। Latency কম হলে Communication দ্রুত হয়। Network Latency প্রধানত চারটি উপাদানের সমন্বয়ে গঠিত: Transmission Delay, Propagation Delay, Queuing Delay এবং Processing Delay।
  সংক্ষেপে: Bandwidth = Network-এর Capacity, Throughput = Actual Data Transfer Rate এবং Latency = Data Destination-এ পৌঁছাতে প্রয়োজনীয় সময়।
- 3
  A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute, with each frame carrying an average of 1,000 bits. What is the throughput of this network?
  Formula:
  Throughput = (Number of Frames × Average Frame Size) / Time
  Given:
  Number of Frames = 12,000 frames/minute
  Average Frame Size = 1,000 bits
  Time = 60 seconds
  Calculation:
  Throughput = (12,000 × 1,000) / 60
  = 12,000,000 / 60
  = 200,000 bits/second
  Since, 1 Mbps = 1,000,000 bits/second
  Throughput = 200,000 / 1,000,000
  = 0.2 Mbps
  Answer: The throughput of the network is 0.2 Mbps.
- 4
  Latency and Its Components
  Latency, also called Delay, is the total time required for data to travel from the source to the destination. It is an important measure of network performance. Latency consists of four main components: Transmission Delay, Propagation Delay, Queuing Delay, and Processing Delay.
  Latency = Transmission Delay + Propagation Delay + Queuing Delay + Processing Delay
  1. Transmission Delay: Transmission delay is the time required to place the entire data packet onto the transmission medium. It depends on the message size and bandwidth.
  Formula: Transmission Delay = Message Size / Bandwidth
  2. Propagation Delay: Propagation delay is the time required for a bit to travel from the sender to the receiver through the transmission medium. It depends on the distance and propagation speed.
  Formula: Propagation Delay = Distance / Propagation Speed
  3. Queuing Delay: Queuing delay is the time a packet waits in a queue at an intermediate device before it can be processed or transmitted. It is variable and generally increases when the network has heavy traffic or congestion.
  4. Processing Delay: Processing delay is the time required by a network device to examine and process a packet, such as checking its header, detecting errors, and determining where to forward it.
  In short: Transmission Delay depends on message size and bandwidth; Propagation Delay depends on distance and propagation speed; Queuing Delay depends mainly on network traffic; and Processing Delay depends on the processing capability of the network device.
  
  Latency, যাকে Delayও বলা হয়, হলো Source থেকে Destination-এ Data পৌঁছাতে মোট যে সময় প্রয়োজন। এটি Network Performance-এর একটি গুরুত্বপূর্ণ পরিমাপক। Latency প্রধানত চারটি উপাদান নিয়ে গঠিত: Transmission Delay, Propagation Delay, Queuing Delay এবং Processing Delay।
  Latency = Transmission Delay + Propagation Delay + Queuing Delay + Processing Delay
  ১. Transmission Delay: Transmission Delay হলো সম্পূর্ণ Data Packet-কে Transmission Medium-এর উপর স্থাপন বা পাঠাতে যে সময় লাগে। এটি Message Size এবং Bandwidth-এর উপর নির্ভর করে।
  Formula: Transmission Delay = Message Size / Bandwidth
  ২. Propagation Delay: Propagation Delay হলো Transmission Medium-এর মধ্য দিয়ে একটি Bit Source থেকে Destination-এ পৌঁছাতে যে সময় লাগে। এটি Distance এবং Propagation Speed-এর উপর নির্ভর করে।
  Formula: Propagation Delay = Distance / Propagation Speed
  ৩. Queuing Delay: Queuing Delay হলো কোনো Intermediate Device-এর Queue-তে একটি Packet Process বা Transmit হওয়ার আগে যে সময় অপেক্ষা করে। Network-এ Traffic বা Congestion বেশি হলে এই Delay সাধারণত বৃদ্ধি পায়।
  ৪. Processing Delay: Processing Delay হলো কোনো Network Device-এর একটি Packet পরীক্ষা ও Process করতে যে সময় লাগে। যেমন Packet Header পরীক্ষা, Error Detection এবং কোথায় Packet Forward করতে হবে তা নির্ধারণ করা।
  সংক্ষেপে: Transmission Delay নির্ভর করে Message Size ও Bandwidth-এর উপর; Propagation Delay নির্ভর করে Distance ও Propagation Speed-এর উপর; Queuing Delay প্রধানত Network Traffic-এর উপর নির্ভর করে; এবং Processing Delay নির্ভর করে Network Device-এর Processing Capability-এর উপর।
- 5
  What is the propagation time if the distance between the two points is 12,000 km? Assume the propagation speed to be 2.4 x 10⁸m/s in cable.
  Given:
  Distance = 12,000 km = 12 × 10⁶ m
  Propagation Speed = 2.4 × 10⁸ m/s
  Formula:
  Propagation Delay = Distance / Propagation Speed
  Propagation Delay = (12 × 10⁶) / (2.4 × 10⁸)
  Propagation Delay = 0.05 seconds = 50 ms
  Answer: The propagation time is 0.05 seconds (50 milliseconds).
- 6
  Round-Trip Time (RTT)
  Round-Trip Time (RTT) is the total time required for a data packet to travel from the source to the destination and for a response or acknowledgment to return to the source.
  RTT is an important measure of network latency. It is commonly measured in milliseconds (ms). A lower RTT generally indicates faster communication between two devices.
  Formula: RTT = Forward Trip Time + Return Trip Time
  For a symmetric path, RTT is approximately twice the one-way propagation delay, although actual RTT can also include transmission, queuing, and processing delays.
  
