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Oppenheimer

Top-Down Network Design Chapter Eleven Selecting Technologies and Devices for Enterprise Networks. Oppenheimer. Enterprise Technologies and Devices. Remote access networks Wide area networks (WANs) Devices End user remote access devices Central site remote access devices

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Oppenheimer

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  1. Top-Down Network DesignChapter Eleven Selecting Technologies and Devices for Enterprise Networks Oppenheimer

  2. 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 AAB-2013

  3. Selection Criteria • Business requirements and constraints • Cost • Technical goals • Bandwidth requirements • QoS requirements • Network topology • Traffic flow and load • Etc. AAB-2013

  4. Remote Access Technologies • The Point-to-Point Protocol (PPP) • Cable modems • Digital Subscriber Line (DSL) AAB-2013

  5. 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 AAB-2013

  6. PPP Layers Network Control Protocol (NCP) Link Control Protocol (LCP) Encapsulation based on High-Level Data-Link Control Protocol (HDLC) Physical Layer AAB-2013

  7. ISDN Analog Multichassis Multilink PPP Stack group Offload server AAB-2013

  8. Remote Node CHAP Access Server Connect Database of Users and Passwords Challenge Name: 760_1Password: sfy45 Name: 760_1Password: sfy45 Name: 760_2 Password: kingsford Hashed Response Accept or Deny AAB-2013

  9. Cable Modem Service • Operates over the coax cable used by cable TV • Much faster than analog modems • No dialup required • Cable-network service providers offer hybrid fiber/coax (HFC) systems that connect CATV networks to the service provider’s high speed fiber-optic network. • This allow users to connect their PCs/small LAN to the coax cable and use this connection to access to the internet. • A typical cable network system offers 25 to 50 Mbps downstream and upstream bandwidth. AAB-2013

  10. Continue.. • If you plan to use this technology : • Ask the service provider the number of users who share a single cable and the types of applications they use. • Ask also about Qos for video, audio and other delay sensitive applications. • Provide info about your needs – bandwidth , applications you are using - find tune on the given solution. AAB-2013

  11. DSL-digital subscriber line • 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-layer factors • Asymmetric DSL (ADSL) very popular • Downstream faster than upstream AAB-2013

  12. WAN Technologies- connecting geographically dispersed sites • Leased lines • Synchronous Optical Network (SONET) • Frame Relay • Asynchronous Transfer Mode (ATM) AAB-2013

  13. Leased Lines • Offered by many telephone companies. • Dedicated digital, copper circuits that a customer leases from a carrier 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 • Dedicated to a single customer-no sharing • Good choice if the topology is truly point-to-point. AAB-2013

  14. The North American Digital Hierarchy • the amount of capacity that WAN must provide. • selecting the right amount of capacity is called provisioning. • it requires an analysis of traffic flow – chapter 4 and analysis of scalability goals –chapter 2. • WAN bandwidth for copper cabling is using NADH-a channel in the hierarchy is called a digital signal (DS). • DS are multiplexed together to get high-sped WAN circuits. AAB-2013

  15. Synchronous Optical Network (SONET) • Physical-layer specification for high-speed synchronous 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 • Support multiplexing and de multiplexing of individual signals. • A SONET network is usually connected in a ring topology using two self-healing fiber paths. • A path provides full-duplex communication and consists of a pair of fiber strands. AAB-2013

  16. Continue.. • One path acts as the full-time working transmission facility. • The other path acts as a backup protection pair-remain idle while the working path routes data. AAB-2013

  17. SONET Optical Carrier (OC) Levelsaka Synchronous Transport Signal (STS) Levels AAB-2013

  18. Typical SONET Topology SONET Multiplexer Backup Pair Working Pair AAB-2013

  19. Frame Relay • High-performance WAN protocol that operates at the physical and data link layer of the OSI ref model. • 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) AAB-2013

  20. Frame Relay (continued) To Router B: DLCI 100 To Router A: DLCI 200 Router A Router B Virtual Circuit (VC) AAB-2013

  21. Frame Relay Hub-and-Spoke Uses Subinterfaces hostname centralsite interface serial 0 encapsulation frame-relay interface serial 0.1 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 Central-Site Router DLCI 100 DLCI 200 AAB-2013

  22. 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 AAB-2013

  23. 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 AAB-2013

  24. 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 AAB-2013

  25. 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. AAB-2013

  26. 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 • Certificate authorities • Network management using SSH or HTTP with SSL • Etc. AAB-2013

  27. Selection Criteria for Enterprise Routers • Number of ports • Processing speed • Media and technologies supported • MTTR and MTBF • Throughput • Optimization features • Etc AAB-2013

  28. 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 AAB-2013

  29. 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. AAB-2013

  30. Summary • A major task during the physical design phase 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 AAB-2013

  31. 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? AAB-2013

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