US Robotics USR2410 Bedienungsanleitung PDF herunterladen (Seite 19)

Wireless mesh networks can be broken down into two broad architecture categories,

infrastructure mesh networks and client mesh networks. Infrastructure wireless mesh networks

allow regular clients to connect to a mesh backbone that takes care of the packet routing. This

routing is transparent to the client. Client mesh networks involve the clients in the routing

process. Packets may be forwarded to a client or a mesh router, and the devices are expected to

forward the packet as necessary. In this architecture, clients must run specialized routing

software, and give up system resources to maintain the mesh network [3].

2.4

DSDV Routing Protocol

There are a number of multi-hop routing protocols for mesh networks. One such protocol is

Destination-Sequenced Distance-Vector (DSDV) Routing, which is used in the project. Multi-

hop routing protocols can be separated into two broad categories: reactive routing protocols and

proactive routing protocols. Reactive protocols will discover route information dynamically,

whenever a packet arrives and no current route information is available. Proactive protocols,

such as DSDV, keep track of routing information through periodic updates, so that it is always

available. [4]

Under the DSDV routing protocol, every host will maintain distance estimations to every other

host participating in the network. This distance is measured in the number of hops needed to

reach a given host. The route information is determined through the broadcast of route

advertisement packets to all hosts within communication range.

There are two types of broadcasts. The full dump broadcast occurs periodically, and sends all

entries from the host’s route table to all adjacent hosts. The other type is an incremental

advertisement. This is sent between full dump broadcasts, if a large change in routing

information has occurred. For example, if a host has gone offline, an incremental advertisement

would be made.

Routes are based on the age of the route information, and on the shortest path available to the

desired host. Packets received by a host that are addressed to another host in the network are

forwarded along to the next hop, until the packet reaches its destination. Gateway hosts

connected to external networks are flagged and packets destined for systems outside of the

network are forwarded to the closest gateway host. [4]

2.5 Address Resolution Protocol

The Address Resolution Protocol (ARP) is a protocol used to discover the MAC address of a

system given its IP address. A system that wants to know a MAC address will broadcast an ARP

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US Robotics USR2410 Bedienungsanleitung Seite 19