Network Design - Chapter 8: Access Network Design Continued - University of Pittsburgh

Nội dung text: Network Design - Chapter 8: Access Network Design Continued - University of Pittsburgh

1. Access Network Design Continued David Tipper Associate Professor Department of Information Science and Telecommunications University of Pittsburgh Slides 8 Top Down Network Design Approach A top down network design project approach should follow three phases: – Conceptual Model • Objectives, Requirements, Constraints – Logical Model • Technology, network graph, node location, etc. – Physical Model • Specific hardware/software implementations (e.g., wiring diagram, repeater locations, etc.) TELCOM 2110 2 1
2. Technology Choices • Access Networks Technology Choices • For circuit switched voice traffic – STM, ATM – constant bit rate service (CBR), MPLS CBR emulation • For packet data traffic – STM, ATM, SMDS, X.25, Frame Relay, Token Ring, FIDDI, Ethernet, cable modem, dSL, wireless technology, etc. • Choice depends on cost and features needed • Given technology selection and logical design – create physical design (select equipment, etc) TELCOM 2110 3 Example • Consider a cellular network in a downtown urban environment as shown below with distances in 1Km. The nodes represent base stations and the hub node 0 a base station controller co-located with a base station. We choose STM technology for connecting the nodes with T1s or multiple of T1s 0 1 2 AUC EIR 1 HLR IBM VLR 3 4 5 1 MSC SD B ay Network s Centillion 1400 6 78 ETHERLINK RS 232C INS ACT ALM P*8x 50 RST OOO130 A O N 6 PC C ARD SD BayNetwork s Centillion1400 ALM PWR ALM FAN0 FAN1 PWR 0PWR1 ETHERLINK RS232C INS ACT ALM P*8x 50 RST OOO130 A O N 6 PCC ARD ALM PWR ALM FAN0 FAN1 PWR 0PWR1 BSC BSC BSC SD B ay Network s Centillion 1400 ETHERLINK RS 232C INS ACT ALM P*8x 50 RST OOO130 A O N 6 PC C ARD ALM PWR ALM FAN0 FAN1 PWR 0PWR1 1 1 BSC BS3 BS BS3 BS2 BS4 BS2 BS4 BS1 BS1 BS7 BS5 BS7 BS5 BS6 BS6 TELCOM 2110 4 2
3. Example • If for example the cellular network uses GSM (Global System for Mobile) technology with a frequency reuse cluster of 7 then six of the base stations have 72 voice traffic channels and 1 base station has 64 traffic channels. (Nodes 0-5 have 72, Node 6, 64, Nodes 7 and 8 have 72 – part of a different reuse cluster) 0 1 2 1 3 4 5 1 6 78 1 1 TELCOM 2110 5 Example Normalizing the weight of each individual node to a T1 capacity (T1 can handle 24 traffic channels. Nodes 0-5 and 7,8 have weight 72/24 = 3, Node 6 has weight 64/24 = 2.667 . Links are considered are 6T1 link => W = 6 Cost = 400 + 50 d. Initial Design Applying E-W algorithm Initialize with every node having a direct link cost 0 1 2 1 Ci0 = [450, 500, 450, 470.7, 511.8, 500, 511.8, 541.4] 3 4 5 1 6 78 1 1 TELCOM 2110 6 3
4. Example Tradeoff(i)=minj Cost(Ni,NJ) -Cost(Comp(Ni),Center) Tradeoff(1) = 450 - 450 = 0 Tradeoff(2) = 450- 500 = -50 Tradeoff(3) = 450-450 = 0 Tradeoff(4) = 450 – 470.7 = -20.7 Tradeoff(5) = 450 - 512 = 62 Tradeoff(6) = 450 – 500 = -50 Tradeoff(7) = 450 – 512 = -62 Tradeoff(8) = 450 – 541 = -91 Pick 8 to merge with either 7 or 5 0 1 2 Pick 7 since 1 Checking capacity w +w = 6 ≤ W = 6 7 8 3 4 5 1 6 78 1 1 TELCOM 2110 7 Example Tradeoff(i)=minj Cost(Ni,NJ) -Cost(Comp(Ni),Center) Tradeoff(1) = 450 - 450 = 0 Tradeoff(2) = 450- 500 = -50 Tradeoff(3) = 450-450 = 0 Tradeoff(4) = 450 – 470.7 = -20.7 Tradeoff(5) = 450 - 512 = 62 Tradeoff(6) = 450 – 500 = -50 Tradeoff(7) = 450 – 512 = -62 not allowed Tradeoff(8) = 450 – 512 = -62 not allowed Pick 5 to merge with either 2 or 4 0 1 2 Pick 4 1 Checking capacity w +w = 6 ≤ W = 6 4 5 3 4 5 1 6 78 1 1 TELCOM 2110 8 4
