-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 node (hail) can register as follows:
dtnsend -s tca://hail/tca_admin -d tca://registry -t m -p ""

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

- Unimplemented. Change-Of-Address notification and reverse path
destruction is not complete. This will occur when a mobile node has
re-registered in a new place in the network. The previous path to the
mobile should be destroyed and bundles en-route to the mobile should
be re-directed.

- 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 is 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.

- Limitation. TCA Routers won?t work across firewalls that apply NAT
(Network Address Translation) because in this case their ?published?
address will be different from their actual address. Currently, all
routers publish their actual tcp address.

- Bug. When a registry bundle is processed resulting in a new link
being created, bundles are immediately tested to go out on this new
link. This causes duplicate handling of the registry bundle. The logic
is correct but performance is sub-optimal.


4 Modified Files

This is a complete list of files that were modified or added in the
TCA implementation. In files that are part of the core DTN
implementation, modifications to the source code are flagged with the
string ?DK:? in a comment line.

TCPConvergenceLayer.*
Added code to append listener?s link_id to outgoing bundles.

Bundle.*
Added last_hop_ field to Bundle class to contain link_id of previous hop.

BundleProtocol.* 
Added code for optional ROUTERECORD header to
format_headers and parse_headers to handle last_hop info.

TCAScheme.* 
Initial checkin. New singleton class, borrowed heavily
from DTNScheme.

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

RouteTable.*
Added function del_entries_for_dest.

InterfaceTable.*
Added a public find function.

BundleRouter.cc
Added TcaRouter instantiations to factory method.

TableBasedRouter.h
Made handle_bundle_received virtual.

tca_lib/*
New checkins. Third-party tools.

TcaTypes.*
Initial checkin. Common TCA classes

TcaRegistry.*
Initial checkin. Class for accessing the TCA registry.

TcaRouter.*
Initial checkin. Main TCA implementation.