However, parallel communications do have issues with crosstalk across wires, especially as the wire length increases. Based on this theory, a parallel connection sends a byte (eight bits) in the time that a serial connection sends a single bit. As shown in Figure 3-2, a parallel connection theoretically transfers data eight times faster than a serial connection. This is in contrast to parallel communications in which bits can be transmitted simultaneously over multiple wires. A serial port is bidirectional, and often referred to as a bidirectional port or a communications port. Multiple balls can go into the pipe, but only one at a time, and they only have one exit point, the other end of the pipe. This is equivalent to a pipe only wide enough to fit one ball at a time. Understanding how point-to-point serial communication across a leased line works is important to an overall understanding of how WANs function.Ĭommunications across a serial connection is a method of data transmission in which the bits are transmitted sequentially over a single channel. Leased lines are a frequently used type of WAN access, and they are generally priced based on the bandwidth required and the distance between the two connected points. Companies pay for a continuous connection between two remote sites, and the line is continuously active and available. This is because the lines are leased from a carrier (usually a telephone company) and are dedicated for use by the company leasing the lines. Figure 3-1 Serial Point-to-Point CommunicationsĪ LAN-to-WAN point-to-point connection is also referred to as a serial connection or leased line connection.