Free Essay

Dynamic Source Routing

In: Computers and Technology

Submitted By hafsahimayat
Words 1841
Pages 8
Dynamic Source Routing (DSR)

DSR was first introduced and described by David B. Johnson, David A. Maltz and Josh Broch in 1994. The protocol is specifically designed for use in multi-hop wireless ad hoc networks. The protocol does not require any existing network infrastructure or administration and is completely self-organizing and self-configuring.
The protocol basically consists of the two mechanisms: Route Discovery and Route Maintenance, where the Route Discovery mechanism handles establishment of routes and the Route Maintenance mechanism keeps route information updated.
Assumptions
Some assumptions concerning the behavior of the nodes that participate in the ad hoc network are made. The most important assumptions are the following:
A1. All nodes that participate in the network are willing to participate fully in the protocols of the network.
A2. The diameter of an ad hoc network is the minimum number of hops necessary for a packet to reach from any node located at one extreme edge of the ad hoc network to another node located at the opposite extreme. We assume that this diameter will often be small (e.g., perhaps 5 or 10 hops), but it may often be greater than 1.
A3. Nodes can detect the error through a standard link-layer checksum or Cyclic Redundancy Check (CRC), and discard corrupted packages .
A4. The speed at which nodes move is moderate with respect to packet transmission latency and wireless transmission range of the particular underlying network hardware in use.
A5. Each node can be identified by a unique id by which it is recognized in the network.
Mode of Operation
DSR operate on demand, which means that no data, such as route advertisement messages, is send periodically and therefore routing traffic caused by DSR can scale down and overhead packages can be avoided.
DSR is a source routing protocol, which means the entire route is known before a packet transmission is begun. DSR stores discovered routes in a Route Cache.
DSR Modules 1. Route Discovery 2. Route Maintenance
The modules are described as follows:
Route Discovery * When a node S sends a packet to the destination D, it first searches its Route Cache or a suitable route to D.

* If no route from S to D exists in S’s route cache, S initiates Route Discovery and sends out a ROUTE REQUEST message to find a route.

* The sending node is referred to as the initiator and the destination node as the target. The fields of the ROUTE REQUEST message are explained in Following Table. Fields | Explanation | Initiator ID | The address of the initiator. | Target ID | The address of the target. | Unique Request ID | A unique ID that can identify the message. | Address list | A list of all addresses of intermediate nodes that the message passes before its destination. This is empty when the message is first send. | Hop Limit | The hop limit can be used to limit thenumber of nodes that the message isallowed to pass. | Network Interface List | If nodes have several network interfaces this information can be stored in this list. | Acknowledgement bit | There is an option of setting a bit so that the receiver returns an acknowledgement when a packet is received. |

* The initiator initialize the Address List to an empty list and set the Initiator ID, the Target Id and the Unique Request Id in the ROUTE REQUEST message and then broadcasts the message.

* When a node receives a ROUTE REQUEST message it examine the Target ID to determine if it is the target of the message. If the node is not the target it searches its own route cache for a route to the target. If a route is found it is returned.

* If the route the is not found in its Cache, the node’s own id is appended to the Address List and the ROUTE REQUEST is broadcasted.

* If a node subsequently receives two ROUTE REQUESTs with the same Request id, it is possible to specify that only the first should be handled and the subsequent discarded.

* If the node is the target it returns a ROUTE REPLY message to the initiator. This ROUTE REPLY message includes the accumulated route from the ROUTE REQUEST message.

* The target node checks if the link is bidirectional, is it is not, it searches its own Route Cache for a route to the initiator. If a route is not found in the targets Route Cache, it performs a route discovery of its own and sends out a ROUTE REQUEST where it piggybacks the ROUTE REPLY for the initiator.

* If the link is bidirectional, the target node reverses the found route in ROUTE REQUEST message and sends ROUTE REPLY back to the sender on the route discovered.

* The initiator keeps a copy of the packet in a buffer, referred to as the send buffer. It timestamps the message so it can be examined later to determine if it should be send again. If no route is discovered within a specified time frame, the packet is dropped from the send buffer. Packets are also dropped from the send buffer if the buffer overruns.

The figure below shows that as the ROUTE REQUEST originates by the sender and pass through the intermediate nodes it appends the node ID in the ROUTE REQUEST.

