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Module 7: WAN Concepts, image, image, image, image, image - Coggle Diagram
Module 7: WAN Concepts
7.1. Purpose of WANs
- LANs (Local Area Networks) connect users and devices in a small geographical area (e.g., home, office building) and are usually managed by a single organization.
- WANs (Wide Area Networks) interconnect LANs across large geographical areas (e.g., cities, countries), often using services provided by a telecommunications carrier.
- 7.1.2 Private and Public WANs
- Private WANs are dedicated links or services (like MPLS, Leased Lines) contracted from a carrier to connect specific organizational sites securely.
- Public WANs primarily use the Internet to connect sites, typically relying on VPN (Virtual Private Network) technology for security and privacy.
- Common WAN topologies include Point-to-Point (dedicated link between two endpoints), Hub-and-Spoke (central site connects to multiple remote sites), and Full/Partial Mesh (multiple interconnections for redundancy).
- The choice of topology depends on requirements for cost, availability, and traffic flow.
- 7.1.4 Carrier Connections
- WAN access requires an access link provided by a carrier (e.g., ISP, Telco) and specific Customer Premises Equipment (CPE) on the customer side.
- The CPE router is the DTE (Data Terminal Equipment) and connects to the DCE (Data Circuit-terminating Equipment) provided by the carrier.
- Traditional WANs are transitioning to SD-WAN (Software-Defined WAN) architectures, which centralize control and allow intelligent management of traffic across multiple connections (e.g., MPLS and Internet broadband).
- This evolution prioritizes application performance, flexibility, and cost efficiency.
7.2. WAN Operations
- WAN standards are typically defined and governed by recognized bodies like the ISO, ITU-T, and IEEE, as well as local regulatory agencies.
- These standards ensure interoperability and proper communication across different carrier technologies and equipment.
- 7.2.2 WANs in the OSI Model
- WAN technologies primarily focus on the Physical Layer (Layer 1) and Data Link Layer (Layer 2) of the OSI model.
- They define the physical cabling, signaling, and framing protocols (like PPP or Frame Relay) used for data transport between geographically distant sites.
- 7.2.3 Common WAN Terminology
- Key terms include CPE (Customer Premises Equipment), DCE (Data Circuit-terminating Equipment, provided by carrier), and DTE (Data Terminal Equipment, the customer's router).
- Other terms are Local Loop (connection from CPE to carrier), and Central Office (CO) (carrier's switching facility).
- Essential WAN devices include Routers (DTE), CSU/DSUs (DCE), and Modems (DCE for analog or DSL).
- These devices terminate the local loop and convert the customer's data into the format required for the carrier's wide area network.
- 7.2.5 Serial Communication
- Most traditional WANs use serial links to transmit data one bit at a time over a single channel.
- Serial communication is defined by various protocols (e.g., HDLC, PPP) and often requires a clock source (DCE) to synchronize transmission.
- 7.2.6 Circuit-Switched Communication
- A dedicated circuit (fixed bandwidth and path) is established between the sender and receiver before data transfer begins (e.g., analog dial-up, ISDN).
- The circuit remains active and reserved for the duration of the communication, offering guaranteed bandwidth but often being inefficient.
- 7.2.7 Packet-Switched Communications
- Data is segmented into packets which are transmitted over a shared, dynamic path (e.g., Frame Relay, MPLS, Ethernet WAN).
- This is more cost-effective as bandwidth is shared among multiple users, leading to flexible and efficient resource utilization.
- 7.2.8 SDH, SONET, and DWDM
- These are high-speed, carrier-level optical transmission technologies: SONET (US/Canada) and SDH (rest of the world) are standards for synchronous digital transport.
- DWDM (Dense Wavelength Division Multiplexing) increases capacity by sending multiple data streams using different light wavelengths over a single optical fiber.
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