-TCA Readme

These are some basic configuration and usage notes about the TCA
(Tetherless Computing Architecture) implementation. For a higher-level
view of TCA, see the documentation at www.mindstream.watsmore.net


1 Configuration

The following are important TCA directives in dtn.conf :

# There are two types of tca nodes: routers and gateways:
route set type [ tca_router | tca_gateway]

# A tca endpointid uses the tca scheme, of the form: "tca://guid/app"
route local_eid "tca://hail"

# All tca nodes must have a tcp0 contact interface
interface add tcp0 tcp local_addr=192.168.1.6 local_port=5000

# All tca_routers must have a default route toward a gateway as follows:
# Note that tca_gateways must *not* have a default route
link add default hurricane.cs.uwaterloo.ca:5000 ONDEMAND tcp
route add tca://* default


2 Using TCA

A new mobile endpoint (hail/app) can register as follows:
dtnsend -s tca://hail/app -d tca://registry -t m -p "register"

Once hail has registered, another node (windstorm) can send it a
bundle like this: 

dtnsend -s tca://windstorm/test_app -d
tca://hail/test_app -t m -p "windstorm says hi"


3 Unimplemented Features, Known Bugs, and Limitations

- Limitation. OpenDHT nodes are hard-coded at the moment. There should
be a file of nodes to use instead.

- Limitation. OpenDHT nodes are tested on startup and only those nodes
that are responsive are kept. This process should be repeated
periodically to refresh the list of "live" OpenDHT nodes.

- Limitation. Entries in the DHT are set to time out at 1 week, the
maximum TTL allowed by OpenDHT. This value is hard-coded.

- Unimplemented. The rules for registration lifetime are not quite
settled. When a gateway receives a bundle for an unregistered node
(perhaps never registered, perhaps previously registered but expired)
the bundle is kept in the gateway's queue until the bundle times out.

- Bug. Undeliverable control bundles are not deleted. They remain in the
pending bundle list until timeout. This is an error but it affects performance,
not correctness.

4 Modified Files

The key new classes in the implementation are TcaController and TcaRouter.

This is a complete list of files that were modified or added to DTN
as part of the TCA implementation:

servlib/naming/TCAScheme.* 
New singleton class, borrowed heavily from DTNScheme.

servlib/naming/SchemeTable.cc
Added an instance of TCAScheme to the scheme table.

servlib/routing/BundleRouter.cc
Added TcaRouter instantiations to factory method.

servlib/routing/TableBasedRouter.h
Made some bundle handler functions virtual.

apps/tca_admin
New directory for tca controller app.

apps/tca_admin/tca_lib/*
Third-party tools.

apps/tca_admin/TcaRegistry.*
New class for accessing the TCA registry.

apps/tca_admin/TcaEndpointID.*
New class for manipulating TCA endpoint ids.

apps/tca_admin/TcaController.*
Main implementation of TCA Control logic at the control layer.

apps/tca_admin/tca_admin.cc
The TCA controller's command-line parsing and main() function.

/servlib/routing/TcaEndpointID.*
New class for manipulating TCA endpoint ids, subclassed from EndpointID.

/servlib/routing/TcaControlBundle.*
New class for manipulating TCA control bundles.

/servlib/routing/TcaRouter.*
Main implementation of TCA Control logic at the bundle routing layer.

servlib/Makefile
Modified to include TcaRouter and related sources

apps/Makefile
Modified to include tca_admin app and related sources