2. 1/28/2010 Network Plus Unit 4 - Section 1 Wide Area Network Technologies

3. Connecting to the Internet Internet connections may be Wired or Wireless. In this section we will look at wired connections using either the Telephone or Cable networks.

4. PSTN PSTN (Public Switched Telephone Network) –Network of lines, carrier equipment providing telephone service –POTS (plain old telephone service) –Encompasses entire telephone system –Originally: analog traffic –Today: digital data, computer controlled switching Dial-up connection –Modem connects computer to distant network –Works from almost anywhere DSL –Provides high speed, continuous Internet connect where available –Multiple types of DSL connections 13

5. 4 PSTN Topologies Figure 7-2 A bus topology WAN Figure 7-3 A ring topology WAN

6. Network+ Guide to Networks, 5 th Edition10 Mesh and Tiered Figure 7-5 Full-mesh and partial-mesh WANs

7. DSL DSL (digital subscriber line) –Operates over PSTN at physical layer –Directly competes with other PSTN services such as ISDN and T1 –Shares voice and data over same line Uses high frequency range, inaudible telephone line frequencies –Voices uses only 300 – 3000 Hz –Uses advanced data modulation techniques Amplitude or phase modulation 37

8. Network+ Guide to Networks, 5 th Edition38 Types of DSL xDSL refers to all DSL varieties –ADSL, G.Lite, HDSL, SDSL, VDSL, SHDSL Two DSL categories –Asymmetrical and symmetrical Downstream –Data travels from carrier’s switching facility to customer Upstream –Data travels from customer to carrier’s switching facility

9. Network+ Guide to Networks, 5 th Edition40 Types of DSL (cont’d.) How DSL types vary –Data modulation techniques –Capacity –Distance limitations –PSTN use Table 7-2 Comparison of DSL types

10. Network+ Guide to Networks, 5 th Edition43 DSL Connectivity (cont’d.) Figure 7-17 A DSL connection

11. Broadband Cable Cable companies connectivity option Based on TV signals coaxial cable wiring –Theoretically transmission 150 Mbps downstream, 10 Mbps upstream –Real transmission 10 Mbps downstream, 2 Mbps upstream Transmission limited ( throttled) Shared physical connections Best use –Web surfing –Network data download Network+ Guide to Networks, 5 th Edition45

12. Network+ Guide to Networks, 5 th Edition46 Broadband Cable (cont’d.) Requires cable modem –Modulates, demodulates transmission, reception signals via cable wiring –Operates at Physical and Data Link layer –May connect to connectivity device Figure 7-18 A cable modem

13. WAN Technologies WAN technologies are used to provide high bandwidth connection between major data centers. In this section we will look at some older as well as current WAN technologies.

14. X.25 and Frame Relay X.25 ITU standard –Analog, packet-switching technology from 1970s Mainframe to remote computers: 64 Kbps throughput –Update: 1992 2.048 Mbps throughput Client, servers over WANs –Operates at Physical, Data Link, and Network layers. –Verifies transmission at every node Excellent flow control, ensures data reliability Slow for time-sensitive applications Network+ Guide to Networks, 5 th Edition15

15. Network+ Guide to Networks, 5 th Edition16 Frame Relay Frame relay –Updated X.25: digital, packet-switching –Protocols operate at Data Link layer Supports multiple Network, Transport layer protocols –No data delivery guarantee –Customer chooses data speed –Use Virtual Circuits PVC – Permanent Virtual Circuit SVC – Switched Virtual Circuit

16. Network+ Guide to Networks, 5 th Edition20 Frame Relay Figure 7-9 A WAN using frame relay

17. Network+ Guide to Networks, 5 th Edition21 ISDN Digital data transmitted over PSTN Gained popularity: 1990s –Connecting WAN locations Exchanges data, voice signals Protocols at Physical, Data Link, Transport layers Relies on PSTN for transmission medium Dial-up or dedicated connections –Dial-up relies exclusively on digital transmission

