Networking Concepts · Topic 8 of 11
Network Types and WAN Links
Compare LAN, WAN, MAN, WLAN, PAN, CAN and SAN types, client server and peer to peer models, WAN technologies, provider links and virtual networking.
- 5 min
- LAN is one site. CAN links buildings. MAN covers a city. WAN spans long distances.
- PAN is short range and personal. SAN is a dedicated storage network.
- Client server has dedicated servers. Peer to peer shares resources between equals.
What it is
Networks are named by the area they cover and by how devices share services. Wide area connections come from a service provider, and virtual networking recreates switches and network interfaces in software.
The exam asks you to classify a network from a description and to choose a wide area network (WAN) link that fits a requirement.
How it works
Network types
| Type | Meaning | Typical scope |
|---|---|---|
| Local area network (LAN) | Devices on one site | A building or floor |
| Wireless LAN (WLAN) | A LAN that uses 802.11 radio | A building or campus |
| Personal area network (PAN) | Very short range, for one person | Bluetooth earbuds and a phone |
| Campus area network (CAN) | Several linked buildings of one organization | A university or business park |
| Metropolitan area network (MAN) | Links sites across a city | A city wide fiber ring |
| Wide area network (WAN) | Links distant sites, often through a provider | Cities, countries |
| Storage area network (SAN) | A dedicated network for block storage | A data center |
In a client server model, dedicated servers provide services to clients. In a peer to peer model, every device can both share and use resources, with no central server.
WAN technologies
Multiprotocol Label Switching (MPLS) is a provider service that forwards traffic by short labels instead of looking up full Internet Protocol (IP) addresses at every hop. Customers buy it for predictable performance and for linking many sites.
A software defined WAN (SD-WAN) uses software to steer traffic over several links, such as broadband and MPLS, based on policy and link quality. It is covered further in the modern use cases page.
Multipoint Generic Routing Encapsulation (mGRE) lets one tunnel interface on a hub build tunnels to many spokes. It is often combined with IPsec in hub and spoke virtual private network (VPN) designs.
Provider links
| Link | Notes |
|---|---|
| Digital subscriber line (DSL) | Uses existing telephone wiring, speed falls with distance from the provider |
| Cable | Uses the cable television coax network, which is shared among neighbors |
| Leased line | A dedicated point to point circuit with guaranteed capacity, higher cost |
| Metro optical (Metro Ethernet) | Ethernet delivered over fiber in a metropolitan area |
| Satellite | Reaches remote places, with high latency |
| Cellular | Mobile data for backup or remote sites |
Demarcation point
The demarcation point (demarc) is where the provider's responsibility ends and the customer's begins. A smartjack is a network interface device at the demarc that lets the provider test the circuit remotely, for example with a loopback.
Equipment on the customer side is called customer premises equipment (CPE). If a test shows the line is fine up to the smartjack, the fault lies in the customer's equipment or cabling.
A channel service unit/data service unit (CSU/DSU) is the older device that connects a customer's router to a digital leased line such as a T1.
Virtual networking
A hypervisor is software that runs virtual machines on a physical host. A virtual switch (vSwitch) connects virtual machines to each other and to the physical network. A virtual network interface card (vNIC) is the network adapter of a virtual machine.
Network function virtualization (NFV) runs network functions such as firewalls, routers and load balancers as software on standard servers instead of dedicated hardware.
What to remember for the exam
- LAN is one site. CAN links buildings. MAN covers a city. WAN spans long distances.
- PAN is short range and personal. SAN is a dedicated storage network.
- Client server has dedicated servers. Peer to peer shares resources between equals.
- MPLS forwards by labels and is a provider WAN service.
- A leased line is dedicated and predictable. Cable is shared. DSL speed depends on distance.
- Satellite links work almost anywhere but have high latency.
- The demarc is where provider responsibility ends, and a smartjack allows remote testing.
- NFV replaces dedicated appliances with virtual functions. A vSwitch connects virtual machines.
When a question asks which link has guaranteed capacity and a service level, choose a leased line. When it asks which is cheapest with variable speed, choose cable or DSL.
Common mistakes
Confusing CAN and MAN. A CAN joins buildings of one organization. A MAN covers a city and may serve many customers.
Calling every wireless network a PAN. A PAN is very short range. Wi-Fi in a building is a WLAN.
Assuming MPLS encrypts traffic. It separates customers with labels inside the provider network, but it does not encrypt by itself.
Blaming the provider for every outage. If the smartjack test passes, the problem is on the customer side of the demarc.
Mixing up vSwitch and physical switch roles. A vSwitch is software on the hypervisor, but it still forwards frames between virtual and physical ports.
Satellite latency is high because of the distance the signal travels, so bandwidth upgrades do not fix slow interactive applications.
Check yourself
Use these three items to check your understanding.
What is the name of the point where the provider's line meets the customer's equipment?
The demarcation point, often with a smartjack for remote testing.
Which WAN link type is a dedicated point to point circuit with guaranteed bandwidth?
A leased line.
What does a hypervisor's virtual switch do?
It connects the virtual machines to each other and to the physical network.
Topic 8 of 11 in Networking Concepts
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