31 Jan 2013

Network fundamentals - implementing a network

   This post will be focused on explaining the main elements needed to consider when implementing a network. I will talk about the main aspects that I know are important to check before you start thinking of implementing a network from scratch. Of course I will talk about middle sized networks and not about home networks or small LAN implementations.
   I don't know the exact order of things to consider, if you think there are more things to consider please leave a comment and explain your idea.
   One of the most important think to address is of course how much will cost to implement the whole network. At this point, as a network architect you'll have to consider what type of equipment will the network contain. The following devices are the most common things that a network can contain:
hubs - used to interconnect devices by using a shared channel of communication (one collision domain).
switches - interconnect devices between each other but separates collision domains ( more expensive then hubs, but faster because dedicated bandwidth is used and no collisions occur). Switches create logical point-to-point communications between devices.
Routers - intermediary devices used to interconnect networks.
Access points - used by devices to have wireless access to the corporate network or the Internet  .
Storage equipment (NAS ,SAS etc.) - used to store information. You'll have to consider here the type of storage equipment needed, the capacity, the speed etc.
IP telephones - telephones that communicate trough the IP protocol.
Printers - printing equipment.
Servers - machines dedicated to host critical services and applications.
Computers (Laptops, Desktops) - network hosts.
I'm sure there are many more but these are the main that I could think of.
   When buying network devices like switches or routers think about the modular feature of them. This is an important aspect to check if your network is dynamic and you will have to install/uninstall modules on intermediary devices. Read more about Cisco Catalyst devices and their modular feature on Wikipedia: http://en.wikipedia.org/wiki/Cisco_Catalyst.
Intermediary devices can have different types of interfaces connected to them:
Lan - used on Local Area Connections.
Wan - used on Wide Area Connections.
Console - used by administrators to connect directly to the network device.
Aux - auxiliary port is usually used to connect an external modem.
You'll have to consider the individual and overall cost for all devices.
    Another important factor is scalability. You'll have to think how will the network change in future and how easy will it be to expand it. By designing a good topology and by using good equipment and wiring, a network can be easily expanded.
   A network topology can be either physical or logical. Physical topology refers on how devices are connected with each other while the logical topology refers to how devices communicate between them. There are many types of physical topologies but among them are:
Bus, Ring, Hierarchical, Star, Mesh, Partial Mesh, Line . The following image will display this concepts:
Network Topologies

   Another important factor to consider when designing a network is the speed. You will have to measure the network load, the bandwidth that you will need, the speed priority of devices (a server will need a higher bandwidth and better wiring then a normal network host).
The main types of network connections are made usually with:
UTP cable - most common type of wiring, used to interconnect devices, medium speed. A problem with this type of cable is that the attenuation increases with cable length (read more on Wikipedia: http://en.wikipedia.org/wiki/Attenuation).
UTP types can be:
Straight-through - they are used to interconnect devices that operate on different network layers (switch to computer, switch to router etc.).
Crossover - used to interconnect devices that operate on the same network layers  (switch to switch, router to router, computer to computer, computer to router, switch to hub etc.).
You can find more information about these two types of cables by searching with Google (www.google.com).
Fiber Optic - more expensive than UTP cable, much faster but harder to manage.
Wireless - Uses radio or microwave transmissions. Wiring is not used but this type of connection can interfere with other devices.
   Redundancy is another factor that you'll have to keep in mind. The following quote from Wikipedia explains what exactly redundancy is:
"A goal of redundant topologies is to eliminate network downtime caused by a single point of failure. All networks need redundancy for enhanced reliability. Network reliability is achieved through reliable equipment and network designs that are tolerant to failures and faults. Networks should be designed to reconverge rapidly so that the fault is bypassed.
In a redundant mesh topology network devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network. A mesh network with redundant connections is an example of a redundant topology. The level of redundancy can be measured by network connectivity.
On a redundantly connected network if a router were to fail connectivity would be preserved by routing traffic through a redundant connection. Furthermore, each router should have two or more points, or 'legs', with which to keep redundancy."
This next image will show the different between a redundant and a non-redundant topology:
Redundant topolgy

   You will also have to consider IP addressing, choose a network address and a network mask. Consider creating different subnets for different departments or services (servers can be in a different subnet than normal hosts). You can either use VLSM or CIDR, I will talk about these two in a future post.
   Another aspect to address is network security. You will have to implement network rules and policies, install firewalls, anti virus software etc. A network would have to be resistant against outside and inside threats. This is one of the most important things to consider.
   Usually any big company has a telecommunications room (also known as server room). This is a specially designed place in which the most important network equipment is stored under strict rules. Most server rooms are equipped with ventilation systems that keep devices under a cooler temperature (in normal conditions under 20 degrees). Here all intermediary devices(switches, routers) that make up the network are installed in special designed racks among with patch cords and cables that interconnect them. Devices like Servers, UPS (Uninterruptible power supply), KVM switches, phone systems, firewalls, network patch panels are also stored in this room. This is where administrators interact with physical equipment, that's why devices have to be easy to manage. Network management is an important element to address, read about it on this article : http://en.wikipedia.org/wiki/Network_management
  What services will devices host? Servers can host services like E-mail, DNS, DHCP, Web-hosting etc. Network devices can have features like QoS (Quality of Service), NAT (Network address translation), VoIP (Voice over IP) etc. Installation, maintenance and troubleshoot of network services and applications is another important factor.
These are most important elements that you will need to take care of when implementing a network. I hope this will be an interesting post, stay tuned for more to come and have a wonderful day.


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  2. Interesting things, thank you April!

  3. I hope you happy and wish you good luck!
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  4. This Article really helped me. Thank you for sharing your valuable knowledge with us. :)

  5. not very standerd
    But gud

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