Introduction To Lan Tdc 363

Transcript

Introduction to LAN TDC 363 Week 4 Connecting LAN to WAN Book: Chapter 7 TDC363-04 01/24/08 1 Outline „ „ „ Wide Area Network (WAN): definition WAN Topologies Choices of WAN technologies „ „ „ „ „ „ „ Dial-up DialISDN T1 Frame Relay DSL Remote network connections Midterm TDC363-04 01/24/08 2 What is WAN? Internet and Intranet Branch Office Public Network Home Private Network Remote Headquarters Branch Office Branch Office Remote 1. Relatively long physical distance 2. Requiring a service provider (carrier) 01/24/08 TDC363-04 3 1 WAN Interface Customer router CPE E t Enterprise i N Network t k Demarcation D ti point Carrier Network Internet/ Internet ISP Central Office TDC363-04 01/24/08 4 WAN Topologies „ Wide area network (WAN) topologies Peer-toPeerto-peer Ring „ Star St r „ Mesh „ Tiered (Hierarchy) „ „ TDC363-04 01/24/08 5 Wide Area Network (WAN) Topologies (bus) T1 Note: You cannot use DSL for interoffice communications. 01/24/08 TDC363-04 6 2 Ring Topology on WAN „ Each site is connected to two other sites so that entire WAN forms a ring pattern ISDN 01/24/08 TDC363-04 7 Star Topology on WAN „ Single site acts as the central connection point for several other points 01/24/08 TDC363-04 8 Meshed Topology on WAN „ Many directly interconnected locations forming a complex mesh 01/24/08 TDC363-04 9 3 Tiered Topology on WAN „ Sites connected in star or ring formations are interconnected at different levels, with interconnection points organized into layers TDC363-04 01/24/08 10 WAN Technology „ „ „ „ „ „ „ „ Dial-up (PSTN) DialISDN (BRI) ISDN (PRI) – voice only X 25 – out of date X.25 Frame Relay Leased Line (T(T-carrier) Leased Line (OC(OC-x) ATM – too expensive „ „ „ xDSL Cable Modem SONET – not for enterprise „ „ Ethernet Wireless TDC363-04 01/24/08 11 Technology Classification Leased Line FT1 T1/E1 Circuit Switching PSTN ISDN DS3/T3 01/24/08 X.25 Frame Relay ATM OC-3c OC-x Packet Switching Ethernet Q: where is IP? TDC363-04 xDSL 12 4 PSTN (Public Switched Telephone Network „ Designed for voice traffic (not for data traffic) „ Also called plain old telephone service (POTS) „ PSTN for WAN connection: „ Modem (V.92) „ ISDN „ Downlink: 53 kbps, uplink: 48 kbps TDC363-04 01/24/08 13 PSTN to Internet Tandem Switch PSTN Local Switch modem Local Switch ISDN-PRI/T1 router Internet 01/24/08 T1 TDC363-04 server ISP Remote Access Server (modem pool) 14 ISDN BRI (Basic Rate Interface) „ „ „ „ „ International standard for transmitting data over digital lines BRI: Basic Rate Interface (2B+D) A variety of ISDN using two 6464-kbps bearer (B) channels and one 1616-kbps p data ((D)) channel,, as indicated by the following notation: Through bonding, the two 6464-kbps channels can be combined to achieve an effective throughput of 128128-kbps ISDN PRI (23B+D) over T1 01/24/08 TDC363-04 15 5 ISDN Network Connections Service Provider BRI 2B+D Customer A BRI Customer B 2B+D PRI PSTN Central Office 23B+D BRI 2B+D Cf. Fig.7-10, 7-11 Customer C 01/24/08 TDC363-04 16 T-Carriers „ „ The most common T T--carrier implementations are T1 and T3 Signal level (DS0, DS1, etc.) „ ANSI standard for T T--carrier technology that refers to its Ph i l layer Physical l electrical l t i l signaling i li characteristics h t i ti „ DSO (digital signal, level 0) „ Fractional T1 (FT1, n ×64K) „ „ 01/24/08 Equivalent of one voice channel (64K) Arrangement allowing an organization to use only some channels on a T1 line, paying for what they use TDC363-04 17 Types of TT-Carriers T1: 64K×24 = 1.536 vs. (24×8+1) × 8K = 1.544M channels: telephone calls 01/24/08 TDC363-04 18 6 T-Carrier Connectivity „ Wiring „ CSU/DSU (Channel Service Unit/Data Service Unit) „ CSU provides termination for the digital signal and ensures connection „ „ Can use unshielded or shielded twistedtwisted-pair copper wiring integrity through error correction and line monitoring DSU converts the digital signal used by CPE into the digital signal sent via the outside cabling to the carrier. TDC363-04 01/24/08 19 T1: DataData-only Service Customer router CSU/DSU Enterprise Network T1 Carrier Network Internet channelized core router DS3 (built-in CSU/DSU) multiplexer TDC363-04 01/24/08 20 DS3 Deployment „ Typically, fiber (often deployed as STS1/STS3) is used to transport the signals from the central office to the premise wiring closet where the STS1/STS3 fiber line is segmented into single or multiple DS3 coaxial lines for further deployment to individual offices or floors. Central Office Network Device (router) 01/24/08 fiber coax TDC363-04 21 7 Need Higher Data Rate „ „ „ „ „ „ „ „ T1: 1.544M bps N × T1 where N = 1, 2, 4, 6, 8 DS3 = 28 × T1 = 45M bps OC--3 ≈ 3 × DS3 = 155M bps OC b OC--12 = 4 × OCOC OC-3 = 622M bps OC--48 = 4 × OCOC OC-12 = 2.4G bps OC--192 = 4 × OCOC OC-48 = 10G bps OC--768 = 4 × OCOC OC-192 = 40G bps TDC363-04 01/24/08 22 Packet Switching Service „ „ X.25 „ Analog, packet packet--switched LAN technology optimized for long long--distance data transmission Frame Relay „ Updated (and simplified) digital version of X.25 „ Variable rates: from 56K bps to 1.544M bps (new standards to 45M bps) TDC363-04 01/24/08 23 Frame Relay Overview DCE or Frame Relay Switch Frame Relay CSU/DSU Router Ethernet „ Virtual circuit connections „ „ „ Connection--oriented service Connection „ 01/24/08 One physical circuit Multiple virtual circuits Permanent Virtual Circuit (PVC) TDC363-04 24 8 Frame Relay (cont.) „ „ Address: Data Link Connection Identifier (DLCI), 10 10--bit, local significance. CIR (committed information rate) Guaranteed minimum amount of bandwidth selected when leasing a frame relay circuit Can burst higher than CIR Users get more than they pay for. „ „ „ b burst t (512k) CIR (768k) TDC363-04 01/24/08 25 Why Frame Relay? (compared with T1) „ X.25 too much overhead, ATM too expensive A popular service for WAN „ Switched technology: „ „ „ „ The paragraph in the book is incorrect. (p. 355) not ot se sensitive s t ve to ddistance sta ce in pricing p c g Cheaper than T1 for long distance „ Physical Connection: point to multi multi--points „ Logical Connection: point to point „ Security: as good as PSTN (which is very secure) „ „ 01/24/08 Significant cost saving for a mesh topology As secured as T1 TDC363-04 26 Digital Subscriber Lines (DSL) Uses advanced data modulation techniques to achieve extraordinary throughput over regular phone lines (2(2-wire or 44-wire) „ DSL can span only limited distances. distances „ DSL types can be divided into two categories: „ Asymmetrical (download ≠ upload) „ Symmetrical (download = upload) „ 01/24/08 TDC363-04 27 9 Types of DSL ADSL: Asymmetric DSL HDSL: High Bit Rate DSL (4-wire) SDSL: Symmetric (or Single line [one pair]) DSL VDSL: Very High Bit Rate DSL (not for WAN) New standards: HDSL2 (2-wire) g.shdsl, symmetric New: ADSL2 and ADSL2+ TDC363-04 01/24/08 28 DSL Connectivity „ „ „ Once inside the customer’s home or office, the DSL line must pass through a DSL modem One RJ RJ--11 port to PSTN One RJ RJ--45 port to home/office LAN 01/24/08 TDC363-04 29 TDC363-04 30 ADSL Connectivity Note: ADSL requires a splitter at customer premise DSLAM: DSL Access Multiplexer 01/24/08 10 DSL Connectivity (G.lite) router DSL modem local loop splitter voice switch core router + (ATM Switch) DSLAM filter Internet Note: G.lite does not need a splitter at customer premise TDC363-04 01/24/08 31 Cable Modem „ Cable connections require that the customer use a special cable modem, a device that transmits and receives digital signals for transmission and