Installation of MBone
PS: To do this on the machines in Europe untar the file MBone.tar in /space This will put all the required software in /space/MBone. Then make a softlink (using ln -s) of all the executables to an existing binary directory(like /usr/bin or /usr/sbin).
The directories found in MBone obtained by untarring MBone.tar are
If you want to transmit text use white board. We don't have any text tools installed.
To start an MBone session type the command sdr.
CAUTION: Make sure sdr is in your path. Also make sure that the video tool audio tool and the white board are in your path. Otherwise sdr will not be able to invoke video and audio tools as soon as sdr is invoked. You will have to invoke them manually. So please make sure all these files are in your path.
You will get a sessions directory interface.
To participate in
a session click on the session you want to join.
New sessions can be created by pressing the "New'' button on the sdr main window. Every session must have a name, a short description, a scope, contact information, a start time and a stop time. In addition, sessions may optionally also possess links to further information in the world wide web, a number of detailed media descriptions, and more detailed timing information.
When you click on the 'New' button on the sdr interface you will get an interface where various fields have to be filled in.
This is description of various fields.
Give a name for the session.
You should give a description for your session.
Links to the World Wide Web
A session announcement can contain an Uniform Resource Locator (URL) as a link to related information in the world wide web. The preferences menu determines how sdr follows such references - three options are supported:
If you have an color display of depth 8 bits, using the built in browser is recommended as external browsers use a significant number of the 256 available colors, leaving you with few colors remaining for any tools you wish to use in a multimedia conference. If you have a 24bit display, external browsers are likely to provide you with better performance and prettier displays than the built-in browser. When creating a session, it is recommended that the URL be tested (using the Test button) as typing mistakes here will make the URL useless.
You can test the URL by clicking on the test URL button.
Media descriptions are the main reason for describing a session, as they allow the receiver of an announcement to start the correct media tools directly from sdr with all the correct flags and settings to join the conference. Sdr allows you to create conferences with up to one media tool of each of the following types:
In fact sdr can receive and start sessions with more than one of each media, but the standard interface does not permit the creation of such sessions in an effort to make the session creation interface simpler to use. To include a media in your session, select the media by clicking on the left "X'' button When a media is selected, a default media format will be selected, along with default addresses, transport protocol and ports. The media format and transport protocol can be changed using the relevant pull down menus. The address and port are allocated in such a way that they should avoid clashes with other scheduled sessions - the addresses sdr provides should normally be used, although user specified ones can be substituted if required. In particular, ports are chosen such that rate-limiting in MBone routers will preferentially forward audio rather than video when a multicast tunnel is congested. If everyone you expect to participate in your session is likely to wish to receive all the media you have selected, then using one multicast address for all your media is appropriate. If some receivers are likely to not wish to receive some media - for example some sites have insufficient bandwidth to receive video - then selecting one multicast address per media is appropriate as this permits unwanted traffic to be pruned back from these low bandwidth participant sites.
If your session is not going to be active continuously between its start and stop times, then this detailed timing information should be provided so that users that wish to participate know the precise times, and users that do not wish to participate can know when to expect your traffic to be active.
Sdr allows you to specify up to three active times or repeat intervals for your session - each active time or repeat interval specifies an addition set of times when the session will be active. The limit of three is not imposed by the protocol - if sdr receives an announcement with more than three repeat times it can decode and display it - but rather to simplify the user interface for session creation.
Each scope range (whether TTL scoped or administratively scoped) has a recommended maximum bandwidth associated with it. This is the maximum bandwidth a session should use at that scope. Most of the MBone is currently configured for only a small number of concurrent sessions, (although this is likely to change as the MBone is increasingly provided using native multicast in routers rather than an overlay of multicast tunnels). For this reason it is important to be able to see if a session I wish to schedule will clash with other sessions already scheduled, and to automatically set the maximum bandwidth of the tools to comprise my session.
Unfortunately many users do not know sufficient about the network to be able to decide on appropriate bandwidth figures for their session. To get around this, sdr allows users to specify their sessions as "meetings'' or as "broadcasts'', and lets the audio and video rates be set as "low'', "normal'' and "other'', where "other'' requires that a bandwidth value be inserted. "meetings'' also allow the user to specify "number of simultaneous video streams''. Sdr users this information to set fields indicating the total bandwidth of the conference and the bandwidth to be used by each tool in the conference.
If a user attempts to schedule a session that will exceed the recommended available bandwidth for that scope (based on what other sessions are scheduled) then it will issue a warning and indicate which other session the new session will clash with.
