how to determine bandwidth is enough?

[rachelhor]

Hi,

Q1) When doing network design on paper (without any tools), how to determine that the bandwidth planned is enough?

Given a network with the following applications

- VoIP of 1Mbps to multipoint (total 5 sites)

- video conferenc of 3Mbps to multipoint (total 5 sites)

Q2) How do I calculate the total traffic/bandwidth needed above?

Q3) Do I have to multiply the VoIP 1Mbps by 2 to get 2Mbps mean 2-way communication? (Likewise multiply 3Mbps by 2 to get 6Mbps for 2-way video conference?)

Q4) Since it is multicast, do I also have to multiply VoIP 2Mbps (see above q2) by the number of sites, in this case 5, to get 10Mbps in total? (Likewise multiply 6Mbps by 5 to get 30Mbps in total?)

Thanx!

[david.bradley]

hi,

You shouldn't need to multiply by 2 (assuming you link will be sychronous) because your uploads/downloads for example would be of equal bandwidth.

If your traffic is multicast, only one copy of the data is sent and is accepted by many hosts that subscribe to the multicast group, as opposed to when unicasts are used one seperate packet is sent to each destination host.

I hope this helps.

Dave

[rachelhor]

Hi

It sure helps.

Just one more clarification.

By not need to multiply by 2, does it appply to all kinds of traffic, including TCP/IP traffic?

Also, if the network is not multicast but multiple point-to-point (unicast), must I also multiply TCP/IP traffic by the number of users?

Thanx a lot!

rachel

[mheusinger]

Actually it depends on what you mean by "VoIP of 1 Mbps". Does it mean you get EXACTLY 1 Mbps all the time? Or is this peak load? How does this change over time? Did you just give a guess or do some measurements? Do you mean you get to 5 locations each 1Mbps? This would mean 5 Mbps in total.

In any case, usually bandwidth you buy in the WAN is full duplex, i.e. a T1 means 1.544 Mbps in both directions all the time.

regards

Martin