1. Information Networks COMT 625 Hans Kruse

2. COMT 625 - Hans Kruse2 What is a network? Nodes End (User) Nodes Interior (Network) Nodes Links

3. COMT 625 - Hans Kruse3 Nodes  End Nodes ° Contain the User Equipment CPE - Customer Premise Equipment Demarcation - Interface to the Network  Interior Nodes ° Switching, Routing, and Cross-Connects ° Signaling, Routing, User Databases ° Collection of Billing Information

4. COMT 625 - Hans Kruse4 Some Terminology  Central Office or “CO” ° Local Switching Center with direct connection to subscribers  Class 5 Office - same as Central Office  POP - Point of Presence ° Switching office operated by long distance carriers  ISP – Internet Service Provider

5. COMT 625 - Hans Kruse5 Network Structure Backbone Access End Nodes

6. COMT 625 - Hans Kruse6 Multi-Vendor Structure Backbone Access End Nodes

7. COMT 625 - Hans Kruse7 The “Protocol Stack”  Each application ° Requires network services ° Adheres to a set of rules  Standards ° Define a subset of the services and/or rules

8. COMT 625 - Hans Kruse8 OSI Model for Networks 7Application Layer 6Presentation Layer 5Session Layer 4Transport Layer 3Network Layer 2Data Link Layer 1Physical Layer

9. COMT 625 - Hans Kruse9 Standards in a Layered Model Layer N Layer N-1 RequestRespond ConfirmIndicate

10. COMT 625 - Hans Kruse10 Node Implementation  Nodes implement layers from the bottom up  Implementation stops at the lowest layer that provides sufficient functionality  “Exceeding” Expectations ° Nodes that implement higher layers than “needed” are said to “violate” layering

11. COMT 625 - Hans Kruse11 Different Protocol Stacks  User Plane ° The protocol stack that makes an application work E.g. ISDN voices bearer channel E.g. HTTP/TCP/IP/Ethernet  Control Plane ° Protocols needed for call or network control E.g. ISDN D (signaling) channel E.g. IP/ARP, DNS

12. COMT 625 - Hans Kruse12 Different Network Logic  Circuit Switching ° Traditionally used for voice ° Fixed, Predictable capacity ° Precise timing ° Non-shared No Competition No easy way to share capacity  Datagram Packet ° Example: IP ° Capacity is shared among all users ° Facility utilization is very efficient ° Service guarantees and timing constraints are difficult to obtain.

13. COMT 625 - Hans Kruse13 Access to Datagram Networks  Small End Nodes ° Have little chance to share traffic ° Use essentially circuit switched access ° Access is a performance and cost bottleneck  Large End Users ° Can implement circuit sharing (multiplexing) on their own premises

14. COMT 625 - Hans Kruse14 Voice over Datagrams (IP)  Performance ° Better use of facilities ° Difficult to do with good quality  Price ° Regulation Artifacts ° Different pricing for best-effort networks  Features ° Combined networks offer enhanced signaling