# Networking Essentials Notes Section 3
Section Titles: Network Architectures | Ethernet Topologies | 10 Mbps Topologies 100 Mbps Topologies | Token Ring | AppleTalk | ARCnet
Network Architectures
#### Ethernet Baseband signaling. Linear or star-bus topology. Usually transmits at 10 Mbps with 100 Mbps possible. Uses CSMA/CD for traffic regulation. IEEE specification 802.3. Uses thicknet, thinnet or UTP cabling Media is passive => it draws power from the computer #### Ethernet Frames Ethernet breaks data into frames. A frame can be from 64 to 1,518 bytes long in total. The ethernet frame itself takes up 18 bytes, so the actual data can be from 46 to 1,500 bytes. Preamble: marks the start of a frame. Destination and Source: addressing information. Type: Identifies network layer protocol. CRC: error checking data.
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Ethernet Topologies
10 Mbps Topologies
10Base-T (10 = 10 Mbps; Base= Baseband; T = Twisted Pair) 10 Mbps, baseband over UTP. Usually wired in a physical star with a hub or multiport repeater. Internally it uses a bus signaling system like other Ethernet configurations Maximum segment length 100 meters (328 feet). Minimum between computers 2.5 meters (8 feet). 1024 nodes maximum on the LAN Category 3, 4 or 5 UTP. RJ-45 connectors, 4 twisted pair. Coaxial or Fiber backbone for larger LAN's 10BaseT UTP NETWORK LAYOUT Limitations maximum segment length of 100 Meters Hub to Hub or repeater to repeater links limited to 100 Meters Rules star topology 4 repeater/5 segment rule of 10Base5 is retained only two nodes per segment are allowed Cabling RJ-45 Connectors Category 3 UTP minimum, preferably Category 5 10Base-2 (10 = 10 Mbps; Base= Baseband; 2 = 2x 100 meters) 10 Mbps, baseband over thinnet. Uses bus topology. Maximum segment length 185 meters (607 feet). Minimum between computers 0.5 meters (20 inches). Maximum of 30 computers per segment. Obeys 5-4-3 rule: Five segments, joined by four repeaters, 3 populated giving a total length of 925 meters (3035 feet). Physical Bus Cable Limits 10Base2 THIN ETHERNET NETWORK LAYOUT Limitations maximum number of trunk segments = 5 maximum trunk segment length = 607 feet (185 meters) maximum network trunk cable = 3035 feet (925 meters) maximum number of stations on a trunk segment = 30 minimum distance between T connectors = 1.5 feet (0.5 meters) Rules each end of the trunk segment is terminated in 50-ohms one of the terminators is grounded connector splices are kept to a minimum Cabling BNC-T type connectors RG58-AU 50-ohm cable, 0.2" Note that you can't mix RG58 /AU and RG58 /U cable on the same network. 10Base-5 (10 = 10 Mbps; Base= Baseband; 5 = 5 x 100 meters) 10 Mbps, baseband over thicknet. Also called Standard Ethernet Designed to support a backbone for a large department or building. Transceivers attach to the thicknet cable and the cable AUI connector plugs into a repeater . The branching segments of thinnet plug into the repeater and connect to the computers on the network. Uses bus topology. Maximum segment length 500 meters. Minimum between transceivers 2.5 meters (8 feet) 100 computers per segment, 300 per network. Obeys 5-4-3 rule: maximum distance can be extended to 2500 meters (8200 ft) using 4 repeaters and 3 populated segments. Transceiver is attached to main segment with a vampire tap. DIX or AUI connector is used to attach the transceiver to the network card. Maximum computer to transceiver distance is 50 meters. This distance is not included in the 5-4-3 calculation. 10Base-5 Summary
Maximum segment length | 500m (1640 ft) Typically used as backbone to connect Thinnet-based network.
Speed | 10 Mbps
Maximum taps | 100
Maximum segments | 5
Maximum repeaters | 4
Maximum segment with nodes | 3 Due to attenuation, only 3 of 5 segments can actually contain network connection. Other 2 segments can be used to connect the network over long distance.
Maximum nodes per segment | 100
Maximum nodes for network | 300
Minimum distance between nodes | 2.5m (8 ft)
Maximum overall length with repeaters | 2.5 km
Maximum AUI drop cable length | 50m
10Base-F? (10 = 10 Mbps; Base= Baseband; FL =fibre optic) Allows long cable runs between repeaters, like between buildings Maximum segment length 2000 meters. 10BaseFL - Used for linking computers in a LAN environment. 10BaseFP - Used for linking computers with passive hubs from maximum cable distance up to 500m 10BaseFB - Used as a backbone between hubs. Baseband signal over a fiber-optic cable. Need concentrator (fiber-optic hub) ® Star wired (star topology) . Either active or passive Long distance. Very expensive. Difficult to install. Maximum segment length - 2000m Maximum segments- 1024 Maximum segment with nodes- 1024 Maximum nodes per segment- 1 Maximum nodes per network- 1024 Maximum hubs in a chain- 4
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100 Mbps Topologies
100VG-AnyLAN (IEEE 802.12) 100 Mbps data rate. Star topology over Category 3, 4 and 5 UTP. Uses demand priority access. Combines element of traditional Ethernet and Token Ring and supports Ethernet and token ring packets. Faster than Ethernet Demand priority access method => two priority levels, low and high Intelligent hubs can filter individually addressed frames for enhanced privacy. Expensive Uses RJ-45. Cable - require 4 pairs wire Categories 3, 4 UTP- 100m Category 5 UTP - 150m Fiber-optic- 2000m Uses star topology and defines how child hub can be connected to a parent hub to extend the network. Minimum length between nodes - 2.5m Maximum segments- 1024 Maximum nodes per segment- 1 Maximum nodes for network- 1024 100BaseT? (Fast Ethernet) Uses CSMA/CD on a star-wired bus. There are 3 specifications: 100BaseT4: Uses pair category 3, 4 or 5 UTP. 100BaseTX: Uses 2-pair category 5 UTP or STP. 100BaseFX: Uses 2-strand fiber-optic.