  Round-Trip Time (RTT) হলো একটি Data Packet-এর Source থেকে Destination-এ পৌঁছাতে এবং সেখান থেকে Response বা Acknowledgment আবার Source-এ ফিরে আসতে মোট যে সময় লাগে।
  RTT হলো Network Latency পরিমাপের একটি গুরুত্বপূর্ণ উপায়। এটি সাধারণত Milliseconds (ms)-এ পরিমাপ করা হয়। RTT কম হলে সাধারণত দুইটি Device-এর মধ্যে Communication দ্রুত হয়।
  Formula: RTT = Forward Trip Time + Return Trip Time
  যদি Forward এবং Return Path একই ধরনের হয়, তাহলে RTT প্রায় One-Way Propagation Delay-এর দ্বিগুণ হয়। তবে বাস্তবে Transmission, Queuing এবং Processing Delay-ও RTT-এর মধ্যে থাকতে পারে।
- 7
  Bandwidth Delay Product
  Bandwidth-Delay Product (BDP) is the amount of data (in bits) that can be present or “in transit” on a network link at a given time. In other words, it represents the capacity of the link in terms of how many bits can fill the link while data is traveling from the sender to the receiver.
  BDP is calculated by multiplying the Bandwidth of the link by the Propagation Delay.
  Formula:
  BDP = Bandwidth × Delay
  For example, if a network has a bandwidth of 1 Mbps and a delay of 5 seconds, then the BDP is 1 Mbps × 5 seconds = 5 Mb. This means up to 5 megabits of data can be in transit on the link.
  BDP is important in high-speed and long-distance networks because it helps determine how much data can be sent before the first bits reach the destination. A larger bandwidth or longer delay results in a larger BDP.
  
