Foundation Concepts, Hardware and Protocols
1. What is the difference between a Wide Area Network and a Local Area Network?
A wide area network (WAN) is a computing network that is available in a large area and generally accessible to the public. WAN is a form of communication across geographic regions, which surpasses or links routers and computers so that persons can communicate between locations on a grand scale. Local Area Networks are computer networks committed to a specific area, so that computers can communicate to persons in the same area. Schneider (p 57 2004) explains that “A network of computers that are located close together—for example, in the same building—is called a local area network, or a LAN. Networks of computers that are connected over greater distances are called wide area networks, or WANs.” So, a network of computers that can communicate with each other within a smaller proximity is considered a LAN, while a network of computers that can communicate with each other across a large, even global, proximity is considered a WAN.
What is the difference between an Intranet and an Extranet?
Laudon and Luadon (p 284 2006) explain that an Intranet is a private network that uses similar functionalities and systems as the Internet, except that it is local to a specific organization and thus accessibility is controlled by said organization. According to Laudon and Laudon (p 284 2006) the Intranet “uses the existing company network infrastructure along with Internet connectivity standards and software developed for the World Wide Web. “ Furthermore, the Intranet specific to an organization has the ability to establish networked applications which run throughout multiple computers within the organization’s domain, thus allowing remote access when necessary (Laudon and Laudon p 284 2006).
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The Extranet is different from the Intranet because it allows users external to the organization to “have limited access to its internal intranet” (Laudon and Laudon p 285 2006). Where the Intranet does not allow external usage by vendors because it is a network determined by the organization to be accessible only to specific members of the organization, the Extranet allows network usage by persons that are not members of the organization. This access is specific to the external person’s functional role to the organization, and so it is still controlled by the organization.
Intranets and Extranets are similar in their functionality, but it is the actual personnel authorization and accessibility that determines if a network is an Intranet or Extranet. The benefits of Intranet and Extranet are also similar, where “Both intranets and extranets reduce transaction and agency costs by providing additional connectivity for coordinating disparate business processes within the firm and for linking electronically to customers and suppliers” (Laudon and Laudon p 285 2006).
In both questions above who would be likely use each?
Wide Area Networks (WANs) and Local Area Networks (LANs) are used by millions of computer users every day to access the Internet, which is really a “collection of hundreds of thousands of local and wide area networks that are now connected together via the Internet backbone” (Bagranoff, Simkin and Strand-Norman p 464 2005). Bagranoff, Simkin and Strand-Norman (p 464 2005) examine that the persons using a LAN or WAN connection to access the Internet are universities, commercial services, businesses, governments, organizations, and private citizens. Most agencies have LAN networks, such as businesses and universities, and even some businesses are dedicated to providing private citizens with LAN accessibility as the core service.
Intranets and Extranets are generally utilized by private organizations, educational facilities, government agencies, and businesses. In short, any organization or agency requiring limited access because of privatized sensitive information, such as employee names and social security numbers or financial records benefits from using an Intranet because of the additional security offered. Furthermore, “A variety of organizations understand the value of extranets—connections that enable selected outside users to access their intranets.” (Bagranoff, Simkin and Strand-Norman p 465 2006).
2. What is Dynamic Host Configuration Protocol?
Dynamic Host Configuration Protocol (DHCP) is “A network protocol that provides a way for a host to automatically assign an IP address to a workstation on its network” (Palmer, Walters, Badgett and Jonker p 206 2004). Basically it is a plan of action carried out by a host server that assigns a specific numerical set of packets called IP (Internet Protocol) which allow a computer on a network to deliver data and information from one computer to another computer. DHCP is, at its most basic definition, an automatic address assigning system.
How does it work?
According to Microsoft TechNet’s online publication Dynamic Host Configuration Protocol: Frequently Asked Questions (2007), DHCP works as a protocol that allows a client to request an “an IP address configuration from a DHCP server on the network.” As Microsoft TechNet explains, the servers the client makes the request from store all the “ available IP addresses and related configuration information in a database.” When a client makes a request, the DHCP server responds with an available IP address automatically until the client find an available IP address and requests the usage of that IP address (Microsoft TechNet 2007). This is a method of temporary, or lease, automatic IP address allocation. Thus, the client must renew the assigned address prior to expiration or find another IP address if it expires and becomes unavailable (Microsoft TechNet 2007).
