Breeze Article
Network Latency and Breeze Meeting
Table of Contents
Section 2: Managing Bandwidth in Your Breeze Meeting Room Using the Built-In Tools
Once you have found and eliminated sources of excessive latency, you will want to use the built-in tools in Breeze Meeting to manage Meeting performance. This section of this article will show you how to best tune the Meeting experience.
There are tools in the meeting room to use to manage bandwidth. Participants can individually make bandwidth adjustments and hosts and presenters can make adjustments either for themselves individually or for the entire meeting room; each attendee can specify their own connection speed setting and the host or presenter can set an average value for the meeting room. Individual settings optimize how much information is sent to and from an individual client computer. The host or presenter should set an overall setting for the meeting room under the Meeting menu option: Optimize Room Bandwidth. By matching the room bandwidth with the average participant bandwidth, the host or presenter helps ensure a uniform experience. The options are Modem, DSL & LAN. The default setting is LAN; it sends high-quality audio, video and screen sharing, but the LAN setting should be used judiciously as it may try to send too much data to participants with slower connections. The DSL setting is a good choice when you have a mixture of users on cable, broadband and LAN pipes. The DSL setting will limit the maximum amount of data sent from the Meeting server without markedly slowing performance for LAN users. The Modem option is more restrictive, but will ensure that slow connections are not lagging behind the rest of the participants in the Meeting. The LAN setting also may tax the CPU on the client of the host or presenter. If the presenter’s platform’s CPU is running high (that is, running consistently over 80%) it may be a good idea to throttle the connection to DSL or get a higher-end presenter client workstation or laptop.
Figure 4. Optimize room bandwidth
The room connection settings above have the following delimiting effect on the Meeting room:
- LAN: 400 up-kbps 800 down-kbps
- DSL: 250 up-kbps 600 down-kbps
- Modem: 28 up-kbps 40 down-kbps
The default connection speed setting for each host, presenter or participant is LAN. Set the connection speed to the actual connection speed: Meeting > My Connection Speed. This should be lowered if an individual user experiences latency.
Figure 5. My Connection Speed
The individual connection settings above have the following delimiting effect on the Meeting room:
- LAN: Unlimited up-kbps Unlimited down-kbps
- DSL: 250 up-kbps 600 down-kbps
- Modem: 28 up-kbps 40 down-kbps
Hosts may view the connection status of all participants in a meeting by clicking the pod options button in the attendee list pod and selecting Show Connection Status. In the illustration below, the host would want to throttle the room down from LAN to at least DSL speed if not modem, based on the connection speed of the participants. The red bar attendee connection indicators represent modem connections and the yellow represent DSL connections. Sometimes the connection status of participants may change throughout a Meeting based on varying network throughput.
Figure 6. Attendee List
Clients may select Help > Connection Status in the meeting room. This will launch a test page at the Adobe-hosted cluster to help the client gauge the latency for their specific session. This tool is most helpful when a single client or a couple of clients are experiencing latency, as it does not run a test from the client to the licensed server hosting the Meeting.
Figure 7. Breeze Meeting Connection Status
Once in a Breeze Meeting room, you will see a small room status indicator in the upper-right corner of the room. If the indicator is green, then you are online and experiencing excellent throughput; if it is yellow, there is some limited network congestion; if it is red, you are on the brink of being disconnected or have been disconnected due to network problems. You can click the connection indicator; if it is green or yellow, it will display information about connection. The first number that appears represents the average roundtrip time to the nearest Breeze Edge server, while the second number indicates the “ping” time to the nearest Breeze origin server. If it is red, it may still display connection information or if disconnected it will attempt to reconnect your session. If the Meeting servers are in a cluster, Meeting server failover may have occurred if the indicator goes from green or yellow, to red and then back to green or yellow in a matter of seconds. The SSL indicator is the padlock in the middle of the connection indicator.
Note: If there is a “T” in the connection indicator output it means that the RTMP connection is tunneling (RTMPT). RTMPT connections use HTTP tunneling and consequently, they are slower than regular RTMP connections by approximately 20%. It is best to avoid tunneling when possible; we will discuss this further in a future article.
Figure 8. Connection SSL Indicator
Figure 9. Connection Status Message
You may find that RTMPS traffic is often manifesting a yellow connection indicator, but your tuning or troubleshooting should be triggered by the actual experience of the participants in the room rather than as a reaction to the connection indicator. A yellow connection indicator or an indicator that switches between green and yellow is normal as long as the experience of the participants is good. You will find that the less traffic there is in a meeting room, the more latency will be reported by the connection indicator. As RTMPS traffic begins to ramp up, it also begins to speed up.
Along with the built in Breeze bandwidth management tools, good meeting room practices such as limiting the use of screen sharing in favor of showing uploaded Captivate screen captures or Flashpaper documents helps to economize on bandwidth usage without having a negative impact on the user experience. Frugal use of the Camera & Voice (C&V) pod also helps limit bandwidth usage: if high-quality images are not needed and bandwidth is limited, then use the C&V pod options button to use a less bandwidth-intensive setting. You may also remove the C&V pod or pause it, leaving a still photo of the presenter displayed in the pod. Below are some estimated bandwidth usage calculations that will be helpful gauging room settings and meeting practices. When you (or your participants) are not on a LAN, you will want to consider the following: a T1 connection has 1.544 MB per second up and down bandwidth, DSL and cable can vary in the range of 350 up and 1MB down. DS0 is a single 64 Kbps channel; an ISDN is two DS0 line plus signaling. When multiple users are sharing a T1 or a DSL connection, the bandwidth is divided up among the users. Here is an estimate of what Breeze 5 will use:
Webcam:
- In a room set to LAN connection with Webcam set to the following: slow images: 26 kbps & 2 fps, fast images 250kbps & 15 fps, high-quality images 250 kbps & 12 fps.
- In a room set to DSL connection with Webcam set to the following: slow images: 26 kbps & 2 fps, fast images 125 kbps & 15 fps, high-quality images 125 kbps & 12 fps.
- In a room set to modem connection with Webcam set to the following: slow images: 26 kbps & 2 fps.
Screen Sharing:
- In a room set to LAN connection: 400 kbps & 2 fps.
- In a room set to DSL connection: 100 kbps & 2 fps.
- In a room set to modem connection: 28 kbps & 1 fps.
Audio:
- In a room set to LAN connection: 44 kbps & 22 kHz.
- In a room set to DSL connection: 22 kbps & 11 kHz.
- In a room set to modem connection: 10 kbps & 5 kHz.
FLV will play with original encoding rate and SWF will use http delivery.
Where to Go From Here
If you experience excessive latency, find the problematic network switch, NIC or router, etc.! In most cases the latency will be on a device located between the VIP on the HLD/SSL accelerator and the client; it seldom will be between the SSL accelerator and the Breeze server. It will often require the assistance of an IT networking team to discover the source of the latency. General tips are to have them update any suspect IOS; all network switches should be brought up to date. Look for link-speed mismatches and NICs that are set to half duplex. You may find that the IT network engineer has been looking for an excuse to throw out that old 2900 switch in favor of a nice fast 3560.
Once you have optimized your network bandwidth, you will want to train all your Meeting administrators to manage the bandwidth setting in each meeting room. Make sure they are attentive to the connection speeds of their clients as they may change throughout a meeting.
Look for upcoming detailed, example-based articles describing how to integrate a Breeze server pool with popular high-end SSL accelerators and hardware-based load balancing devices.