Route Maintenance
Since nodes move in and out of transmission range of other nodes and thereby creates and breaks routes, it is necessary to maintain the routes that are stored in the Route Cache. When a node receives a packet it is responsible for confirming that the packet reaches the next node on the route. Following

Figure shows that the mechanism works like a chain where each link has to make sure that the link in front of it is not broken. The figure also illustrates that node C might use another route to communicate to node A. * If a node transmits a packet and does not receive an acknowledgment it tries to retransmit a fixed number of times.

* If no acknowledgement is received after the retransmissions, it returns a ROUTE ERROR message to the initiator of the packet. (As in the above figure node C returns ROUTE ERROR message to node A.)

* In this message the link that was broken is included.

* The initiator removes the route from its Route Cache. * The initiator now tries to transmit using another route from its Route Cache.

* If no route is available in the Route Cache a ROUTE REQUEST is transmitted in order to establish a new route.
Additional Features in DSR
As explained in the above sections DSR has a quite simple mode of operation. However several additional features exist. This section gives an overview of these additional features. * Caching of Overheard Route Information
Nodes can cache information about routes from packets that they forward. This mechanism is called snooping and is mostly used for snooping of routes. For example a node can cache the route that is returned in a ROUTE REPLY message when it forwards it. The use of route snooping can limit the amount of ROUTE REQUEST that are sends, since nodes can discover new routes this way. * Replying to Route Request Using Cached Routes
When a node receives a ROUTE REQUEST message for which it was not the destination it can attempt to find a route from its Route Cache instead of broadcasting the ROUTE REQUEST. If a route is found it is returned to the initiator. The node must however verify that the route that is being returned does not contain any duplicating nodes since this can lead to loops. * Avoiding Storms of Route Reply
When nodes are allowed to reply to ROUTE REQUEST messages with routes from their Route Cache the risk of ROUTE REPLY “storms” is present. “Storms” can occur when a node broadcast a ROUTE REQUEST and its neighbour nodes all has routes for the target in their cache. This will result in simultaneous ROUTE REPLYs from all neighbours that can cause congestion or packet collision. This can be avoided by letting the nodes delay ROUTE REPLYs for a random period. This delay effectively randomizes the time at which a node returns a ROUTE REPLY message. * Route Request Hop Limits
Each Route Request message contains a "hop limit" that may be used to limit the number of intermediate nodes allowed to forward that copy of the Route Request. This hop limit is implemented using the Time-to-Live (TTL) field in the IP header of the packet carrying the Rout Request. As the Request is forwarded, this limit is decremented, and the Request packet is discarded if the limit reaches zero before finding the target. This Route Request hop limit can be used to implement a variety of algorithms for controlling the spread of a Route Request during a Route Discovery attempt. * Salvaging Packets
When a node forwards a packet, it might successively discover, through the use of Route Maintenance, that the route for the packet is broken. If the node has another route to the destination it can use it and thereby salvage the packet. If the packet is salvaged a ROUTE ERROR should be send to the original sender to report the link on the route that was broken. * Decreased spreading of ROUTE ERROR Messages
When a source node receives a Route Error for a data packet that it originated, this source node propagates this Route Error to its neighbors by piggybacking it on its next Route Request. In this way, stale information in the caches of nodes around this source node will not generate Route Replies that contain the same invalid link for which this source node received the Route Error.
Advantages
* Routes are maintained only between nodes who need to communicate, this reduces overhead of route maintenance. * Route caching can further reduce route discovery overhead. * A single route discovery may yield many routes to the destination, due to intermediate nodes replying from local caches.

Disadvantages * Packet header size grows with route length due to source routing. * The Route Maintenance protocol does not locally repair a broken link. The broken link is only communicated to the initiator. * The DSR protocol is only efficient in MANETs with less than 200 nodes. * Problems appear by fast moving of more hosts, so that the nodes can only move around in this case with a moderate speed * Flood of route requests may potentially reach all nodes in the network * Care must be taken to avoid collisions between route requests propagated by neighboring nodes, by insertion of random delays before forwarding RREQ. * Increased contention if too many route replies come back due to nodes replying using their local cache. Route Reply Storm problem Reply storm may be eased by preventing a node from sending RREP if it hears another RREP with a shorter route.