Explain the domain name system. How does these two relate to each security?
The Domain Name System (DNS) is the hierarchical manner in which domain names and their IP addresses are identified (Dean p 598 2003). This system relies on a database of 13 root servers so that the system will not fail if several computers fail (Dean p 598 2003). A host computer is a member of a domain in which a group of computers operate, each having separate but similar IP addresses that are identified by the domain name (Dean p 598 2003).
ICANN co-ordinates the DNS system: it delegates the management of top level domains and ensures the global database is coherent. The Internet root is a file, whose maintenance is delegated by the Department of Commerce of the American government and ICANN to a technical service provider. This file is then replicated on the other root servers. The Internet Corporation for Assigned Names and Numbers (ICANN) is a technical co-ordination body for the Internet, which are specifically co-coordinating Internet domain names, IP address numbers, and Protocol parameter and port numbers. Security is thus controlled for the DNS through assignation and ICANN root servers, in coordination with this, Microsoft TechNet (2007) explains that “The authorization process for DHCP server computers depends on the installed role of the server on your network.” There are three processes of security and authorization, the Domain Controller which maintains a database that manages domain users; the member server which maintains a connection within the domain; and the stand alone server which is not either of the former, but functions under a specific workgroup name for browsing without secure access (Microsoft TechNet 2007). Thus, all accessing computers must have the correct DNS protocol and authorized as domain controller or domain member to provide DHCP service (Microsoft TechNet 2007).
3. What is the Hypertext Transfer Protocol?
Hypertext Transfer Protocol is a protocol used in the World Wide Web to transfer requests from an Internet browser (like Internet Explorer) to a Web-based server which receives and processes the request, sending information back to the original requestor (Shelly, Cashman and Serwatka p 205 2004). HTTP is necessary because it is an application protocol that allows information to be sent between computers via a file, such as video and text (Shelly, Cashman and Serwatka p 205 2004). Information is stored in what is referred to as a backend information system, and this information is available to requestors via browsers based on the ability of a computing system to interact with Internet software and networks (Bandyo−padhyay p 139 2002). HTTP works by ensuring that the stored information is compatible with applications and interfaces based on the type of language that the system is utilizing to transfer information (Bandyo−padhyay p 139 2002).
How does it work?
HTTP communication between computers is based on a request from a source to another server. The World Wide Web Consortium (1999) explains this as the basic form of request:
request chain ————————>
UA ——————-v——————- O
<———————– response chain
According to Becerra-Fernandez, Gonzalez and Sabherwal (p 206 2004), HTTP functions when “The browser sends a packet to that address asking for the Web page indicated by the user.” When the packet is received, the Web page server responds by “sending the requestor an HTML file containing the Web page requested” ( Becerra-Fernandez, Gonzalez and Sabherwal p 206 2004). This file is then shown on the client’s screen and the client server connection is closed ( Becerra-Fernandez, Gonzalez and Sabherwal p 206 2004).
What standards govern syntax and semantics?
Govern may not be the appropriate term, because in general to govern something means to control and remit penalties for not being compliant. However, to answer the question, the group of persons most involved in developing standards of syntax and semantics is the World Wide Web Consortium (W3C), which according to their Website “is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards.”
HTTP’s functionality is based on a set of syntax and semantics that is referred to as a document mark-up language. This means that it is a set of streaming text is written in a ‘tag’ format, which allows for information transfer described above. The standards that govern (for lack of a better term) syntax and semantics in the HTTP department are developed and distributed by W3C, and have been since the early 1990’s. According to W3C (p 22 2007) the most basic syntax and semantics of HTTP standards are:
The following rules are used throughout this specification to describe basic parsing constructs. The US-ASCII coded character set is defined by ANSI X3.4-1986 .
