3_10

(10) LAN Pros & cons:

3 IDF's were chosen & placed - one for each of the three main (imaginary) faculties
- each faculties is responsible for it's own IDF

pros:

This scheme increases overall simplicity & management
- MDF connects to admin, servers & (obviously) IDFs - it does not directly connect with any curriculum computers
- IDFs connect with all curriculum (& teacher) computers
Any expansions can be easily incorporated, with minimal cable length
- Any extra demountables should be easily in reach of an IDF.
Cumulative cable lengths have been reduced slightly
Network is functional, scalable, adaptable, and manageable.

cons:

The school was just small enough to begin with to have just a single MDF & no IDFs
- A single MDF could have reached all classrooms (without repeaters)
- Using a single MDF, teachers could have been placed on a separate subnet (different switches) to students.
VLANs would then become unnecessary.
i.e. The network would be much simpler & ACLs would control all access rights.
More IDFs means more wiring cabinets means greater expense.
- In retrospect, three IDFs is probably overkill (although at least one IDF for the demountables makes sense).
Many classrooms are closer to the MDF than the IDF they are attached too - i.e. more wire length than necessary.
This is an expensive solution as multiple switches are used.
This extended star topology allows a major point of failure at the router - if the router fails curriculum students won't be able to access the dns server, and no-one will be able to access outside the school.

Logical Topology

pros:

This chosen logical scheme increases simplicity
2 subnets (508 hosts) are more than enough for teachers & curriculum.
The spare subnet will come in useful if another building (needing an IDF) is built
The VLAN scheme was essential to isolate teachers & students (since they connect to the same switches in the IDFs)
Very short, efficient ACLs permit curriculum access to the main enterprise server, but deny them access to admin.
From the main admin section broadcasts can be sent to all admin, teachers and/or students - (e.g. network administrator may wish to netsend important messages to all computers)

cons:

Using this VLAN scheme, teacher computers cannot access student computers - teachers must go to the main admin section (& a vacant admin computer) to do that.
Under the current configuration, the 3 student cables running into each room are configured as VLAN1. Meaning that, if a printer is put in a classroom & connected to one of the three switches, it will effectively be VLAN 1 and therefore will be inaccessible by the teacher computer in the same room.

pros:

Collisions are minimised due to all devices being switches or routers which creates micro-segmentation
- Our origional plan was to use 3 hubs per classroom (to provide for 24 stdudent computers), but we discovered very cheep ($120) hubs which servered the same purpose, but were better.
Estimated bandwidth for all hosts (teachers, students & admin) is 100Mbps - which is 100 times larger than the requirement
Our expendature comes to about $86,000 US (including all components cable) - well under budget.
- In general, we found the cheapest component for each device - which means sacrificing quality.

cons:

No layer 1 hubs were used in this design - switches were used instead, and this cost us slighly more
Our router and router modules in the MDF, although on of the cheepest available, set us back $20,000 - 10% of our budget gone already

pros:

cons:

Due to the way this network is microsegmented with switches, there will be very few collisions within this network.
- Using SPX (Sequenced Packet Exchange) service, the IPX network becomes connection-oriented and any collisions or buffer overflows will result in retransmission.
The estimated minimum bandwidth per student computer is 100 Mbps - to see the calcualtion click "see it all working together" (in the menu bar)