Computer Networks- pre study Flashcards
Design and analysis, communications architecture/ protocols, LAN vs WAN
That process starts with identifying business and technical requirements and continues until just before the network implementation stage (when you actually do the work to deploy and configure what was designed). Network analysis, IP addressing, hardware selection, and implementation planning are all part of network design.
In simple networks, like those found in most homes and small offices, network design is a straightforward process. In large enterprise networks, the network design process is often very complex and involves multiple stakeholders.
Designing a network step by step
- Identify the requirements
- Assess the current state of the network
- Design your network topology
- Choose the hardware and software
- Plan for implementation and beyond
When it comes to physical network design you’ll need to address things like:
Running copper and fiber cabling
Number of switch ports required
WiFi access point positioning
Rack layout
Cooling and power
Logical network design deals with things like:
IP addressing/subnetting
VLANs
Data flows
Network topology
A traditional hierarchical network design is based on the idea of three basic network layers. Each layer handles a separate portion of the dataflows on a network. Those layers are:
Core layer
Distribution layer
Access layer
Core layer
This is the layer that routes traffic between different geographical sites. In other words, it’s the network backbone. The core layer is where high-throughput, expensive core routers shine.
Distribution layer
The distribution layer sits between the core and access layers. It acts as a boundary and implements network policies to restrict or allow data flows between different subnets within the network. Less expensive routers and L3 switches are the common workhorses of the distribution layer.
Access layer
The access layer is the layer for endpoint devices like user PCs, printers, and VoIP phones. Smaller “access switches” are responsible for switching packets and routing traffic at this layer.
networks bypass the ____ _____ altogether.
distribution layer
Top-down and bottom-up are two approaches to network design based on the OSI model. With a top-down approach, you start designing your network at the application layer and work your way down the model finishing with the physical layer. The bottom-up design is exactly the opposite.
Top-down is generally considered a better approach when you start with business requirements and work your way down. However, top-down is also often more time-consuming. Bottom-up network design starts with the physical aspect of the network and works upwards.
As a result, bottom-up can be quicker but can often lead to missed requirements or compromises on desired outcomes, as designing a network from the bottom up locks you into certain outcomes before you get to the application layer where users get work done.
- Choose the hardware and software
This step entails identifying the hardware and software you’ll use. In some cases, this will happen in parallel with step 3. In others, some of the hardware or software may be specified early in the project. As a rule, selecting the specific hardware and software you’ll use after you know what the network needs to do gives you the most flexibility.
During this stage, you’ll choose specific cables, racks, network devices, servers, applications, cloud services, etc. to make your design a reality. For custom parts or large orders, keep in mind potential supply-chain issues. If you can’t get your structured cabling or access switches in time, you can slow down project completion.
- Plan for implementation and beyond
With your network design and hardware/software selections ready, you can now plan for the implementation and beyond. This step entails creating a plan to deploy, configure, and test the network. In some cases (usually larger networks) this step may include small-scale test deployments to validate the design works before scaling out.
Tight project management and keeping stakeholders informed are key parts of getting your plan right. A network deployment has a lot of moving parts and your plan should account for project milestones, change management, and key deliverables. Additionally, if the network will be managed by a different team than those doing the implementation, you’ll need a transition plan. If you’re responsible for network management going forward, developing a plan for how you’ll monitor and maintain the network is important as well.
Top 5 network design best practices
- Integrate security early on
- Know when to use top-down vs bottom-up
- Standardize everything
- Plan for growth
- Create and maintain network documentation
If it can be standardized, standardize it. It will make troubleshooting, patching, maintenance, and asset management drastically easier in the long run.
Here are some examples of things you can and should standardize:
Hostnames (e.g. printer5.office2.lan3)
Hardware models
IP address schemes
Cable colors (e.g. one color for VoIP, one for data, etc)
Security policies
Copper vs fiber, logical topologies, IP addressing, VLANs, bandwidth, and WiFi coverage are some of the most obvious considerations when you’re designing a network. However, that’s far from an exhaustive list.
There is a lot that goes into designing a network, and it can be easy to overlook things. Here are some key considerations to keep in mind for your next project.
regulatory requirements
When you’re designing a network, you need to account for legal regulations that impact both the physical and logical design of your network. For example, local building codes may impact how you run structured cabling. Similarly, the National Electrical Code in the US has requirements relevant to the electrical power your network devices will require. From a logical perspective, regulations like HIPAA, PCI DSS, and GDPR can impact both data in transit and data at rest.
During the network design process, you’ll need to keep these requirements in mind to build a compliant network.
Because of the importance of network availability to business operations, enterprise networks need some level of fault tolerance. To make that happen, N+1, 2N, or 2N+1 redundancy (or even higher) is often part of modern network design.
Of course, resilience and redundancy come with a budgetary cost. Your network design will need to balance resilience and redundancy against the expense. In other words, reliably achieving five-nines (99.999% uptime) is great if you can do it, but it ain’t cheap!
A good way to frame this tradeoff is: considering your cost of downtime (i.e. how many dollars per minute/hour will you lose if the network goes down) and balancing that against your exposure to downtime with your current redundancy plan.
Cloud vs. on-prem
It’s no longer a given that on-premises are the best place to run a given workload. Once you have your business and technical requirements, you should carefully consider whether or not a cloud network makes sense as a solution. We won’t rehash the entire cloud vs on-prem debate here, but make sure you don’t lock yourself into an on-premises solution when the cloud may be a better fit (or vice versa!).
It can be easy to overlook the cooling and power requirements of a network. Don’t make this mistake! If you can’t meet your power requirements, you’ll never get your deployment off the ground. If you don’t account for all the heat dissipation of your new network equipment, devices can overheat and prematurely fail. Here are a few points to consider about power and cooling:
Make sure your electrical panels and electrical outlets can accommodate your new equipment.
Make sure to account for power-over-Ethernet (PoE) loads when sizing UPS (battery backups) and other power equipment.
Make sure your server room cooling can handle the additional heat generated by your new network gear or plan to invest in supplemental cooling.
There’s no one size fits all network design. With the right approach, however, you can create a design that matches your business requirements. Of course, as network lifecycle models like PPDIOO demonstrate, it doesn’t stop after the design stage!
Address resolution protocol (ARP)-
ARP translates IP addresses to MAC addresses and vice versa so LAN endpoints can communicate with one another. ARP is necessary because IP and MAC addresses are different lengths. Below is a breakdown of the various address lengths:
IP version 4 (IPv4) addresses are 32 bits.
IPv6 addresses are 128 bits.
MAC addresses – a device’s physical hardware number – are 12 hexadecimal digits split into six pairs.
Border Gateway Protocol (BGP)
makes the internet work. This routing protocol controls how packets pass through routers in an autonomous system (AS) – one or multiple networks run by a single organization or provider – and connect to different networks. BGP can connect endpoints on a LAN to one another, and it can connect endpoints in different LANs to one another over the internet.
