Notes On Chapter Nineteen -- Networking Technologies Past and Present

• 19.1 Introduction
  
  
  • Major Technologies
  • Significant Features and Characteristics
  • The Variety of Technologies
  • The Rapidity of Change
  
  
• 19.2 Connection and Access Technologies
  
  
  • 19.2.1 Synchronous Optical Networks or Digital Hierarchy (SONET/SDH)
    • "permits a physical ring to be constructed with the purpose of providing redundancy"
    
    
  • 19.2.2 Optical Carrier (OC)
    • Signaling used on optical fiber
    
    
  • 19.2.3 Digital Subscriber Line (DSL and Cable Modems
    • Principle current technology for broadband to homes and small businesses.
    • DSL offers 1 to 6 Mbps
    • Cable modem offers up to 53 Mbps to be shared by a group
    • Fiber to the curb or home is expected to eventually replace DSL and cable modem.
    
    
  • 19.2.4 WiMAX and WiFi
    • Wi-Fi is a set of LAN technologies widely adapted to implement small inexpensive LANs. Data rates have increased impressively over a relatively short period of development.
    • WiMAX is a wireless broadband technology that can provide the infrastructure for a MAN.
    • WiMAX is in use providing access to subscribers, and also in backhaul applications, e.g. between cell towers and a service providers central network facility.
    • There are two versions of WiMAX - one for fixed stations and one for 'mobile endpoints'.
    
    
  • 19.2.5 Very Small Aperture Satellite
    • Provides Internet service to homes and small businesses.
    • High data rates
    • Long Delays
    
    
  • 19.2.6 Power Line Communications (PLC)
    • Uses high frequency to send data through power lines.
    • Much research has been done, but not much deployment.
  
  
• 19.3 LAN Technologies
  
  
  • 19.3.1 IBM Token Rings
    • IBM created this token-passing ring LAN technology.
    • Originally 4 Mbps and later 16 Mbps
    • Widely accepted in the corporate sector for many years
    
    
  • 19.3.2 Fiber and Copper Distributed Data Interconnect (FDDI and CDDI)
    • In the late 1980's and early 90's, this was the answer to slow 10 Mbps Ethernets and 16 Mbps IBM Token Rings.
    • FDDI offered 100 Mbps data rates and a redundant counter-rotating ring technology
    • There was some reluctance to adopt it because of the expense and expertise required to deal with fiber.
    • Once Ethernet speeds overtook FDDI and CDDI, they were obsolete.
    
    
  • 19.3.3 Ethernet
    • Ethernet is now extremely dominant as a network technology.
    • However Ethernet evolved and changed drastically compared to its original form.
  
  
• 19.4 WAN Technologies
  
  
  • 19.4.1 ARPANET
    • A project of the US Defense Department Advanced Research Projects Agency (DARPA).
    • One of the first packet-switched WANs
    • Originally connected researchers in academia and the military
    • Precursor to the Internet
    • Provided the first Internet backbone
    
    
  • 19.4.2 X.25
    • Early standard for WAN technology developed by what is now the International Telecommunications Union (ITU).
    • Popular with public carriers in its time
    • Was more popular in Europe than the US
    • Had a traditional WAN design: leased lines connected by packet switches having directly-connected computers.
    • Connection oriented
    • Invented before the era of PC's.
    • Often used to connect remote terminals
    
    
  • 19.4.3 Frame Relay
    • Invented by long-distance voice carriers
    • Inventors envisioned it to bridge LAN segments
    • Connection oriented
    • Expensive
    • Popular until lower cost alternatives came along
    
    
  • 19.4.4 Switched Multi-megabit Data Service (SMDS)
    • Invented by long-distance voice carriers
    • Based on a IEEE standard
    • High Speed
    • Small packet headers
    • Connectionless
    • Didn't catch on - partly because telephone companies were more comfortable with connection-oriented technologies.
    
    
  • 19.4.5 Asynchronous Transfer Mode (ATM)
    • Designed to "do it all" - WAN, LAN, voice, video, data
    • Promised superior scalability, partly through the use of "label switching" technology that would get packets through switches faster than conventional forwarding methods.
    • Features included quality of service guarantees (e.g. bandwidth minimums and delay maximums)
    • It didn't catch on too well
    • It's not used much now
    
    
  • 19.4.6 MultiProtocol Label Switching (MPLS)
    • A follow-on from ATM technology
    • Label switching used at the center of the Internet
    • Provides a way to allow packets to follow a specific path (a service for which some users will pay extra).
    
    
  • 19.4.7 Integrated Services Digital Network (ISDN)
    • An early service created by phone companies to perform better than dial-up modem service.
    • Now mostly supplanted by DSL, cable modem and 3G cellular services.