ISDS 4120 Exam 2 Study Guide

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Louisiana State University *

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4120

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Computer Science

Date

Jan 9, 2024

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Uploaded by mitchmitchell31

ISDS 4120 Exam #2 Exam 2 will be a closed note, closed book, closed Internet exam taken through ProctorU. The exam will consist of multiple-choice questions and short answer questions and you will have 2 hours to complete the exam. The content will cover lectures 5 to 9 and chapters 1 to 9 of the book. What follows is a list of the concepts and models on the exam. It is not enough to simply memorize the definitions or concepts – the key will be your ability to take the concepts and models and apply them to information presented to you. If you cannot locate a concept, reach out to your colleagues for assistance – I highly recommend forming study groups to assist you. Concept Questions  What does an application layer address using TCP look like?  The application Layer contains software that converts incoming and outgoing data from one format to another. Ex. www.lsu.edu  The functions of the application layer Presentation Logic – the presentation of information to the user and the acceptance of the user’s commands Application Logic – Can be simple or complex Data Access Logic – Processing required to access the data. Often means DB queries in SQL Data Storage - Servers ?????? ( P.A.D.D)  The division of software on clients versus servers for three tier and two-tier architecture Two-tier: The server is responsible for the data and the client ( Application and Presentation) Three-tier: The use three sets of computers…. The client’s computer uses software for presentation logic. The application server is used for application logic. The database sever is used for the data access logic and data storage.  Where server name resolution is done Domain Name Service takes place at the ISP(Internet Services Provider) Network Layer  What does TCP use to reassemble packets in the correct order? Sequence Numbers

 The attributes of a sound wave Amplitude – Height of wave decibels Wavelength – Distance between successive peaks of wave Phase - wave direction (degrees) or point at which the wave begins Frequency – waves per second (Hertz) *Wavelength is the inverse of frequency*  What routing means; the three fundamental approaches to routing; and different types of dynamic routing Routing- Process of identifying what to have a packet takes through a network from sender to receiver Three fundamental approaches to routing 1. Centralized - all routing decisions are made by one central computer or router 2. Static - decentralized, means all computers and routers on the network make their own routing decision 3. Dynamic – decisions made in a decentralized manner by individual computers. Attempts to improve performance by routing messages over the fastest route possible Different types of Dynamic Routing 1. Distance Vector Dynamic Routing - routers count the number of hops along a route and communicate that number to other computers to give information 2. Link State Dynamic Routing - tries to determine how fast each route is  What does the transport layer do to the messages? Segmentation and reassembly Session management End-to-end delivery of messages The transport layer links the application software in the application layer with the network and is responsible for the end-to-end delivery of the message. One of the first issues facing the application layer is to find the numeric network address of the destination computer.  How the capacity of a circuit is determined The bandwidth of the circuit determines its capacity

 The different types of data Digital - transmission involves discrete binary values (i.e., 0 or 1) Analog - transmission involves continuous waves  The factors to consider when selecting media to be used in a network Type of network Cost Transmission Distance Security Error Rates Transmission Speeds  How contention and collision work and which is better for different types of networks With high traffic, controlled access is better because of the high collisions of contention. Works better than contention approaches for larger networks that have high usage With low traffic, the higher overhead of controlled access makes contention more efficient. Computers wait until the circuit is free before they send data  What polling means from a networking perspective Polling is the process of sending a signal to a client computer that gives it permission to transmit Clients store all messages that need to be transmitted The process of sending a signal to a client that gives its permission to transmit or asks it to receive. It typically involves some waiting because the server has to wait for a response from the polled client or termina  How an application layer address is translated to an IP address Host (server) name resolution Domain Name Service (DNS) DNS Request Packet  The difference between the logical and physical design of a circuit Physical Circuits - connect devices and includes wires Logical Circuits - refers to the transmission characteristics of the circuit  The definition of a bottleneck A circuit that's filled almost to its capacity and thus is the critical point that determines whether user get good or bad response times

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 How a star, ring, and mesh network work Star Advantage: Simpler management Messages requires 1 or 2 hops Circuit failure primarily affects a single site. Disadvantage: Susceptible to traffic problems Failure of the central site will cause complete network failure Ring Advantage: Robust to loss of any one circuit Disadvantage: Long routes may increase communication latency Mesh Advantage: Generally short routes Robust to the circuit loss or overloaded circuits Disadvantage: Expensive  The difference between a hub, router, and switch Hub- Least expensive, least intelligence If a message comes in for a specific computer, sends that message to all computers Router - Most expensive, most intelligence Using protocols, know where every computer is located on a network Switch - Similar to hub, but learns, based upon experience, where a specific computer is located  Different types of backbone networks and their logical and physical topologies Switched Backbones Most common type of BN used in the distribution layer Uses layer 2 switches Switches come in different form factors Desktop, rack-mounted, chassis Topology- Star Physical location of devices- More common to locate centrally in main distribution facility (MDF) or other wiring closet Routed Backbones Sometimes called sub-netted backbones or hierarchical backbones Typically used at core layer, but sometimes at distribution layer Advantages - LAN segmentation Disadvantages

