Control Streaming Media

Instructions to manage the performance of streaming media.

We'll consider streaming media as any content that is played (video or audio) as it arrives at its network destination. Streaming media that arrives with stutter and static is not likely to gain many fans. On the other hand, too many fans can undermine performance for everyone, including users of other types of applications. PacketWise can help keep the equation balanced — smooth performance without taking over the network.

PacketWise's recommendation for managing streaming media entails identifying the streaming-media traffic, reserving a portion of the network to support the media, protecting individual media users from each other, and protecting other applications from the swelling media demand.

For help managing Voice over IP or Video over IP specifically, see the more tailored recommendation Manage Voice and Video Sessions.

Steps:

1. Determine which streaming-media traffic you'd like to manage.
   
   PacketWise automatically discovers many types of multimedia and streaming traffic including Multicast, NetShow, NetMeeting, QuickTime, RTPReal, AudioStreamworks, RTSP, MPEG, Media Gateway Control Protocol (H.248 and Megaco), ST2, SHOUTcast, WebEx, WindowsMedia, and VoIP. Autodiscovered Voice-over-IP traffic includes Clarent, CU-SeeMe, Dialpad, H.323, I-Phone, MCK Communications, Micom, and VDOPhone.
   
   You can start determining the types of streaming traffic that are active on your own network by examining your Monitor page after PacketWise has run for about a week with traffic discovery enabled.
   
   
2. Create a traffic class to identify and isolate your streaming traffic, if one does not already exist.
   
   For example, if the streaming-media traffic you want to classify is MPEG, then create a traffic class for HTTP with a matching rule that selects based on content type. See Application-Specific Criteria for details.
   
   For background information, see Traffic Tree Overview and/or Traffic Classification Overview.
   
   
3. If you have several types of streaming applications that you'd like to view and control together, create a folder class called Stream and move all your streaming-media traffic classes into it. Make sure you have folders in both the Inbound and Outbound branches.
   
   
4. Determine appropriate minimum and maximum amounts of bandwidth for each streaming traffic class (if you did not make a folder) or for all streaming traffic (if you did). These sizes will be used in partitions that you'll create in the next step.

   The minimum and maximum sizes of your partitions depend on how restrictive you want to be and the relative importance of streaming media with other traffic. For help determining correct minimum and maximum sizes, consult Sizing a Static Partition.
   
   It is not uncommon to decide on a minimum size of zero (0 Kbps) if your organization does not need streaming applications and your primary concern is protecting other applications. The maximum size, for these types of situations, should be the maximum portion of the WAN link you are willing to devote to streaming media even when there are more sessions than anticipated.
   
   For environments where streaming-media applications are essential, the minimum size is the portion of the WAN link required for reasonable performance of the anticipated number of sessions. You could allow the partition to burst to the link size by specifying no maximum, or you could specify a maximum that would accommodate peak streaming usage.

5. Create partitions to limit the total amount of bandwidth for streaming applications. Remember to create partitions for both the Inbound and Outbound branches. If you created a Stream folder, apply the partition to the folder.
   
   For background information, see Partition Overview.
   

6. Set a rate policy on each of your streaming traffic classes to accomplish several goals:
   
   - to indicate the relative importance of your streaming traffic so that PacketWise knows how to distribute excess bandwidth
   
   - to insulate streaming users from each other so that one high-capacity user doesn't take the whole Stream partition
   
   - to gain the benefits of TCP Rate Control and in particular, to reduce retransmissions that waste bandwidth
   
   - to reserve the appropriate per-session bandwidth to ensure smooth streaming performance
   
   In the policy definition, if you want to preserve smooth per-session performance, use a guaranteed rate of the minimum Kbps for adequate performance. For one of the examples in the previous step, the guaranteed rate would be 15 Kbps.
   
   If you want to protect low-capacity users from high-capacity sessions, cap each session at a Kbps that is more than sufficient for optimal streaming performance. Make sure the limit allows a reasonable number of concurrent sessions within the partitions you created in the previous step.
   
   Assign a priority that communicates the relative importance between the streaming-media application and other applications. It will be used to determine access to the partition's maximum size instead of the minimum.
   
   For example, a rate policy for VoIP could be: Guaranteed: 22K, Limit: 30K, Burstable at priority: 5
   
   For background information, see Policy Overview.
   
   
7. Determine the strategy you'd like to follow if more users want access to streaming media than your partitions, policies, and link size can accommodate. Would you like to reject latecomers during busy times? Would you like to squeeze them in with a tiny amount of bandwidth and just string them along until more becomes available? Would you like to redirect them to a web page that explains the problem?
   
   Apply admission control settings to your policies to enforce your strategy.