Lecture 17: Design Technologies Prof. Shervin Shirmohammadi SITE, University of Ottawa Prof. Shervin Shirmohammadi CEG 4185 17-1
Design Goals From the architecture and its components and simulation, we have an idea in terms of physical requirements of network elements such as routers, hubs, links, etc. In the design phase, choices are made about cabling, physical and data-link-layer protocols, and internetworking devices (hubs, switches, and routers). The network architecture models form the foundation for physical design. The business goals, technical requirements, network traffic characteristics, and traffic flows all influence the physical design. Prof. Shervin Shirmohammadi CEG 4185 17-2
Types of Cable Shielded copper, shielded twisted pair (STP), coaxial (coax), and twin-axial (twinax). Popular early days of LANs. Thick Ethernet (10base5) double shielded 50 ohm coax cable, 0.4 diameter. Later thin Ethernet (10Base2), 75 ohm cable. Unshielded copper (Typically UTP). Must adhere to strict distance requirements: Cat 1&2 not recommended due to lack of support for high bandwidth. Cat 3 tested to 16 MHz, Ethernet and 4Mbps token ring configuration. Cat 4 tested to 20 MHz, 16 Mbps token ring configuration. Not common. Cat 5 tested up to 100 MHz, 100 Mbps Ethernet and FDDI. Cat 5e (enhanced) tested up to 350 MHz, suitable for 100 Mbps and Gigabit Ethernet, and ATM. Cat 6 tested up to 200 MHz, also suitable for 100 Mbps and Gigabit Ethernet, and ATM. Cat 6 is recommended by TIA (Telecommunications Industry Association) fro all future installments. Fiber optics Becoming a standard now for MAN and WAN. NIC equipment is expensive. There is no cross talk or EM interference. Runs in single or multi-mode. Prof. Shervin Shirmohammadi CEG 4185 17-3
LAN Technologies - Ethernet Ethernet Developed by Xerox in 1970s. Ethernet 2 & IEEE 802.3 Version 2 of Ethernet was published in 1982 by DEC, Intel, and Xerox IEEE 802.3 published in 1983 evolved from Ethernet 2. IEEE 802.3 Choices: Half- and full-duplex Ethernet 10-Mbps Ethernet 100-Mbps Ethernet a.k.a. Fast Ethernet (IEEE 802.3u initially) Gbps Ethernet (IEEE 802.3z initially) 10-Gbps Ethernet (IEEE 802.3ae initially) Metro Ethernet, Long Range Ethernet, and CISCO Fast EtherChannel. Ethernet Can be used at access, core, or distribution. Originally designed for a share medium using the CSMA/CD protocol for managing data collisions. In a shared Ethernet stations listen before sending data. (Half-duplex mode) Point-to-point Ethernet support full duplex mode. Transmission rate theoretically double the half-duplex mode. Requires 2 path cabling One of the most significant rules for Ethernet is that the round-trip propagation delay in one collision domain must not exceed the time it takes a sender to transmit 512 bits. (This is 51.2 microseconds for 10-Mbps Ehternet. A single collision domain must be limited in size such that a minimum sized frame (64 bytes) can detect a collision reflecting back from the opposite end while the station is still sending the frame. Prof. Shervin Shirmohammadi CEG 4185 17-4
10-Mbps Coax and UTP Ethernet Scalability Constraints 10Base5 10Base2 10BaseT Topology Bus Bus Star Type of cabling Thick coax Thin coax UTP Maximum cable length (m) Max attachments 500 100 185 30 100 Hub to station 2 Max collision domain (m) Max topology of a collision domain 2,500 Five segments 2,500 Five segments 2,500 Five segments Prof. Shervin Shirmohammadi CEG 4185 17-5
10-Mbps Multimode Fiber-Optic Ethernet Scalability Constraints Prof. Shervin Shirmohammadi CEG 4185 17-6
100 Mbps Ethernet a.k.a. Fast Ethernet Four physical implementations: 100Base-TX: Two pairs of Cat 5 UTP Cabling 100Base-T2: Two pairs of Cat 3 UTP Cabling 100Base-T4: Four pairs Cat 3 UTP Cabling 100Base-FX: Two Multi-mode or single-mode fiber. Follows the same physical constraints as 10BaseT in that the round trip delay cannot exceed the time it takes to transmit a 512 bit frame (5.12 micro seconds). Limiting the distance to 205 meters when using 2 Class II repeaters. Prof. Shervin Shirmohammadi CEG 4185 17-7
100-Mbps Maximum Collision Domains Class I Repeater: latency of 0.7 microseconds or less Class II Repeater: latency of 0.46 microseconds or less Prof. Shervin Shirmohammadi CEG 4185 17-8
