Lectures Top-Down Network Design - Chapter 11: Selecting Technologies and Devices for Enterprise Networks

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1. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Top-DNtkDiDown Network Design Chapter Eleven Selecting Technologies and Devices for Enterprise Networks Copyright 2010 Cisco Press & Priscilla Oppenheimer Enterprise Technologies and Devices • Remote access networks • Wide area networks (WANs) • Devices – End user remote access devices – Central site remote access devices – VPN concentrators – Routers Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 1
2. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Selection Criteria • Business requirements and constraints • Cost • Technical goals • Bandwidth requirements • QoS requirements • Network topology • Traffic flow and load •Etc. Remote Access Technologies • The Point-to-Point Protocol (PPP) • Integrated Services Digital Network (ISDN) • Cable modems • Digital Subscriber Line (DSL) Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 2
3. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Point-to-Point Protocol (PPP) • Used with synchronous, asynchronous, dial- up, and ISDN links • Defines encapsulation scheme for transport of different network-layer protocols • Supports authentication: – Password Authentication Protocol (()PAP) – Challenge Handshake Authentication Protocol (CHAP) • CHAP more secure than PAP PPP Layers NkClPl(NCP)Network Control Protocol (NCP) Link Control Protocol (LCP) Encapsulation based on High-Level Data-Link Control Protocol (HDLC) Physical Layer Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 3
4. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Multichassis Multilink PPP Stack group ISDN Offload server Analog CHAP Remote Node Access Server Connect Database of Users and Challenge Passwords Name: 760_1 Password: sfy45 Name: 760_1 Hashed Response Password: sfy45 Name: 760_2 Accept or Deny Password: kingsford Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 4
5. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks ISDN • Digital data-transport service offered by regional telephone carriers (telcos) • Circuit-switched service that carries voice and data • Cost-effective remote-access solution for telecommuters and remote offices – Cost of an ISDN circuit is usually based on a monthly fee plus usage time • Good choice as a backup link for another type of link, for example, Frame Relay ISDN Interfaces Basic Rate Interface (BRI) 64 Kbps 2B 64 Kbps 144 } Kbps D 16 Kbps Primaryy() Rate Interface (PRI) 64 Kbps 1.544 Mbps in U.S. 23B or 30B } 2.048 Mbps in Europe D 64 Kbps Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 5
6. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks ISDN Components Non-ISDN R S/T U device TA NT1 To ISDN (()TE2) 4-wire 2-wire service circuit circuit ISDN S/T U To ISDN device NT1 service (TE1) S T ISDN U To ISDN device NT2 NT1 service (TE1) U ISDN device (TE1) To ISDN with built-in NT1 NT1 service Cable Modem Service • Operates over the coax cable used by cable TV • Much faster than analog modems, and usually much faster than ISDN (depending on how many users share the cable) – 25 to 50 Mbps downstream from the head end – 2 to 3 Mbps upstream from end users • Standard = Data Over Cable Service Interface Specification (DOCSIS) Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 6
7. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks DSL • High-speed digital data traffic over ordinary telephone wires • Sophisticated modulation schemes mean higher speeds than ISDN – Speeds range from 1.544 to 9 Mbps • Actual bandwidth depends on type of DSL service, DSL modem, and many physical- lftlayer factors • Asymmetric DSL (ADSL) very popular – Downstream faster than upstream WAN Technologies • Leased lines • Synchronous Optical Network (SONET) •Frame Relay • Asynchronous Transfer Mode (ATM) Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 7
8. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Leased Lines • Dedicated digital, copper circuits that a custltomer leases from a carri ifer for a predetermined amount of time, usually for months or years • Speeds range from 64 Kbps to 45 Mbps • Enterprises use leased lines for both voice and data traffic The North American Digital Hierarchy Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 8
9. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Synchronous Optical Network (SONET) • Physical-layer specification for high-speed synchtiifkthronous transmission of packets or cells over fiber-optic cabling • Service providers and carriers make wide use of SONET in their internal networks • Gaining popularity within private networks SONET Optical Carrier (OC) Levels aka Synchronous Transport Signal (STS) Levels STS Rate OC Level Speed STS-1 OC-1 51.84 Mbps STS-3 OC-3 155.52 Mbps STS-12 OC-12 622.08 Mbps STS-24 OC-24 1.244 Gbps STS-48 OC-48 2.488 Gbps STS-96 OC-96 4.976 Gbps STS-192 OC-192 9.952 Gbps Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 9
10. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Typical SONET Topology SONET Multiplexer Backup Pair Working Pair Frame Relay • Industry-standard data-link-layer protocol for transporting traffic across wide -area virtual circuits • Optimized for efficiency on circuits with low error rates • Attractively-priced in most parts of the world • Carriers agree to forward traffic at a Committed Information Rate (CIR) Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 10
11. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Frame Relay (continued) TRTo Rout er B : DLCI 100 To Router A: DLCI 200 Router A Router B Virtual Circuit (VC) Frame Relay Hub-and-Spoke Uses Subinterfaces hostname centralsite interface serial 0 Central-Site Router encapsulation frame-relay interface serial 0.1 DLCI 100 DLCI 200 ip address 10.0.1.1 255.255.255.0 frame-relay interface-dlci 100 interface serial 0.2 ip address 10.0.2.1 255.255.255.0 frame-relay interface-dlci 200 Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 11
12. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Asynchronous Transfer Mode (ATM) • Used in service provider internal networks • Gaining popularity within private networks, both WANs and sometimes LANs • Supports very high bandwidth requirements – Copper cabling: 45 Mbps or more – Fiber-optic cabling: OC-192 (9.952 Gbps) and beyond, especially if technologies such as wave-division multiplexing (WDM) are used ATM (continued) • Provides efficient sharing of bandwidth among applications with various Quality of Service (QoS) requirements – Cell-based system inherently better for QoS than frames • Application can specify upon connection establishment the QoS it requires • Peak and minimum cell rates, cell-loss ratio, and cell-transfer delay Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 12
13. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Ethernet over ATM • ATM router interfaces are expensive • Some providers allow a customer to use an Ethernet interface to access the provider’s ATM WAN • May require a converter • Expected to gain popularity because it has the advantages of both worlds – Easy-to-use LAN – QoS-aware WAN Selection Criteria for Remote Access Devices • Support for VPN features • Support for NAT • Reliability •Cost • Ease of configuration and management • Support for one or more high-speed Ethernet interfaces • If desired, wireless support •Etc. Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 13
14. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Selection Criteria for VPN Concentrators • Support for: – Tunneling protocols such as IPSec, PPTP, and L2TP – Encryption algorithms such as 168-bit Triple DES, Microsoft Encryption (MPPE), RC4, AES – Authentication algorithms, including MD5, SHA-1, HMAC – Network system protocols, such as DNS, RADIUS, Kerberos, LDAP – Routing protocols – Cer tificat e auth oriti es – Network management using SSH or HTTP with SSL –Etc. Selection Criteria for Enterprise Routers • Number of ports • Processing speed • Media and technologies supported • MTTR and MTBF • Throughput • Optimization features •Etc Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 14
15. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Selection Criteria for a WAN Service Provider • Extent of services and technologies • Geographical areas covered • Reliability and performance characteristics of the provider’s internal network • The level of security offered by the provider • The level of technical support offered by the provider • The likelihood that the provider will continue to stay in business Selecting a Provider (continued) • The provider’s willingness to work with you to meet your needs • The physical routing of network links • Redundancy within the network • The extent to which the provider relies on other providers for redundancy • The level of oversubscription on the network • QoS support •Etc. Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 15
16. Top-Down Network Design, Ch. 11: Selecting Technologies and Devices for Enterprise Networks Summary • A major task during the physical design philtithliddihase is selecting technologies and devices for enterprise networks – Remote access networks –WANs – Service providers – Devices • End user remote access devices • Central site remote access devices • VPN concentrators • Routers Review Questions • Compare and contrast technologies for supporting remote users . • Compare and contrast WAN technologies. • What selection criteria can you use when purchasing internetworking devices for enterprise network customers? • What criteria can you use when selecting a WAN service provider? Copyright 2004 Cisco Press & Priscilla Oppenheimer Page 16