18. Network+ Guide to Networks, 5 th Edition22 ISDN Channel Types Two channel types –B channel: “bearer” Circuit switching for voice, video, audio: 64 Kbps –D channel: “data” Packet-switching for call information: 16 or 64 Kbps BRI (Basic Rate Interface) connection PRI (Primary Rate Interface) connection

19. Network+ Guide to Networks, 5 th Edition23 BRI: two B channels, one D channel (2B+D) –B channels treated as separate connections Carry voice and data Bonding –Two 64-Kbps B channels combined Achieve 128 Kbps Figure 7-10 A BRI link

20. Network+ Guide to Networks, 5 th Edition24 PRI: 23 B channels, one 64-Kbps D channel (23B+D) –Separate B channels independently carry voice, data –Maximum throughput: 1.544 Mbps PRI and BRI may interconnect Figure 7-11 A PRI link

21. ATM (Asynchronous Transfer Mode) Functions in Data Link layer Asynchronous communications method –Nodes do not conform to predetermined schemes Specifying data transmissions timing –Each character transmitted Start and stop bits Specifies Data Link layer framing techniques Fixed packet size sets ATM apart from Ethernet –Packet (cell) 48 data bytes plus 5-byte header = 53 byts Network+ Guide to Networks, 5 th Edition49

22. Network+ Guide to Networks, 5 th Edition50 ATM (cont’d.) Smaller packet size requires more overhead –Decrease potential throughput –Cell efficiency compensates for loss ATM relies on virtual circuits –ATM considered packet-switching technology –Virtual circuits provide circuit switching advantage Circuit path setup by switches in advance –Reliable connection Allows specific QoS (quality of service) guarantee –Important for time-sensitive applications Often used on SONET rings

23. Network+ Guide to Networks, 5 th Edition25 T-Carriers T1s, fractional T1s, T3s Physical layer operation Single channel divided into multiple channels –Using TDM (time division multiplexing) over two wire pairs Medium –Telephone wire, fiber-optic cable, wireless links

24. Network+ Guide to Networks, 5 th Edition26 Types of T-Carriers Many available –Most common: T1 and T3 Table 7-1 Carrier specifications

25. Network+ Guide to Networks, 5 th Edition31 Smart Jack –Terminate T-carrier wire pairs Customer’s demarc (demarcation point) Inside or outside building –Connection monitoring point Figure 7-12 A T1 smart jack

26. Network+ Guide to Networks, 5 th Edition32 T-Carrier Connectivity (cont’d.) CSU/DSU (Channel Service Unit/Data Service Unit) –Two separate devices –Combined into single stand-alone device Interface card –T1 line connection point At customer’s site CSU –Provides digital signal termination –Ensures connection integrity

27. Network+ Guide to Networks, 5 th Edition34 T-Carrier Connectivity (cont’d.) Incoming T-carrier line –Multiplexer separates combined channels Outgoing T-carrier line –Multiplexer combines multiple LAN signals Figure 7-14 A point-to-point T-carrier connection

28. Network+ Guide to Networks, 5 th Edition52 SONET (Synchronous Optical Network) Four key strengths –WAN technology integration –Fast data transfer rates –Simple link additions, removals –High degree of fault tolerance Synchronous –Data transmitted, received by nodes conforms to timing scheme Advantage –Interoperability

29. Network+ Guide to Networks, 5 th Edition54 SONET (cont’d.) Fault tolerance –Double-ring topology over fiber-optic cable SONET Ring –Begins, ends at telecommunications carrier’s facility –Connects organization’s multiple WAN sites in ring fashion –Connect with multiple carrier facilities Additional fault tolerance –Terminates at multiplexer Easy SONET ring connection additions, removals

30. Network+ Guide to Networks, 5 th Edition55 SONET (cont’d.) Figure 7-21 SONET connectivity

31. Network+ Guide to Networks, 5 th Edition53 SONET (cont’d.) Figure 7-20 A SONET ring

32. Network+ Guide to Networks, 5 th Edition56 SONET (cont’d.) Data rate –Indicated by OC (Optical Carrier) level Table 7-3 SONET OC levels

33. Network+ Guide to Networks, 5 th Edition58 WAN Technologies Compared Table 7-4 A comparison of WAN technology throughputs

34. Remote Access Remote access is used to allow users to connect to a network or single computer from a remote location.

