Dedicated vs. Switched WAN Technologies Video Transcript
Dedicated vs. Switched WAN Technologies Howard Rinehart Professor Gateway Community College Length: 3:58 There are two types of long distance communication technologies that are used for WANs. The first is a dedicated connection, and the other is a switched connection. Additionally, there are several types of switched connections: packet switched, circuit switched, and cell switched. When a WAN connection is required, a network administrator may choose a fulltime connection, called a dedicated or leased line, or choose a switched service. A dedicated line is a full-time point-to-point connection provided by a communication carrier that lasts for the length of the lease period. T-1, the most popular type of dedicated connection, and T-3 are examples of dedicated lines. The network administrator chooses and implements a Layer 2 protocol such as PPP or HDLC. The customer pays a monthly tariff based on mileage for a leased line. The administrator may choose between several switched technologies: circuit switched, packet switched, or cell switched. The customer pays for the use of the service monthly and may additionally pay for a connection time charge. The bandwidth is provided on demand. In circuit switching, circuits are established prior to the transmission of data and torn down at the end of the transmission. During transmission of data, all of the packets take the same path. The Public Switch Telephone Network (PSTN) is an example of a circuit switch system. A call is placed and a circuit established when the other end of the circuit is answered. Modems that operate between computer systems are a specific example. ISDN is a digital connection used for voice, video, and data transmission. ISDN is a circuit switched technology. ISDN charges may include a substantial connection time element. Therefore, it is frequently used for back up to other connections as opposed to an always-available connection. In packet switching, circuits may be selected on a packet-by-packet basis. The Internet widely uses packet switch networks, for individual packets in the same transmission may take different routes through the network to the same destination. Upper layers of the OSI model place the packets into the correct order. Frame Relay, a popular WAN technology, is packet switched. For Frame Relay, the charge is for the service, but no mileage fee. This makes Frame Relay a popular choice for long distance WAN links and connections for full and partial networks. Let’s look at the relationships between different WAN technologies. Dedicated or Point-to-Point connections include T-1/E-1, and Fractional T1/E1, T-3 and E-3 lines, and xDSL lines. 1-2
Video: Dedicated vs. Switched WAN Technologies
Copyright 2001, Cisco Systems, Inc.
Circuit switched technologies include ISDN, POTS for Plain Old Telephone System, and Switched 56K. Packet Switched technologies include Frame Relay, X.25, SMDS, and ATM. Packet Switch networks are scalable and manageable. They’re ideal when data can withstand delays in transmission, like e-mail and web pages. Circuit switched charges are based on connection time. They’re ideal when data must be transmitted quickly and arrive in the order sent. Dedicated lines are used when traffic is heavy and predictable.
Copyright 2001, Cisco Systems, Inc.
Video: Dedicated vs. Switched WAN Technologies
1-3
