pamoja-routing

Reverse-path routing that learns the cheapest route from overheard traffic. One capability of pamoja, one memory-safe Rust core with bindings for TypeScript, Python, and C#.

Install

pip install pamoja-routing

from pamoja import routing

This pulls in pamoja-native, the compiled engine. pip install pamoja is the whole framework in one package.

Example

The script the test suite runs, spliced here as it ran.

From bindings/python/guides/routing.py:

from pamoja.routing import ForwardAction, Router

# The nodes on this mesh. An address is just a number; naming them is what makes the
# table below read as a map of the site rather than a list of numbers.
GATEWAY = 1
PUMP = 9
TANK = 10
NORTH_RELAY = 5
EAST_RELAY = 7
SOUTH_RELAY = 3
SILO = 32

# A node learns the way to another from traffic it already hears: a packet from the pump
# that arrived through a relay proves that relay is a way back, at the cost the packet
# reports. The table keeps the cheapest way it has heard, and a tie keeps the way in use so
# two equal paths do not flap. Word from the relay already in use is taken even when it is
# worse, which is how a failing link lets a detour win.
router = Router(GATEWAY, 4)
for via, cost in [
    (NORTH_RELAY, 2),
    (EAST_RELAY, 1),
    (SOUTH_RELAY, 4),
    (NORTH_RELAY, 1),
    (EAST_RELAY, 3),
    (NORTH_RELAY, 2),
]:
    changed = router.observe(PUMP, via, cost)
    route = router.route(PUMP)
    outcome = "so the route is" if changed else "and the route stays"
    print(
        f"heard     the pump via {via} at cost {cost}, {outcome} {route.next_hop} "
        f"at cost {route.cost}"
    )

# The table lists what it holds, one route for each node it has heard from.
router.observe(TANK, NORTH_RELAY, 3)
held = [f"to {route.dst} via {route.next_hop} at cost {route.cost}" for route in router.routes()]
print(f"table     {len(router)} routes of {router.capacity}: {', '.join(held)}")

# Every packet gets one of three answers: deliver it here, relay it to the neighbor on the
# way, or flood it because no route is known yet.
for name, address in [("gateway", GATEWAY), ("pump", PUMP), ("silo", SILO)]:
    decision = router.forward(address)
    if decision.action == ForwardAction.DELIVER:
        print(f"{name:<10}deliver here")
    elif decision.action == ForwardAction.RELAY:
        print(f"{name:<10}relay via {decision.next_hop}")
    else:
        print(f"{name:<10}flood, no route known")

# The table keeps no clock, so a route through a relay that has gone quiet stays until the
# caller forgets it, typically when a relayed packet goes unanswered. Forgetting returns the
# node's traffic to flooding, the answer that always works.
router.forget(PUMP)
if router.forward(PUMP).action == ForwardAction.FLOOD:
    print(f"forgot    the pump, so it floods again, and {len(router)} route is left")

The same capability in every language

Documentation

• pamoja.routing reference, every class and function in this module.
• The Routing guide, with the same example in Rust, TypeScript, and C#.
• Every capability, and the install page.

License

MIT