High-Speed LAN and Backbone Networks After studying this Chapter you should: u Know which internetworking devices are used in backbone networks u Describe several types of fast Ethernet and fast Token Ring u Describe FDDI u Describe ATM and fiber channels u Know ways to improve performance on BN Chapter 8 3/19/2018 1
Definition u Backbone Network (BN) - a large high-speed central network that connects all the terminals, microcomputers, mainframes, local area networks, and other communications equipment on a single company or site. Sometimes called a Campus Area Network (CAN). Use Higher speed circuits for connectivity. Chapter 8 3/19/2018 2
Definition u Enterprise Network (EN) - a supernetwork that interconnects all of an organizations networks (LANs and WANs), regardless of whether it crosses state, national, or international boundaries. Chapter 8 3/19/2018 3
Why interconnect networks? u Reliability u Performance u Security Chapter 8 3/19/2018 4
Introduction There are two approaches to providing high speed networking. u “speed up” the technologies currently used in local area networks. Fast Ethernet u Fast Token Ring u u develop new high speed technologies that provide dedicated point-to-point communication circuits Switched Ethernet u Switched Token Ring u ATM u Chapter 8 3/19/2018 5
Backbone Network Components u Two basic components to the BN u hardware devices that connect the networks to the backbone hubs u bridges u switches u routers u brouters u gateways u u network Chapter 8 cable 3/19/2018 6
Hubs u very simple devices that pass all traffic in both directions between the LAN sections they link u same or different cable types u use physical layer protocols u pass on every message u used to connect LANs of similar technology, or to extend the distance of one LAN u can be called repeaters or amplifiers Chapter 8 3/19/2018 7
HUB Devices Repeater/Amplifier HUB (MAU) Chapter 8 3/19/2018 8
Hubs u inexpensive u easy to Install u can connect different media u very little delay u limited distance between devices u limited on the number of repeaters u no protocol or rate conversion u no error detection u does not filter Chapter 8 3/19/2018 9
Bridges u connect two LAN segments that use the same data link and network protocol u operated at the data link layer u same or different cable types u forward only those messages that need to go out (filtering) u “learn” whether to forward packets u internal routing table u combination of “black box” hardware and software Chapter 8 3/19/2018 10
Bridges There are three types of bridges: u Simple bridge u Learning bridge u Multiport bridge Chapter 8 3/19/2018 11
Bridges Interconnecting Bridge Repeater/ Amplifier HUB (MAU) Chapter 8 3/19/2018 12
Bridges u may be different data rates and different media easy to Install u no modifications required to the communications software u can learn the ports for data transmission u understand only data link layer protocols and addresses u no protocol conversion u broadcasts when it does not know the address Chapter 8 3/19/2018 13
Switches u connect more than two LAN segments that use the same data link and network protocol. u operate at the data link layer u same or different type cable u ports are usually provided for 4, 8, 16, or 32 LAN segments u ports are used simultaneously u connect lower speed segments to high speed BN Chapter 8 3/19/2018 14
Switches u Cut-through switches u use circuit-switching to immediately connect the port with the incoming message to the correct outgoing port u very fast as decisions are done in hardware u outgoing packet is lost if port is in use u Store-and-forward switches u copy the incoming packet to memory prior to processing the destination address -- transmit it when the outgoing port is ready Chapter 8 3/19/2018 15
Switches Interconnecting Wing A Wing B First Floor Switch Chapter 8 Wing C 3/19/2018 Wing C 16
Switches u much more sophisticated than previously u enable all ports to work at the same time u can convert protocols u configurable u high speed u understand only data link layer protocols and addresses u much more expensive then previous options u higher maintenance Chapter 8 3/19/2018 17
Routers u connect two or more LANs that use the same or different data link protocols, but the same network protocol. u same or different cable types u operate at the network layer u forward only messages that need to go out u routers use the internetwork address u internal routing tables u only processes messages addressed to it Chapter 8 3/19/2018 18