- Tend to be slower - More expensive - Harder to manage Virtual LANs Advantages - More flexible sub-netting - Better managed traffic flow which may lead to faster performance - Traffic prioritization - Can include quality of service information in tag Disadvantages - Complex -May increase management when VLAN memberships change - Layer 3 switches are more costly than Layer 2  Different backbone network options for a firm, the topologies of each, and the benefits and drawbacks Switched - good for distribution layer Pros: inexpensive and fast Cons: not as flexible Routed - good for core layer Pros: LAN segmentation Cons: tend to be slower, more expensive, harder to manage Virtual - good for very large networks Pros: very flexible LAN segmentation Cons: very complex to manage  Different approaches to monitor connections on a network  The definition and purpose of network segmentation Process of defining what parts of a network should be accessible to other parts of the network Breaking a network into smaller parts. If there is more traffic on a LAN than it can handle you can divide the LAN into several smaller segments. Improving Circuit Capacity Wired LAN, adding and spreading the computer across these new switches Wireless LAN, adding more APs that operate on different channels

 The activities associated with each of the stages of network design Needs analysis - Understand current and future network needs (users and applications) Technology Design - Examine available technologies to determine which meet or exceed needs - If needs are difficult to estimate, build higher capacity Cost assessment - Evaluate financial costs of technology  The definition and types of media access control Definition: Controls which device transmits and when Contention - Transmit whenever circuit is available with no centralized control Controlled - Each device must get "permission" to transmit, similar to raising a Hand  Media access control is important on Multipoint (shared) circuits Half-duplex point-to-point circuits  Contention access vs. Control Access Contention - Transmit whenever circuit is available with no centralized control - Common in Ethernet LANs - When devices transmit at the same time, a collision occurs - Devices must be "polite" and follow these steps: - "Listen" for traffic - If another device is transmitting, wait to transmit - Otherwise, transmit (and keep listening) - If another device beings to transmit, stop and wait Controlled - Common in wireless LANs - Access Request - Each device must get "permission" to transmit - Polling - Roll-call polling - Central device (controller) determines which devices can transmit - Each client is checked periodically to see if it needs to transmit

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- Hub Polling (token passing) - One device begins the poll and then passes it to another device until it reaches them all  The different layers of the backbone architecture Access Layer - How users access network (LAN, WLAN) (closest to the users) Distribution Layer - BN that connects access layer to core layer (within building) Core Layer - Connects BNs between buildings and to WAN/ Internet  The advantage of a VPN versus a private WAN connection Low Cost Flexible VPN is low cost but... WAN connection is not affected by internet disruptions and it's more compatible  Options to improve backbone performance Reducing network demand Move files to client computers Encourage off-peak usage Consider blocking or throttling unnecessary network traffic Devices Upgrade server Software and hardware (CPU, Memory, Disks) Redundant array of inexpensive disks (RAID) Add a new server Upgrade Clients Circuits Buy faster circuit (e.g., 100BASE-T to 1000BASE-T) Add circuits Add access points on different channels Segment network  The definition of visioning Planning for future needs The vision for the network in a company

 Options to monitor and control a network 1. Managed networks - consist of managed devices that enable a network manager to consistently monitor the performance of the network (may be more expensive for initial investment, but save more money in management) 2. Network managed software - allows managers to monitor performance and configuration of devices on network (system and management software) 3. Simple network management protocol (SNMP) - Most commonly used protocol for managing network devices - The network management software uses SNMP to communicate with software agents on managed devices - Data is stored in management information base (MIB)  Be able to state the five layers of the OSI model in order 5.Application 4. Transport 3. Network 2. Data Link 1. Physical  Be able to identify the functionality of each of the layers Application User's access to network/software to perform work. Transport End-to-End management 1. Link application layer to network 2. Segmenting and tracking 3. Flow control Network Deciding where the message goes 1. Addressing 2. Routing Data Link

Move a message from one device to the next 1. Controls hardware 2. Formats the message Error checking Physical Transmits the message  Be able to match the protocols to the layers of the OSI model Application HTTP, SMTP, DNS, DHCP, IMAP, POP SSL Transport TCP UDP Network IP ICMP Data Link Ethernet Physical 100Base-T, 802.11n  The three choices when outsourcing to the cloud and be able to match them to the grid -Software as a Service (SaaS) All application components and associated hardware/software outsourced Based on multi-tenancy e.g. Salesforce.com -Platform as a Service (PaaS) Application logic and data are managed internally e.g., Microsoft Azure -Infrastructure as a Service (IaaS) All hardware is outsourced  The six components of a LAN and the two broad choices that are available when designing the LAN

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1. Clients 2. Servers 3. Network interface cards (NICs) 4. Network cables (wiring) 5. Hubs / switches / access points 6. Software Two Choices: Wired vs wireless Applications  Best practices for architecture and technology for LAN design Architecture Switched has best cost to performance ratio at the distribution layer Most organizations use routed at the core layer VLANs are becoming more widely used, especially for organizations needing the flexibility Technologies Gigabit Ethernet for distribution layer and faster for core layer Redundant devices and connections  Should companies build to network capacity? Why or why not? Turnpike effect means that traffic increases much faster than originally forecasted Should network designers plan for excess capacity? Upgrading costs 50-80% more than designing higher capacity time Very few complaints about overcapacity Most organizations intentionally overbuild The turnpike effect occurs when traffic increases faster than forecasts When networks are efficient and fast, users will use them more frequently Most networks designed with excess capacity end up using overcapacity within 3 years  The advantage of layers, from an OSI model perspective (be able to identify 3) 1. Networking functionality is modular and the software/hardware at any layer can be more easily substituted. e.g. substitute wired for wireless at the physical layer 2. Easier to troubleshoot or make changes to one layer at a time

3. Application developers only need to worry about the application layer in their Programs  Should companies build to network capacity? Give two reasons why or why not No companies should build overcapacity. Generally companies build over capacity to avoid paying upgrading cost which are normally 50-80% higher.

ISDS 4120 Exam 2 Study Guide

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