Appendix B

Troubleshooting

Overview

This section will address some common problems and answers some questions that may be encountered when using the Communique! software.

Common Questions about Networking

Many problems that you may encounter while using the Communique! software are network related. Communique! uses some important, low level networking functions that many other programs may not require to function. For this reason, many irregularities in network configuration do not manifest themselves until attempting to use Communique! or other network intensive applications. If you are experiencing problems operating the Communique! software, here are a few areas that you may want to investigate.

Why can’t I locate other conference members?

Try reselecting the From Notebook button on the Start Conference panel to update the list of available conference members on your local network. The list is updated each time you bring up the From Network list.

If there is heavy traffic on your network it is possible that all available network users may not be detected. You can try reselecting the From Notebook list several times until your party appears.

Communique! will locate other possible conference members on your local network automatically. When traveling to remote and secondary networks, the broadcast message used to detect other Communique! users has a TTL value of 4. If you wish to assure that Communique! will detect users on remote networks you must set up a Broadcast Tunnel. Information on setting up a Broadcast Tunnel can be found in the Technical Issues appendix of the Communique Administrator’s Guide.

If you are attempting to contact someone on a remote or secondary network and are not using Broadcast Tunneling, the person may not appear in the Start Conference control panel and will have to be added with the Custom Address entry, as described in the "Conference Manager" chapter of the Communique! User’s Guide. In any case, Communique! must be able to contact the host machine of those persons with whom you wish to conference.

Why can’t I contact a remote conference member?

Make sure that each host can ping all other hosts which will be in the conference, including itself. For example, in a conference with workstations host1 and host2, host1 should be able to successfully

ping host1

and

ping host2

The other workstation, host2, should be able to do the same. A successful ping indicates only that a minimal level of networking infrastructure is working; there could still be problems.

Make sure that each host can telnet to all other hosts which will be involved in the conference, including itself.

What is IP Multicast?

Multicast is a networking technology that reduces duplication of network data in multipoint conferences. If you are using Unicast routing, a separate stream of data is sent to each user receiving video or audio. This means that in a 4 way conference in which everyone is sending audio and video, there are 12 audio and video streams being sent, 3 per user. Multicast enables Communique! to send out only one stream of video data and one stream of audio date regardless of the number of users receiving the data. If the same group of users described earlier were using multicast routing, there would be only 4 audio and video streams total for the conference, greatly reducing the amount of network bandwidth usage, and freeing up resources on the machines that are sending data.

Multicast packets are received only by workstations interested in the packets. This "packet filtering" is done in low-level hardware, not by the CPU.

For multicast to function correctly, an explicit route to the multicast address must be defined so that the workstation will recognize it as a valid local address. The multicast address is normally 224.0.0.0. The route is normally added to /etc/rc.local during installation, and is done with the following command:

route add "224.0.0.0" hostname 0

You will also want to make sure that all of your network hardware includes support for multicast routing. If you will be conferencing with users across a router, you will need to make sure that the router supports multicast.

You can find out if your network interface supports multicast using the ifconfig command. For example, to see if multicast was supported on an HP-UX 9.05 machine, you would type:

ifconfig lan0

Time To Live (TTL) is an attribute of IP multicast that defines how far a multicast packet travels out across the network. Each time a multicast packet travels through a gateway, its TTL value is decremented by 1. Some gateways may decrement the TTL value by 2, 3, or more to control the distribution of multicast packets. Although there are no set standards for TTL values, there are a few conventions that have been established:

1 Restrict the packets to the local subnet

32 Restrict the packet to the site

64 Restrict the packet to the region

128 Restrict the packets to the continent

256 Do not restrict the packet’s travel at all

You will want to use the lowest TTL possible to avoid wasting bandwidth on uninterested segments of your network.

What if I have multiple network interfaces on my workstation?

If you are running multiple network interfaces on one workstation verify that the interface associated with the hostname of the workstation is up and running. Make sure that the hostname of each interface is unique and assigned to what you think it is assigned to.

Many problems can be avoided if there is only one interface active.

The interface lo0 is the local network loopback interface and should never be removed. Most network activity relies on this interface.

Make sure that each interface is set up properly. Use the ifconfig command to show you the current settings. Make sure each interface has its netmask and broadcast address set properly.

Make sure that you bring up any extra network interfaces at the same time the standard interfaces are brought up and make sure you do not disable any interfaces after they have come up. This is because certain processes, such as the portmapper, should only be run after all network interfaces are configured and running. Bringing new interfaces up or existing interfaces down can cause unpredictable results. In most configurations, by ifconfig’ing all interfaces at the same time at system boot you will start everything in the proper order.

