XNSrouted - NS Routing Information Protocol daemon
/sbin/XNSrouted [ -s ] [ -q ] [ -t ] [ logfile ]
XNSrouted is invoked at boot time to manage the Xerox NS routing tables. The NS routing
daemon uses the Xerox NS Routing Information Protocol in maintaining up to date kernel
routing table entries.
In normal operation XNSrouted listens for routing information packets. If the host is
connected to multiple NS networks, it periodically supplies copies of its routing tables
to any directly connected hosts and networks.
When XNSrouted is started, it uses the SIOCGIFCONF ioctl to find those directly connected
interfaces configured into the system and marked ``up'' (the software loopback interface
is ignored). If multiple interfaces are present, it is assumed the host will forward
packets between networks. XNSrouted then transmits a request packet on each interface
(using a broadcast packet if the interface supports it) and enters a loop, listening for
request and response packets from other hosts.
When a request packet is received, XNSrouted formulates a reply based on the information
maintained in its internal tables. The response packet generated contains a list of known
routes, each marked with a ``hop count'' metric (a count of 16, or greater, is considered
``infinite''). The metric associated with each route returned provides a metric relative
to the sender.
Response packets received by XNSrouted are used to update the routing tables if one of the
following conditions is satisfied:(1) No routing table entry exists for the destination network or host, and the metric
indicates the destination is ``reachable'' (i.e. the hop count is not infinite).
(2) The source host of the packet is the same as the router in the existing routing ta-
ble entry. That is, updated information is being received from the very internet-
work router through which packets for the destination are being routed.(3) The existing entry in the routing table has not been updated for some time (defined
to be 90 seconds) and the route is at least as cost effective as the current route.(4) The new route describes a shorter route to the destination than the one currently
stored in the routing tables; the metric of the new route is compared against the
one stored in the table to decide this.
When an update is applied, XNSrouted records the change in its internal tables and gener-
ates a response packet to all directly connected hosts and networks. Routed waits a short
period of time (no more than 30 seconds) before modifying the kernel's routing tables to
allow possible unstable situations to settle.
In addition to processing incoming packets, XNSrouted also periodically checks the routing
table entries. If an entry has not been updated for 3 minutes, the entry's metric is set
to infinity and marked for deletion. Deletions are delayed an additional 60 seconds to
insure the invalidation is propagated to other routers.
Hosts acting as internetwork routers gratuitously supply their routing tables every 30
seconds to all directly connected hosts and networks.
Supplying the -s option forces XNSrouted to supply routing information whether it is act-
ing as an internetwork router or not. The -q option is the opposite of the -s option. If
the -t option is specified, all packets sent or received are printed on the standard out-
put. In addition, XNSrouted will not divorce itself from the controlling terminal so that
interrupts from the keyboard will kill the process. Any other argument supplied is inter-
preted as the name of file in which XNSrouted's actions should be logged. This log con-
tains information about any changes to the routing tables and a history of recent messages
sent and received which are related to the changed route.
``Internet Transport Protocols'', XSIS 028112, Xerox System Integration Standard.
4.3 Berkeley Distribution November 1, 1996 XNSROUTED(8)