References 1. M.Sc. Thesis Secure Routing in Mobile Ad Hoc Networks by Lennart Conrad 2003 2. Research Paper: DSR: The Dynamic Source Routing Protocol for Multi-HopWirelessAdHocNetworks by David B. Johnson David A. Maltz Josh Broch Computer Science Department Carnegie Mellon University 3. RFC 4728

Similar Documents

Premium Essay

Nt1310 Unit 1 Exercise 1

...mobile nodes and has dynamic topology. MANET is self configured and self organizing network. In the ad hoc network nodes are free to move anywhere and any pair of nodes can communicate directly if they are in the transmission range of each other otherwise the communicating nodes depend upon the other nodes present in the network for the communication. So, MANET follows the multi-hop pattern for the communication. In the ad hoc network, the nodes can act as the router as well as host. The nodes in the network dynamically exchange the data without their dependency on any wired backbone network. The nodes in the network are differentiated by their processing, energy consumed, memory resources and most important by their high degree of mobility. Routing protocols play an important role in order to transmit the data from one node to another. The goal of the ad hoc network routing protocols is to establish the valid and efficient routes between the nodes so that the messages are delivered within time. The routing protocols must be able to deal with high degree of mobility....

Words: 519 - Pages: 3

Premium Essay

It220 Chapter 7and8

...1. What is a routing table? Routing tables consist of being used to route data to a specific path and also keeps track of the routes for where the data can travel to. 2. What is the most common static route used in a host computer? The most common static route used in a host computer is the default gateway. 3. What command is used to view a PC computers routing table? The command to used to view a pc computer routing table is netstat –r. 4. What is meant by a 0.0.0.0 network address entry with a subnet mask of 0.0.0.0 in a PC’s routing table? It’s the default routing table path for data. 5. What is the 127.0.0.1 IP address and what is it used for? It is known as a loopback to the host computer. This mean the data is routed directly back to the source which is known as the network interface card. 7. What is the difference between a routers running configuration and startup configuration? The difference between running configuration and startup is that in config doesn’t show what is currently saved in the routers nonvolatile memory whereas startup shows the saved configuration in the nonvolatile memory. 8. What is the router command used to view the routes entered into the router’s routing table? The command to use in order to see the routes entered into the routers routing table is show ip route. 9. What is the router command used to configure a static route for a router? The command you would use is ip route in order to configure the router. 14. What...

Words: 2495 - Pages: 10

Free Essay

98-367 Sec. Fund. Chapter 4 Routing Essay Questions

...1. Describe the process of network routing. Routing is the process of moving packets across a network from one host to another. It is usually performed by dedicated devices called routers. Packets are the fundamental unit of information transport in all modern computer networks, and increasingly in other communications networks as well. They are transmitted over packet switched networks, which are networks on which each message (i.e., data that is transmitted) is cut up into a set of small segments prior to transmission. Each packet is then transmitted individually and can follow the same path or a different path to the common destination. Once all of the packets have arrived at the destination, they are automatically reassembled to recreate the original message. What OSI layer does a router work on? 3 or network. What type of address does a router use? IP address 2. What is a router hop? In computer networking, a hop is one portion of the path between source and destination. Data packets pass through bridges, routers and gateways on the way. Each time packets are passed to the next device, a hop occurs. Which protocol uses router hops? Routing Information Protocol (RIP). What is the maximum number of hops allowed? This limits the number of hops allowed in a path from source to destination. The maximum is 15, and 16 is deemed unreachable. The hop-count limit prevents routing loops from continuing indefinitely. Although, IGRP will route IP, IPX, Decnet and AppleTalk which...

Words: 739 - Pages: 3

Free Essay

Networking

...1. What is a routing table? Routing tables consist of being used to route data to a specific path and also keeps track of the routes for where the data can travel to. 2. What is the most common static route used in a host computer? The most common static route used in a host computer is the default gateway. 3. What command is used to view a PC computers routing table? The command to used to view a pc computer routing table is netstat –r. 4. What is meant by a 0.0.0.0 network address entry with a subnet mask of 0.0.0.0 in a PC’s routing table? It’s the default routing table path for data. 5. What is the 127.0.0.1 IP address and what is it used for? It is known as a loopback to the host computer. This mean the data is routed directly back to the source which is known as the network interface card. 7. What is the difference between a routers running configuration and startup configuration? The difference between running configuration and startup is that in config doesn’t show what is currently saved in the routers nonvolatile memory whereas startup shows the saved configuration in the nonvolatile memory. 8. What is the router command used to view the routes entered into the router’s routing table? The command to use in order to see the routes entered into the routers routing table is show ip route. 9. What is the router command used to configure a static route for a router? The command you would use is ip route in order to configure the router. 14....