Routers u choose the best route to send the packet (path) u IDs of other networks u paths to the networks u relative efficiency of the paths Chapter 8 3/19/2018 19
Routers u The router must deal with network differences: u addressing schemes u minimum packet size u interfaces u reliability Chapter 8 3/19/2018 20
Routers Interconnecting Router X. 25 Network the “cloud” Chapter 8 Token Ring LAN 1 3/19/2018 Ethernet LAN 2 21
Routers u can mix-in-match protocols and convert them u enable all ports to work at the same time u can be used as an extra layer of security u configurable u high speed u hard to configure and manage u access lists must be kept current u high maintenance/high training costs u very expensive Chapter 8 3/19/2018 22
Brouters u devices that combine the functions of both bridges and routers u operate at both the data link and network layers u same or different data link protocol u same network protocol u as fast as bridges for same data link type networks Chapter 8 3/19/2018 23
Gateways u complex machines that are interfaces between two or more dissimilar networks u connect two or more LANs that use the same or different data link layer, network layer, and cable types u operates at the network layer (3) or higher layers (4 -7) u forwards only those messages that need to go out u a combination of both hardware and software Chapter 8 3/19/2018 24
Gateways u translates one network protocol to another u translates data formats u translates open sessions between application programs u translates to mainframes Chapter 8 3/19/2018 25
Gateways u Exists in four major types: u LAN-to-IBM mainframe u Network-to-network u System-to-system Chapter 8 3/19/2018 26
LAN-to-IBM Mainframe u Allow LANs using TCP/IP and Ethernet to be connected to IBM mainframe using SNA u Eliminates the need for each PC on the LAN to have SNA hardware/software that makes it act like an IBM 3270 terminal Mainframe Chapter 8 Gateway 3/19/2018 27
Network-to-Network X. 75 Gateway X. 25 Network A X. 25 Network B X. 75 provides terminal address translation Chapter 8 3/19/2018 28
System-to-Network Gateway X. 25 Network Minicomputer or Microcomputer Chapter 8 3/19/2018 29
System-to-System u allows connecting one vendor’s architecture to another vendor’s architecture u allows both the existence of OSI-based and proprietary architectures (like SNA or Apple. Talk) u gives management to tools necessary to plan a gradual migration to a completely OSI environment u applications can work with other application Chapter 8 3/19/2018 30
System-to-System Profs E-mail Gateway X. 25 Network LAN E-mail Server Profs E-mail LAN E-mail Gateway Chapter 8 3/19/2018 31
Backbone Network Devices Physical Data Link Network Layer Device Operates at Messages Hub Bridge Physical Data link S/D Same Switch Data link S/D Same Router Network S/D Same Brouter Data link & Network All transferred Filtered using data link layer add. Switched using data link layer add. Routed using network layer add. Filtered & routed S/D Same Routed using network layer add. S/D S/D Gateway Chapter 8 3/19/2018 32
Terminology Warnings u Multiprotocol bridges translate between different data link layer protocols. u Multiprotocol routers translate between different network layer protocols. u Protocol filtering bridges forward only packets of a certain type, i. e. , token-ring or ethernet u Encapsulating bridges connect networks with different data link protocols, encapsulating messages with correct protocol for transmission u Layer-3 switches (IP switches) - can also switch messages based on their network layer address Chapter 8 3/19/2018 33
Shared Media Technologies u Fast Ethernet u Fast Token Ring u Fiber Distributed Data Interface Chapter 8 3/19/2018 34
Fast Ethernet u 100 Base-X Ethernet u 100 VG-Any. LAN u Gigabit Ethernet u Iso-ENET (isochronous ethernet) Chapter 8 3/19/2018 35
100 Base-X Ethernet u IEEE 802. 13 u identical to 10 Base-T Ethernet u three data link layer protocols u 100 Mbps data rate u standard ethernet bus topology u ethernet data link packets u ethernet CSMA/CD media access protocol Chapter 8 3/19/2018 36
100 Base-X Ethernet Three versions of 100 Base-X Ethernet u 100 Base-TX u 100 Base-FX u 100 Base-T 4 Chapter 8 3/19/2018 37
100 VG-Any. LAN u IEEE 802. 12 u both Ethernet or token-ring u Demand Priority Access Method (DPAM) polling u polls each computer to see if it has data to send u can use a priority system (notification system) u four sets of twisted pair running at 25 Mbps u faster than 100 Base-T Chapter 8 3/19/2018 38