TTL Scope is constrained by the "Time To Live'' (TTL) field in the IP packets a multicast application sends. An application sends its data with a fixed TTL. Each multicast router that the data traverses decreases the TTL on the packets by one. Each multicast router also has a threshold associated with each multicast capable interface or multicast tunnel. If the TTL on the data packets arriving at a router is lower that the threshold of the interface or tunnel, then the packet is not forwarded out of that interface.
The multicast tunnels comprising the MBone are configured so that it is possible to constrain a conference to a particular region of the MBone by careful setting of the TTL. Thus the multicast tunnels in Europe are generally configured with the following thresholds:
Low Speed Tunnels:
Thus if I'm sending from the UK, and want my traffic to reach Europe only, I would send with a TTL of 63, which would traverse the international tunnels but not the intercontinental ones.
Click on menu to change the settings of the audio tool. You can click on help if you need help. Be careful to see that your speakers are not muted when you are listening. If you want to connect to external speaker device be careful to set to external device. To change these options click on the speaker icon. If you want to talk click on talk. If you want to transmit audio you have to follow the following steps.
If you want to change the settings click on options. Click on mute to see your speakers are not muted. You can click on the icon below mute button to change your option of speakers. If you are using external speakers be careful to see that you have changed this setting.
If there is no video transmitted you will get a message "no network sources" on the video tool. You can change your settings like frames per sec by clicking on the button "menu" on the video tool. We can also change the Kbps rate here. IF you need help click on help button on the video tool.
To transmit video you have to follow the following steps:
You can configure the tunnel by configuring the file /etc/mrouted.conf.
CAUTION: MTRACE should be run as root. We can also configure this so that any user without root privileges can make a trace route. To do this login as super user and make a chmod u+s on the executable.
NAME mtrace - print multicast path from a source to a receiver
The output of mtrace is in two sections. The first section is a short listing of the hops in the order they are queried, that is, in the reverse of the order from the source to the receiver. For each hop, a line is printed showing the hop number (counted negatively to indicate that this is the reverse path); the multicast routing protocol (DVMRP, MOSPF, PIM, etc.); the threshold required to forward data (to the previous hop in the listing as indicated by the up-arrow character); and the cumulative delay for the query to reach that hop (valid only if the clocks are synchronized). This first section ends with a line showing the round-trip time which measures the interval from when the query is issued until the response is received, both derived from the local system clock. A sample use and output might be:
The second section provides a pictorial view of the path in the forward direction with data flow indicated by arrows pointing downward and the query path indicated by arrows pointing upward. For each hop, both the entry and exit addresses of the router are shown if different, along with the initial ttl required on the packet in order to be forwarded at this hop and the propagation delay across the hop assuming that the routers at both ends have synchronized clocks. The right half of this section is composed of several columns of statistics in two groups. Within each group, the columns are the number of packets lost, the number of packets sent, the percentage lost, and the average packet rate at each hop. These statistics are calculated from differences between traces and from hop to hop as explained above. The first group shows the statistics for all traffic flowing out the interface at one hop and in the interface at the next hop. The second group shows the statistics only for traffic forwarded from the specified source to the specified group.
These statistics are shown on one or two lines for each hop. Without any options, this second section of the output is printed only once, approximately 10 seconds after the initial trace. One line is shown for each hop showing the statistics over that 10-second period. If the -l option is given, the second section is repeated every 10 seconds and two lines are shown for each hop. The first line shows the statistics for the last 10 seconds, and the second line shows the cumulative statistics over the period since the initial trace, which is 101 seconds in the example below. The second section of the output is omitted if the -s option is set.
Waiting to accumulate
statistics... Results after 101 seconds:
Because the packet counts may be changing as the trace query is propagating, there may be small errors (off by 1 or 2) in these statistics. However, those errors should not accumulate, so the cumulative statistics line should increase in accuracy as a new trace is run every 10 seconds. There are two sources of larger errors, both of which show up as negative losses:
Note that these negative losses may mask positive losses.
In the example, there is also one negative hop time. This simply indicates a lack of synchronization between the system clocks across that hop. This example also illustrates how the percentage loss is shown as two dashes when the number of packets sent is less than 10 because the percentage would not be statistically valid.
A second example shows a trace to a receiver that is not local; the query is sent to the last-hop router with the -g option. In this example, the trace of the full reverse path resulted in no response because there was a node running an old version of mrouted that did not implement the multicast traceroute function, so mtrace switched to hop-by-hop mode. The Route pruned error code indicates that traffic for group 220.127.116.11 would not be forwarded.
Last Updated: 7/21/00
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