ENSA-ch07

Module 7: WAN Concepts

Module Objectives

  • WAN Concepts: Explaining WAN access technologies for business needs.
  • Purpose of WANs: Understand WAN functionalities.
  • WAN Operations: Insights on how WANs function.
  • Traditional vs Modern WAN Connectivity: Evaluating differences.
  • Internet-Based Connectivity: Assessing internet services for WANs.

Purpose of WANs

  • Definition: WAN is a telecommunications network covering a large area, connecting multiple LANs.
  • Comparison with LAN:
    • LAN (Local Area Network):
    • Operates within a small geographic area.
    • Managed by organizations or home users.
    • High bandwidth with low costs (e.g. Ethernet, Wi-Fi).
    • WAN (Wide Area Network):
    • Services large geographical areas, interconnecting remote sites and users.
    • Managed by ISPs or telecom providers with bandwidth fees.
Characteristics of WANs
  • Private WAN:
    • Dedicated to a single customer.
    • Benefits: Guarantee of service, consistent bandwidth, enhanced security.
  • Public WAN:
    • Provided by ISPs; service levels and security are variable.

WAN Topologies

  • Types of Topologies:
    • Point-to-Point: Direct connection between two endpoints; economic only for a few links.
    • Hub-and-Spoke: Central hub distinguishes spoke communication; single point of failure if the hub fails.
    • Dual-Homed: Redundancy and load balancing; more costly and complex due to added hardware.
    • Fully Meshed: Connections between all sites; highly fault-tolerant.
    • Partially Meshed: Some but not all sites interconnected.
Carrier Connections
  • Definitions:
    • Single-Carrier: One service provider for connection; single SLA.
    • Dual-Carrier: Two providers for redundancy; separate SLAs.

Evolving Networks

  • Adaptability: Networks evolve with business needs.
  • Growth: Transition from small LANs to complex global networks.
    • Examples from SPAN Engineering:
    • Small LAN using DSL.
    • Transition to Campus Area Network (CAN) with a secure firewall.
    • Development of Metropolitan Area Network (MAN) as the business grows regionally.

WAN Operations

  • Standards: Governed by TIA/EIA, ISO, IEEE.
  • OSI Model: Primarily involving the physical (Layer 1) and data link (Layer 2) layers.
WAN Technologies
  • Layer 1 Protocols: SDH, SONET, DWDM.
  • Layer 2 Protocols: DSL, wireless, Ethernet WAN, MPLS, PPP, etc.

Common WAN Terminology

  • DTE: Connects LANs to WAN devices.
  • DCE: Communicate with the provider.
  • CPE: Location of DTE and DCE on the edge.
  • POP: Connection point to the provider's network.
    • Demarcation Point: Separates customer and provider equipment.
    • Local Loop: Connection between CPE to Central Office (CO).
WAN Devices and Communications
  • Modems: Dial-up, DSL, cable.
  • CSU/DSU: Digital leased line interfacing.
  • Serial Communication: Most WANs use this; conveys bits sequentially.
    • Circuit-Switched: Establishes dedicated circuits.
    • Packet-Switched: Segments data into packets for routing; includes MPLS, Frame Relay, etc.

Traditional WAN Connectivity

  • Leased Lines: Monthly fees for point-to-point connections; fixed capacities.
    • T-carrier: North America system, offers T1 and T3.
    • E-carrier: European counterpart.
Circuit-Switched vs Packet-Switched
  • Circuit-Switched: PSTN and ISDN allow dedicated connections.
  • Packet-Switched: Economical; includes Frame Relay and ATM which are being replaced by modern options like Metro Ethernet.

Modern WAN Connectivity

  • New Technologies: Focus on speed and flexibility.
  • Options:
    • Dedicated Broadband: Fiber connections directly between locations.
    • Metro Ethernet: Replacing traditional WANs.
    • MPLS: Connects various access technologies efficiently.

Internet-Based Connectivity

  • Wired vs Wireless:
    • Wired: Consistent bandwidth (DSL, cable, fiber).
    • Wireless: Less expensive, though subject to interference.
DSL and Cable Technologies
  • DSL: Always-on, high-speed; ADSL vs SDSL for different upload/download specifications.
  • Cable: High-speed over coaxial; DOCSIS standard governs.
Fiber Technology Types
  • FTTx: Variants for different connection depths (like FTTH, FTTB, FTTN).
VPN Technology
  • Secure connections over public networks; includes site-to-site and remote access VPNs.
ISP Connectivity Options
  • Single, Dual, Multihomed: Different connection redundancy levels.

Summary of Key Concepts

  • WAN necessary for broad-area connections; private vs public characteristics defined.
  • Various topologies inform design choice.
  • Protocol standards crucial for understanding WAN operations.
  • Cost and clarity vary across WAN technologies.
  • Modern connectivity options advancing with tech improvements.