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Computer Network
Module 6
| Question | Answer |
|---|---|
| Access Method | A Network's method of controlling how nodes access the communications channel. |
| Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) | A network access method useed on 802.11 wireless networks. Before a node begins to dend data it checks the medium. If it detects no transmission activity, it waits a brief, random amount of time, and then sends its transmission. |
| Carrier Sence Multiple Access with Collision Detection (CSMA/CD) | A network access method specified for use by IEEE 802.3 (Ethernet) networks. In CSMA/CD, each node waits its turn before transmitting data to avoid interfering with other nodes' transmissions. |
| Circuit Swtiching | A type of switching in which a connection is established between two network nodes before they begin transmitting data. |
| Message Switching | A type of switching in which a connection is established between two devices in the connection path; one device transfers data to the second device, then breaks the connection. |
| Packet Switching | A type of switching in which data is broken into packets before it is transported. Packets can travel any path on the network to their destination, because each packet contains a destination address and sequencing information |
| Jamming | A part of CSMA/CD in which, upon detecting a collision, a station issues a special 32-bit sequence to indicate to all nodes on an Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty. |
| LAN Emulation (LANE) | A method for transporting token rign or Ethernet frames over ATM networks. Encapsulates incoming Ethernet or token ring frames, then converts them into ATM cells for transmission over an ATM Network. |
| Simple Topologies Two main categories: | Physical and Logical |
| Physical Topologies | is concerned with the physical layout or pattern |
| Logical Topologies | is concerned with how signals travel from one point to another on the network |
| Identify the three fundamental shapes of physical topologies. | Bus, ring, and star |
| How many communication channels does a simple physical bus have? | One |
| Which is a combination of topologies? | Extended Star and Hybrid |
| Which physical topology requires the most cabling? | Star |
| Logical Topologies | • Refers to the way nodes transmit data • Logical topology may or may not match physical |
| Identify common logical topologies. | Bus and ring |
| Serial Backbone | oDevices connected together by a single cable oAllows for simple expansion oNot practical for larger networks |
| Distributed Backbone | oDevices connected together by a series of devices/cables that reveal a hierarchy oEasy to expand and implement |
| Collapsed Backbone | oDevices connected to a single connection point oSwitch or router must act as the central device |
| Parallel Backbone | oSimilar to collapsed backbone oFeatures multiple connections to the central device |
| Mesh Backbones | oTopology that uses more than one backbone type in its design |
| Switching Methods | •Determines how connections are established between network nodes |
| Circuit Switching | oBandwidth is dedicated as long as the connection is established oMay be many intermediate points along the way from source to destination |
| Message Switching | Connections made only between each intermediate point along the way |
| Packet Switching | oData is broken into packets and sent in smaller units oPackets can arrive at the destination in a different order than transmitted oPackets may have taken a different path during the trip |
| Multiprotocol Label Switching(MPLS) | oIntegrates Layer 2 information into Layer 3 within a particular network segment oSimplifies and improves IP-packet exchange (Often used in VoIP/Video segments) |
| The switching method used by Ethernet is: | Packet Switching |
| Ethernet | •One of the oldest network LAN technologies •Shared medium where collisions and jamming take place |
| Many implementations with a high-level of compatibility | 10Base-2 and 10Base-5 >> 10Base-T >> 100Base-T >> 1000Base-T >> 10GBase-T |
| Identify the access method used by all forms of Ethernet. | Carrier Sends Multiple Access / Collision Dectection (CSMA/CD) |
| Above what percentage is the collision rate deemed excessive? | Greater than 5% |
| Voice Grade Ethernet | oDemand priority access method so certain package get thruoNot common implementations of Ethernet oRequire an intelligent hub that can manage traffic |