  Bandwidth-Delay Product (BDP) হলো একটি নির্দিষ্ট সময়ে Network Link-এর মধ্যে সর্বোচ্চ কত পরিমাণ Data (Bit) অবস্থান বা In-Transit অবস্থায় থাকতে পারে তার পরিমাণ। অন্যভাবে বলা যায়, এটি Link-এর Capacity নির্দেশ করে।
  BDP নির্ণয় করতে Network-এর Bandwidth এবং Propagation Delay গুণ করা হয়।
  Formula:
  BDP = Bandwidth × Delay
  উদাহরণস্বরূপ, কোনো Network-এর Bandwidth যদি 1 Mbps এবং Delay যদি 5 seconds হয়, তাহলে BDP হবে 1 Mbps × 5 seconds = 5 Mb। অর্থাৎ Link-এ সর্বোচ্চ 5 Megabits Data In-Transit অবস্থায় থাকতে পারে।
  High-Speed এবং Long-Distance Network-এর ক্ষেত্রে BDP গুরুত্বপূর্ণ। কারণ এটি নির্দেশ করে যে প্রথম Data Destination-এ পৌঁছানোর আগেই Link-এ কত পরিমাণ Data পাঠানো যেতে পারে। Bandwidth বা Delay বৃদ্ধি পেলে BDP-ও বৃদ্ধি পায়।
- 8
  If the bandwidth of a channel is 50 Mbps and the Round-Trip Time (RTT) is 30 ms, calculate the Bandwidth-Delay Product (BDP) in bits and KB.
  Formula:
  BDP = Bandwidth × Delay
  Given:
  Bandwidth = 50 Mbps = 50 × 10⁶ bits/s
  RTT = 30 ms = 30 × 10^-3 s
  Calculation:
  BDP = (50 × 10⁶) × (30 × 10^-3)
  = 1,500,000 bits
  Converting bits to bytes:
  1,500,000 ÷ 8 = 187,500 bytes
  Converting bytes to KB:
  187,500 ÷ 1024 ≈ 183.11 KB
  Answer: Bandwidth-Delay Product = 1,500,000 bits ≈ 183.11 KB.

Previous Job Question: Network Transmission Mode and Network Latency

Topic Wise Question Bank

Computer Network

- ☆
  1
  Computer NetworkTransmission Mode and Network Performance
  How many types of modes are used in data transferring through networks? Briefly explain those modes. Differentiate between TCP vs UDP.
  Data transmission mode is a process by which data is sent from a source to one or more destinations. Simply put, it defines how data flows from one device to another. It is also known as Communication Mode.
  Types of Data Transmission Modes
  1. Simplex Mode
  - Communication is one-way only.
  - Data flows in a single direction, meaning one device can only send data while the other can only receive it.
  - No two-way communication.
  Example: Keyboard to Computer, Radio, Television.
```
[Source] ----> [Destination]
```
  2. Half-Duplex Mode
  - Data can flow in both directions, but only one direction at a time.
  - The entire communication channel is used for sending data in one direction at a time.
  - Error detection is possible.
  Example: Walkie-Talkie Communication.
```
[Source] ----> [Destination]
[Source] <---- [Destination]
```
  3. Full-Duplex Mode
  - Data flows in both directions simultaneously.
  - Both devices can send and receive data at the same time.
  - Uses two simplex channels, where one channel sends data in one direction, and the other channel sends data in the opposite direction.
  Example: Mobile Phones, Telephones.
```
[Source] <----> [Destination]
```
- ☆
  2
  Computer NetworkTransmission Mode and Network Performance
  Suppose Bangladesh bank is designing a nation of communication network for office located in Dhaka and Rangpur. Their offices are connected via wide area network (WAN). The team needs to ensure that applications with low latency requirements (such as VOIP and video conferencing) can operate efficiently between these offices.
  Given:
  Distance between Dhaka and Rangpur = 30 km
  Speed of fiber optic link = 2 × 10⁸ m/s
  Link capacity = 1 Gbps
  Average size of data packets = 15,000 bytes
  Delay at each router/switch along the path = 5 ms
  RTT between Dhaka and Rangpur = 50 ms
  
  Calculate the total network latency between office at Dhaka and Rangpur, considering the propagation delay and transmission delay.
  - Distance between Dhaka and Rangpur = 30 km = 30,000 meters
  - Speed of fiber optic link = 2 × 10⁸ m/s
  - Link capacity = 1 Gbps = 1 × 10⁹ bps
  - Average size of data packets = 15,000 bytes = 120,000 bits (15,000 × 8)
  - Delay at each router/switch = 5 ms
  - RTT between Dhaka and Rangpur = 50 ms
  Propagation Delay
  Propagation Delay = Distance / Propagation Speed
  = 30,000 meters / (2 × 10⁸ m/s) = 0.00015 seconds = 0.15 ms
  Transmission Delay
  Transmission Delay = Packet Size (bits) / Link Capacity (bps)
  = 120,000 bits / (1 × 10⁹ bps) = 0.00012 seconds = 0.12 ms
  Router Delay
  There are 1 routers and 1 switch each with 5 ms delay:
  Router Delay = 2 × 5 ms = 10 ms
  Total One-Way Latency
  Total Latency = Propagation Delay + Transmission Delay + Router Delay
  = 0.15 ms + 0.12 ms + 10 ms = 10.27 ms (Answer)
  Round Trip Time (RTT)
  RTT = 2 × One-way latency (since round trip includes going and coming back)
  The given RTT (50 ms) is higher, which suggests additional delays are present such as queuing delay, processing delay, or other network factors not explicitly included in the simple calculation.
  
