Your company intends to make extensive use of video conferencing and multimedia applications. How do you determine which bandwidth solution (T1, DS3, OCx/Sonet, etc.) would best meet your needs and incorporate that decision into your network to cover these applications?
I would say it depends on the type of service and QoS you are looking for. For example, when you say “video”, you mean video conferencing and not something like VoD. Bandwidth requirements will vary based on your service requirements.
For example: for IPTV services, the image quality depends on the implemented encoding: MPEG-2 consumes approx. 3.75 Mbps, while MPEG-4 needs approx. 2 Mbps for the same high-quality image production. Furthermore, the TV broadcast is delivered using IP Multicast, which makes the required bandwidth dependent on the number of channels offered and the encoding rate. 200 channels of MPEG-2 in standard definition will take approx. 750Mbps of bandwidth. VoD, on the other hand, is a unicast channel per viewer. 1000 standard definition VoD users will need approx. 3.75Mbps
QoS requirements for video conferencing using H.323 (SIP could be different again) can be planned in the “Rule of 75” as follows: Calculate the minimum bandwidth required by each of your applications (eg , video, voice, data). The total of this bandwidth is the minimum requirement for any link and should not consume MORE than 75% of the total available bandwidth on the link. The 75% rule takes into account the bandwidth required for air traffic such as routing, Layer 2 keepalives, and other applications such as email, HTTP, etc.
Therefore, capacity planning for H.323 should look like this:
Video data + 20% = bandwidth required.
Example:
Video Data Rate: Required Bandwidth:
512kbps = 614kbps
1.5Mbps=1.8Mbps…
For issues like the number of concurrent users and more about video conferencing, you may want to consider looking at solutions offered by Cisco and also boxes from TANDBERG.
Cisco considers anything over 766 Kb a “slow link” for VOIP. You also need to consider the criticality of the sites, so you may need two separate connections. All media apps run on top of your other apps, so QoS only allows for a preference of who goes first.
You need a good baseline of non-media (VOIP) applications. Therefore, the bandwidth must be able to handle all the necessary applications on the network.
Also, you will need to remember that the bandwidth aggregation in the data center must meet or exceed all incoming traffic from the remote site. In other words, if I have three remote sites, all with T1. I will need more than one T1 in the data center to manage the traffic. Remember, unless it’s a new field, then baseline, baseline, baseline!
When it comes to bidirectional video streaming, you’ll need to consider the quality of compression you plan to use. If you plan to use a high-definition video address, it is recommended to have at least 2 MB in the video access address.
So if you are streaming video to your computer, then you need to make sure that you have a download capacity of 2MB. Also, another thing to consider is latency and packet loss. I would recommend staying away from wireless for this type of application as it will add latency and cause problems later on. The bandwidth of DS3 and anything above might be excessive, but it could easily handle your demands.
Without knowing the details, it is difficult to give a precise answer, but a systematic method for calculating the required bandwidth can still be specified. Once you know the bandwidth requirement, it’s a matter of negotiating the cheapest way to request that bandwidth from a network provider in the area.
This is what I would suggest:
1. Calculate the maximum external link bandwidth requirements (inter-office data transfer, video conferencing, email transfers. With attachments running at tens of megabytes, email traffic cannot be ignored these days ).
2. Real-time applications are mostly sensitive to jitter and delays, so make sure you have enough bandwidth when they need it. Video bandwidth depends on the mpeg profiles used (without going into specifics, generally 1.5 Mbps can give you very good video on a PC (equal to VCD quality). HDTV pictures can take around 20 Mbps, but that is a domain more reserved for IPTV service providers). Most of today’s users of interactive video communications will be satisfied with images encoded and transmitted at 512 Kbps. This includes audio and video as well as control signaling. So one should provide at least 512 Kbps per video stream, and more the better (I’d say 1.5 Mbps is best if you’re a large organization and use a large TV for video conferencing). So multiply the bandwidth for a single stream by the number of parallel streams required. Now that determines the total peak usage in real time.
3. There is no specific rule, but experienced experts advise keeping the maximum real time between 60-75% of the available network bandwidth, leaving the remaining capacity for background traffic. In a small organization of 5 people, it’s easy to tell people not to download gigabyte attachments when video conferencing, but in larger organizations it’s hard to enforce such things except with router policies (assuming they have QoS support). ), and you can deal with occasional dissatisfied users.
4. Now, once you know your bandwidth requirements, it’s time to talk to your network operator about how they can provide that bandwidth in the most cost-effective way.