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diff --git a/assignments/1/README.md b/assignments/1/README.md index 4bb2501..ab0c6a9 100644 --- a/assignments/1/README.md +++ b/assignments/1/README.md @@ -178,7 +178,7 @@ Key Findings: > What are the five layers in the Internet protocol stack? Develop a table to summarise what each layer does. -The Internet protocol stack consists of five layers, each with specific responsibilities: +The Internet protocol stack consists of five layers, each with specific responsibilities (Kurose & Ross, 2021, Section 1.5): | Layer | Name | Function | | ------ | ------------- | ----------------------------------------------------------------------- | @@ -207,14 +207,15 @@ are independently routed through the network. Each packet contains destination information, headers, and a portion of the original message. Packets can take different paths to reach the destination and are reassembled at the receiver. The network resources are -shared among multiple users through statistical multiplexing. +shared among multiple users through statistical multiplexing +(Kurose & Ross, 2021, Section 1.3.1). Circuit-switched network: A dedicated communication path (circuit) is established between sender and receiver before any data transmission begins. This circuit reserves network resources for the entire duration of the communication session, providing a guaranteed path with fixed bandwidth. The circuit must be torn down when communication -is complete. +is complete (Kurose & Ross, 2021, Section 1.3.2). | Aspect | Packet-Switched | Circuit-Switched | | ------ | ------ | ------- | @@ -257,6 +258,8 @@ is complete. ### Four Types of Network Delays +The following four types of delays occur in packet-switched networks (Kurose & Ross, 2021, Section 1.4.1): + 1. Processing Delay (`d_proc`): - Definition: Time required for a router to examine the packet header and determine where to direct the packet - Where it occurs: At routers and switches when they process packet headers @@ -276,7 +279,7 @@ is complete. ### Traffic Intensity -Definition: Traffic intensity `(ρ) = La/R`, where: +Definition: Traffic intensity `(ρ) = La/R` (Kurose & Ross, 2021, Section 1.4.2), where: - `L` = average packet length (bits) - `a` = average packet arrival rate (packets/sec) @@ -305,7 +308,7 @@ A safety margin (typically `ρ ≤ 0.7-0.8`) is often used to account for traffi ### What is Web Caching? -Web caching is a technique where frequently requested web content (HTML pages, images, videos, etc.) is stored temporarily in locations closer to users than the origin server. When a user requests cached content, it can be served from the cache instead of fetching it from the distant origin server, reducing response time and network traffic. +Web caching is a technique where frequently requested web content (HTML pages, images, videos, etc.) is stored temporarily in locations closer to users than the origin server (Kurose & Ross, 2021, Section 2.2.5). When a user requests cached content, it can be served from the cache instead of fetching it from the distant origin server, reducing response time and network traffic. Components: @@ -334,7 +337,7 @@ Web caching is particularly useful in university environments due to: Problem Addressed: -The conditional GET mechanism solves the problem of cache consistency - ensuring that cached content is up-to-date without unnecessarily downloading unchanged content. +The conditional GET mechanism solves the problem of cache consistency - ensuring that cached content is up-to-date without unnecessarily downloading unchanged content (Kurose & Ross, 2021, Section 2.2.6). How it works: @@ -365,7 +368,7 @@ Benefits: > the communication. Ignore everything between your ISP and Alice's > ISP. -Scenario: Web-based email (Gmail) sent to Alice who accesses email via IMAP on smartphone over Wi-Fi. +Scenario: Web-based email (Gmail) sent to Alice who accesses email via IMAP on smartphone over Wi-Fi (Kurose & Ross, 2021, Section 2.3). ### Network Protocols Involved @@ -573,7 +576,7 @@ This represents the "capacity" of the network pipe - the total number of bits th ### e) Bandwidth-delay product implications -The bandwidth-delay product represents the network pipe capacity and has several important implications: +The bandwidth-delay product represents the network pipe capacity and has several important implications (Kurose & Ross, 2021, Section 1.4.3): 1. Buffer Requirements: - Minimum buffer size needed for optimal performance @@ -593,7 +596,7 @@ The bandwidth-delay product represents the network pipe capacity and has several ## 2.3 Web Cache Implementation and Performance (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. +> 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. > Assume your family has six members. Each member likes to download short videos from the Internet to watch on their personal devices. All these devices are connected to the Internet through Wi-Fi. Further assume the average object size of each short video is 100 MB and the average request rate from all devices to servers on the Internet is three requests per minute. Five seconds is the average amount of time it takes for the router on the ISP side of your Internet link to forward an HTTP request to a server on the Internet and receive a response. > > * What is the average time α for your home router to receive a video object from your ISP router? @@ -732,7 +735,7 @@ Key insight: Even a modest 50% cache hit rate transforms an unstable system into ## 2.4 File Distribution Comparison (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. +> You have learned that a file can be distributed to peers in either client–server mode or peer-to-peer (P2P) mode (Kurose & Ross, 2021, Section 2.5). 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. Given parameters: |