Ethernet Frame types
Ethernet 802.2 - NetWare 3.12 and 4.x - IEEE 802.3 standard compliance. Includes field in Ethernet 802.3 and LLC (Logical Link Control) Ethernet 802.3 - NetWare 3.11 and before Includes CRC Ethernet SNAP (SubNetwork Address Protocol) - AppleTalk Ethernet II - TCP/IP #### Segmentation Can be performed with bridges or routers. Reduces traffic on network segments to increase performance.
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Token Ring
IEEE 802.5 specification. Star wired ring topology (logical ring) Uses token passing access method. Can have higher transmission speeds than Ethernet It has larger frames than Ethernet => more can get transferred over the wire in any given time. Uses IBM STP Types 1, 2 and 3 cabling. (Can be UTP) Transmits at 4 and 16 Mbps. (16 Mbps cards will slow down to 4 Mbps if put on that kind of network, but the 4 Mbps cards can't speed up. Baseband transmission Data travels in one direction only Each computer acts as a unidirectional repeater Deterministic method of cable access. Computers cannot use the cable unless they have the token. Therefore, computers can't force their way onto the network like CSMA/CD (Ethernet) First computer online is assigned to monitor network activity. #### Token Ring Components Multistation Access Units (MAU's) Multistation Access Units (MSAU's) Smart Multistation Access Units (SMAU's) Computers attach directly to the MSAU in a physical star to form a logical ring. Each MSAU has 10 connection ports ==> can support 8 clients with 2 ports for ring in and ring out. Each ring can have as many as 33 MSAU's 70 computers with UTP 260 computers with STP. Up to 12 MSAU's can connect to each other The MSAU can sense if a computer is down and then disconnect it from the ring => built-in fault tolerance Cabling Most token ring systems use IBM type 3 cabling. STP or UTP to a hub, IBM type 1,2,3 cable Type 1: 101m from MSAU to PC STP: 100m from MSAU to PC UTP: 45m from MSAU to PC Type 3: 150 feet from MSAU to PC Token ring networks are well suited to fiber optic cable: data travels in only one direction in it. Here are some limitations of Token Ring: The maximum number of workstations is 260 on Type 1 or fiber optic cable at 16 Mbps. The maximum number of workstations is 72 on Type 3 cable at 4 Mbps. The distance between MSAUs (Multistation Access Units) is 100 meters (Type 1 cabling) to 45 meters (Type 2 cabling). Each ring can have up to 33 MSAUs. Maximum distance of the ring is 4 kilometers with fiber optic cable. Token Ring and Ethernet Comparison Token Ring can have higher transmission speeds than Ethernet supports more computers on a single segment (up to 260) more expensive than Ethernet harder to install than Ethernet is more fault tolerant because of the beaconing process
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AppleTalk
local talk CSMA/CA access method 3 things happen when devices attached device assigns itself an address randomly device broadcasts the address to see if it's used if not, the device will use it the next time it's online again bus or tree STP max. 32 devices Apple share file server on an AppleTalk network divided into zones EtherTalk 802.3 allows protocols to run on ethernet coaxial cable TokenTalk 802.5 allows Macintosh to connect to token ring network
ARCnet
IEEE 802.4 specification - almost Cable Uses RG-62 (93 ohm) (most common)or RG-59 (75ohm) coaxial cable. Can also use UTP. Uses token passing on a star-bus topology. Token moves from computer to computer in numerical order. Transmits at 2.5 Mbps. ArcNet plus - 20 Mbps connected by cable to hub 93 ohm RG-62 A/U - 610m max., star 93 ohm RG-62 A/U - 305m max., bus <= notice less distance on hub RJ-11, RJ-45 UTP - max. 244m on star or bus Hubs can be Passive => merely relay signal Active => regenerate and relay signal Smart => add diagnostic features, such as reconfiguration detection Here are some limitations of ARCNet: Bus segment length for coaxial cable is a maximum of 1000 feet, with a limit of 8 workstations per coaxial segment. Bus segment length for twisted pair is a maximum of 400 feet, with a limit of 10 workstations per twisted-pair segment. There is a maximum of 255 workstations per network. Workstations can be located up to 600 feet from the active hub. The maximum distance from passive hubs to active hubs is 100 feet; the maximum distance between two active hubs is 2000 feet. The maximum distance allowed between workstations is 20,000 feet. There can be no more than four workstations on a passive hub, no more than 100 feet from a hub. Passive hubs cannot be connected to other passive hubs.
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Comments and suggestions? E-mail me at grantwil@sk.sympatico.ca
Last Updated: Wednesday, March 10, 1999 | Grant Wilson, Tisdale, SK. Canada