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diff --git a/assignments/1/README.md b/assignments/1/README.md index 0ee9636..6314e48 100644 --- a/assignments/1/README.md +++ b/assignments/1/README.md @@ -1,6 +1,6 @@ --- title: "COMP-347: Computer Networks" -author: "munir khan - 3431709" +author: "Munir Khan (ID: 3431709)" date: "September 2025" subtitle: "Assignment 1" institute: "Athabasca University" @@ -38,6 +38,8 @@ Summary (using hop 7 as last responding hop): - Number of routers observed in the path: at least 7 (later hops did not reply due to filtering) - Note: These RTTs are for the last responding hop (Telus backbone node). The destination and later hops likely rate-limit or drop probes; this is common. +Reference: Kurose & Ross, 8th ed., Ch. 1 (tools and measurement; traceroute concepts), Sec. 6.7 (example path behavior). + Full traceroute outputs Run 1 @@ -187,6 +189,8 @@ traceroute to www.athabascau.ca (3.175.64.80), 30 hops max, 60 byte packets | 2 | Link | Node-to-node delivery on a link (Ethernet, Wi-Fi) | | 1 | Physical | Bits on the wire/air (signals over copper, fiber, radio) | +Reference: Kurose & Ross, 8th ed., Ch. 1 (Internet structure and protocol stack overview). + ## 1.3 Packet-Switched vs Circuit-Switched Networks (5%) > (5%) What are packet-switched network and circuit-switched network, respectively? Develop a table to summarise their features, pros, and cons. @@ -206,6 +210,8 @@ traceroute to www.athabascau.ca (3.175.64.80), 30 hops max, 60 byte packets | Performance | Variable delay and jitter possible | Predictable, consistent latency | | Examples | Internet, Ethernet | PSTN, leased lines | +Reference: Kurose & Ross, 8th ed., Sec. 1.3 (circuit vs packet switching). + ## 1.4 Network Delays and Traffic Intensity (5%) > (5%) What are processing delay, queuing delay, transmission delay, and propagation delay, respectively? Where does each delay occur? What is traffic intensity? Why should the traffic intensity be no greater than one (1) when designing a computer network? @@ -216,6 +222,8 @@ traceroute to www.athabascau.ca (3.175.64.80), 30 hops max, 60 byte packets - Propagation delay: Time for signal to travel = distance/speed (on the medium) - Traffic intensity: rho = L a / R. Design requires rho <= 1 (preferably well below) so queues do not grow without bound. +Reference: Kurose & Ross, 8th ed., Sec. 1.4 (delays in packet switching and traffic intensity). + ## 1.5 Web Caching and Conditional GET (5%) > (5%) What is Web-caching? When may Web-caching be more useful in a university? What problem does the conditional GET in HTTP aim to solve? @@ -224,6 +232,8 @@ traceroute to www.athabascau.ca (3.175.64.80), 30 hops max, 60 byte packets - More useful at a university because many users request the same resources, raising cache hit rate and lowering Internet link load. - Conditional GET (If-Modified-Since or If-None-Match) lets caches validate freshness without re-downloading unchanged objects (304 Not Modified vs 200 OK). +Reference: Kurose & Ross, 8th ed., Sec. 2.2 (HTTP, Web caching, conditional GET). + ## 1.6 Email Protocol Analysis (5%) > (5%) Suppose you have a Web-based email account, such as Gmail, and you have just sent a message to a friend, Alice, who accesses her mail from her mail server using IMAP. Assume that both you and Alice are using a smartphone to access emails via Wi-Fi at home. List all the network protocols that may be involved in sending and receiving the email. Discuss in detail how the message went from your smartphone to Alice's smartphone - that is, how the message went through all the network protocol layers on each of the network devices involved in the communication. Ignore everything between your ISP and Alice's ISP. @@ -241,6 +251,8 @@ How the message flows: - Gmail to Alice's server: DNS