ISE 218: Fundamentals Of Information Technology Stony Brook

ISE 218: Fundamentals of Information Technology Stony Brook University Homework #8 Fall 2017

Neatly write or type your answers to the following problems on a separate sheet of paper and submit a hard copy at the start of lecture on the due date. For any problems involving mathematical calculations, you must show all work to receive full credit. Please clearly print or type your full name and Stony Brook ID # on your paper. Submissions that are not stapled will be docked 5 points.

Paper For Above instruction

This paper addresses a series of questions related to fundamental concepts of networking and internet protocols covered in ISE 218 at Stony Brook University. The focus is on understanding the differences between network and transport layer protocols, classifying IP addresses, calculating data transmission sequences, implications of protocol negotiations, and understanding network addressing capacities.

1. Difference Between Network Layer Protocol and Transport Layer Protocol

The Network Layer and Transport Layer are two fundamental components of the OSI and TCP/IP models responsible for different aspects of data communication. The network layer (Layer 3) primarily handles the routing and delivery of packets across different networks. Its main functions include addressing, routing algorithms, and packet forwarding, which ensure that data packets are directed from the source to the destination across multiple networks. Protocols such as Internet Protocol (IP), ICMP, and others operate at this layer. They are responsible for logical addressing (IP addresses), fragmentation, and best path determination.

In contrast, the Transport Layer (Layer 4) is responsible for providing end-to-end communication services for applications. It establishes, manages, and terminates connections between hosts and ensures complete data transfer. Transport layer protocols such as TCP and UDP facilitate reliable or unreliable data delivery, respectively. TCP provides error checking, flow control, sequencing, and acknowledgment features, ensuring data integrity and ordered delivery. UDP, being connectionless, offers minimal overhead but does not guarantee delivery or ordering.

In essence, the network layer focuses on the "where" and "how" of packet delivery across networks, while the transport layer deals with "how much" and "when" data is transferred between applications. The network layer routes packets based on addresses, whereas the transport layer manages data integrity and session control for applications.

2. Classification of IP Addresses

Classifying IP addresses involves analyzing the leading bits of the IP address to determine its class. The classes include A, B, C, D (multicast), and E (experimental). The key ranges for IPv4 classes are:

  • Class A: 1.0.0.0 to 126.255.255.255 (leading bits 0)
  • Class B: 128.0.0.0 to 191.255.255.255 (leading bits 10)
  • Class C: 192.0.0.0 to 223.255.255.255 (leading bits 110)
  • Class D: 224.0.0.0 to 239.255.255.255 (leading bits 1110)
  • Class E: 240.0.0.0 to 255.255.255.255 (leading bits 1111)

Given IP addresses:

  1. a. 223.52.176.62 — This address starts with 223, which falls in the range 192.0.0.0 to 223.255.255.255, indicating it is a Class C address.
  2. b. 127.255.255.2 — The 127.0.0.0 to 127.255.255.255 range is reserved for loopback addresses, which are used for internal testing within a host. Therefore, this IP address belongs to Class A, specifically a loopback address.
  3. c. 191.57.229. — This address begins with 191, which places it within 128.0.0.0 to 191.255.255.255, classifying it as a Class B address.

3. TCP/IP File Transfer Data Sequence Calculations

In this scenario, a file of 10 KB (10,240 bytes), with a payload size of 100 bytes per TCP segment, and a window size of 2000 bytes, is being transferred. The sender receives an acknowledgment for byte 900. We analyze what happens next in terms of data transmission.

a. Which bytes will be sent next?

Initial sequence: The sender's sequence number starts at byte 0. After receiving an ACK for byte 900, the sender assumes that all bytes up to byte 900 are received successfully. The sender can now transmit the remaining data starting from byte 901. Given the payload size of 100 bytes, the next segment will contain bytes 901 to 1000, provided that the window size allows.

Since the window size is 2000 bytes, and the last acknowledged byte is 900, the sender can transmit data starting from byte 901 up to byte 900 + 2000 = 2901, provided that all previous data has been acknowledged. The next segment will likely contain bytes 901 to 1000, as this falls within the window.

b. What is the last byte number that can be sent without an ACK being sent by the receiver?

The last byte that can be sent without waiting for an ACK is byte 900 (the last one acknowledged) plus the window size of 2000 bytes, which is byte 2900. Therefore, the sender can transmit bytes 901 through 2900 without further acknowledgment.

4. Problems Without Negotiated Timeout Windows in TCP

TCP relies on adaptive timeout mechanisms to determine how long the sender should wait for an acknowledgment before retransmitting data. If TCP did not allow negotiation or dynamic adjustment of timeout windows, several issues could arise:

  • Increased Packet Loss: Fixed timeouts may be too short or too long. If set too short, the sender may prematurely retransmit packets, leading to unnecessary retransmissions and network congestion. If too long, the sender may wait excessively before resending lost packets, degrading performance.
  • Reduced Efficiency: Lack of negotiation impairs TCP's ability to adapt to varying network conditions, such as delays, congestion, or jitter, which vary over time and across different network paths.
  • Increased Congestion and Inefficiency: Static timeout periods can lead to congestion collapse if the sender retransmits too frequently when the network is congested or does not recover quickly from packet loss.
  • Poor Reliability: Without proper timeout negotiation, TCP cannot balance retransmission timing optimally, risking data loss or delays.

Adaptive timeout negotiation enables TCP to dynamically adjust retransmission timers based on round-trip time measurements, leading to improved efficiency and reliability in data transfer.

5. Maximum Number of Hosts in a Class B Network (IPv4)

Class B addresses allocate 16 bits for host addresses within the network portion of the address. The total number of hosts they can support is 2^16 – 2, since the all-zeros address (network identifier) and all-ones address (broadcast) are reserved for special functions.

Therefore, maximum hosts = 65,536 – 2 = 65,534 hosts per Class B network.

6. Maximum Number of Class B Networks (IPv4)

The class B address space uses the first two octets for network identification, with 14 bits remaining for network addresses (excluding the reserved bits). The total number of Class B networks is 2^14, minus the reserved network addresses.

Total Class B networks = 16,384.

Conclusion

The relationships between network protocols, IP address classes, and network capacities form the foundational knowledge for understanding how the internet and intranet networks operate. Recognizing the differences between layers of protocols enables better comprehension of data transfer mechanisms. Calculating data sequences, understanding protocol negotiations, and grasping addressing limits are essential skills for networking professionals, contributing to more effective network design, troubleshooting, and management.

References

  • Comer, D. E. (2018). "Internetworking with TCP/IP: Principles, Protocols, and Architecture" (6th Edition). Pearson.
  • Stallings, W. (2017). "Data and Computer Communications" (10th Edition). Pearson.
  • Kurose, J., & Ross, K. (2017). "Computer Networking: A Top-Down Approach" (7th Edition). Pearson.
  • Postel, J. (1981). RFC 791: Internet Protocol. IETF.
  • Harrison, W. (2015). Understanding TCP/IP. Network World.
  • Valencia, M. (2016). IP Address Classes and Subnetting. TechTarget.
  • Shin, H. (2020). TCP congestion control mechanisms. IEEE Communications Surveys & Tutorials.
  • Tanenbaum, A. S., & Wetherall, D. J. (2011). Computer Networks (5th Edition). Pearson.
  • Odom, W. (2019). CCNA 200-301 Official Cert Guide. Cisco Press.
  • RFC 2131: DHCP. (1997). IETF.

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