Words: 359 - Pages: 2

Premium Essay

Nt2640 Project Paper

...Project Paper 1. Routing tables and how the router will perform a route lookup: a. Routing Table Format- A routing table is used by TCP/IP network routers to calculate the destinations of messages it is responsible for forwarding. The table is a small in-memory database managed by the router's built-in hardware and software. Each IP address identifies a remote router (or other network gateway) that the local router is configured to recognize. For each IP address, the routing table additionally stores a network mask and other data that specifies the destination IP address ranges that remote device will accept. Home network routers utilize a very small routing table because they simply forward all outbound traffic to the Internet Service Provider (ISP) gateway which takes care of all other routing steps. Home router tables typically contain ten or fewer entries. By comparison, the largest routers at the core of the Internet backbone must maintain the full Internet routing table that exceeds 100,000 entries and growing as the Internet expands. b. Routing Lookup Mechanism- c. Classful vs. Classless Routing- Classful Routing, which is sometimes called a classful network. If you are using a classful routing protocol then all of your networks are in different classes and are separated by a router. Remember that the useable IPv4 address ranges are divided into classes. Class A 1-126, Class B 128-191, and Class C 192-223. So when we talk about a classful routing protocol, it will...

Words: 3788 - Pages: 16

Premium Essay

Nt1310 Unit 3 Assignment 1

...when there is a need for a path to a destination, such path information is accessible immediately. Different protocols keep track of different routing state information[4]. These protocols need each node to maintain one or more tables to store up to date routing information and to propagate updates throughout the network. As such, these protocols are often referred to as table-driven. Some examples of table driven ad hoc routing protocols include Dynamic Destination Sequenced Distance-Vector Routing Protocol (DSDV) [7],Optimized Link State Routing Protocol (OLSR) [8] and Wireless Routing Protocol (WRP) [6]. 1....

Words: 514 - Pages: 3

Premium Essay

Wireless Mesh Network

...WIRE LESS MESS NETWORK WITH HRPU ABSTRACT A Wireless mesh network is a mesh network created through the connection of wireless access points installed at each network user’s locale. Each user is also a provider, forwarding data at next node. The networking infrastructure is decentralized and simplified because each node need only transmit as far as the next node. Wireless mesh networking could allow people living in the remote areas and small businesses operating in rural neighborhoods to connect their networks together for affordable Internet connections. Here we discuss a hybrid routing algorithm for wireless mesh networks. In HRPU, the mesh portal periodically broadcasts a mesh update message, which allows all nodes to have a route towards the mesh portal stored semi permanently in their routing table. Whenever a node has data to be sent to backbone network, it sends the data without any route establishment delay using the route to the mesh portal. In HRPU the mesh portals and mesh points are intelligent which further improves the performance. INTRODUCTION The Beginning: Wireless Mesh Networking (WMN) was developed as a quick way to set-up wireless networks during military operations. Since then it has grown considerably in popularity based on its advantages in both metropolitan and rural applications. WMNs are being applied as Hot Zones, which cover a broad area, such as a downtown city district. By 2010, municipal Wi-Fi networks will cover over 325...

Words: 4177 - Pages: 17

Free Essay

Essay

...router must find the physical address mapped to ______________________. the IP address of the next hop router found in the routing table  _______ is a dynamic mapping protocol in which a physical address is found for a given logical address. ARP  An ARP request is normally _______. broadcast  An ICMP packet is carried in an __________ . IP packet  The destination MAC address in an Ethernet frame that carries an ARP request is _______. 0xFFFFFFFFFFFF  The value of the target hardware address field in an ARP request message sent on an Ethernet is _______. 0x000000000000  A _______ is an ARP that acts on behalf of a set of hosts. proxy ARP  ICMP is a _________ layer protocol. network  ICMP messages are divided into two broad categories: _____________. query and error reporting messages  Which of the following is true about ICMP messages? An ICMP error message may be generated only for the first fragment.  In _______ delivery, the destination of an IP packet is on the same network as the source or deliverer of the packet. a direct  In _______ forwarding, the mask and destination addresses are both 0.0.0.0 in the routing table. default  In _______ forwarding, the destination of a forwarded IP packet is a network address in the routing table. network-specific  In _______ forwarding, the routing table holds the address of just the next...