If you are running a License Server on a machine with multiple interfaces make sure that the license file specifies the hostname of an active interface.

What if I am using a router?

If the machines are connected through a router, the router must be able to pass tcp and udp packets. Many routers have an option to block specified packets types. Make sure the above types are enabled in both directions.

If you are running through a router, make sure that the router can keep up with large amounts of data. You can test this by ftp’ing a large file (at least 1MB in size) both ways across any routers. If you see any time-outs, Communique! may have problems as well. This especially applies when you are routing from a high speed network (such as ATM or FDDI) to a slower network (such as Ethernet). Sometimes routers cannot do packet size conversions quickly enough.

If you are using IP Multicast routing, you must make sure that your router supports the Multicast protocol.

What if I am using an ATM interface card?

If you are using the TV Tool with an ATM card that relies on the workstation for packet conversion, you may experience performance problems at higher video frame rates because of the overhead required to process the incoming packets.

Check the version number of the switch software and the card revision. The card switch software must be newer or equal to the card. If it is not, you will experience severe problems using Communique!

If you are experiencing problems, try ftp’ing a large file across the ATM network. If it does not succeed, it is likely that there is a compatibility problem between your ATM card and switch software.

If you are using Multicast routing, you must make sure that your ATM card supports the Multicast protocol.

Common Questions about Licensing

Why do I get "Can’t connect to license server" errors?

The MDL software is unable to contact the license manager daemon (lmgrd) on the License Server. There are several situations where this error will occur.

A good source for determining the problem is to the license.log file on the License Server. This is normally on the machine that runs the lmgrd process. By default, it is located in etc/insoft/license.log.

Verify that the workstation specified as the license server in the license.dat file is running and is reachable through other network commands such as ping or telnet. If you receive "unknown host" messages, you probably have a problem with hostname resolution. Verify that the insoftd and lmgrd daemons are running on the server. You may want to examine the server’s license.log file for errors. If you are using DNS, the license.dat file should contain the fully qualified hostname. An example of a complete hostname is host1.conglomerate.com

Verify that the lmgrd and insoftd processes are running on the license server machine.

Because of security concerns, the lmgrd daemon will refuse license requests from a client whose time is more than 5 minutes different from its own after differences for time zones are taken into account. Make sure both machines have their dates and times set correctly, and that they are in the correct time zones.

Why do I get "inconsistent encryption code" errors?

There is a problem with the license key you have entered. Examine the license.dat file to verify that you have entered the correct license keys for your host. Verify that you selected the correct type of key (floating or node-locked). Check to make sure that you entered the correct expiration date. Make sure that your keys were generated for the correct hostid.

Why do I get "key not yet valid" errors?

The start date of your license keys has not yet arrived. Check your workstation’s system date to verify that it is correct.

Why do I get "license key has expired" errors?

The system date on your workstation has passed the license key expiration date. Verify that your system date is correct. This message should only occur with temporary evaluation keys.

Why do I get "maximum number of users reached" errors?

This message indicates that no more licenses are available for the requested feature. This could be caused by several things. If you have floating licenses, it indicates that all available licenses are in use by other users. You will have to wait until a user quits Communique!, releasing the license. If you are on a node-locked workstation, the license could be claimed by an already running Communique! application or a defunct process failed to release its license. The root user can run the license/lmremove program found in the Communique! Install Directory or kill and restart lmgrd to release licenses.

Why do I get "No FLEXlm nodes found to shut down" errors at boot?

This is normal. The start-up scripts attempt to bring down any active license managers at system boot. This assures that there will be no conflicts when the license manager is started. The next step in the start-up process will run the license manager, and you will see a message indicating that it has been started successfully.

Common Questions About Video

What compression algorithm does Communique! use?

This depends on the type of compression selected in the TV Tool control panel. The compression schemes that you can select from depends on the type of video capture board installed on your workstation. The currently supported compression options are:

CellB—CellB compression was developed by Sun Microsystems to support compression and decompression of video with minimal hardware requirements. CellB is supported by all Communique! platforms. The MDL CellB codec for the PC has the ability of transcoding. This means that it can recompress video that has already been compressed with another format.

DVE2—DVE2 compression was developed by MDL to support compression and decompression in software. DVE2 provides a high level of image quality by taking advantage of today’s more powerful processors. DVE2 is currently available to PCs only. The MDL DVE2 codec for the PC also has the ability to do transcoding.

