Creativity Within Structure

Lets take a quick look into the network traffic that is generated when an activity occurs such as a file download via an HTTP request. We will also look further into the TCP protocol handshake, sequence numbers, and their values. We will examine their significance resulting from the HTTP request. What role does TCP play during HTTP requests? Is TCP a connection-oriented protocol? Explain in details. A TCP header has Flags field. Describe the meaning of flags "SYN", "SYN ACK" and "FIN". Transmission Control Protocol is, as its name states, controls the transmission of an application between end points. HTTP is the application layer in this case, TCP provides for the reliable delivery of HTTP requests. It passes over to the network layer. A user initiates an HTTP request by opening a browser and requesting a web page via a URL. The server will then deliver the request, and any objects such as images, movies, PDF files etc that the web page may have em

There are 4 pseudo-class expressions that are part of the :nth-child pseudo-class. Structural pseudo-class selectors target HTML elements based on the DOM tree. Basically, elements that cannot easily be targeted by simple selectors or combinations of selectors. What makes pseudo-classes so handy is the ability style elements dynamically based on its position in the DOM. :nth-of-type(N) :nth-last-child(N) :nth-child(N) :nth-last-of-type(N) :nth-of-type(N) selector My favorite of the 4 is the :nth-of-type(N) selector. The nth-of-type selector allows you to select child elements of a parent based on the particular type of the element, for example every 5th "li" element in a list. You can select even or odd elements, or the nth (order number) child in the group of elements. The class accepts the argument "n" which can can be a keyword, a number, or strings "odd", "even", or an expression "-n+3". Let's look at a simple but ef

Triggers are SQL statements which are stored with the intention of being activated or fired when an event associated with a database table occurs. This could be any event including an INSERT, UPDATE and DELETE. Lets begin by creating a few simple insert triggers CREATE a trigger on the ORDERLINE table for the insert event. The trigger will update the corresponding PRODUCT record QTY_ORDERED by adding the value of QTY to QTY_ORDERED. CREATE TRIGGER tr_qty_ordered_value_insert ON Orderline FOR INSERT AS BEGIN UPDATE product SET QTY_ORDERED = QTY_ORDERED + ((SELECT qty from INSERTED) * (SELECT unitprice from INSERTED)) WHERE product.ProductID = (SELECT ProductID from INSERTED); END; Command(s) completed successfully. CREATE a trigger on the ORDERLINE table for the delete event. The trigger will update the corresponding PRODUCT record QTY_ORDERED by subtracting the value of QTY FROM QTY_ORDERED. CREATE TRIGGER tr_qty_ordered_value_delete ON Orde

Let's look into the ICMP protocol. Specifically, ping and traceroute. ICMP is the Internet Control Message Protocol and is a component of the IP Layer. Basically, used by hosts to communicate diagnostic network layer information that is carried in the IP payload. It communicates error messages which are acted on by the IP layer or the UDP or TCP protocols. All of the exercises were carried out using the open source network protocol analyzer "Wireshark". www.wireshark.org Describe in detail the protocols ARP and ICMP. ARP is the Address Resolution Protocol is similar to that of DNS. Where DNS resolves IP addresses to domain names, ARP resolves network layer IP addresses to link layer MAC addresses. In order to send a datagram the source must give the adaptor the IP address and the MAC address. For example, host A wants to send a packet to host B. Host A uses a cached ARP table to look up the IP address for any existing records of host B's MAC address. If the MA

What does it mean for a wireless network to be operating in "infrastructure mode?" Clients connected to a base station (an access point or router) are operating in infrastructure mode. They communicate indirectly through this access point or router which serves as a bridge to a wired network. Ad-hoc mode networks are networks that do not rely on a router or access point infrastructure. As a result, each client participates in the routing by forwarding data to the other connected clients. What are the differences between the following types of wireless channel impairments:  path loss, multipath propagation, interference from other sources? Multipath propagation is when packet loss occurs due to electromagnetic waves reflecting off of ground objects which then take paths of different lengths between sender and receiver. Interference from other sources happens when there is interference from radio sources transmitting in the same frequency band. Wireless phones and wirel