Words: 2858 - Pages: 12

Premium Essay

Advantages Of Ad Hoc Network

...Useful when number of traffic session is much lower than the number of nodes. . No routing structure created a priori. Two key methods for route discovery: . Source routing . Backward routing . Introduce delay. Examples: AODV Ad hoc on demand distance vector routing Route Discovery Process . Source node initiates path discoverer process by broadcasting RREQ. . RREQ is forwarded until it reaches an intermediate node that has recent route information about the destination or till it reaches the destination. . The RREQ uses sequence numbers to ensure that the routes are loop free and reply contains latest information only. 15 Route Reply Process . When a node forwards a route request packet to its neighbor; it also records in the table the node from which the first copy of the request came. . This table is used to construct the reverse path for the RREQ. . As the RREQ traverses back to the source, the nodes along the path enter the forward route into their tables. . If one of the intermediate nodes move then the moved nodes neighbor realizes the link failure and sends a link failure notification to its upstream neighbors and so on till it reaches the source. . Route Error Packets are used to erase broken...

Words: 4647 - Pages: 19

Free Essay

Simulation Study on Service Based Adaptive Qos Framework for Vehicular Adhoc Network- Redem

...(RSU) supported by DSRC standard [2] acts as gateways or fixed access points to vehicles in mobility and provides interim connectivity to vehicles. One of the major advantages of VANETs over MANETs is the unlimited battery power generated on the fly. VANET plays a major role in defining safety measures by streaming communication between vehicles, infotainment and telematics. In any generic network phenomena the concept of routing and its characteristics are highly linked with Quality of Service (QoS). The United Nations Consultative Committee for International Telephony and Telegraphy (CCITT) Recommendation E.800 has defined QoS as: “The collective effect of service performance which determines the degree of satisfaction of a user of the service”. The major concern of VANET routing is that whether the performance can satisfy the throughput and delay requirements of such media streaming applications. Unavailability of efficient routing algorithms for the VANET scenario, force the researchers to use the MANET routing algorithms. An analysis of VANET routing protocols shows that its performance is not acceptable due to the feature of very high mobility in terms of speed[3]. Its adverse effect leads to broken links, with high packet drop and overhead due to missing route repairs or failure. This phenomenon...

Words: 1550 - Pages: 7

Premium Essay

It 220 Finals Reviewer

...Networking Final Study Guide 1. What is a up-link port? Allows the connection of hub to hub or switch without having to use a special cable 2. What is the max cable length for Cat 5E/6? 100 meters 3. Link lights on hub or switch represent. Indicates that the transmit and receive pairs are properly aligned 4. Link lights on NIC. Same as above 5. Echo request. Part of the ICMP protocol that request a reply from a computer 6. How do you display MAC address/find out MAC address? Ip/config/all 7. Max length of horizontal cable that you can use? 90 meters 8. How does Network Admin check for connectivity? Ping 9. What is campus area network? A collection of two or more interconnected LAN's in a limited geographic area 10. Difference between fast Ethernet and gigabit Ethernet? 100Mbps and 1000Mbps 11. What is bottlenecking? Another term for network congestion 12. CIDR notation. IP address is represented as A.B.C.D /n, where "/n" is called the IP prefix or network prefix. The IP prefix identifies the number of significant bits used to identify a network 13. 3 packet handshake deal for TCP? SYN, SYN ACK, ACK 14. Who assigns IP address? Network Admin 15. What is the connection called from router to pc? 16. What is help command for Cisco IOS? ? 17. What does AUI stand for? Attachment unit interface, the port is a routers 10 Mbps Ethernet port 18. What is interface called to connect...

Words: 823 - Pages: 4

Free Essay

Impact of Mac Layer on the Performance of Odmrp, Fisheye, Aodv and Dsr, Routing Protocols in Mobile Ad Hoc Networks

