Introduction: ^{reference (local copy)}

Review of Switching and Access Modalities: ^reference 

Circuit Switched Networks Revisited:

In the beginning there was a monolithic hierarchy based on analog signals and FDMA…

Simple hierarchy
Typical network

Then came PCM, TDMA and the digital hierarchy…

Packet Switched Networks:

Simple packet switching network
Packet switching schematic

Packet switching: datagram approach
Packet switching: virtual-circuit approach
Virtual-circuit configuration

The Need for Network Protocols:

A brief introduction to network propocols

SDH and SONET: ^reference

Schematic Multiloop Network 

DWDM channels - 100 GHz separation

An extended discussion of SONET

References:

Internetworking Technology Overview: extensive and uthoritative information on internet issues from Cisco Systems.

Data Communication Networks and Distributed Systems: a quite extensive set of lecture notes by Saleem N. Bhatti, University College London.

Nortel Tutorials

Telephony 101: (pdf) A basic introduction to how public network telephone services are provided in North America.
SONET 101: (pdf) An introduction to synchronous optical networks.
Introduction to SONET Networking: A tutorial handbook of advanced SONET networking concepts.
Long Distance 101: An introduction to how long distance service is delivered in North America, and opportunities for network providers in the long distance arena.

Frame Relay: a vitual textbook by John H. Petrangelo at Worcester Polytechnical Institute
on the subject of Frame Relay

Tutorials and Technical Notes from Sangoma Technologies

Tutorials fron Scan Technologies