Which of the following devices is used to connect a lan to a packet switched wan?
This topic introduces common WAN terminology and devices and differentiates between circuit-switch and packet-switch networks. Show
WANs in the OSI Model (2.1.2.1)As shown in Figure 2-6, WAN operations focus primarily on the physical layer (OSI Layer 1) and the data link layer (OSI Layer 2). Figure 2-6 WANs Operate in Layer 1 and Layer 2 WAN access standards typically describe both physical layer delivery methods and data link layer requirements, including physical addressing, flow control, and encapsulation. WAN access standards are defined and managed by a number of recognized authorities, including the
Layer 1 protocols describe how to provide electrical, mechanical, operational, and functional connections to the services of a communications service provider. Layer 2 protocols define how data is encapsulated for transmission toward a remote location, and the mechanisms for transferring the resulting frames. A variety of different technologies are used, such as the Point-to-Point Protocol (PPP), Frame Relay, and Asynchronous Transfer Mode (ATM). Some of these protocols use the same basic framing or a subset of the High-Level Data Link Control (HDLC) mechanism. Most WAN links are point to point. For this reason, the address field in the Layer 2 frame is usually not used. Common WAN Terminology (2.1.2.2)One primary difference between a WAN and a LAN is that an organization must subscribe to an outside WAN service provider and use the WAN carrier network services to interconnect its sites and users. A WAN uses data links provided by carrier services to access the Internet and connect different locations of an organization to each other, to locations of other organizations, to external services, and to remote users. The physical layer of a WAN describes the physical connections between the company network and the service provider network. As illustrated in Figure 2-7, common terminology is used to describe WAN components and reference points. Figure 2-7 Common WAN Terminology Specifically, these terms include
WAN Devices (2.1.2.3)As illustrated in Figure 2-8, there are various methods, and therefore devices, that are used to access the WAN connection. Service providers also have specific WAN devices within their network and devices that are required to interconnect to other WAN providers. Figure 2-8 WAN Devices The example in the figure identifies the following WAN devices:
NOTE The preceding list is not exhaustive, and other devices may be required depending on the WAN access technology chosen. The type of devices used depends on the WAN technology implemented. These WAN technologies are implemented over either circuit-switched or packet-switched networks. Circuit-Switched Networks (2.1.2.4)A circuit-switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. As illustrated in Figure 2-9, circuit switching dynamically establishes a dedicated virtual connection for voice or data between a sender and a receiver. Before communication can start, it is necessary to establish the connection through the network of the service provider. It is important to note that the circuit must remain established and never change or communication will be terminated. Figure 2-9 Circuit-Switched Connection As an example, when a subscriber makes a telephone call, the dialed number is used to set switches in the exchanges along the route of the call so that there is a continuous circuit from the caller to the called party. Because of the switching operation used to establish the circuit, the telephone system is called a circuit-switched network. If the telephones are replaced with modems, then the switched circuit is able to carry computer data. If the circuit carries computer data, the usage of this fixed capacity may not be efficient. For example, if the circuit is used to access the Internet, there is a burst of activity on the circuit while a web page is transferred. This could be followed by no activity while the user reads the page, and then another burst of activity while the next page is transferred. This variation in usage between none and maximum is typical of computer network traffic. Because the subscriber has sole use of the fixed capacity allocation, switched circuits are generally an expensive way of moving data. The two most common types of circuit-switched WAN technologies are the public switched telephone network (PSTN) and the Integrated Services Digital Network (ISDN). Video 2.1.2.4: Circuit-Switched Network Go to the course and play the animation to see how a packet-switch network connects host A to host B. In the animation, SRV1 is sending data to SRV2. As the packet traverses the provider network, it arrives at the second provider switch. The packet is added to the queue and forwarded after the other packets in the queue have been forwarded. Eventually, the packet reaches SRV2. What is the device used to connect devices to a LAN?Hub. A hub is a physical device used to join multiple devices on the same LAN. For example, a laptop, desktop computer and printer can connect into a hub's ports with Ethernet cables and be part of the same local network.
Which of the following devices is used to connect a LAN to the Internet?LANs generally consist of cables and switches, which can be connected to a router, cable modem, or ADSL modem for Internet access. LANs can also include such network devices as firewalls, load balancers, and network intrusion detection.
What device is used to connect a WAN?Routers operate alongside switches in a reciprocal manner to provide access to the WAN. Switches deliver traffic to routers at the network boundary, to access the Internet or transmit information across the WAN.
How is LAN connected to WAN?So how do LANs and WANs connect? LANs have a router/firewall at each facility that is connected to an Internet Service Provider (ISP). The ISP assigns an IP address to the modem. LAN's are connected to each other using Virtual Private Networks.
|