OCTET = <any 8-bit sequence of data>
CHAR = <any US-ASCII character (octets 0 – 127)>
UPALPHA = <any US-ASCII uppercase letter “A”..”Z”>
LOALPHA = <any US-ASCII lowercase letter “a”..”z”>
ALPHA = UPALPHA | LOALPHA
DIGIT = <any US-ASCII digit “0”..”9″>
CTL = <any US-ASCII control character
(octets 0 – 31) and DEL (127)>
CR = <US-ASCII CR, carriage return (13)>
LF = <US-ASCII LF, linefeed (10)>
SP = <US-ASCII SP, space (32)>
HT = <US-ASCII HT, horizontal-tab (9)>
<“> = <US-ASCII double-quote mark (34)>
Other syntax standards include hexadecimal numeric characters, special characters that must be in a quoted string, the string of text and backslash are also standards used within HTTP according to the W3C Organization.
4. Explain SMTP in detail.
According to Patterson (p 278 2000) SMTP facilitates “the exchange of e-mail between computers across the Internet.” Where the SMTP is the protocol used to control “the receipt by the ISP’s mail server of outgoing mail and the POP3 protocol controls the handling of incoming mail” (Patterson p 278 2000). SMTP is a text based protocol that allows a user to specify a recipient of an email. Once the recipients are specified, the message in the email is sent to the recipient server. This is called a client-server protocol because the client (user) transfers a message onto an SMTP server, and then the message is relayed by either the email client or a relaying server. The email client has already specified the outgoing recipient via the SMTP server. In a relaying server, the SMTP server is determined based on domain name system records for the domain name. SMTP client creates a connection to the server’s port which “pushes’ the email through to the recipient, it does not transfer information the opposite “pull” way, thus it does not enable information to be “pulled” from the relaying server or SMTP server. The POP3 protocol is the “pull” protocol where it pulls information from the server so the user can receive email.
What do we mean by encapsulation and decapsulation?
According to the Network Working Group’s paper “Request for Comments: 2432” by K. Dubray (1998) encapsulation and decapsulation are a manner in which frames of information are imbedded into a ‘payload’ frame for distribution through a network, where the maximum rate of transfer is measured in frames per second.
Decapsulation is the manner in which a frame is presented to an unsupported device and each frame or portion of the embedded payload acts as another frame of the payload and is returned to the correct formation, which is characterized by the backwards (from non-formatted to formatted) translational process, where encapsulation is characterized by the forwards translational process. Palmer and Sinclair (p 391 2003) explain that “adapters or modules are installed in all of the frame relay edge devices, including switches and routers, to perform the necessary encapsulation of frames to cells for transmitting and decapsulation back to frames for receiving.”
5. What are some of the problems in using UTP cable?
The unshielded twisted pair cable is made of one or more pairs of insulated wires, the amount of twists per foot is determined by the cable’s use (Toshmo, Tittle and Johnson p 81-82 2004). UTP is very common in organizational environments because it is the same cable used for telephones (Toshmo, Tittle and Johnson p 81-82 2004). However, it is more demanding in terms of bandwidth and signal quality (Toshmo, Tittle and Johnson p 81-82 2004). The main problem with UTP cables is that they are “UTP is particularly prone to crosstalk, and the shielding included with STP is designed specifically to mitigate this problem” (Toshmo, Tittle and Johnson p 81-82 2004).
According to Mohawk Cabling Excellence for Open Architecture, the main problems with UTP cable are exceeding the minimum bend, particularly at the wall outlet of the work station and within the wiring closet while routing the cable into a formfitting structure. If the cable is pulled too tightly or the cable becomes overstressed due to suspension, twisting, and pressure from walking on the cable.
How can these problems be overcome?
Appropriate installation is important, the UTP cable should be used in accordance with the length specified by the manufacturer’s standards, ensuring that the cable cannot be pulled or have pressure applied to it is also important. Not bending the cable can prevent many issues, the cable should be gently placed in sweeping curves along the cable path to avoid sharp breaks and bends along the wall (Mohawk).
To eliminate crosstalk, Toshmo, Tittle and Johnson (p 81-82 2004) explain that STP includes a “shielding to reduce crosstalk as well as to limit the effects of external interference.” STP uses a wire braid inside the sheath with foil wrapped around each individual wiring pair, thus it supports “higher bandwidth over longer distances than UTP” (Toshmo, Tittle and Johnson p 81-82 2004). The problem with STP is that it does not conform to UTP standards, but they can often be purchased with the same categorical standards (Toshmo, Tittle and Johnson p 81-82 2004).
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