Indeo—Indeo is a video codec developed by Intel. Indeo provides high image quality and very efficient software decompression. However, Indeo does not lend itself well to compressing in software, so generally you will want to use this format only if your video capture card supports Indeo compression in hardware. Indeo is currently available to PCs only.

JPEG—JPEG, developed by the Joint Photographic Experts Group, generally produces the highest quality video image, but requires more processing power than other compression algorithms. Unlike Indeo, JPEG requires substantial processing power to decompress in software so you will generally want to use this format only if your video capture card supports JPEG compression and decompression or you are using a fast workstation.

H.261 and IP64—H.261 is the telephony video compression standard developed by CCITT. H.261 works by first selecting the bandwidth available for video and the desired frame rate. The video is then compressed to fit into the given constraints. H.261 on a workstation is a software compression and decompression algorithm that requires substantial processing power. H.261 is currently available on HP workstations only. IP64 is almost identical to H.261, but the data is packetized in a format optimal for TCP/IP networks. It is available for most video capture boards on most workstations.

The receiving conference member does not have to support hardware decompression of the sender’s compression type since the Communique! software can use software decompression techniques if no hardware is available.

Why does the video I receive seem slow?

If your video is uncharacteristically slow there are several things you should check.

What is the quality of the source video signal being sent to you? If the incoming video signal quality is poor and full of static, the compression algorithm cannot function properly. The sender should obtain a more stable video signal. If the quality of the input signal can not be improved, reducing the frame rate and video frame size may help improve performance.

What frame rate has been selected in the sender’s TV Tool control panel? Each person in the conference has control over her or his own sending frame rate. The remote conference member may have purposely (or accidentally) selected a slower frame rate.

If the person sending video has used the Bandwidth control under the TV Tool Networking options to limit the bandwidth they are using make sure it has not been set at an unnecessarily low setting.

What other applications are in use while the Communique! TV Tool is running? If the frame rate is high, slower workstations may not be able to reproduce the desired frame rate. This is especially true if other processes are using up workstation resources. Try reducing the number of other applications running on the workstation.

Is network traffic high or available bandwidth constrained? Bandwidth limitations or an increase in ambient network traffic will reduce the amount of information that can be sent out to the conference.

Do you have enough RAM and swap space? See the "System Requirements" chapter of the Administrator’s Guide for your workstation’s requirements.

If you are receiving H.261 or IP64 video and your workstation does not feature hardware decompression you will experience reduced performance. Ask the sender to select CellB as their sending compression, reduce the captured video image size, or reduce the frame rate.

If you are receiving JPEG video and do not have a video card that supports hardware decompression of JPEG you will experience reduced performance. Ask the sender to select CellB as their sending compression.

Why can’t others see my video?

If your video capture card has multiple video inputs, have you selected the correct one from the TV Tool Video options?

Have you disabled video transmissions from the TV Tool control panel? You must click on the TV Tool’s Start button to begin sending video from your workstation.

Have you selected the desired conference member(s) to receive video from the TV Tool’s Members option? You should verify that the user not receiving your video is in the "Offer Video To" list and click on Apply to make the changes take effect.

Enable the Local Monitor option and verify that your video card and equipment is functioning properly.

Is there a problem with your video equipment or cabling? Verify that the video source is connected to the TV Station properly. Try using another video source or connect your video source to another output like a television display to verify that it is operating properly.

Have you correctly installed your video board and any necessary drivers? Most video capture boards come with demonstration or test programs that you can use to verify correct installation of the video board.

Is the correct video board selected in the TV Tool control panel? The TV Tool control panel will allow you to select from several different types of video boards, even if they are not installed on your workstation. If you are not sure which type of video board is installed on your workstation contact your system administrator.

There may be a problem with the configuration of the network. Verify correct network configuration as outlined in the "Common Questions about Networking" section.

Why does the video I receive seem distorted or grainy?

To conserve network bandwidth and increase the frame rate of video, Communique! employs various types of data compression techniques. The compression algorithms that the sender can use will depend on the type of video board that they are using. JPEG generally will produce the best quality video, but takes more bandwidth and is harder to decode in software than CellB. Ask the sender to choose a different compression method to view your options.

Be aware that not all video boards are alike. Some video cards such as SunVideo produce a different level of video quality than boards such as Parallax. The quality of image is directly related to the compression and display hardware contained on the card.

What compression settings have been selected on the sender’s TV Tool Video options? Each person in the conference has control over her or his own video compression settings. The remote conference member may have purposely (or accidentally) selected a higher compression setting, which could have a dramatic effect on image quality.

