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links to neighbors. This is the only database that operates on non-main-addresses as it works on specific interface-to-interface links.
Neighbor Set

All registered one-hop neighbors are recorded here. The data is dynamically updated based on information in the link set. Both symmetric and asymmetric neighbors are registered.
2-hop Neighbor Set

All nodes, not including the local node, that can be reached via a one-hop neighbor is registered here. Notice that the two hop neighbor set can contain nodes registered in the neighbor set as well.
MPR Set

All MPRs selected by the local node is registered in this repository. The MPR concept is explained in section 3.4.
MPR Selector Set

All neighbors that have selected this node as a MPR are recorded in this repository.
Topology Information Base

This repository contains information of all link-state information received from nodes in the OLSR routing domain.
Duplicate set

This database contains information about recently processed and forwarded messages.

3.2.1 Timeouts

Most information kept in these repositories is registered with a timeout. This is a value indicating for how long the registered information is to be considered valid. This value is set according to a validity time fetched from the message from which the data was last updated. The use of such a distributed validity time allows for individual message emission intervals for all nodes in the network. All database entries are removed when no longer valid according to the registered timeout. Such entries are said to be timed out.

3.3 Control traffic:

All OLSR control traffic is to be transmitted over UDP on port 698. This port is assigned to OLSR by the Internet Assigned Numbers Authority (IANA). The RFC states that this traffic is to be broadcasted when using IPv4, but no broadcast address is specified. When using IPv6 broadcast addresses does not exist, so even though it is not specified in the RFC, it is implicit understood that one must use a multicast address in this case.

3.3.1 Packet format

All OLSR traffic is sent in OLSR packets. These packets consist of an OLSR packet header and a body as displayed in fig 3-1.

The fields in the OLSR packet header are given on next page.

Packet Length – The length in bytes of the entire packet, including the header.
Packet Sequence Number - A sequence number incremented by one each time a new OLSR message is transmitted by this host. A separate Packet Sequence Number is maintained for each interface so that packets transmitted over an interface are sequentially enumerated. An OLSR packet body consists of one or more OLSR messages. OLSR messages use a header as shown in fig 3-1.

All OLSR messages must respect this header. The fields in the header are:
Message type - An integer identifying the type of this message. Message types of 0-127 are reserved by OLSR while the 128-255 space is considered “private” and can be used for custom extensions of the protocol.
Vtime - This field indicates for how long after reception a node will consider the information contained in the message as valid. The time interval is represented in a mantissa-exponent format.

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