Gigabit Ethernet u IEEE 802. 3 Z u 1000 Base-X u 1000 Mbps (1000 Mbps = 1 Gbps) u high speed of transmission may cause collisions to go undetected u mainly used for point-to-point full-duplex communication links (BN, MAN) u PCs send or receive data at rates up to 100 Mbps Chapter 8 3/19/2018 39
Gigabit Ethernet Four versions of 1000 Base-X Ethernet u 1000 Base-LX (fiber up to 440 meters) u 1000 Base-SX (fiber up to 260 meters) u 1000 Base-T (four pairs twisted-pair up to 100 meters) u 1000 Base-CX (one cat 5 cable up to 24 meters) Chapter 8 3/19/2018 40
Iso-ENET u IEEE 802. 9 A u isochronous Ethernet u standard 10 Base-T Ethernet + 6. 144 Mbps u both transmitted on the same twisted pair u 6. 144 circuit configured for ISDN for transmission of voice and video u mainly used for desktop videoconferencing and multimedia products Chapter 8 3/19/2018 41
Fast Token Ring u high-speed token ring (HSTR) u standard token ring topology u standard token ring protocols u token passing media access control u 100 Mbps instead of 16 Mbps u category 5 or fiber optics cable u IBM working on 1 Gbps version Chapter 8 3/19/2018 42
Fiber Distributed Data Interface (FDDI) u ANSI X 3 T 9. 5 u Topology - token-passing u 2 counter-rotating rings u Each ring operates at 100 Mbps over fiber optic cable u maximum of 1000 stations u distance 120 mile path (200 k) u required repeaters to push transmission (2 K) u data is usually carried on the primary ring Chapter 8 3/19/2018 43
FDDI Station Types u Dual-Attachment Station (DAS) u connects to both primary and secondary rings u requires 4 fibers to the desk u allows the ring to continue to operate even if a break occurs in the line by rerouting through the secondary ring (backwards) u Single-Attachment Station (SAS) u connects only to the primary ring u requires 2 fibers to the desk Chapter 8 3/19/2018 44
FDDI Topology Mainframe DAS Workstations Primary Ring DAS Secondary Ring Gateway SAS DAS FDDI Hub SAS DAS Bridge Chapter 8 3/19/2018 45
FDDI - How does it work? u Media accesss control u variation of token-passing standard u FDDI allows multiple messages to attach to the token increases throughput above 100 Mbps u An FDDI-to-IEEE 802. x bridge is required to connect to lower speed corporate LANs u At each node the optical signal is: u converted to an electrical signal u amplified u copied (if necessary) u converted back to light to send to the next node Chapter 8 3/19/2018 46
Types of FDDI u Basic FDDI previously discussed u FDDI-C (FDDI on Copper) u Copper Distributed Data Interface (CDDI) u uses copper wire instead of fiber optic u FDDI-II u permits transmission of voice and video over the same cable as FDDI token-passing data u uses time division multiplexing u 17 channels 1 - 768 Kbps channel (token-passing) u 16 - 6. 144 Mbps channels (wide band - voice/video or data) u Chapter 8 3/19/2018 47
Switched Networks u Switched Ethernet u Full-Duplex Ethernet u Switched Token Ring u Switched FDDI u Asynchronous Transfer Mode (ATM) u Fibre Channel Chapter 8 3/19/2018 48
Switched Ethernet u the switch replaces the hub u creates a point-to-point circuit to the switch u allows multiple transmissions between computers u store-and-forward u improves LAN performance u circuit to the server is the network bottleneck Chapter 8 3/19/2018 49
Other Ethernet Solutions u Full-Duplex Ethernet u uses the same cables as regular Ethernet u 10 Base. T but full-duplex u doubles the speed of connections to 20 Mbps u full-duplex only from the switch to the server u may have several connections to one server u 10/100 switched ethernet u combines 10 Base. T and 100 Base. T to the server u cheaper to install than 100 Base-T u maybe as fast ethernet Chapter 8 3/19/2018 50
Switched Token Ring u token ring switch replaces the token ring hub u provides a series of point-to-point connections u star topology u no token to pass because of full duplex switch u called “token-ring” because it uses token ring packet format and is compatible with 802. 5 hardware u dedicated token ring (DTR) full duplex u 32 Mbps data rate due to full duplex (16 Mbps each direction) Chapter 8 3/19/2018 51
Switched FDDI u FDDI witch replaces the FDDI hub u point-to-point connctions to computers u star topology u no token because all computers can transmit and receive at will u same packet format and is fully compatible with other FDDI hardwar Chapter 8 3/19/2018 52