5. Example Tradeoff(i)=minj Cost(Ni,NJ) - Cost(Comp(Ni),Center) Tradeoff(1) = 450 - 450 = 0 Tradeoff(2) = 450- 500 = -50 Tradeoff(3) = 450-450 = 0 Tradeoff(4) = 450 – 470.7 = -20.7 not allowed Tradeoff(5) = 450 – 470.7 = -20.7 not allowed Tradeoff(6) = 450 – 500 = -50 Tradeoff(7) = 450 – 512 = -62 not allowed Tradeoff(8) = 450 – 512 = -62 not allowed Pick 2 to merge with 1 0 1 2 1 Checking capacity w2+w1 = 6 ≤ W = 6 3 4 5 Similarly will have 6 merge with 3 1 6 78 In next iteration w3+w6 = 5.66 ≤ W = 6 Final topology as shown 1 1 TELCOM 2110 9 Example • Once topology known move to Alcatel BSC data sheet physical design. • Need to select equipment: BS, BSC, interfaces, cables etc. • Price vendor equipment and link options from service provider – Equipment Vendors: Lucent, Nortelnetworks, Siemens, Nokia, Ericsson, Alcatel, etc. • Service provider may implement link as a Add/Drop Multiplexer (ADM) drop off of a higher capacity link TELCOM 2110 10 5
6. Technology Choices • For Packet Data traffic • Choice depends on distances – Connect Pitt branch campuses and labs (Johnstown, Bradford etc.) to main Pitt campus computer center – – options, Frame Relay, ATM, SMDS, IP/STM, X.25, ISDN, etc. – Connect hosts/servers in different locations of a building to campus backbone • Ethernet, Fast Ethernet, Gigabit Root Ethernet,Token Ring, WiMAX, 802.11, etc. • Need to factor in performance needs and user requirements (e.g., lease vs. 1 2 buy, security etc.) • Consider LAN physical design 3 45 6 TELCOM 2110 11 LAN Technology Choices • Choices for LAN equipment • Ethernet • Token Ring •FDDI • Fast Ethernet • Gigabit Ethernet •ATM • 802.11 (Wi-Fi), etc. • Majority of installations today are Ethernet to the desktop – growing interest in 802.11 TELCOM 2110 12 6
7. Classical Ethernet • IEEE 802.3 Standard 1983 • Bus topology LAN • 10 Mbps • CSMA/CD medium access control protocol • 10Base5 – coax cabling – 10 Mbps – 50-ohm coaxial cable bus – Maximum segment length 500 meters – extend with repeaters • 10Base-T cabling (1987) – Twisted pair, maximum length 100 meters – Star topology (hub at central point) TELCOM 2110 13 Ethernet Evolution • Ethernet Protocol so wide spread that evolution rather than replacement • Multiport Bridges and Switches to increase throughput and extend configuration options • Higher speed versions of Ethernet – Fast Ethernet 100 Mbps Ethernet • Called 100BaseTX • IEEE 802.3u standard in 1995 • Uses Fiber or Cat5 UTP – Gigabit Ethernet 1, 10 Gbps Ethernet • IEEE 802.3z standard in 1998 • Full Duplex to build backbones or connect servers • Fiber cabling and UTP – IEEE 802.11 (Wireless Ethernet) TELCOM 2110 14 7
8. Current Ethernet Options •Bus •Transmission from a station broadcast to all stations on the bus •Hub Transmission from a station received by central hub and retransmitted on all outgoing lines Only one transmission at a time •Layer 2 Switch Incoming frame switched to one outgoing line Many transmissions at same time TELCOM 2110 15 Ethernet LAN Building Blocks • Network Interface Card – I/O device that interfaces computer to network – Frame transmission and reception • Repeater – Physical Layer – No Address review – Broadcast Device – Transparent to end devices – Extends range of LAN •Hub – Multicast device - broadcasts frame to all output ports – Star Configuration – Data Link Layer TELCOM 2110 16 8
