NT1210 Introduction to Networking Unit 7: Chapter 7, Wide Area Networks

Class Agenda 2/2/16 Learning Objectives. Lesson Presentation and Discussions Lab Activities will be performed in class. Assignments will be given in class. Break Times will be consistent with school rules. Student are encourage participate in discussion in class. Your contribution is very important. Note: Submit all Assignment and labs due today.

Objectives  Differentiate among WAN technologies available from service providers  Evaluate how WAN devices function  Define and describe WAN protocols  Evaluate troubleshooting techniques for WAN connections 3

Introducing Wide Area Networks: Basic Telco Services  Telephone, Telcos, and companies that grew from original Bell System impact how today’s WANs work  Telcos built huge networks to support voice traffic, long before computers could create and send bits Figure 7-1Timeline Comparison of Inventions Compared to Telephone 4

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching Figure 7-2 Early Voice: Telco Creates One Analog Electrical Circuit Between Phones 5

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching  Switched Analog Circuits for Data: To create first WAN connections, early computing devices had to act like telephones  One computer device would “make phone call” to other computer, encoding its bits using analog electrical signals  Example a Dial-Up-Connection using internal or external modem  Modem is a Modulation and Demodulation system. 6

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching Figure 7-4 Connecting from a PC to an ISP, Using Modems and an Analog Telco Circuit 7

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching  Beginning mid-20 th century Telcos transformed  Invention and commercialization of computers: Started with few computers being rare and unusual to world where most companies owned computers  Migration from Telcos as government monopolies to free- market competition: Governments started removing monopoly status from different parts of Telcos’ business so allowed competition  Computerization of Telco’s own network: Revolutionized how Telco built its internal network to create better services at lower cost 8

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching  Digital Circuits and Leased Lines: Telcos started offering service that used digital circuit between customer devices  Endpoints still had circuit between them but could encode signal as bits with different electrical signals that followed encoding rules Figure 7-5More Modern Routers Using a Digital Leased Line 9

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching  Switched Circuits and Circuit Switching: When user calls phone number, various circuit switches connect circuit on both sides of switch (see arrowed lines)  Circuit switches create effect of end-to-end circuit by switching/connecting circuits on various links Figure 7-6Circuit Switching 10

Introducing Wide Area Networks: Basic Telco Services – Circuit Switching  Circuit: Communication path between two endpoints  Circuit Switching: Logic used by Telco network and devices called “circuit switches” that allows them to switch circuits in and out of different physical trunks to create end-to-end circuit through network  Switched Circuit: End-to-end circuit through Telco that changes over time because user calls number, hangs up, calls another number, and so on  Dedicated Circuit (leased line): Circuit between two specific devices Telco never takes down 11

Introducing Wide Area Networks: Basic Telco Services – Packet Switching  Packet Switching: Telcos next started offering WAN services using packet switching services Figure 7-7 General Timeline: Circuit Switching, Digital Circuits, and Packet Switching 12

Introducing Wide Area Networks: Basic Telco Services – Packet Switching  All customer devices need direct connection to WAN via circuit to packet switching service  Customers: All devices can send data to every other device connected to packet switched service  Telco (service provider): Must look at meaning of bits in customer’s headers and make forwarding decision per packet 13

Introducing Wide Area Networks: Basic Telco Services – Packet Switching Packet Switching Example Figure 7-8Example of Packet Switching Service 14

Introducing Wide Area Networks: Routers  Connect LANs to WANs Figure 7-9Layer 3 IP Forwarding Logic 15

Introducing Wide Area Networks: Routers  LAN might be simple Ethernet-only LAN  LAN might be simple WLAN  LAN might be more complex campus LAN with both wired and wireless LANs Figure 7-10Example Enterprise Network, With LAN and WAN Details Revealed 16

Introducing Wide Area Networks: Routers  Encapsulation and De-encapsulation Figure 7-11Encapsulation that Happens During the IP Packet Forwarding Process 17

Introducing Wide Area Networks: Topologies  Point-to-Point Topology: Basic WAN service  LAN with10BASE-T or 100BASE-T cable has 2-pair: 1 pair for sending data in each direction  Both LAN and WAN topologies allow full duplex operation and can share 1 link Figure 7-12Point-to-Point Topologies in WAN and LAN 18

Introducing Wide Area Networks: Topologies  Hub and Spoke Topologies  Reduces number of leased lines  Provides way for packets to reach all sites  Connects one router (hub router) to all other routers using leased lines Figure 7-13WAN Hub and Spoke Topology Vs. LAN Star Topology 19

Introducing Wide Area Networks: Topologies  Multipoint topologies: Hub-and-spoke topology has some disadvantages  Uses leased lines that might have to run hundreds or thousands of miles at large expense  Packets that go from one spoke site to another spoke site have to cross multiple WAN links Figure 7-14WAN Multipoint Topology 20

Understanding Leased Line WAN Links  Distance limitations: No single circuit extends entire distance between two routers  “Point to point” circuits really series of circuits Figure 7-16Leased Line: Shorter Electrical Circuits, Knitted Together 21