What is the quality of the source video signal being sent to you? If the incoming video signal quality is poor and full of static the received image will be poor. The sender should obtain a more stable video signal.

Why do I see color flashing when I move among windows?

On an 8-bit workstation, the video image must share a color palette with all other applications. Since there are only 256 colors available, the video window creates its own private colormap, active only when the window is selected. You may experience color flashing in the Local Monitor or TV Viewers. From the TV Viewer options you can select "Suppress Color Flashing" to eliminate the flashing. However, this will reduce the number of colors available and thus the quality of the video. If your workstation has the ability to run in a 24-bit display mode you may be able to eliminate this problem completely.

Common Questions About Audio

Why does the audio I receive seem so loud?

Check the Audio Tool settings for playback volume. This option controls the volume level of the audio you hear. Reduce the playback volume to a reasonable level.

If you are using an external speaker make sure the volume is adjusted to a reasonable level.

Each person in the conference has control over their own sending volume. Ask the person to reduce his or her sending volume.

Some microphones feature an adjustable gain control. If the sender is using such a microphone and adjusting the sending volume has little effect, ask them to reduce their gain to a reasonable level.

What is the level of the sender’s input audio signal? If the level is too high it will overload the workstation’s audio inputs producing a loud muffled sound or severe clipping. This situation can occur if they are using audio input from a line level device such as a VCR connected through the microphone-in port of the workstation. See the section "Audio Input Devices" section in the Installing Optional Hardware chapter of this guide for more information.

Why don’t other people in the conference hear me?

They can enable their AudioScope to see if they are not receiving audio or just can not hear it. The AudioScope is available from the Audio Tool and will show which users are currently sending you audio. This is very helpful in tracking down the problem.

You may have muted your audio from the Audio Tool. Bring up the Audio Tool control panel and verify that the mute option has not been enabled.

Your sending volume may be too low. Adjust the sending volume level for the Audio Tool to a reasonable level.

The remote conference member’s playback volume may be too low to hear you. Have conference members verify that their playback volume has been set to a reasonable level in the Audio Tool control panel. Have them check the connection and volume setting of any external speakers they are using.

Have you selected the desired conference member(s) to receive audio from the Audio Tool’s Members option? You should verify that the user not receiving your audio is in the "Offer Audio To" list and click on Apply to make the changes take effect.

They may be refusing your audio. Have them check their Members option and verify that they are accepting audio from you.

Your microphone may not be hooked up correctly, or may be defective or in need of a new battery. Verify that the microphone is on and plugged into the microphone-in port of your workstation. You can use enable Local Monitor from the Audio Tool’s Device options to verify that your microphone is functioning properly.

You may have selected the wrong input device. Check the Audio Tool’s Device options and verify that you are using the selected input device.

Your Silence Sensor may be set too high. Try reducing the level of the Silence Sensor from the Audio Tool’s Advanced options.

Another application may have gained control of the audio port. Only one application at a time can access the audio port, so you will need to exit any other applications that attempt to use the audio port.

The Echo Cancellation value in the Audio Tool’s Advanced options may be set too high. If the Silence Sensor is set too low and the Echo Cancellation too high, no one will be able to speak without Echo Cancellation cutting them off. This doesn’t happen often, but the situation could arise if your microphone or speaker produces a constant hum that confuses the Echo Cancellation process.

Why don’t I hear other conference members?

You can enable the AudioScope to see if you are not receiving audio or just can not hear it. This is very helpful in tracking down the problem.

Which audio output device has been selected in the Audio Control Panel? If headphones have been selected as the audio output device you will not hear audio from the workstation’s speaker.

Your playback volume may be set too low to hear other conference members. Verify that your playback volume has been set to a reasonable level in the Audio Tool.

The remote conference member may not be sending you audio. Have them check their Members option and verify that you are being offered audio.

You may be refusing their audio. Check your Members option and verify that you are accepting audio from that person.

The remote conference member may have a problem sending audio. Refer to the section Why don’t other people in the conference hear me?.

Your speaker may be defective or your external speaker box hooked up incorrectly. Verify that the speaker or speaker box is functioning correctly.

If you are using an external speaker, is it on? Verify that it is connected properly. If it uses batteries, are they dead? If your external speakers connect to the workstation through the headphone port then verify that Headphones have been selected in the Audio Tool Device options.

There may be a problem passing audio data through the network. Refer to the section entitle "Common Questions About Networking" to verify that your network is functioning properly.