reception via cable wiring TDC363-04 01/24/08 32 Cable Modem Network Infrastructure fiber HFC: Hybrid Fiber Coax 01/24/08 TDC363-04 33 11 Notes on Cable Modem „ Shared Medium „ „ Performance degradation if everyone is surfing. Security Concern „ Infrastructure „ Comparison and Competing with xDSL „ „ Not available to the business community There is no right answer. Note: Any packet switching technology allow multiple users to share the media. The goal is to improve the utilization of the media. Wherever there is resource sharing, there is potential bottleneck. The question is where the media is being shared. TDC363-04 01/24/08 34 SONET in Metro Network Core Router ADM ADM Carrier Central Office Metro SONET Ring ADM ADM ADM Access Ring Access Ring Access Ring ADM ADM T1 c.f. Fig. 7-18 CPE TDC363-04 01/24/08 35 Add--Drop Multiplexer (ADM) Add ADM ADM ADM SONET Ring ADM Pass through drop add c.f. Fig. 7-19 01/24/08 TDC363-04 36 12 Notes on SONET „ „ „ „ SONET is a popular technology (and widely deployed) for a carrier to build its metro backbone. It may also used by an enterprise in a campus network. G Government also l b builds ild its i own SONET S T backbone. b kb SONET is not the technology to access the Internet. An enterprise may connect its SONET to a carrier SONET via a leased trunk (OC(OC-3 or higher). TDC363-04 01/24/08 37 SONET for Enterprise and Residential Users ADM SONET Ring (owned by carrier) ADM ADM ADM The ADM is owned and maintained by a carrier, but it could be physically located at a company premise, or it could be at a multi-tenant environment (MTE). Example of MTE: office building, apartment complex. TDC363-04 01/24/08 38 Remote Connectivity „ Need: access private resources on the corporate network „ Remote access methods: „ Direct dial to the LAN „ „ Terminal Services (p. 386) „ „ Through a browser, a user at home or on the road connects to a LAN whose files are made visible to the Web through Web server software Virtual Private Network (VPN) „ 01/24/08 Software running on both remote user’s computer and LAN computer allows remote user to “take over” the LAN workstation. Web Portals (p. 387) „ „ The computer dialing into the LAN becomes a remote node on the network (see the slide on RAS/modem pool) a private data network over the public Internet TDC363-04 39 13 Virtual Private Networks (VPNs) „ VPN is a private network over a public network (internet). A VPN may or may not be IPIPbased. TDC363-04 01/24/08 40 Remote Access Remote Access Server Security Server PSTN Intranet Internet VPN Gateway Terminal server 01/24/08 TDC363-04 41 Review Questions „ „ „ „ „ „ „ 01/24/08 What are the characteristics distinguishing WAN from LAN? Speed of T T--carrier and OCOC-x Comparison of T1 and Frame Relay. Give a scenario that you will use T1 and another scenario to use Frame Relay. Relay Draw a network diagram to show the T1 connection to the Internet. (CSU/DSU + router + …) What is CSU/DSU? What is the addressing scheme of frame relay? Is there an addressing scheme for T1? Comparison of different DSL and their speeds. TDC363-04 42 14 Review Questions „ „ „ „ „ Describe the differences between ADSL and ADSL.lite (or G.lite). What is the network device to distribute traffic to/from SONET? Given a network diagram of three locations connected via Frame Relay, design the IP subnet scheme. What are the choices of remote access? What is VPN? TDC363-04 01/24/08 43 Midterm Exam „ „ „ „ 02/05 (Tuesday), 01:30pm Exam time: 90 minutes Exam seating will be given by the instructor. Exams are closed book, closed notes. „ „ „ „ No makemake-up exam Study Guide: „ „ 01/24/08 C l l Calculator iis allowed ll db but no palm l computer. You are allowed to bring a 22--page note (double sides) Review questions Homework TDC363-04 44 15