Application Index

NOX itself only provides very low-level methods for interfacing with the network. All higher-level functions and events are created by network applications. The current release contains applications which reconstruct the network topology (discovery and topology), perform network routing (routing), track the movement of hosts on the network (authenticator), and enforce network policy (sepl).

To run NOX with routing, topology discovery, and host tracking issue the following command (note python must be enabled):

./nox_core -v routing

Warning

This section is largely notes at the moment.

Discovery

Discovery sends LLDP packets out of every switch interface. It uses received LLDP packets to detect switch links, at which time it generates Link_events.

Topology

The topology application provides an in-memory record of all links currently up in the network. It does not post any events, but rather exposes methods to retrieve the links sourced at any given datapath in the network.

Authenticator

The authenticator application keeps an in-memory record of all authenticated hosts and users in the network, indexed on network location. A network location is defined by a 3-tuple consisting of a link layer address, a network layer address, and an access point (datapath, port pair). Usually the authenticator will listen for Auth_events to know when to add a new host entry - however, with the current setup all packet-sending hosts “authenticate” by default.

Other applications having a handle to the authenticator can ask for a host’s Connector record (defined in “flow-in.hh”) by calling “get_conn” and specifying a location. Hosts are indexed by network identifiers in the order dladdr->nwaddr->access point, and so partial lookup methods “get_dlconns” and “get_nwconns” requiring only the dladdr and dladdr+nwaddr, respectively, have also been exposed (useful for finding all network layer addresses on a link layer address etc).

On packet-in events, the authenticator creates a Flow_in_event containing the source and destination access points, which the routing application then listens for and uses to set up the flow’s route through the network.

Lastly, the authenticator posts host join and leave events when a new network location becomes active or times out from inactivity, respectively. However, a join event is not posted when a new network address for an already active link layer address/access point pair is seen (as it is not a new host).

Routing

The routing application keeps track of shortest-path routes between any two authenticated datapaths in the network. On link changes, the set of affected routes is updated.

Routing currently listens for Flow_in_events and routes them by setting up exact match flow entries in all switches along the path from the source to destination access points.

Other applications can also ask the routing module for a specific route using the “get_route” method.

SEPL

TODO