Topic 7: LANs & Backbone Networks - Chapter 15: LAN Systems Business Data Communications, 4 e Business Data Communications
Ethernet Standards Ethernet Cable Features 10 Base-2 10 Base-5 10 Base-T 100 Base-T 4 100 Base-TX 100 Base-FX RG-58 coax (thin) RG-8 coax (thick) Cat 3 UTP x 4 Cat 5 UTP/STP Fiber optic 185 m, 10 Mbps 500 m, 10 Mbps 100 m, 100 Mbps Business Data Communications 2
Types of Ethernet w 10 BASE-T (10 Mbps) n Uses a twisted-pair cable with maximum distance of 100 meters w 100 BASE-T (100 Mbps) n Based on 10 Base-T standard, 10 times faster, uses cat-5 UIP/STP cable. NIC is downward compatible to 10 Base-T w Gigabit Ethernet w Three new types of Ethernet. They can use Ethernet traditional half-duplex approach, but most are configured to use full-duplex. Also they can run over fiber-optic cables. n n n 1000 Base-T Ethernet, sometimes is called 1 Gb. E. 10 Gb. E 40 Gb. E Business Data Communications 3
802. 3 10 Base. X Media Options Business Data Communications 4
High-Speed LANs w Why? n n Extraordinary growth in speed, power, and storage capacity of PCs Increasing use of LANs as computing platforms w Examples n n n Server farms Workgroups with “power” requirements High-speed backbones Business Data Communications 5
100 Base-T Ethernet (IEEE 802. 13) w It gives a 100 Mbps data rate using the standard Ethernet bus topology, data link packets and CSMA/CD media access protocol. w Three versions of 100 Base-X differing only at the physical layer: n n n 100 Base. TX uses cat 5 UTP 100 Base. FX uses fiber optic cable 100 Base. T 4 uses 4 sets of cat 3 UTP (inverse multiplexed) w 100 Base-T Ethernet can co-exist with 10 Base-T Ethernet. Business Data Communications 6
Fast Ethernet (100 Mbps) w Easy to integrate with existing systems w Can use UTP (-TX) or fiber (-FX) w Uses star-wired topology, using a central multiport repeater (broadcast method) w If NICs support full-duplex mode, switched hub must be used Business Data Communications 7
100 Base-T Ethernet (IEEE 802. 13) Virtually identical to 10 Base-T (IEEE 802. 3). It gives a 100 Mbps data rate using the standard Ethernet bus topology, data link packets and CSMA/CD media access protocol. Three versions of 100 Base-X differing only at the physical layer: n n n 100 Base. TX uses cat 5 UTP 100 Base. FX uses fiber optic cable 100 Base. T 4 uses 4 sets of cat 3 UTP (inverse multiplexed) Business Data Communications 8
802. 3 100 Base-T Options Business Data Communications 9
802. 3 100 Base. X Media Options Business Data Communications 10
Gigabit Ethernet w Still under development w Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path w Uses optical fiber over short distances w 1 -Gbps switching hub provides backbone connectivity w May not be good for LAN (explain why) and has been used in backbone networks for point -to-point connections. Business Data Communications 11
Gigabit Ethernet w 1000 BASE-LX: Long-wavelength, supports up to 550 m (m-mode fiber) or 5 km (single-mode fiber) w 1000 BASE-SX: Short-wavelength, supports up to 275 - 550 m(m-mode fiber) w 1000 BASE-CX: uses copper jumpers in a single room or equipment rack w 1000 BASE-T: uses 4 pairs of Cat-5 UTP Business Data Communications 12
Gigabit Ethernet Media Options Business Data Communications 13
Example 100 -Mbps Ethernet Backbone Strategy Business Data Communications 14
Fibre Channel w combine the best features of channel and protocol-based technologies n n the simplicity and speed of channel communications the flexibility and inter-connectivity that characterize protocol-based network communications. w more like a traditional circuit-switched or packet-switched network, in contrast to the typical shared-medium LAN Business Data Communications 15
Fiber Channel Network N_port F_port Business Data Communications 16
Fibre Channel Elements w Nodes n n The end systems Includes one or more N_ ports for interconnection w Fabric n n n Collection of switching elements between systems Each element includes multiple F_ ports Responsible for buffering and for routing frames between source and destination nodes Business Data Communications 17
Fibre Channel Goals w Full-duplex links with two w w fibers per link Performance from 100 Mbps to 800 Mbps on a single link (200 Mbps to 1600 Mbps per link) Support for distances up to 10 km Small connectors High-capacity utilization with distance insensitivity w Greater connectivity than existing multidrop channels w Broad availability (i. e. , standard components) w Support for multiple cost/performance levels, from small systems to supercomputers w Ability to carry multiple existing interface command sets for existing channel and network protocols Business Data Communications 18
*Fibre Channel Protocol Architecture w FC-0 Physical Media: Includes optical fiber, coaxial w w cable, and shielded twisted pair, based on distance requirements FC-1 Transmission Protocol: Defines the signal encoding scheme FC-2 Framing Protocol: Defines topologies, frame format, flow/error control, and grouping of frames FC-3 Common Services: Includes multicasting FC-4 Mapping: Defines the mapping of various channel and network protocols to Fibre Channel Business Data Communications 19
Fibre Channel - Maximum Distance 800 Mbps 400 Mbps 200 Mbps 10, 000 m 10, 000 m M-mode 500 m 1, 000 m 2, 000 m Coaxial Cable 50 m 71 m 100 m STP 28 m 46 m 57 m 80 m Single Mode Business Data Communications -- 20