Understanding Leased Line WAN Links  Telco installs physical cable between equipment in CO to customer site  2-pair cable typically runs underground into customer buildings terminating near customer’s router Figure 7-18Cables in a Relatively Short Leased Line 22

Understanding Leased Line WAN Links  Customer needs to plan for cabling at end of Telco’s leased line cable  Example: Customer’s router connects to cable installed by Telco Figure 7-19Components and Responsibilities on One Side of a Leased Line 23

Understanding Leased Line WAN Links  Leased line has Channel Services Unit/Data Services Unit (CSU/DSU) function on each side of line at customer site  Each site uses either internal or external CSU/DSU  Internal CSU/DSU sits inside router as part of serial interface card Figure 7-20Customer Equipment and Cabling with External CSU/DSU 24

Understanding Leased Line WAN Links  Example: Cisco router with two slots for removable router interface cards (WICs) where serial cards are install  Serial card on left has built-in CSU/DSU and uses RJ-48 connector  Serial card on right does not have CSU/DSU so relies on external CSU/DSU Figure 7-22Photos of Router and Removable WAN Cards 1921 router… WIC-1CSU:

Understanding Leased Line WAN Links  Key steps for installing leased lines 1.Order leased line from Telco; include specs on line speed, cable connectors required, and exact location where cable should be installed (address, floor, identifying information for exact room) 2.Install router and serial interface cards in router as needed by leased line 3.If interface card does not have internal CSU/DSU, choose CSU/DSU and matching cable 4.Physically connect all cables 5.Configure devices (beyond scope of this chapter) 26

Understanding Leased Line WAN Links: Multiplexing  Possible solution: Telco could install three T1 trunk lines between CO switches Figure 7-24Telco Switching Connecting Incoming Customer T1s to T1 Trunks 27

Understanding Leased Line WAN Links: Multiplexing  More efficient solution: Time Division Multiplexing (TDM) uses TDM switches and one T3 trunk  Telco connects cable using T3 card in each TDM switch to use T3 link ( Mbps—28 times T1 speed) Figure 7-25CO Switches Multiplexing T1 Bits onto Faster T3 Circuit 28

Understanding Leased Line WAN Links  Customer buys T1 line at each site with full T1 speed (1.536 Mbps)  What happens if customer router can only transmit at 768 Kbps? Figure 7-29 Speed Differences on a 768-Kbps Leased Line WAN 29

Understanding Leased Line WAN Links Table 7-3Summary of Carrier TDM Line Standards * 30 E0 channels are available for customer data; 2 E0 channels are for other functions. 30 Type of LineGeographySpeedNumber of Channels DS0USA64 KbpsN/A DS1 (T1)USA1.544 Mbps24 DS0 DS3 (T3)USA Mbps28 DS1 E0Europe64 KbpsN/A E1Europe2.048 Mbps32* E0 E3Europe Mbps16 E1 J0Japan64 KbpsN/A J1Japan1.544 Mbps24 J0 J3Japan Mbps20 J1

Understanding Packet Switching and Multi- Access WANs  With packet switching, link capacity between switches used to forward packets as needed or available 31

Understanding Packet Switching and Multi- Access WANs: Frame Relay  Frame Relay: Allows any device connected to network to communicate with any other network and details of Frame Relay design do not matter Figure 7-44 Typical Drawing of a Frame Relay Design, One Customer, Ignoring Details 32

Understanding Packet Switching and Multi- Access WANs: Frame Relay  Frame Relay physical links: Edge between customer site and Frame Relay network  Point of Presence (PoP): Where Telco devices/cables interface with customer premises  DTE (Data Terminal Equipment): Customer device (e.g., router)  Frame Relay switch: Telco device that forwards customer frames (also called DCE [Data Communications Equipment])  Access link: Physical link between DTE and DCE  DLCI: Data Link Control Identifier, used instead of IP address 33

Understanding Packet Switching and Multi- Access WANs: Frame Relay  Frame Relay terms Figure 7-45One Possible Telco Implementation of the Frame Relay Network 34

Understanding Packet Switching and Multi- Access WANs  Packet Switching Services: SONET speeds Table 7-5SONET Optical Carrier (OC) Names and (Rounded) Line Speeds Name (Rounded) Line Speed (in Mbps) OC-152 OC-3155 OC OC OC OC OC

Unit 7 Assignment Unit 7 Assignment 1: Wide Area Networks Review Complete the multiple-choice questions Complete the Define Key Terms table and the List the Words Inside the Acronyms table. Reading Assignment. Read Chapter 8

Unit 7 Lab Complete all Labs in Chapter 7 of the lab book. Unit 7 Lab 7.1: Distance Considerations Unit 7 Lab 7.2: WAN Connections Unit 7 Lab 7.3: Communication Paths Unit 7 Lab 7.4: Linux Networking Unit 7 Lab 2.5: Linux man Pages Unit 7 Lab 7.4: Linux Networking Lab should be completed in class. Uncompleted Lab must be submitted in the next class.

Research Project Unit 7 Research Project 1: Chapter 8 Mind Maps (NT1210 Graded Assignments)