WAN

Wide Area Network (WAN)

• Large geographic separation
• Connection types:
  • Site-to-site / leased line
    • Circuit between sites.
  • Internet
    • Internet access might cost you a small fraction of what a site-to-site leased line will cost. And with the Internet we can build a VPN topology on top of it, and we can connect our offices without having to pay those expensive leased lines.
• Recurring cost
  • One of the things that we wanna think about.
• Service Level Agreement possible
  • Gives you some amount of speed depending on the city, some cities are faster/slower.
  • ISP Guarantee a level of performance.
  • Gives you office-to-office communication, we can do everything over a single link, it's easy, it's cheap, it's very common.
  • If the level of performance/reliability that you get from an ISP isn't quite what you need. What's neat about moving to a dedicated link is if there was some type of an attack on the internet, the leased line is a separate network that wouldn't have those attackers on it, so it does tend to be a little bit more secure.

WAN Technologies

• Single Mode Fiber (SMF)
  • Fiber provides tens of kilometers of distance
  • Coax can go further than traditional copper can but not as far as fiber.
  • Radio frequencies are susceptible to interference while fiber is the least susceptible interference.
• Serial link
  • Old technology
    • A router that has a serial cable that came of of it and it went to this other device that was basically a modem for a T1 circuit, called a CSU/DSU, then this CSU/DSU took the signal that came across the serial line and it put out over a T1 circuit, This was what the ISP was expecting to see from us.
    • A T1 is really a WAN technology , that's the only place you'll ever use it.
    • What routers often do is that they connect a LAN to a WAN, and one of the critical pieces for that in contrast with layer 3 switches is that they have the ability to accept something called a WAN Interface Card (WIC) When you get to the WAN side, it has a different type of interface, not only from a layer one perspective, using RJ45 or fiber, but also from a layer two perspective. Within the LAN what protocol do we use at layer 2? Ethernet / MAC addresses, well WAN can also be ethernet and more commonly, it is today. But historically going back, it was almost never ethernet, you had to use some other type of technology. A router had the ability to do media translation. You would do regular LAN ethernet coming in, and then maybe you do something weird out the other side, just a WAN technology, DSL, dial-up for example.
  • Serial links were used to hook up an external device, and today what you will typically found is a WIC, and that'll be like a T1 or T3 module card that you can just install into a router
    • It is probably gonna be like a 5G cellular adapter that you are putting in, and that would be for a backup to whatever your traditional broadband connection is, very common.
• Internet w/VPN
  • Opposite of the country connected together
  • Leased links take around two weeks or more for a price quote, and you might be waiting more weeks to get that circuit provision.
  • Slow process