ATM u Isochronous networks provide very low and predictable node-tonode delays. They are capable of dealing with steady, immediate delivery, and high-bandwidth requirements of multimedia technology. u Asynchronous Transfer Mode (ATM) is the ultimate isochronous technology by allocating bandwidth on demand via virtual circuits. u u u Chapter 8 high-speed, hardware-based, circuit-switching technology cell-relay LANE (LAN Emulation/LAN Encapsulation) connection-oriented ATM desktop - point-to-point full duplex - “low speed” version for the desktop 3/19/2018 53
ATM is a switched network but differs from switched ethernet and switched token ring in four ways: 1. ATM uses fixed-length packets of 53 bytes (ATM encapsulation) 2. no error correction on the user data 3. ATM uses a very different type of addressing from traditional data link layer protocols such as ethernet or token ring 4. ATM prioritizes transmissions based on Quality of Service (Qo. S). Chapter 8 3/19/2018 54
Asynchronous Transfer Mode (ATM) Asynchronous Transfer Mode is connectionoriented so all packets travel in order through the virtual circuit. A virtual circuit can either be a: u Permanent Virtual Circuit (PVC) - defined when the network is established or modified. u Switched Virtual Circuit (SVC) - defined temporarily for one transmission and deleted with the transmission is completed. Chapter 8 3/19/2018 55
LAN Translation u two approaches for translation u LANE (LAN Emulation/LAN Encapsulation) u Multiprotocol over ATM (MPOA) Chapter 8 3/19/2018 56
LAN Encapsulation u usually referred to as LAN Emulation u data link layer packets left intact; broken down and encapsulated u reassembled on the LAN side u LAN thinks that the packets are token ring or Ethernet u requires ATM edge switches at each side Chapter 8 3/19/2018 57
Multiprotocol over ATM u extension of LANE u uses network layer addresses and data link layer addresses u destination determines which address to use u route servers required (MPOA servers) Chapter 8 3/19/2018 58
ATM to the Desktop ATM-25 is a low speed version of ATM which provides point-to-point full duplex circuits at 25. 6 Mbps in each direction. It is an adaptation of token ring that runs over cat 3 cable and can even use token ring hardware if modified. ATM-51 is another version designed for the desktop allowing 51. 84 Mbps from computers to the switch. Chapter 8 3/19/2018 59
ATM Classes of Service ATM provides five classes of service: u Constant Bit Rate (CBR) u Variable Bit Rate-Real Time (VBR-RT) u Variable Bit Rate-Non-Real Time (VBR-NRT) u Available Bit Rate (ABR) u Unspecified Bit Rate (UBR) Chapter 8 3/19/2018 60
Fiber Channel Fiber channel is relatively new networking technology, although it has been used inside computer and disk storage devices for several years. Fiber channel was originally designed to provide high speed transmission over fiber optic cable. The maximum data rate is 1. 062 Gbps up to 10 k with higher rates under development. Chapter 8 3/19/2018 61
Improving Backbone Performance u change network protocol u check impact of applications u replace the hubs with switches and make point -to-point connections available u increase circuit capacity u make sure BN devices have sufficient memory, so packets don’t get lost and have to be resent Chapter 8 3/19/2018 62
Improving Backbone Performance u use faster routing protocol u upgrade computers that perform routing u use switches from a single vendor u eliminate need for switch-to-switch routing by use of collapsed backbone switch Chapter 8 3/19/2018 63
Collapsed Backbone Networks u uses point-to-point circuits when possible u uses a switch and a set of circuits to each LAN u uses more cable, but fewer devices u “backbone” exists in the switch u improved performance u switch replaces multiple bridges or routers u lowers costs u simplifies network management u if the switch fails, the network is down Chapter 8 3/19/2018 64
Improving Circuit Capacity u increase overall circuit capacity or place additional circuits alongside heavily used circuits u move from shared circuit to switched circuit BN u increase capacity to the server Chapter 8 3/19/2018 65
Improving Circuit Capacity How much bandwidth to expect LAN Type Ethernet Token Ring Fast Ethernet Faster Ethernet Fast Token Ring FDDI ATM Chapter 8 Speed 10 Mbps 16 Mbps 100 Mbps 1 Gbps 100 Mbps 2. 4 Gbps 3/19/2018 66
Reduce Network Demand u restrict high-bandwidth applications: u video conferencing u medical imaging u multimedia u set routing devices to filter broadcast messages Chapter 8 3/19/2018 67
Selecting a Backbone Network 5 important factors to consider: u Throughput u Network cost u Type of application u Ease of network management u Compatibility with current and future technologies Chapter 8 3/19/2018 68
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