Gigabit Ethernet Gigabit Ethernet is mostly used in the core part of the network where flows tend to be aggregated. Four types: 1000Base-SX: short wavelength specification 1000Base-LX: long wavelength specification 1000Base-CX: telecommunications closet 1000Base-T: intended fro Category 5 UTP cabling Prof. Shervin Shirmohammadi CEG 4185 17-9
10-Gbps Ethernet Slowly taking off in terms of deployment. 10-Gigabit Ethernet is used in the core part of the network. * Up to 40 Km, depending on link attenuation. Prof. Shervin Shirmohammadi CEG 4185 17-10
Token Ring Defined in IEEE 802.5. More susceptible to problems than Ethernet. Runs in half or full-duplex with speeds that include 4-Mbps to 16 Mbps. The IEEE 8022.5 MAC Layer specifies timers that are used to monitor the state of the ring. When a station sends a frame into the ring it must see the frame return within the value of TRR=4 ms. This determines the length of the ring. Not a good choice for new network design but there are many options for upgrading which include shared and switched token ring, half and full-duplex, UTP support, and new initiatives on 100 Mbps and Gigabit Token Ring. Prof. Shervin Shirmohammadi CEG 4185 17-11
FDDI Fiber Distributed Data Interface (FDDI) is the ANSI / ISO standard for 100 Mbps transmission of data on fiber-optic cabling. It also can run on copper as specified by the CDDI specification of FDDI. Uses a timed token-rotation protocol similar to token ring concept for media access control. Has good long distance characteristics and therefore only used where distance warrants it due to the fact that it is more expensive, more complex, and harder to install than Fast Ethernet. Topology Max Cable Length Maximum number of attachments per segment Maximum network size Multi-mode Fiber Dual ring, tree of concentrators,.. 2 km between stations 1,000 or 500 dual attached stations 200 km Single-Mode Fiber Dual ring, tree of concentrators,.. 40 km between stations 1,000 or 500 dual attached stations 200 km UTP Star 100 meters from hub to station 2 200 km Prof. Shervin Shirmohammadi CEG 4185 17-12
ATM Asynchronous Transfer Mode (ATM) is a a non-broadcast multiple-access (NBMA) connection-oriented, circuit-switched technology. ATM tends to be more complex and more expensive than Fast Ethernet. It is a good choice though for applications that have high QoS performance and multimedia requirements (video conferencing, medical imaging, distance learning, etc ) End to end QoS is only guaranteed when ATM is deployed over the whole network. Can be used for backbone traffic, but as Ethernet has been scaling upwards and managing to support QoS performance, ATM is not as popular as once the case. Supports more bandwidth than Ethernet (OC-192 [10 Gbps] is currently supported with ATM), but Ethernet is catching up. ATM overhead slightly higher than Ethernet. A 5-byte header is required for each 53-byte ATM cell = 9.4% overhead. This can go up to 24.5% if ATM adaptation modules are used. ATM is also good for WANs. Prof. Shervin Shirmohammadi CEG 4185 17-13
LANE and MPOA LAN Emulation: most LAN protocols are broadcast-multiple-access, connectionless, packet-switching technologies. ATM is nearly the anti-thesis of Ethernet LAN. This has led to the development of LANE for emulating Ethernet and Token ring on an ATM network. Multiprotocol over ATM (MPOA) standardizes the forwarding of Layer-3 packets between subnets in an ATM LANE environment. It allows a subnet to be bridged across an ATM/LAN boundary, but requires that inter-subnet traffic be forwarded through routers. MPOA is an enhancement to LANE for efficient and direct transfer of intersubnet unicast data. Network Layer Logical Link Layer LAN Emulation Layer ATM Adaptation Layer ATM Physical Layer LUNI ATM Network Network Layer Logical Link Layer LAN Emulation Layer ATM Adaptation Layer ATM Physical Layer Figure 9.3 Layered Architecture of LAN Emulation Prof. Shervin Shirmohammadi CEG 4185 17-14
Remote Access Technologies Point to Point Protocol (PPP): IETF standard for a data link layer protocol for transporting various network layer PDUs across erial, point to point links. Typically used for dial-up lines, leased lines, ISDN, etc. Integrated Services Digital Network (ISDN), typically offered by regional telephone carriers; works over telephone lines. Cabel Modem: operates over coax cable that is used by cable TV (CATV) typically faster than ISDN (due to higher speed supported by coax) depending on how many users share the coax. 1 cable offers 25 to 50 Mbps downstream and 2 to 3 Mbps upstream, shared by a number of users. Digital Subscriber Line (DSL): high-speed access over telephone lines 1 Asymmetric DSL (ADSL) line offers 1.5 to 9 Mbps downstream and about 640 Kbps upstream Prof. Shervin Shirmohammadi CEG 4185 17-15