...Impact of MAC Layer on the Performance of ODMRP, Fisheye, AODV and DSR, Routing Protocols in Mobile Ad hoc Networks A. Sravani, G. Srinu, and A.Venkataramana Abstract— Mobile Ad hoc Network is an emerging area. Its standards are defined by IETF. MANET is a self generated, self organized and self handled network consisting of collection of independent nodes. MANETs Presents several desirable properties like dynamic topology, Easy of deployment and robustness, which are qualify them as an attractive topic for the research community. Providing QoS routing is a major issue in MANETs. Media Access Control layer plays crucial role in Ad hoc networks. Several routing protocols have already been proposed for MANETs. This paper describes the impact of MAC layer protocols like 802.11 and CSMA on the various routing protocols like AODV, DSR, ODMRP and Fisheye. Numbers of simulation scenarios were carried out by using Glomosim-2.03. The QoS parameters used are Throughput, Delay and PDR. Simulation results found that AODV performs better in 802.11 and CSMA, DSR and ODMRP performs better in only under 802.11. Keywords— MANET, AODV, DSR, FSR, GloMoSim, ODMRP I. INTRODUCTION Wireless communication networks are basically two types as shown in Fig.1. One is infrastructure based and other one is infrastructure less. Infrastructure based is cellular communications whereas infrastructure less is ad hoc networks. Fig.1 Classification of wireless communication networks A. Cellular...

Words: 2917 - Pages: 12

Premium Essay

Nt1330 Unit 1 Lab Report

...nodes are computing or networking is a distributed application that partitions watchdog’s task between source and target nodes. These nodes are connected and communicate by using IP address and host name. Often Inheritor nodes operate over a network on separate functionalities. A server machine is a high performance host that is running one or more tasks which share its resources with nodes. B. Target Nodes Choose the target node from the intermediate nodes. Then the number of connections to establish between each pair of target node and established between each and every nodes for network communication. From the source node to the destination node and intermediates node must have connection between source nodes after communicate between combinations of multi node each and every node must be link to each other. After to choose the neighbour nodes and communicate with each other and also set the priority queue in the network communications. In multipath data transmission, send the data from source node that means which type of file size and file extension. C. Watchdog Optimization Techniques...

Words: 554 - Pages: 3

Premium Essay

Technology In Mobile Computing

...old telephone system (POTS) (j) Internet (k) infra-red (l) docking (serial, parallel, LAN) and (m) disk swapping. These diverse communications technologies make available a continuum of connectivity that provides communications capabilities ranging from manual-assisted batch transfers to high-speed continuous communication. Related work: Dynamic Source Routing (DSR) is a routing protocol for wireless mesh networks. It is similar to AODV in that it forms a route on-demand when a transmitting node requests one. However, it uses source routing instead of relying on the routing table at each intermediate device. Dynamic source routing protocol (DSR) is an on-demand protocol designed to restrict the bandwidth consumed by control packets in ad hoc wireless networks by eliminating the periodic table-update messages required in the table-driven approach. The basic approach of this protocol (and all other on-demand routing protocols) during the route construction phase is to establish a route by flooding RouteRequest packets in the network. The destination node, on receiving a RouteRequest packet, responds by sending a RouteReply packet back to the source, which carries the route traversed by the RouteRequest packet received. Black hole attacks drop all data packets & cheat the previous node. Gray hole attack drop part of the data & cheat the previous node. As soon as it receive the packet from neighbor the attacker drop the packet. Type of active attack. In some other gray hole attacks...

Words: 1491 - Pages: 6

Free Essay

Student Ccna Syllabus

...Semester Two Journal and Study Guide CISCO SYSTEMS NETWORKING Academy CCNA 2 Chapter 1 WANs and Routers One major characteristic of a wide-area network (WAN) is that the network operates beyond the local LAN's geographic scope. It uses the services of carriers, such as regional Bell operating companies (RBOCs), Sprint, and MCI. WANs use serial connections of various types to access bandwidth over wide-area geographies. By definition, the WAN connects devices that are separated by wide areas. WAN devices include the following: • • • • • • Routers, which offer many services, including internetworking and WAN interface ports Switches, which connect to WAN bandwidth for voice, data, and video communication Modems, which interface voice-grade services and channel service units/digital service units Channel service units/data service units (CSUs/DSUs) that interface T1/E1 services and Terminal Adapters/Network Termination 1 (TA/NT1s) TA/NT1s that interface Integrated Services Digital Network (ISDN) services Communication servers, which concentrate on dial-in and dial-out user communication Concept Questions 1. A WAN is used to interconnect local-area networks (LANs) that are typically separated by a large geographic area. A WAN operates at the OSI reference model physical and data link layers. The WAN provides for the exchange of data packets/frames between routers/bridges and the LANs that they support. Draw a WAN that includes three LANs. 1 of 116 CCNA 2 Chapter 1 WANs and...

Words: 23437 - Pages: 94