Another application may have gained control of the audio port. Only one application at a time can access the audio port, so you will need to exit any other applications that attempt to use the audio port.

The Echo Cancellation value in the Audio Tool’s Advanced options may be set too high. If the Silence Sensor is set too low and the Echo Cancellation too high, no one will be able to speak without Echo Cancellation cutting them off. This doesn’t happen often, but the situation could arise if your microphone or speaker produces a constant hum that confuses the Echo Cancellation process.

Why do I hear an echo of myself or feedback?

This situation occurs when your voice is picked up from a remote user’s speaker by her or his microphone and retransmitted into the conference. This loopback can be minimized and prevented in several ways.

Ask the remote conference member to move his or her microphone away from the speaker. If they are using an external speaker, have them point it away from the microphone.

Reduce your Sending Volume or have the remote conference member reduce her or his playback volume to decrease the likelihood that the microphone will pick up the sound from the speaker.

Ask the remote conference member to raise his or her Silence Sensor. This will decrease the likelihood that the remote microphone will pick up sound from the conference member’s speaker.

Try increasing the Echo Cancellation value from the Audio Tool’s Advanced settings.

If you are unable to correct the echo situation, you may want to consider using external headphones instead of sending audio through a speaker.

Why does the audio sound choppy or clipped?

Make sure that the person using the microphone is directing her or his voice towards the microphone and from no more than a foot away. Most high quality microphones, including those available directly from MDL, are unidirectional. Unidirectional microphones only pick up sound whose source is directly in front of them. If you turn your head from side to side or walk around the room the microphone will not pick up your voice.

The person sending audio may have his or her Silence Sensor level set too high. Often, as conference participants speak, their voices drop down in volume on some syllables, especially at the ends of words. The Silence Sensor will recognize these dips in volume as "silence" and not send them to the other conference members. Ask the person whose audio is clipping to reduce the level of his or her Silence Sensor.

If your network is very busy, try reducing the level of the A/V Sync slider. If Communique! is unable to synchronize your video and audio together, it may begin dropping some of the audio information.

If there are several other people involved in the audio conference it is critical to properly set the Silence Sensor control to the proper level.

Why do I hear lots of background noise or constant humming?

What type of microphone is being used? Lower quality microphones are often omnidirectional. Omnidirectional microphones pick up sound from all directions, and are likely to give unsatisfactory results. MDL strongly recommends purchasing a high quality, unidirectional microphone.

Some low quality or damaged microphones are not adequately grounded. This could cause a constant humming sound to be input into the conference. Try to locate the offending equipment and replace it.

If you are using external speakers a buzzing sound could be caused by electrical interference. If you can not eliminate the source of the interferences try reducing the treble controls (if available) to reduce high frequency noise.

The Silence Sensor level of the person sending audio may be set too low. The Silence Sensor allows the microphone to send audio only above a given threshold, ideally when someone speaks. By raising the level of the Silence Sensor, you can filter out a good portion of the low level background noise.

If you are using compressed audio, you should expect some loss of audio quality.

How Can I Minimize My Bandwidth Consumption?

By reducing the amount of network traffic you generate, you can speed things up for other network users, better Communique!’s performance under low bandwidth conditions, and speed up Communique!’s functions. There are several things that can be done to reduce the amount of network bandwidth that you use.

Video Frame Size—The larger the video frame size, the more video data that must be transmitted across the network. Lowering frame size reduces network traffic. Shrinking the video window size will also give you more space on the desktop.

Video Frame Rate—Bandwidth usage is directly proportional to the video frame rate. Reducing the frame rate can greatly reduce the amount of traffic being generated.

Video Compression—By increasing the amount of compression being used on your video signal, you can significantly reduce the amount of bandwidth you consume. Increasing the amount of compression will reduce the quality of the video image, but often a slight increase in compression will yield dramatic bandwidth reduction with only a modest decrease in image quality.

Bandwidth Controls—By selecting a Bandwidth setting from the TV Tool’s Network options you can specify the maximum bandwidth that your video will generate. This will set the maximum amount of bandwidth that one stream of video will create.

Audio Compression—By enabling audio compression from the audio tool, you are able to reduce the audio conference’s bandwidth consumption by almost half. You will notice a reduction in sound quality, but under low bandwidth availability the savings may be worth it.

Silence Sensor—By keeping the Silence Sensor set as high as possible—so that you are not transmitting audio data when you are not speaking—you lower the amount of network traffic you generate. You must of course avoid setting it too high or you will affect audio quality.

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