Frame Relay, ATM and VPN Metropolitan Area Ethernet Overview

2 Packet-Switched Services u Offered by Carriers u X.25 u Old, slow, and not sufficiently cheaper than frame relay u Frame Relay u Speeds in main range of user demand u Attractive prices u Dominates the market today u ATM u High speeds and costs

3 X.25 Packet-Switched Data Networks u Oldest packet switched network service (1970s) u Low speed (maximum around 64 kbps) u Mature: easy to implement u Uses PVCs u Reliable service, so latency in transmission u Mostly replaced by Frame RelayFrame Relay

4 Frame Relay Packet-Switched Data Networks u Software upgrade to X.25 switches u Uses PVCs u Unreliable, so much faster on same switches u Good speed range: 56 kbps - 40 Mbps: Meets most corporate needs (most under 2 Mbps) – Grew rapidly in the 90s, to equal leased line WANs in terms of market share (about 40%) u Best-selling packet switched network service See more here.here

5 ATM (Asynchronous Transfer Mode) u Offers very high speeds: 622 Mbps, 2.5 Gbps to 40 Gbps. Speeds are beyond most corporate needs today and high costs. u Connection-oriented (PVCs), unreliable u Quality of Service (QOS) guarantees critical traffic u Minimize latency (delays) u Inherent reliability (low loss rate) u Seen as the next generation u But Frame Relay keeps increasing in speed in low Mbps range where market demand is highest

6 Pricing Packet Switched Services u Customer Premises Equipment u Access Line to Point of Presence u Port Speed u Per PVC Price u Distance and Traffic Volume

7 Customer Premises Equipment u Access Device u Has link to internal system (often a LAN) u Has CSU/DSU to put internal traffic into format for Frame Relay transmission u In Frame Relay, called Frame Relay Access Device (FRADS) Access Device LAN Access Line to Network

8 Modular Routers u CSU/DSUs are removable expansion boards Router Switching Circuitry Port 1 CSU/DSU (T1) Port 1 CSU/DSU (T1) Port 2 CSU/DSU (56 kbps) Port 2 CSU/DSU (56 kbps) Port 3 CSU/DSU (T3) Port 3 CSU/DSU (T3) Port 4 CSU/DSU (56 kbps) Port 4 CSU/DSU (56 kbps) Modular Router T1 Line56 kbps LineT3 Line56 kbps Line

9 Elements of a Packet Switched Network Customer Premises A LEC Switching Office POP at LEC Office Leased Access Line to POP Leased Access Line to POP You need a leased access line to the network’s POP. Sometimes the packet switched network vendor pays the cost of the access line for you and bundles it into your service charges.

10 Elements of a Packet Switched Network Switched Data Network Trunk Line Network Switching Office POP Customer Premises B Leased Access Line

11 Pricing of Frame Relay u Speed of the Access Line from Site to Network u Determines maximum transmission rate to the network u Often called the Port Speed u Often the most important price determinant u Must be fast enough for needs See Frame Relay vs. DSL -- a price issueFrame Relay vs. DSL

12 Pricing of Frame Relay u In Some Frame Relay networks, two speeds u Committed Information Rate (pretty much guaranteed) u Available Bit Rate (like flying standby) for bursts. Not guaranteed. u Price depends both on CIR and ABR u Access line speed must be fast enough for ABR

13 Pricing of Frame Relay u Additional price per PVC u Usually small compared to the access line charge u One access line can multiplex all PVCs to/from site u PVCs share access line speed Site PVC1 PVC2

14 Calculations u Situation u You have four sites u You want any one to be able to reach any other u Questions u How many PVCs do you need? u How many access lines do you need?