lookup of MX, then SMTP over TCP to deliver message - Alice's phone to her server: IMAP over TCP/993 via her Wi-Fi/router/ISP; server returns the new message; her app displays it +Reference: Kurose & Ross, 8th ed., Sec. 2.2 (HTTP/HTTPS basics), Sec. 2.3 (Electronic mail: SMTP, IMAP/POP), Sec. 2.5 (DNS). + # Part 2: Long Answer Questions (70%) I provide short, clear answers first, then 1-2 sentences of reasoning. @@ -292,6 +304,8 @@ e) Time when the last packet arrives at the server Method note on traceroute filtering - Many networks de-prioritize or block ICMP/UDP TTL-expired replies. This can hide intermediate and destination hops even when the path is fine. Using TCP to port 443 often elicits more replies, but the assignment requires traceroute; therefore I report the last responding hop and include the full outputs for verification. +Reference: Kurose & Ross, 8th ed., Ch. 1 (delays, throughput, store-and-forward; traceroute context). + ## 2.2 Propagation Delay and Bandwidth-Delay Product (20%) > (20%) Consider that you are submitting another assignment from your home computer to the university server, and you have worked out a list of network links between your computer and the university server. @@ -320,6 +334,8 @@ d) Max bits in links at any time (continuous send) e) What the product implies - Answer: Minimum in-flight/window size of ~3.9 Mb to fully use the path at ~430 Mb/s across a 9 ms one-way path; sets buffer/window requirements. +Reference: Kurose & Ross, 8th ed., Sec. 1.4 (propagation delay) and Ch. 3 (BDP intuition via TCP throughput/window sizing). + ## 2.3 Web Cache Implementation and Performance (20%) > (20%) You have learned that a Web cache can be useful in some cases. In this problem, you will investigate how useful a Web cache can be at a home. First, you need to download Apache server and install and run it as a proxy server on a computer on your home network. Then, write a brief report on what you did to make it work and how you are using it on all your devices on your home network. @@ -346,6 +362,8 @@ Answers with measured average R: - c) beta = 1.763 / (1 - 0.088) ~ 1.763 / 0.912 ~ 1.932 s - d) Total average response time with miss rate 0.5: 0.5 x (5 + 1.932) + 0.5 x (approx 0) ~ 3.466 s +Reference: Kurose & Ross, 8th ed., Sec. 2.2 (Web caching), Sec. 1.4 (M/M/1 intuition for access delay). + ## 2.4 File Distribution: Client-Server vs P2P (10%) > (10%) You have learned that a file can be distributed to peers in either client-server mode or peer-to-peer (P2P) mode. Consider distributing a large file of F = 21 GB to N peers. The server has an upload rate of Us = 1 Gbps, and each peer has a download rate of Di = 20 Mbps and an upload rate of U. For N = 10, 100, and 1,000 and U = 300 Kbps, 7000 Kbps, and 2 Mbps, develop a table giving the minimum distribution time for each of the combination of N and U for both client-server distribution and P2P distribution. Comment on the features of client-server distribution and P2P distribution and the differences between the two. @@ -370,6 +388,11 @@ Takeaways: - Client-server grows linearly with N; the server is the bottleneck. - P2P scales with total peer upload (N x U). With enough peer upload, P2P is much faster and often bounded by each peer’s 20 Mb/s download (8,400 s minimum). +Reference: Kurose & Ross, 8th ed., Sec. 2.6 (P2P file distribution model and formulas). + # References -Kurose, J. F., and Ross, K. W. Computer Networking: A Top-Down Approach (8th ed.). Pearson. +- Kurose, J. F., and Ross, K. W. Computer Networking: A Top-Down Approach (8th ed.). Pearson. + - Ch. 1 The Internet and the Network Edge (delays, switching, traceroute) + - Ch. 2 Application Layer (HTTP/caching, E-mail/SMTP/IMAP, DNS, P2P distribution) + - Ch. 3 Transport Layer (BDP intuition via TCP window/throughput) |