CSIS 4823 Data Communications Networking – Designing Networks

CSIS 4823Data Communications Networking – Designing Networks Mr. Mark Welton

Documentation • Good documentation is key in a network design • Well-written documentation saves both time and money • Makes troubleshooting issues much easier

Requirements Document • Includes all the requirements for the project, as well as all assumptions being made • The should be vetted with everyone who is involved in the project • At a minimum your direct supervisor, project manager, and sponsor should be involved • This will help deal with scope creep

Requirements Document • Does not need to be large or complicated • All points should be made as simply as possible especially the assumptions • A full project plan will be developed later so do not turn the requirement document into one • This document is to help start conversations about the project to make sure everyone understands what is involed

Requirements Document • When a VP says, “We need a network to support 300 users” what does that mean? • Desktops? Laptop? VoIP? • Defining the assumptions tells them what you think it means • You do not want to be the one saying that you did not know it was 300 users with 300 VoIP phone three months later because no one know you where assuming desktops only!

Example Requirement: • The network must support 300 users. Assumptions: • Each user will have one workstation. • Each workstation will have only one Ethernet interface. • All interfaces will be cabled for 1 Gbps Ethernet. • The network does not need to support 1 Gbps for all users at the same time. • Each user will have one phone supporting one phone line. • All phones will be non-IP phones. • VoIP will not be run on the network for the foreseeable future. • Each user will equal one cube or office. • Each cube or office will have two data jacks and one phone jack. • All cabling runs will terminate into the computer room (home runs).

Beginning the Design • The area in a network that will require the most equipment to support is the users • The number of ports needed to support them will drive the overall design of the network • Why? More users leads to devices which leads to more ports which means more traffic • What should be considered when determining the number of ports needed?

Beginning the Design • How many users will the network need to support? • How many servers will the network need to support? • How many printers will be attached to the network, and what will their locations be? • What are the applications running on the network? How will users interact with these applications (HTTP, client software, terminals, Citrix)? • What type of security do you need? • Is high availability desired and/or affordable? • What percentage of growth should you assume? • Do all interfaces need to be gigabit? • Do you need 10-gigabit? • Will the network need to support VoIP? • Will you be supporting one physical location or many (including multiple floors in a single building)?

Beginning the Design • Your goal is to come up with a target number of each interface type for each location • From this you can decide what equipment you need • So if I have 330 devices we can order 7 – 48 port gigabit switches right?

Beginning the Design • 48 x 7 = 336 • Does this allow for growth? • Do all devices need gigabit access? • Do all devices have only one interface?

Beginning the Design • What is the throughput needed for VoIP? • Are we using PoE for VoIP? • Will servers have high availability? • Anything else we should consider?

Beginning the Design • Lets start with growth • What would be a reasonable assumption for growth? • 5%? 10%? 15%? • What if every office in the building has a person assigned to it? • What if half the offices are empty? • Growth can be relative to the project • A good rule of thumb is to plan for a minimum of 15%

Beginning the Design • 330 X 1.15 = 379.5 or 380 ports • Next question, Do all devices need gigabit access? • VoIP needs at most 256Kb for a call right? • The cost of a 100MB switch vs. a gigabit switch can be a lot in a large deployment • Are we going to use the phone as a switch to connect the PC to? • If we are deploying 150 VoIP phones in the design how could this impact the design?

Beginning the Design • 150/48 = 3.125 or 4 switches • 48 x 256Kb = 12.288Mb if every phone is making a call • 24 x 128Kb = 3.072Mb if every phone is making a call • Why am I doing this math????

Beginning the Design • Most VoIP implementation use PoE (Power over Ethernet) to power the VoIP phone • This can add about 15% to 20% to the cost of the switch • It also means that a 48 port switch may need 10 GB uplinks to deal with the calls • By using 24 port switches with PoE you can use gigabit uplinks for the switch • Would this matter?

Beginning the Design • 150/48 = 3.125 or 4 switches • 150/24 = 6.25 or 7 switches • $13,000 Cisco Catalyst 3750 48-port POE Switch – 2- 10GB uplink • $6495 Cisco Catalyst 3560 24-port POE Switch – 4- 1GB uplink • $2495 Cisco Catalyst 2950 24-port POE Switch – 2- 1GB uplink • 4 x 13000 = $52,000 • 7 x 6495 = $45,465 • 7 x 2496 = $17,472 • And we have not even included the optics cost and back end switches yet

Beginning the Design • Even though this is just a example and you would not normal have non-blocking capability for your VoIP deployment you can see how assumptions can affect a design • You would assume 4 switches would cost less • By having all ports meet the highest requirement for a device the cost greatly changes

Beginning the Design • What about servers? • In this example we have 20 servers does that mean 20 ports? • Should servers have more then one port for redundancy? • Should the switches they are connected to be redundant? • Should these switch have redundant connects?

Beginning the Design • Design in book is about $120,000 per switch with a total cost of about $250,000 Can we do better?

CSIS 4823 Data Communications Networking – Designing Networks