I know LAN network can make Ethernet connection using UTP cable and optical connection using SFP module, but it is difficult when it comes to WAN.
So, I have two questions.
I know the limit of UTP cable is 100 meters, so I would like to know what kind of lines are used for WAN connection
In the case of Serial communication, I know that additional devices such as DSU/CSU should be connected when connecting to WAN, but I wonder if it is connected directly from router to router or does it require additional equipment like Serial.
In the past, the WAN and the LAN were very different, where each one used specific technologies, and in general, WAN links were much slower than LAN links. Over the years, the technologies began to converge, WAN and LAN links sometimes use similar or even the same technologies. The differences however still remain especially when it comes to the physical medium used to connect the last mile.
For WAN connections, there are various technologies and media that can be used:
xDSL uses a single pair of category three (telephony) cable that can support distances of up to a few dozen kilometers.
Cable modem (DOCSIS) uses coaxial cable with distances ranging from 150 to 300 meters between the cable modem and the interconnect on the curb. Typically, connections from there on go via fiber optic cables to the headend.
Fiber optics (Fiber to the Home (FTTH)) - You can have fiber optic cables come into your premises delivering technologies such as metro Ethernet, MPLS, or others. Depending on the type of fiber, distances can range from several hundred meters to dozens of kilometers.
Wireless technologies including microwave links, cellular links, as well as WiMAX can be used for WAN links.
In a lab environment, you can connect two routers directly to each other using a serial connection, but you need to configure one of the routers as the DCE to generate the clocking signal. In a production environment, you would always configure your router as the DTE, while the CSU/DSU that the telco gives you would act as the DCE.