Today, I learned about the MAC protocol. Where is the link layer implemented? At each interface of hosts, routers, switches, access points Link layer implemented mainly in "adoptor" (aka network interface card NIC) or on a chip. e.g. Ethernet card (LAN), 802.11 card (WLAN) NIC implements link layer and physical layer Link layer is implemented in both NIC (hardware) Operating System (software) Fr..
Today, I learned about the "Cookies." A web application consists of a series of disconnected HTTP requests to a web server. In HTTP, we can pass information using: Query Strings (URL, header) Hidden Form Fields Use Query Strings to Save State Information Seperate individual name = value pairs within the query string using Ap question mark (?) and a query string are automatically appended to the ..
Today, I learned that how to work PHP with SQL. This is the algorithms: Connect to the database. Handle connection errors. Execute the SQL query. Process the results. Free resources and close connection. PDO: PHP data Objects $connectionString = "mysql:host=localhost; dbname=bookcrm"; $user = "testuser"; $pass = "mypassword"; $pdo = new PDO($connectionString, $user, $pass); Normal MySQL: $host =..
Today, I learned more about the TCP. There are two type of message in TCP: Seq# Byte stream "number" of first byte in segment's data Ack# Seq # of next byte expected from other side So, the packet which is not acknowledged yet is yellow packets. Buffer moves to the next sequence of packets. RTT: Round Trip Time RTT is the length of time it takes for a message to be sent plus the length of time i..
Today, I solved the Merge K sorted Lists. Description: In this question, we are gonna merge several lists. And, the merged list should be sorted in order. Solution: This is the first part of solution. We will look into mergeLists() function later. If the gived lists are empty, we return None. While loop runs until the length of lists is over 1. We make the list for storing merged lists. Since we..
Today, I did the question: Linked List Cycle. Description: We should check whether cycle exist or not. head and pos is given. We can check the pos that which position is cycled back on the list. In example 1, 1st node is the returning node on the list. Then, how do we check the cycle on the list? The solution is similar to previous linked list question: We are gonna make the slow and fast pointe..
Today, I learned about the TCP. These are the features of TCP. Point-to Point (not Bcast) Single sender, single receiver. Routers don't know TCP con. Reliable, in-order byte stream no "message boundaries" Pipelined TCP congestion and flow control set window size TCP connection state Send and receive buffer Congestion ctrl parameters Sequence number, ACK number for reliability Full duplex data Bi..
Today, I learned SQL. SQL: A table is the principal unit of storage in database. It is a two-dimensional container for data that consists of records (rows); each record has the same number of columns. These columns are called fields, which contain the actual data. Each table will have a primary key -- a field (or sometimes combination of fields) that is used to uniquely identify each record in a..
Today, I learned about the TCP/UDP model. First, I would like talk about the UDP. Before talking about the UDP, I want to reviewed the daily network strucutre! This is how our network form using TCP model. In the chat room project, I learned that most interactive software program use the TCP! Then, what is UDP? UDP: User Datagram Protocol "Best effort" service, UDP segments may be: Lost Delivere..
Today, I learned about the Data center, which most big tech companies have. 10's to 100's of thousands of hosts, often closely coupled, in close proximity: e-business (ex. Amazon) Content-servers (ex. YouTube, Akamai, Apple, Microsoft) Search engines, data mining (ex. Google) Challenges: Multiple applications, each serving massive numbers of clients Managing/balancing load, avoiding processing, ..
