Ohio University Always ON DTN Network
Ohio University and NASA Glenn Research Center (GRC) have created mirrored implementations of virtualized DTN networks. Ohio University has implemented an ION network. The details are provided below. Glenn Research Center's DTN network is a DTN-2 network. (GRC DTN-2 DTN Network)
The purpose of these networks is to get some "Disconnection" into the DTNbone as well as provide a place to start implementing network management.
These DTN networks have to following characteristics:
- Stable (names and topology is constant)
- Always ON (Always up and running 24/7)
- Multi-hop
- Disconnection (links will be UP for some period of time and DOWN for others.)
- Multi-Path (Bundles can reach a destination via multiple routes)
Regarding the Ohio University ION Network
Our topology has been documented using both static and dynamic network diagrams. The static diagram is a simple PDF. (View the Network Diagram)
The dynamic application is a Java applet web application, dubbed "When", that contains functionality to to help determine link uptimes, reflect link properties, and compute expected delivery times. (View the Web Application)
Documentation for using the web application is now available. (View the whenGUI Applet Documentation)
A command-line variant of this application that supports arbitrary topologies is also available. Documentation can be found here. (View the WHEN CLI Documentation)
Routing and Links
The routing is performed using a combination of static and contact graph routing (CGR) where appropriate. Each node on the network runs within its own virtual machine under Ubuntu. All links are running LTP-over-UDP with the exception of always-connected links. Always-connected links operate under TCP.
The links are dynamically controlled via cron jobs. These cron jobs enable the dtnbone to mimic DTN disconnections by using iptables to accept or reject incoming and outgoing traffic on ports registered for DTN activity. This approach allows us to administer the nodes normally even when links to the node are considered "down" by DTN protocols. Specific information regarding the disconnection schedule can be found in the "Link Disconnection Schedule" spreadsheet. (View the Link Disconnection Schedule)
Bit error, packet loss, and latency are achieved via usage of tc, though not all of these characteristics are currently enabled. The links currently do not have bit error or packet loss associated with them. They do have time delays. Specific information about link characteristics can be found in the "Link Details" spreadsheet. (View the Link Details)
To get to any DTN bundle agent, you will need to send to "iongateway" the gateway between the virtualized network and the DTNbone machines on the Internet.
Endpoints
All nodes on the the Ohio University ION DTNbone host applications at the following endpoints. Please let us know if there are other applications that you'd like for us to host.
Please substitute <ionX> with the DTN name of the node hosting the endpoint you wish to connect to.
- bpsink
dtn://<ionX>.dtn/sink
- sbp_sink
dtn://<ionX>.dtn/sbp/sink
- sbp_ping
dtn://<ionX>.dtn/ping
- sbp_ack
dtn://<ionX>.dtn/ack
- bpecho
dtn://<ionX>.dtn/echo
Network Management
Network management of the Ohio University dtnbone is still a work in progress.
We greatly appreciate any feedback on the network management. Any requests for "types" of information and any "suggestions" for scripts would be greatly appreciated.
Contacts and Correspondence
It would probably be most useful to provide such feedback to the dtn-interest list so others can see and comment or provide additional input and suggestions.
For comments that would not be useful for the entire group to see, the following are suggested.
Hans Kruse <kruse AT ohiou DOT edu> - Ohio University Professor, Information and Telecommunication Systems