Wireless LANS w LAN extension n Wireless network connected to a main wire-based network w Cross-building interconnect n Point-to-point link between networks in separate buildings w Nomadic access n Wireless link between a LAN hub and a mobile data terminal w Ad hoc networks n a peer-to-peer network (no centralized server) set up temporarily to meet some immediate need. Business Data Communications 21
Wireless LANs (IEEE 802. 11) w Wireless LANs are growing very rapidly. Wireless LANs transmit data through the air (space) rather than through wire or cable. w New terms: n n WLAN (Wireless LAN) LAW (Local Area Wireless Network) w IEEE 802. 11 standard is likely to be the dominant standard for wireless LAN w It is easy to connect wireless LANs to Ethernet. So, it is usually called wireless Ethernet Business Data Communications 22
Wireless LANs (IEEE 802. 11) w Topology. The same as traditional Ethernet. It is both a physical star and a logical bus. n A central wireless access point (AP) is a radio transceiver that plays the role of hub. The maximum range is 100 -500 feet depending on interference w Wireless LANs use CSMA/CA (Carrier Sense Media Access with Collision Avoidance) similar to CSMA/CD by Ethernet. Two methods are simultaneously used: n n Physical carrier sense method. Packets are sent using stopand-wait ARQ. Receiver waits less time to send ACK than other computers waiting for available time slots. Virtual carrier sense method. Using AP hidden node problem must be solved. It is optional. Business Data Communications 23
Hidden Node Problem w When one computer transmits packets, a computer in another side of AP may not detect the signal and send packets as well. This causes collision at AP. w So, AP is the only device that is able to communicate with both computers. To solve the problem, AP uses controlled access method instead of the contention based method. A computer wanting to send packets must send a request (RTS) to AP. If no other computer is using the circuit, AP will respond with a clear to transmit (CTS) specifying the amount of time for the circuit reserved for the computer. w All other computers hear the CTS and remain silent for the specified time period. Business Data Communications 24
Types of Wireless Ethernet w IEEE 802. 11 b. Two basic forms: n n Direct-sequence spread-spectrum (DSSS) Frequency-hopping spread-spectrum (FHSS) w IEEE 802. 11 a. Expected to run at 5 GHz. Not completely defined yet. w Other type of wireless LANs: n Infrared wireless LAN. Less flexible because most require direct line of sight between transmitters and receivers. w The primary advantage: the reduction of wiring. w The primary disadvantage: the low speed (1 -4 Mbps). n Bluetooth. Provide seamless networking of devices in a very small area (up to 30 feet) w Small, cheap w Called Piconet with no more than 8 devices Business Data Communications 25
IEEE 802. 11 b w Two basic forms: n n Direct-sequence spread-spectrum (DSSS), in 2. 4 GHz band. Transmits signals through a wide spectrum of radio frequencies simultaneously. The signal is divided into many different parts and sent on different frequencies. 1, 2, 5. 5, 11 Mbps speeds. 20 Mbps version is in the way out. Frequency-hopping spread-spectrum (FHSS). Uses the same band, but once each frequency in turn. Sender and received synchronize in a frequency. So, minimizes jamming an eavesdropping. 1 Mbps and 2 Mbps. w They are shared media implementation. As the number of devices increases the speed will be reduced. Business Data Communications 26
Infrared Wireless LANs Business Data Communications 27
Fiber Distributed Data Interface (FDDI) is a set of standards originally designed in the late 1980 s, but has since made its way into backbone networks. FDDI is a token-passing ring network that operates at 100 Mbps over two-counterrotating fiber optic cable rings. Business Data Communications 28
Topology The FDDI standard assumes a maximum of 1000 stations and a 200 -kilometers (120 miles) path that requires a repeater every 2 -kilometers. The second ring is for backup. Single attachment stations (SAS) and dual-attachment stations (DAS) are both computer that can connect to one or both of the rings, respectively. If the cable in the FDDI ring is broken, the ring can still operate in a limited fashion. Business Data Communications 29
Topology Business Data Communications 30
Topology Business Data Communications 31
Media Access Control The FDDI-MAC scheme uses a variation of the IEEE 802. 5 token-passing standard. w Messages and the token are sent in different frames separately in a FDDI LAN. A computer can send data only when it captures the token. w When a computer on an FDDI network waiting for transmission receives the token, it holds the token and then transmits all messages that were attached to it. The computer then transmits whatever messages its wants before transmitting the token. w When receiver receives the data frame it simply copy the data frame leaving it to be absorbed by the sender. Business Data Communications 32
Backbone Network Architecture LAN LAN LAN Core Layer Distribution Layer Access Layer Figure 7 -5 Backbone network design layers (FD) Business Data Communications 33