| Modern Ethernet Networks | oSwitched more often than shared due to lower prices of network components oTechnologies are advancing quickly, Gigabit Ethernet now a reality oEthernet technologies are quickly becoming the choice for backbone connections |
| Traditional Ethernet LANs were called | shared Ethernet |
| Contemporary technologies uses | star physical topology and a bus logical topology |
| Twisted-pair cabling maximum segment length | 100 meters |
| 10Base-T (802.3) | 10Mbps throughput, Baseband transmission, twisted-pair cabling. |
| 10Base-T (802.3)uses two of the four wire pairs of | CAT3 or higher UTP |
| 10Base-T (802.3)follows this rule with repeaters | 5-4-3 |
| 10Base-T (802.3)distance limitation with repeaters | 500 meters |
| 100Base-T (802.3u) | 100Mbps throughput, baseband transmission, twisted-pair cabling. |
| 100Base-T uses two of the four wire pairs of | (802.3u)- CAT3 or higher UTP |
| 100Base-T (802.3u)distance limitation with repeaters | 300 meters |
| Identify the maximum number of allowed 100BASE-T network segments. | 3 segments with 2 hubs |
| 1000Base-T (802.3ab) | 1000mbps throughput, baseband transmission, twisted-pair cabling |
| 1000Base-T (802.3ab)uses all four wire pairs of | CAT5 or higher UTP |
| 1000Base-T (802.3ab)follows the rule | 2-1 |
| What is the maximum distance between 1000Base-T nodes using a repeater? | 200 meters |
| 10GBase-T (802.3an) | 10Gbps throughput, baseband transmission, multimode fiber (min of two strands) |
| 10GBase-T (802.3an)Uses all four wire pairs of | CAT6 or 7 UTP |
| Cooper Based Ethernet Standards | 10Base-T, 100Base-T, 1000Base-T, and 10GBase-T |
| Fiber-based Ethernet Standards | 100Base-FX, 1000Base-LX, 1000Base-SX |
| 100Base-FX (802.3u) | o100Mbps throughput, Baseband transmission, multimode fiber (min of two strands) oRuns in half or full duplex modes oCoexists with 100Base-T copper-based networks very well |
| 100Base-FX (802.3u) also called | Fast Ethernet |
| 1000Base-LX (802.3z) (LX – long wavelengths) | o1000Mbps throughput, Baseband transmission, multimode or single-mode fiber oMultimode fiber reaches 550M per segment and allows one repeater oSingle-mode fiber reaches 5000M per segment and allows one repeater |
| 1000Base-SX (SX – short wavelengths) | o1000Mbps throughput, Baseband transmission, multimode fiber only oSegment length is dependent on fiber diameter and modal bandwidth |
| What is the relationship between modal bandwidth and reliable signal carrying over fiber? | The higher the modal bandwidth, the longer a multimode fiber can carry a signal reliably |
| Four types of Ethernet Frames | Ethernet_802.2, Ethernet_802.3, Ethernet_II & Ethernet_SNAP |
| Which Ethernet Frame type is most used today? | Ethernet_II |
| Frame Fields | oMany common fields oAll frames begin with a preamble (Preamble does not count toward frame size) |
| Ethernet frames contain a | 14-byte header (Destination address(6) + Source address(6) + ethernet type(2) |
| Ethernet frame sizes: | Minimum – 64B, Maximum – 1518B |
| What type of address occupies the source field in an Ethernet frame? | MAC Address |
| Is it more efficient to support one or two Ethernet frame types? | One |
| PoE (Power over Ethernet) | oMethod of supplying power over Ethernet oFully compatible with existing 802.3 installations |
| Identify the type of nodes that may benefit from the IEEE 802.3af standard. | Something far away from the source. A wireless access point at an outdoor theater, a telephone used to receive digitized voice signals an internet gaming station in the center of a mall or a critical router at the core of a networks backbone |
| What type of cabling (media) is required for PoE? | Cat 5 or better copper cable |
| 100Base-T (802.3u)follows the rule | 3-2 |
| Rule 5-4-3 means | Between two communicating nodes, the network cannot contain more than 5 network segments connected by 4 repeating devices, and no more than 3 of the segments may be populated (at least 2 must be unpopulated) |
| Ethernet preamble frame is | 8 bytes |
| Destination address frame is | 6 bytes |
| Source address frame is | 6 bytes |
| Ethernet type frame is | 2 bytes |
| Frame check sequence frame is | 4 bytes |
| Padding | The bytes added to the data (or information) portion of an Ethernet frame to ensure this field is at least 46 bytes in size. Padding has no effect on the data carried by the frame. |
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