# Help solving this question plz

Discussion in 'QnA (read only)' started by sridatta, Feb 12, 2007.

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1. ### sridattaAn Esoteric Geek

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consider the following design...

in case you are given the job of designing a network whose network usages are

1. 500 simultaneous web browsing sessions
2. 600 simultaneous internet e-mail sessions
3. 60 simultaneous intranet ftp sessions
4. 6 video streaming based online lecture sessions
5. 4 voIP telephony sessions
6. variety of other possible network usages in small quantum.

what should be the backbone capacity of the resultant intranet?

what wide area network bandwidth would you recommend for connecting to ISP?

2. ### mediatorNew Member

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On average => around 56 Mbps!

3. ### shashank4uMember

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around 40-60 Mbps depending upon performance..required

4. OP

### sridattaAn Esoteric Geek

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Finally ended up with these assumptions guyz...

Band Width Calculations:
~~~~~~~~~~~~~~~~~~~~~~~~

1. Web Browsing :
~~~~~~~~~~~~~~~~~

// Assumptions :-

No. of simultaneous sessions : 500
Estimated bandwidth / user : 10 Kbps

Total Bandwidth : 500 * 10 = 5000 Kbps
(Margins are calculated on total bandwidth)

2. E-mail :
~~~~~~~~~~

// Assumptions :-
// Attachment size < 1 MB (since intranet usage only). Average size of E-mail is 3 KB.
// suppose each user send 10 Email per hour, 40% emails with attachment.

Bandwidth consumed by each user in 1 hr = (4*1000 + 6*3)*8
Required bandwidth per user : 32144/3600 = 8.9 kbps ~ 10 kbps
NO. of intranet e-mail sessions : 600

Total Bandwidth required : 600 * 10 = 6000 Kbps

3. Intranet FTP :
~~~~~~~~~~~~~~~~~

No. of FTP sessions : 60
Bandwidth per user : 1 Mbps
Required Bandwidth : 60 Mbps

4.Video Streaming :
~~~~~~~~~~~~~~~~~~~

// Assumptions :-
// Frames per second : 30
// Resolution : 320 x 240 Pixels
// Webcasting type video streaming

Estimated Bandwidth per session : 512 kbps (Moderate quality)
No. of video sessions : 6

Total Bandwidth required : 512 * 6 = 3072 Kbps ~ 3000 Kbps

5. VoIP calls :
~~~~~~~~~~~~~~~

// Assumptions :-
// Codec G.711 – 64 kbps, 20 ms sample period
// 1 frames per packet (20 ms)
// Standard IP headers, Ethernet transmission medium

One packet is sent every 20 ms => 50 packets per second.
Payload is 64,000 ÷ 50 = 1,280 bits (160 Bytes).
Fixed IP overhead = 40 Bytes. Fixed Ethernet overhead 38 Bytes. Total size 238 Bytes.
Bandwidth required per session is (160 + 40 + 38) x 50 x 8 = 95.2 kbps.

No. of VoIP sessions : 4

Required bandwidth : 95.2 * 4 = 380 Kbps ~ 400 Kbps.

6. Others:
~~~~~~~~~~

// Assumptions :
// Other small bandwidth consumptions are included in the margins.

************************************************************************************************
FINAL SOLUTIONS :
~~~~~~~~~~~~~~~~~

Total Backbone Bandwidth required : ( 5 + 6 + 60 + 3 + 0.4 )* 1.35 = 100 Mbps link.

Total ISP bandwidth required : (5 + 3 + 0.4) * 1.2 = 10 Mbps link (Dedicated Link required)
************************************************************************************************

References :
~~~~~~~~~~~~

VoIP Calculations : http://www.newport-networks.com/pages/voip-bandwidth-calculator.html
Video Streaming : http://sorenson-usa.com/vbe/index.html
bandwidth calculations: http://www.busyaccess.com/calc.cfm