15 Calculations u PVCs u If you have N sites, there are N(N-1)/2 possible connections u In this case, you would have 4(3)/2 or 6 possible connections u Some vendors count this as 6 PVCs, others as 12 PVCs u Access Lines u You would need four access lines (one for each site) u Each will multiplex 3 PVCs u Must be fast enough for the needs of communication with the three other sites

16 Pricing of Frame Relay u May Depend on Distance u But often a flat monthly rate throughout the carrier’s service area u May Depend on Traffic u But often a flat monthly rate based only on the speed of the access line

17 Leased Lines vs. Packet-Switched Data Networks Leased Lines vs. Packet-Switched Data Networks u Leased Lines u Point-to-point, inexpensive for thick routes u Inflexible: must be established ahead of time u Packet Switched Networks u Also must be established ahead of time for PVCs u Competitor for leased line networks u Priced aggressively u Carrier does all the management u Killing the leased line business

18 Virtual Private Network VPN Server Corporate Site A VPN Server Corporate Site B 2. Remote Customer PC (or site) 3. Remote Corporate PC Tunnel Internet Extranet Remote Access for Intranet 1. Site-to-Site

19 VPN advantage u Virtual Private Network (VPN) u Transmission over the Internet with added security u Some analysts include transmission over a PSDN with added security u Why VPNs? u PSDNs are not interconnected u Only good for internal corporate communication u But Internet reaches almost all sites in all firms u Low transmission cost per bit transmitted

20 VPN issues VPN issues u VPN Problems u Latency and Sound Quality u Internet can be congested u Creates latency, reduces sound quality u Use a single ISP as for VoIP (voice over IP) u Security u PPTP for remote access is popular u IPsec for site-to-site transmission is popular

21 ISP-Based PPTP Remote Access VPN u Remote Access VPNs u User dials into a remote access server (RAS) u RAS often checks with RADIUS server for user identification information. Allows or rejects connection RADIUS Server PPTP RAS Internet ISP PPTP Access Concentrator Local Access Corporate Site A Secure Tunnel Unsecure TCP Control Channel

22 VPN and PPTP VPN and PPTP u Point-to-Point Tunneling Protocol u Available in Windows since Windows 95 u No need for added software on clients u Provided by many ISPs u PPTP access concentrator at ISP access point u Some security limitations u No security between user site and ISP u No message-by-message authentication of user u Uses unprotected TCP control channel

23 IPsec in Tunnel Mode IPsec in Tunnel Mode Tunnel Only Between Sites Hosts Need No Extra Software Secure Tunnel Mode IPsec Server IPsec Server Local Network Local Network No Security In Site Network No Security In Site Network

24 IPsec in Transfer Mode IPsec in Transfer Mode End-to-End (Host-to-Host) Tunnel Hosts Need IPsec Software Secure Tunnel Transfer Mode IPsec Server IPsec Server Local Network Local Network Security In Site Network Security In Site Network

25 IPsec alternatives IPsec alternatives u IP Security (IPsec) u Tunnel mode: sets up a secure tunnel between IPsec servers at two sites u No security within sites u No need to install IPsec software on stations u Transfer mode: set up secure connection between two end hosts u Protected even on internal networks u Must install IPsec software on stations, but default in current OSs (Windows, Linux, UNIX).

26 Security at the internet layer Security at the internet layer u IP Security (IPsec) u At internet layer, so protects information at higher layers u Transparent: upper layer processes do not have to be modified Internet Layer with IPsec Protection TCPUDP HTTPSMTPFTPSNMP Protected

27 Common IPsec configuration Common IPsec configuration u IP Security (IPsec) u Security associations: u Governed by corporate policies List of Allowable Security Associations List of Allowable Security Associations Party B Party A IPsec Policy Server

28 SSL/TLS for Browser–Webserver Communication

29 Metropolitan Area Ethernet u Metropolitan Area Network (MAN) u A carrier network limited to a large urban area and its suburbs u Metropolitan area Ethernet (metro Ethernet) is available for this niche u Metro Ethernet is relatively new, but is growing very rapidly u 802.3ad standard u Ethernet in the first mile u Standard for transmitting Ethernet signals over PSTN access lines u 1-pair voice-grade UTP, 2-pair data-grade UTP, optical fiber

30 Metropolitan Area Ethernet u Attractions of Metropolitan Area Ethernet u Low prices per bit transmitted u High speeds u Familiar technology for networking staff u Rapid provisioning u Rapid capacity increases for special events u Carrier Class Service u Basic metro Ethernet standards are insufficient for large wide area networks u Quality of service and management tools must be developed u The goal: To provide carrier class services that are sufficient for customers