WAN Technologies Synchronous Optical Network (SONET) a physical layer specification for high speed synchronous transmission of packets over fiber optics. Proposed by Bellcore in the 80s. Used in North America. Synchronous Digital Hierarchy (SDH) is similar to SONET in terms of functionality, and is used in the rest of the world. Frame Relay: high-performance physical and datalink layer protocol, introduced in early 90s. Typically operates from 64 Kbps to 1.544 Mbps. ATM can also support WANs at very high speed (up to OC-192). Prof. Shervin Shirmohammadi CEG 4185 17-16
WAN Speed Hierarchy North America (DS: digital stream) Europe SDH (STS: Synchronous Transport Signal) Prof. Shervin Shirmohammadi CEG 4185 17-17
Wireless LANs A wireless LAN uses wireless transmission medium Used to have problems with high prices, low data rates, occupational safety concerns, and licensing requirements Today, problems have been addressed for the most part and hence ppopularity of wireless LANs has grown rapidly Advantages: Saves installation of LAN cabling Eases relocation and other modifications to network structure Applications: Cross-building Interconnect: Connect LANs in nearby buildings, Pointto-point wireless link Nomadic Access: Link between LAN hub and mobile data terminal Laptop or notepad computer Also useful in extended environment such as campus or cluster of buildings where users move around with portable computers Prof. Shervin Shirmohammadi CEG 4185 17-18
IEEE 802.11 MAC protocol and physical medium specification for wireless LANs Smallest Building Block (BSS) is basic service set: Number of stations, Same MAC protocol, Competing for access to same shared wireless medium May be isolated or connect to backbone Distribution System (DS) through Access Point (AP) MAC protocol may be distributed or controlled by central coordination function in AP BSS generally corresponds to cell DS can be switch, wired network, or wireless network BSS Configuration: Simple: each station belongs to single BSS, within range of only other stations in the same BSS Overlapped: can have two or more BSSs overlap, so station could participate in more than one BSS. Dynamic: association between station and BSS dynamic, so stations may turn off, come within range, and go out of range Extended Service Set (ESS): Two or more BSS interconnected by DS: appears as a single logical LAN to LLC sub layer. Prof. Shervin Shirmohammadi CEG 4185 17-19
IEEE 802.11 Architecture Prof. Shervin Shirmohammadi CEG 4185 17-20
Services Service Provider Category Association Distribution system MSDU delivery Authentication Station LAN access and security Deauthentication Station LAN access and security Dissassociation Distribution system MSDU delivery Distribution Distribution system MSDU delivery Integration Distribution system MSDU delivery MSDU delivery Station MSDU delivery Privacy Station LAN access and security Reassocation Distribution system MSDU delivery MSDU: MAC Service Data Unit Prof. Shervin Shirmohammadi CEG 4185 17-21
IEEE 802.11 Physical Layer First part in 1997 IEEE 802.11 Includes MAC layer and three physical layer specifications Two in 2.4-GHz band and one infrared All operating at 1 and 2 Mbps Two additional parts in 1999 IEEE 802.11a 5-GHz band up to 54 Mbps Data rates: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps IEEE 802.11b 2.4-GHz band at 5.5 and 11 Mbps In 2005 IEEE 802.11g extends IEEE 802.11b to 108 Mbps Most recent in 2007: IEEE 802.11n supports up to 540 Mbps Prof. Shervin Shirmohammadi CEG 4185 17-22
Other Wireless Networks Wireless Personal Area Network (WPAN): IEEE 802.15 Used mostly for wireless communications among portable digital devices including laptops, cell phones, peripheral devices, and consumer electronics. Not used for LANs or WANs Bluetooth, for example. Broadband Wireless Access: IEEE 802.16 Used for city-wide wireless connectivity A form of MAN WiMax (Worldwide Interoperability for Microwave Access), for example. Comparison: Parameter 802.16 802.11 802.15 Frequency 2-11 GHz 2.4 GHz varies Range ~ 50 Km ~ 100 m ~ 10 m Rate Nodes 70 Mbps Thousands 11 Mbps - 55 Mbps Dozens 20Kbps - 55 Mbps Dozens Prof. Shervin Shirmohammadi CEG 4185 17-23