1. Capacity Unit 26 Design a small or home office network
HND in Computing and Systems Development

2. Capacity bandwidth to internet local internet contention ratio
Internal network bandwidth
internal network contention ratio
bandwidth requirements
applications
users
devices

3. Internet bandwidth
Web bandwidth means the amount of data transferred in a prescribed period of time
Web – need to know:
Number of pages on the site
Average file size of a page
Number of visitors per day
Web bandwidth = Pages x File size x Visitors 10 x 40k x 60 = 2.4MB/day or 72MB/month

4. Web bandwidth Typical page sizes
BBC News, about 650kB
CNN, 900kB
The Verge 7.36MB
Determine the page sizes and number of pages for
Then calculate and graph the web bandwidth required for 10, 100, 1000 page hits/month (use a spreadsheet) 

5. e-mail Average message size 50kB Owners could send up to 100 per day
Attachments
Drawing or solid model files up to 10MB
Say every 10th has an attachment
traffic = 5MB + 100MB = 105MB
An on site server will have 10 times as much spam as legitimate traffic
So traffic could be 1GB per 8 hour working day
Or about 34kBps = 272 kbps
Amend your spreadsheets to add these calculations and calculate total web and transfer rates (Mbps)

6. Streaming 320 x 240 or 384 x 216 = 500kbps HD 1280 x 720 = 2000kbps
Calculate the effects of both types of streaming on the peak demand

7. Actual speeds
There are five main types in the UK, generally offering :
FTTH (Fibre to the Home) - 1Gb
Virgin FTTC (Fibre to the Cabinet) - Up to 152Mb
BT FTTC (Fibre to the Cabinet) - Up to 78Mb
ADSL2+ - Up to 24Mb
ADSLMax - Up to 8M
The key word here is “up to”

8. ADSL Distance from exchange
The further away a property is from a telephone exchange the weaker broadband signal can become and the slower your actual connection
This is due to :
attenuation, the signal getting weaker as it moves further away from its source
the quality of the lines themselves
electromagnetic background 'noise' which interferes with the signal

9. ADSL Contention ratio
Contention ratio is the number of users sharing one unit of data capacity.
A 50:1 contention ratio would mean that up to 50 broadband customers are sharing the same bandwidth at any one time
Average contention ratios
home user 50:1
business 20:1

10. Asymmetry Upload speeds about 10% of download speeds on ADSL
What is the line speed available at MWS?
Is ADSL a suitable solution for the business?
Consider
Limiting streaming
Off site web serving
Uploading to cloud services

11. Internal network File sizes Wired or wireless or both?
10MB drawings/models
Wired or wireless or both?
Wired speeds – 1Gbps standard
Wireless
802.11a and 802.11g offer up to 54 Mbps
802.11n offers up to 300 Mbps
802.11ac offers up to 1 Gbps
Farm buildings in Herefordshire have thick stone walls

12. LAN contention ratio
Ethernet uses Carrier Sense Multiple Access With Collision Detection (CSMA/CD)
A device accessing the LAN senses other transmissions, stops if there is a “collision”, waits a random time then retransmits
If there are a lot of devices, there are a lot of collisions
This is contention and the overall transmission rates drop
Can be fixed by sub-netting to limit the number of devices – typically 254 devices
Will this be needed at MWS?

13. Activity For MWS you now know: Create a communications plan for MSW
The applications (web, , CAD/CAM)
The users
The devices (from the previous session)
Create a communications plan for MSW
Internet connection, speed, data usage
LAN provision
Justify all your choices and demonstrate judgement in selecting from alternatives