摘要:Any node can receive a lot of information about the network by placing its interface into promiscuous mode. The information the node can receive can be used to build trust levels for different modes.
ic Service Set (BSS). A set of two or more BSSs forms an Extended Service Set (ESS).
Ad hoc mode: This is a peer-to-peer mode. This configuration is called Independent Basic Service Set (IBSS), and is useful for establishing a network where nodes must be able to communicate directly and without any centralized access point.
While setting up a MANET, the mode to be used most certainly is The Ad-hoc mode, but one of the most basic requirements is missing here which is ‘Multi hop’. The Ad Hoc mode enables Traffic to be transmitted to the adjacent nodes only within the radio range, therefore there is a need for MANET routing protocols to set up and maintain traffic paths.
2.1.2 Traditional IP routing
Routing is the primary function of IP. IP datagram’s are processed and forwarded by routers which relay traffic through paths set up by various routing protocols. Routing in today’s fixed networks is based on network aggregation combined with best matching. To maintain the knowledge about other IP Networks and IP Hosts, routing table are used by TCP/IP Hosts. IP address and a subnet mask enables to identify the Network and routes to single hosts are rarely set up. When a packet is to be forwarded, the routing table is consulted and the packet is transmitted on the interface registered with a route containing the best match for the destination. A default route is used if no network matches are found.
When a network interface is configured with an IP address, a route to the network address is a member, which is mostly registered on the interface automatically. Since hosts with addresses within this network are assumed to be reachable directly from this interface, the route is not set up with a gateway. This confirms that the job of the traditional IP routing is to maintain an idea of all hosts within the same subnet being on the same link. This shows that on a single one-hop network segment all of the hosts in a subnet are available, typically via routers or switches. The case is entirely different when working on wireless multi-hop networks. So the idea of nodes being available “on the link” must be redefined. In MANETs nodes routes traffic by retransmitting packets on the interface they arrived.
When it comes to routing, different frame of mind is required in MANET. MANETs do not use aggregation, all routing is host based. This means that a sender has a specific route for all destinations within the MANET and in a wired network all nodes in the local network are considered available on the link so this is not necessary there.
2.1.3 The MANET IETF working group
The Internet Engineering Task Force (IETF) has set down a working group for MANET routing. This working group standardizes the IP routing protocol functionality and makes it suitable for wireless routing application for both types of topologies ie ; static and dynamic.
The basic ideas behind the designing were that:
(i) There are some unique routing interface characteristics in the wireless link interfaces and
(ii) Due to the motion or other factors, the node topologies may experience increased dynamics within a wireless routing region.
A wide diversity of protocols have been proposed, but three protocols are accepted as experimental Request for Comments (RFC)
Ad-hoc On-Demand Distance Vector (AODV)
Optimi
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