  🎥 Video Solution: Network Latency Calculation
  
  🎥 Video Solution: Network Delay Types & Round-Trip Time Explained (in Bangla)

Assigment: Network Transmission Mode and Network Latency)

Q1. Transmission Modes

How many types of transmission modes are used in data communication? Explain each type with a suitable example.

Q2. Transmission Delay

A file of size 5 MB is transmitted over a link with a bandwidth of 10 Mbps.a) Calculate the transmission time. b) Convert your answer into milliseconds.

Q3. Propagation Delay

The distance between two routers is 2,000 km, and the propagation speed is 2.5 × 10⁸ m/s.Calculate the propagation delay.

Q4. Network Latency

A data packet experiences the following delays:

Propagation delay = 12 ms
Transmission delay = 4 ms
Queuing delay = 6 ms
Processing delay = 3 ms

Calculate the total network latency.

Q5. Bandwidth-Delay Product

If the bandwidth of a channel is 50 Mbps and the Round-Trip Time (RTT) is 30 ms, calculate the Bandwidth-Delay Product (BDP) in:a) Bits b) KB

Q6. Network Throughput

A network sends a 1,000-byte packet every 10 ms.Calculate the network throughput in Mbps.

Q7. Round-Trip Time (RTT)

A file is sent from one computer to another. The one-way latency is 25 ms.Calculate the Round-Trip Time (RTT).

Q8. Data Transfer Capacity

A system has a bandwidth of 100 Mbps and a transmission delay of 2 ms.Calculate the maximum amount of data that can be transmitted during this time in bytes.

Q9. Jitter

During a video call, the packet delays are recorded as follows:100 ms, 120 ms, 90 ms, 110 ms, 130 msCalculate the average jitter using the average of the absolute differences between successive packet delays.

Q10. Transmission, Propagation & Total Delay

A link has a propagation speed of 3 × 10⁸ m/s and a distance of 3,000 km.If a 1,500-byte packet is transmitted at 100 Mbps, calculate:a) Transmission delay b) Propagation delay c) Total delay

Q11. Total File Transfer Time

You are transferring a file of size 10 MB over a network with:

Bandwidth = 20 Mbps
Propagation delay = 10 ms
Queuing delay = 5 ms

Calculate the total time required to transfer the file, considering transmission, propagation, and queuing delays.

Q12. Network Throughput

A network has a bandwidth of 10 Mbps and can transmit an average of 12,000 frames per minute, where each frame carries an average of 1,000 bits.Calculate the actual throughput of the network in Mbps.

Q13. Propagation Time

What is the propagation time if the distance between two points is 12,000 km? Assume the propagation speed is 2.4 × 10⁸ m/s in the cable.

Q14. Bandwidth-Delay Product

A communication channel has a bandwidth of 100 Mbps and an RTT of 40 ms.Calculate:a) Bandwidth-Delay Product in bits b) BDP in bytes c) BDP in KB

Q15. Network Latency Analysis

Two offices of Bangladesh Bank are connected through a WAN. The distance between Dhaka and Rangpur is 300 km. The fiber-optic propagation speed is 2 × 10⁸ m/s, and the link capacity is 1 Gbps. The average packet size is 15,000 bytes. There are 2 routers along the path, and each router introduces 5 ms of processing delay. The measured RTT between the two offices is 50 ms.Calculate:a) One-way propagation delay b) Transmission delay for one packet c) Total processing delay d) Estimated one-way network latency considering propagation, transmission, and processing delays e) Explain how latency can affect VoIP and video conferencing performance.

Data Transmission Mode and Network Performance 52 questions