XNSrouted Daemon

Purpose

Manages the Xerox Network Systems (XNS) routing tables.

Syntax

/usr/sbin/XNSrouted [ -s ] [ -q ] [ -t ] [ LogFile ]

Description

The /usr/sbin/XNSrouted daemon is invoked during system startup to manage the Network Systems (NS) routing tables. This daemon uses the Xerox NS Routing Information Protocol (RIP) to maintain up-to-date kernel routing-table entries.

In normal operation, the XNSrouted daemon listens for routing information packets. If the host is connected to multiple NS networks, it can periodically supply copies of its routing tables to any directly connected hosts and networks.

When the XNSrouted daemon is started, it uses the ioctl(SIOGIFCONF) subroutine 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 forwards packets between networks. The XNSrouted daemon 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, the XNSrouted daemon formulates a reply based on the information maintained in its internal tables. The generated response packet 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 the XNSrouted daemon are used to update the routing tables if one of the following conditions is satisfied:

• No routing table entry exists for the destination network or host, and the metric indicates the destination is reachable; that is, the hop count is not infinite.
• The source host of the packet is the same as the router in the existing routing table entry. That is, updated information is being received from the very internetwork router through which packets for the destination are being routed.
• The existing entry in the routing table has not been updated for at least 90 seconds, and the route is at least as cost-effective as the current route.
• The new route describes a shorter route to the destination than the one currently stored in the routing tables. The XNSrouted daemon updates the route after comparing the metric of the new route against the one stored in the table.

When an update is applied, the XNSrouted daemon records the change in its internal tables and generates a response packet to all directly connected hosts and networks. The XNSrouted daemon waits a maximum 30 seconds before modifying the kernel's routing tables to allow possible unstable situations to settle.

In addition to processing incoming packets, the XNSrouted daemon 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 ensure that the invalidation is propagated to other routers.

Every 30 seconds, hosts acting as internetwork routers supply their routing tables to all directly connected hosts and networks.

The LogFile parameter interprets the name of the file in which the XNSrouted daemon's actions should be logged. This log contains information about any changes to the routing tables and a history of recently sent and received messages that are related to the changed route.

The XNSrouted daemon does not run as a background process unless an & (ampersand) is specified on the command line. Interrupts from the keyboard kill the process.

Flags

Related Information

The netstat command, route command, XNSquery command.

Xerox Network Systems (XNS) Overview for Programming in AIX Version 4.3 Communications Programming Concepts.