Lecture 11 - Network Design

Question 1

Name and describe 2 types of network designs.

Answer 1

1. Traditional Network Design - structured systems analysis and design process, every detail is looked at very closely, therefore costly and time-consuming, but you get a better end product.
2. Building block approach - Use a few standard components repeatedly to reduce long-run costs by simplification

Both seem to follow the same general processes: Needs analysis, technology design, and cost assessment

Question 2

What is the Iterative approach to network design (3 steps - describe each)?

Answer 2

1. Needs analysis - Goal is to understand why network is being built and what users and applications it will support, Goals differ depending on the network
2. Technology Design - Development of the physical network design, Specify the Clients and Servers needed to support identified applications and users, Specify the circuits, routers, switches, gateways needed to connect computers
3. Cost assessment - Assessment of costs of various network design alternatives (Hardware, Network devices, Software, Network management and operating, Testing and maintenance

Question 3

What steps exist in the Needs analysis of the Iterative approach for network design?

Answer 3

1. Needs analysis baseline - Understand the current operations in terms of application systems and data traffic
2. Needs Analysis Objective - Define the geographic scope, Define the users and applications that use the network, outcome creates a logical network design.
   1. Break network into three parts based on geographic and logical scope (access, distribution, core)
   2. Identify basic technical constraints
   3. Identify constraints imposed by current infrastructure
3. Design process
   1. Start with highest level (WAN)
   2. Next draw individual locations connected to WAN
   3. Gather information and characteristics of environment
4. Application systems
   1. Baseline the applications
   2. Identify applications expected to be used on network in future
   3. Identify hardware and software and protocol requirements for each application
5. Network Users
   1. Assess the number and type of users that will generate network traffic
6. Network Needs
   1. Assess the number and type of users that will generate network traffic
   2. Organize network requirements
7. Deliverables
   1. A set of logical network diagrams
   2. Categorized as “Typical” or “High traffic”
   3. Logical plan – conceptual plan for the network
8. Sample needs assessment - Determining structure of the building where your network will be so that if a fire occurs you will know what part is damaged.

Question 4

What steps exist in the Technology Design of the Iterative approach for network design?

Answer 4

1. Clients and servers - allocating the type of computer (client computers or servers) to users based on what the user needs them for. ex. Allocate “base level” client computers to “typical” users
2. Circuits and Devices - Technology and capacity decisions
   1. Choose the fundamental technology and protocols
   2. Capacity planning – Estimate the size and type of network circuits for each type of network
   - It’s better to gain extra capacity as upgrading later cost 50-80% more then building it the first time, therefore most orgs intentionally overbuild capacity (but it only lasts 3 years on average)
3. Estimate Circuit Traffic - average traffic, peak traffic and estimating future data volume
4. Network Design Tools - Create a diagram showing expected network traffic and try to predict any network delays
5. Deliverables - Physical network designs (building picture showing switches and routers), design of the network circuits and devices

Question 5

What steps exist in the Cost Assessment of the Iterative approach for network design?

Answer 5

1. Request for proposal
   1. Background information (current state of network)
   2. Network requirements
   3. Service requirements
   4. Bidding process
   5. Vendor overview and knowledge
2. Vendor selection - evaluated against specific criteria
3. Sell proposal to management - network is a cost centre to management, must gain acceptance (speak their language, present it in an easily understandable way, avoid technical issues and create a business case)
4. Deliverables
   1. Request for proposal
   2. Physical Network Design
   3. Business Case

Question 6

What should you look at and do in order to increase network performance?

Answer 6

1. Monitor network elements and servers
2. Monitor Traffic and analyse it - Generally important to know which circuits are heavily loaded (Content caching to minimize network traffic - another que card question on this)
3. Network circuits - Important to size the circuit and locate them to match traffic patterns
4. Network devices - Network devices from different vendors perform differently and offer different capabilities (Focus on latency, memory, load balancing, and capacity management - in another que card question on this).
5. Service level agreements (SLA) - Specifies the exact type of performance the ISP will provide, Five “9’s” means a downtime of 5.26 minutes per year
6. Devices management software - detect and report problems before they become critical to the point of crippling the network - focus on latency and memory
7. System management software - Manages the network as a whole, diagnose complex patterns
8. Application management software - focus on delays and latency

Question 7

List and describe 4 network management standards.

Answer 7

1. Simple Network Management Protocol (SNMP) - collects device information and responds to requests from manager in order to configure the device
2. Common Management Interface Protocol (CMIP) - not popular
3. Remote network monitoring (RMON) - collects device information and responds to requests from manager in order to configure the device. Also provides network level information (better than SNMP - SNMP has limited functionalities).
4. Policy-based management - Managed devices allow setting of policies that change the priority of a traffic stream when some condition is met ex. giving priority to specific ports

Question 8

What is Remote network monitoring (RMON)?

Answer 8

• Allows remote monitoring of network data and devices. — Provides network level and device level network information.
• Information is collected on the device and then sent to a person who can then decide how to control the device to mange it most effectively.

Question 9

Draw the diagram of Remote network monitoring (RMON).

Answer 9

Slide 45 of diagram slides.

Question 10

what are the problems associated with using Simple Network Management Protocol (SNMP) to manage devices on the network?

Answer 10

• SNMP has very limited functionality
• Many vendors have thus created proprietary extensions to standard SNMP MIBs or have created proprietary MIBs
• Allows specific and advanced management of their devices, but reduces interoperability in that the devices may not be totally manageable using another vendor’s NMS

Question 11

What four areas of network devices need to be management in order to ensure good network performance?

Answer 11

1. Device Latency - Latency is delay imposed by device in processing messages, high latency = bad, CPU affects latency the most
2. Device Memory - Amount of memory tightly coupled with latency, if the device cannot operate at the correct speed it has to be able to store packets until they can be delivered, more memory = faster, needed for high latency
3. Load Balancing - assumes server clustering, aim is to ensure client request is handled by least busy server
4. Capacity Management - Separate device or functionality built into switch or router, enforces policies to limit bandwidth and can therefore slow user’s data stream

Question 12

Draw the load balancing diagram.

Answer 12

Slide 46 of diagram slides.

Question 13

How can network traffic be minimized to improve network performance?

Answer 13

1. send less traffic (no shit, really?)
2. Store most commonly used data closer to user using Content Caching by storing a copy of static Web Site data closer to users
3. Content delivery - An Internet “Web Acceleration” service provided by Content Delivery Providers (CDP) - servers hold the most requested files from a website to perform faster

Question 14

Draw the content caching diagram.

Answer 14

Slide 58 of lecture 11.

Question 15

Draw the Content Delivery Network diagram.

Answer 15

Slide 61 of lecture 11.

Question 16

What are the benefits of Content Delivery Networks?

Answer 16

1. Faster load time for Web pages
2. Less traffic from its origin servers – less cost
3. Can reduce size of server farm – less cost
4. Can use smaller capacity link to ISP – less cost
5. Less high-level (Tier-1) traffic