*Backbone Network Architectures w Routed backbone – using routers n n Advantage – clearly segment each part of the network Disadvantage – Delay, and more management w Bridged backbone – using bridges, not popular any more n n Advantages – cheaper, simpler Disadvantages – difficulties in management w Collapsed backbone –using switches, is most commonly used. n n n Advantages - Better performance, Fewer network devices are used Disadvantages – switch problem may fail whole network, more cabling work Two types w Rack-based collapsed backbone w Chassis-based collapsed backbone w Virtual LAN (VLAN) Business Data Communications 34
Client Computer 10/100 Ethernet Client Computer Layer-2 Client Switch Computer Client 1000 Base-T Computer Client Computer Router to WAN 1 Gb. E on fiber 10/100 Ethernet Router to Internet Layer-3 Switch Client 1 Gb. E Computer on fiber Client Computer 10/100 Ethernet Client Computer Layer-2 Client Switch Computer Client 1000 Base-T Computer Client Computer 1 Gb. E on fiber Server Figure 7 -11 Central Parking’s collapsed backbone (FD) Business Data Communications 35
*Virtual LAN (VLAN) w A new type of LAN backbone network architecture by intelligent high-speed switches. VLAN is configured using software not hardware. n n Single-switch VLAN – VLAN inside a switch Multiswitch VLAN – VLAN using several switches. w VLAN is normally faster than traditional LANs, and provide better opportunity to manage data flows Business Data Communications 36
Client Computer 10/100 Ethernet Client Computer Client VLAN switch Computer Client 1000 Base-T Computer Client Computer VLAN switch VLAN switch 1 Gb. E on fiber VLAN switch VLAN switch Figure 7 -14 IONA VLAN network (FD) Business Data Communications 37
How is a packet transmitted through the Internet? w An IP address tells the destination w Transmission is done hop after another actually at data link layer w This is just like you bought a flight ticket from Lubbock to New York. The ticket package indicates New York is your destination (IP address). However, you may have three coupons for three flights that connect your route via two more cities between: Dallas and Chicago. Each coupon indicates your arriving airport (destination data link layer address), e. g. DFW, CHI and JFK. Business Data Communications 38
A TCP/IP Example Business Data Communications 39
How TCP/IP Works w How a client access a web server in the same subnet with a known address? w How a client access a web server in a different subnet with a known address? w How a client access a web server in the same subnet with an unknown address? Business Data Communications 40
*Net. BIOS vs. Net. BEUI w Net. BIOS has 18 commands for PC connections. w Net. BEUI adds 8 more and is used as a transport protocol. It is faster and more efficient than Net. BIOS w When Net. BEUI is in use, NETBIOS becomes API that invokes Net. Beui. w They can support a LAN with less than 200 PCs. Business Data Communications 41
*Windows Network Model Internet Model Application layer: I/O Named Pipes Mail Server Environment Subsystem FTP, TELNET, HTTP, etc. Transport layer: TCP, UDP Network layer: IP Data link layer Physical layer Provider Interface Net. BIOS (Redirector) TDI Net. BEUI WINSOCK TCP/IP NDIS 3. 0 NDIS Environment and Drivers Layer 7 Layer 6 Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 802. 2 802. 3 802. 4 802. 5 NDIS: Communications Business Data. Network Driver Interface Specification 42
*NDIS w NDIS (Network Driver Interface Specification) is a Windows specification for how communication protocol programs (such as TCP/IP) and network device drivers should communicate with each other. Business Data Communications 43
*Net. BIOS (Network Basic Input/Output System) w Created by IBM for its early PC Network, was adopted by Microsoft, and has since become a de facto industry standard. w A program that allows applications on different computers to communicate within a local area network (LAN). w Used in Ethernet, token ring, and Windows NT networks. Business Data Communications 44
*Net. BEUI (Net. BIOS Extended User Interface) w Developed by IBM for its LAN Manager product and has been adopted by Microsoft for its Windows NT, LAN Manager, and Windows for Workgroups products. w A new, extended version of Net. BIOS, the program that lets computers communicate within a local area network. w Formalizes the frame format (or arrangement of information in a data transmission) that was not specified as part of Net. BIOS. Business Data Communications 45
*Net. BIOS over TCP/IP w Net. BIOS over TCP/IP runs over the TCP/IP, so that you can share drives and printers over the Internet. w In the "Network" configuration window in Windows 95, there is no option for Net. BIOS over TCP/IP, but a "Net. BEUI" entry, with which Microsoft actually means Net. BIOS over Net. BEUI. w With the installation of TCP/IP protocol, Windows automatically installs the "Net. BIOS over TCP/IP”. w If you do want the TCP/IP protocol, but not "Net. BIOS over TCP/IP" (because of security problem), you should uncheck "Files and Printer Sharing" in the Bindings tab of the TCP/IP entry in Network Configuration. Business Data Communications 46
Data transmission using TCP/IP and Ethernet packet header IP packet TCP packet HTTP packet User Data Ethernet packet trailer IP address Data link layer address Business Data Communications 47
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