35. Network+ Guide to Networks, 5 th Edition63 Remote Access Servers Figure 7-22 Clients connecting with a remote access server

36. Remote Access Protocols SLIP and PPP –Workstations connect using dial-up connection Encapsulate higher-layer networking protocols, in lower-layer data frames –SLIP carries IP packets only Harder to set up Supports only asynchronous data –PPP carries many different Network layer packets Automatic set up Performs error correction, data compression, supports encryption Supports asynchronous and synchronous transmission Network+ Guide to Networks, 5th Edition64

37. Network+ Guide to Networks, 5 th Edition65 Remote Access Protocols (cont’d.) PPPoE (PPP over Ethernet) standard –Connects home computers to ISP Via DSL, broadband cable Figure 7-23 Protocols used in a remote access Internet connection

38. Network+ Guide to Networks, 5 th Edition68 Remote Desktop and Remote Assistance Remote desktop –Windows client and server operating systems –Relies on RDP (Remote Desktop Protocol) Application layer protocol Uses TCP/IP to transmit graphics, text quickly Carries session, licensing, encryption information Exists for other operating systems –Not included in Windows home editions –Uses Port 3389 by default

39. Network+ Guide to Networks, 5 th Edition69 Figure 7-24 Remote tab in the Windows XP System Properties window

40. Remote Desktop Infrastructure RDI Uses virtual machines running on a server –One server can host many desktop OS environments Uses Thin client for users –Remote virtual computing software requires little bandwidth Useful in BYOD environments

41. Network+ Guide to Networks, 5 th Edition73 VPNs (Virtual Private Networks) Uses tunnel to Isolate traffic from other public line traffic Software –Inexpensive –Sometimes included with other widely used software Tailored to customer’s distance, bandwidth needs Two important design considerations –Interoperability and security

42. Network+ Guide to Networks, 5 th Edition74 Tunneling –Ensures VPN carries all data types privately Tunnel –Virtual connection between two VPN nodes Figure 7-26 An example of a VPN

43. Network+ Guide to Networks, 5 th Edition75 VPNs (cont’d.) Types of tunneling –PPTP (Point-to-Point Tunneling Protocol) Microsoft Authentication and minimal encryption –L2TP (Layer 2 Tunneling Protocol) Cisco Uses IPSec encryption at Network Layer to provide strong security –SSL VPN Uses SSL encryption at Presentation level Establishes connection at Browser level

44. SSL VPN An SSL VPN (Secure Sockets Layer virtual private network) is a form of VPN that can be used with a standard Web browser.VPN In contrast to the traditional Internet Protocol Security (IPsec) VPN, an SSL VPN does not require the installation of specialized client software on the end user's computer. Used to give remote users with access to Web applications, client/server applications and internal network connections.

45. Open VPNs There are three major families of VPN implementations in wide usage today: SSL, IPSec, and PPTP. OpenVPN is an SSL VPN and as such is not compatible with IPSec, L2TP, or PPTP. –The IPSec protocol is designed to be implemented as a modification to the IP stack in kernel space, and therefore each operating system requires its own independent implementation of IPSec. –By contrast, OpenVPN's user-space implementation allows portability across operating systems and processor architectures, firewall and NAT-friendly operation, dynamic address support, and multiple protocol support including protocol bridging. –There are advantages and disadvantages to both approaches. The principal advantages of OpenVPN's approach are portability, ease of configuration, and compatibility with NAT and dynamic addresses. The learning curve for installing and using OpenVPN is on par with that of other security-related daemon software such as SSH.

46. Network+ Guide to Networks, 5 th Edition The End