9. LAN Building Blocks • Media Converters, – Connect different physical media types together – 100 Base Tx (UTP) connection to 100 Base Fx (Fiber) • Bridge – Connect different LAN segments – Data Link Layer – Stores frame examines MAC address and Forwards valid frames – Can bridge different speed/media networks •Switch – Star Configuration – Data Link Layer – Layer 2 Switch – examines MAC address to determine port to forward frame too – Multiple ports can handle multiple frames at a time. – Can do cut through switching in hardware TELCOM 2110 17 LAN Building Blocks • Layer 3 switch or Router • Operates at the Network Layer (layer 3) of OSI Model – Uses protocol (IP) to determine action • Used to connect dissimilar LAN’s – can covert frame from one type to another, provide security, etc. • Makes a decision to forward or drop a frame • Maintains routing tables that list connected networks – IP & MAC address of next relay station • Does not forward broadcast frames (layer 2) TELCOM 2110 18 9
10. Typical Physical Topology Often have a mix of speeds and hubs/switches in LAN TELCOM 2110 19 LAN Wiring Cables are connected to network devices and the computer Most networks use a mixture of cable types • Coaxial cable • Plenum Cable – jackets are made of – Known as Thin Net or T nonflammable fluoro- base 2 or T-2 polymers (such as • Twisted-pair cable Teflon). – More expensive than non- – shielded (STP) plenum jackets. – unshielded (UTP) • Non-plenum cable – Five categories of UTP – uses less-expensive • Fiber-optic cable material for jackets such as polyethylene (PE) or – single-mode, polyvinylchloride (PVC), – multi-mode, or graded- which will give off toxic index multi-mode fumes in a fire TELCOM 2110 20 10
11. Medium Options for Ethernet • Coax - .13/ft + 3.00 per connector • UTP category 5 - – Plenum - .33/ft + 1.00 per connector – PVC - .13/ft + 1.00 per connector • Multi-mode Fiber - .35/ft + 15.00 per connector • Single mode Fiber - .50/ft + 15.00 per connector TELCOM 2110 21 Wiring Standards • Large Number of Wiring Standards see • For example TIA/EIA-568 – Commercial Building Telecommunications Cabling Standard • Sets specific requirements for cable – Impedance – Signal Loss or Attenuation – Termination Requirements – Maximum Distances – Other factors for correct use of cable and wire in commercial environment • TIA/EIA-568A covers 6 areas 1. Building Entrance 2. Equipment Room 3. Backbone Cabling 4. Telecommunications Closet 5. Horizontal Cabling 6. Work Area TELCOM 2110 22 11
12. Wiring Closet/Patch Panel • Need to connect the numerous wires (could be hundreds) to the electronics. • A large cable bundle is very heavy and would be hard to move around. • We use wiring closet/patch panels to provide an way to connect the wiring bundles to the electronics. • Location – Accessibility & Security – Environmental concerns (heating/cooling, power) TELCOM 2110 23 Example Backbone Switch Fiber Run Fiber Patch Panel Fiber Patch Panel PC UTP P Panel In Wall Wiring Switch Wall Jack TELCOM 2110 24 12
13. Summary • Top Down Network Design – Conceptual Model – Objectives • Business Goals – Technical Goals – Requirements • Business, Technical (availability, delay, bandwidth, security, etc.,) – Constraints • Business (organizational, budget, etc.,) and Technical TELCOM 2110 26 13