This page describes the current status of our tools and architecture for session announcement. For more details, see
the ACM Multimeda 98 paper.
The Architecture
The architecture consists of two pieces, a new session directory tool, called nsdr, and a session announcement ``agent'', called sdfor. The agent has several roles:
- It listens to all global session announcements and by implementing a soft-state gateway, the start-up time for a session directory application is reduced dramatically.
- It may announce sessions on behalf of a session directory application so that the session directory application does not need to be run continuously to announce a session.
- It may create supplementary announcements for sessions that use layered transmission coupled with administrative scoping. This functionality has not yet been fully implemented or deployed -- see the paper for more details.
If you simply want to use a session directory application, you shouldn't need to worry about the presence of an agent. Any properly configured session directory application can make use of the soft-state gateway for rapid start-up but only nsdr can take advantage of the proxy announcement capability of sdfor.
Using nsdr
For simply receiving and displaying session announcements and launching media applications, nsdr is not very different from Mark Handley's sdr. The main window and a program description window are shown here.
Clicking on a program displayed in the main window displays a program description window. Various information from the session description is displayed in this window. Applications that can be launched to participate in the session are displayed at the bottom left. The command lines that will executed are shown -- you can change the command line arguments by editing this field and then run individual apps by pressing the ``Run'' button.
Creation session announcements from nsdr still needs a bit of work but the basic functionality is in place. If you have questions or suggestions about the session creation process, just send us mail for now.
XXX Need more info on configuring apps, etc...
UCB
The use of administrative scoping on the UCB campus and within the UC system in general has not yet been completely worked out. At this time, the address range 239.192.0.0/14 (that is, all addresses in the range 239.192.0.0 through 239.195.255.255) is scoped to the UCB campus. SAP announcements for sessions in this scope region are announced on address 239.195.255.255, port 9875. To see such announcements, add the following line to ~/.mash/prefs-nsdr:
sapZones: 224.2.128.0/17,239.192.0.0/14,239.255.0.0/16
As of April 1998, the 128.32.130.0/25 subnet (the MASH group subnet) is also connected to the CAIRN high-speed network. Work to make CAIRN available on more campus subnets is underway. See the following section for details on CAIRN.
CAIRN
The CAIRN high-speed research network uses the address range 239.140.173.0/24 (that is, all addresses from 239.140.173.0 through 239.140.173.255) for administratively scoped transmissions. SAP announcements in this region are sent to the address 239.140.173.255, port 9874. To see these announcements, add the following line to ~/.mash/prefs-nsdr:
sapZones: 224.2.128.0/17,239.140.173.0/24/9874,239.255.0.0/16