Ethernet Concepts

What is a characteristic of UTP cabling? A: Cancellation B: Cladding C: immunity to electrical hazards D: Woven copper braid or metallic foil

A: Cancellation Topic 4.4.0 - Cladding and immunization from electrical hazards are characteristics for fiber-optic cabling. A woven copper braid or metallic foil is used as a shield for the inner coaxial cable conductor. Cancellation is a property of UTP cabling where two wires are located adjacent to one another so each magnetic field cancels out the adjacent magnetic field.

MAC Accessing the Media

As shown in the figure, the IEEE 802.3 MAC sublayer includes the specifications for different Ethernet communications standards over various types of media including copper and fiber. I.E. some communication standards -IEEE 802.u - Fast Ethernet -IEEE 802.3z - Gigabit Ethernet over Fiber -IEEE 802.3ab - Gigabit Ethernet over Copper -IEEE 802.3ae - 10 Gigabit Ethernet over Fiber etc........

RJ-45 Connector

As shown in the figure, the RJ-45 connector is the male component, crimped at the end of the cable.

Which statement is true about MAC addresses? A: MAC addresses are implemented by software B: A NIC only needs a MAC address if connected to a WAN C: The first 3 bytes are used by the vendor OUI D: The ISO is responsible for MAC address regulations

C: The first 3 bytes are used by the vendor OUI Topic 7.2.0 - A MAC address is composed of 6 bytes. The first 3 bytes are used for vendor identification and the last 3 bytes must be assigned a unique value within the same OUI. MAC addresses are implemented in hardware. A NIC needs a MAC address to communicate over the LAN. The IEEE regulates the MAC addresses.

What is the limitations of copper media?

Distance, and signal interference

What is a topology of a network?

It is the arrangement, or the relationship, of the network devices and the interconnections between them.

MAC roll in receiving packets.

NIC will only accept frames if the receiving frames' destination MAC address matches its own MAC address. -Ethernet NICs will also accept frames if the destination MAC address is a broadcast or a multicast group of which the host is a member.

What is the process that a source host uses to determine the destination MAC address associated with an IPv6 address?

Neighbor Discovery (ND)

Which part of an Ethernet Frame notifies the receiver to get ready for a new frame?

Preamble

What does the MAC layer do?

controls the NIC and other hardware that is responsible for sending and receiving data on the wired or wireless LAN/MAN medium. -The MAC sublayer also provides media access control, allowing multiple devices to communicate over a shared (half-duplex) medium. Full-duplex communications do not require access control.

What is a multi access nework?

is a network that can have two or more end devices attempting to the network simultaneously. -Some multiaccess networks require rules to govern how devices share the physical media. There are two basic access control methods for shared media: 1. Contention-based access 2. Controlled access

Signaling

- The way that bits are represented is called the signaling method. -The physical layer standards must define what type of signal represents a "1" and what type of signal represents a "0". This can be as simple as a change in the level of an electrical signal or optical pulse. Copper - uses Electrical signals over copper wire Fiber Optic Cable - uses light pulses Wireless media - use microwaves

Cut-through switching (CISCO ONLY)

- This frame forwarding method forwards the frame before it is entirely received. At a minimum, the destination address of the frame must be read before the frame can be forwarded. -The switch buffers just enough of the frame to read the destination MAC address so that it can determine to which port it should forward out the data. -The destination MAC address is located in the first 6 bytes of the frame following the preamble. -The switch looks up the destination MAC address in its switching table, determines the outgoing interface port, and forwards the frame onto its destination through the designated switch port. -The switch does not perform any error checking on the frame.

Store-and-forward switching (CISCO ONLY)

- This frame forwarding method receives the entire frame and computes the CRC. CRC uses a mathematical formula, based on the number of bits (1s) in the frame, to determine whether the received frame has an error. If the CRC is valid, the switch looks up the destination address, which determines the outgoing interface. Then the frame is forwarded out of the correct port. -When an error is detected in a frame, the switch discards the frame. -is required for quality of service (QoS) analysis on converged networks where frame classification for traffic prioritization is necessary.

What is a MAN

- metropolitan area network - spans across city or town - larger than a LAN, uses fiber for backbone

What are the bandwidths Ethernet supports?

-10 Mbps -100 Mbps -1000 Mbps (1 Gbps) -10,000 Mbps (10 Gbps) -40,000 Mbps (40 Gbps) -100,000 Mbps (100 Gbps)

MAC Address Assigning

-All MAC addresses must be unique to the Ethernet device or Ethernet interface. -All vendors that sell Thernet devices must register with the IEEE to obtain a unique 6 hexadecimal (24-bit or 3 byte) code called a Organizationally Unique Identifier (OUI) -First 6 Hexadecimal characters are the OUI -Last 6 Hexadecimal characters are the vendor code - which identifies the specific device IE: OUI: 00-60-2F (Cisco) Vendor ID: 3A-07-B MAC Address: 00-60-2F-3A-07-BC

Multicast MAC Address

-An Ethernet multicast frame is received and processed by a group of devices on the Ethernet LAN that belong to the same multicast group. The features of an Ethernet multicast are as follows: -There is a destination MAC address of 01-00-5E when the encapsulated data is an IPv4 multicast packet and a destination MAC address of 33-33 when the encapsulated data is an IPv6 multicast packet. -There are other reserved multicast destination MAC addresses for when the encapsulated data is not IP, such as Spanning Tree Protocol (STP) and Link Layer Discovery Protocol (LLDP). -It is flooded out all Ethernet switch ports except the incoming port, unless the switch is configured for multicast snooping. -It is not forwarded by a router, unless the router is configured to route multicast packets. ----------------- -If the encapsulated data is an IP multicast packet, the devices that belong to a multicast group are assigned a multicast group IP address. -The range of IPv4 multicast addresses is 224.0.0.0 to 239.255.255.255. -The range of IPv6 multicast addresses begins with ff00::/8. -Because multicast addresses represent a group of addresses (sometimes called a host group), they can only be used as the destination of a packet. -As with the unicast and broadcast addresses, the multicast IP address requires a corresponding multicast MAC address to deliver frames on a local network. -The multicast MAC address is associated with, and uses addressing information from, the IPv4 or IPv6 multicast address.

Fiber Patch Cords

-Are required for interconnecting infrastructure devices. -Yellow Jacket --> Single Mode Fiber cables -Orange (or aqua) --> Multimode Fiber Cables

Physical Components

-Are the electronic hardware devices, media, and other connectors that transmit the signals that represent the bits. -Hardware components such as NICs, interfaces and connectors, cable materials, and cable designs are all specified in standards with the physical layer.

Auto-MDIX

-Automatic Medium-Dependent Interface Crossover -When enabled, the switch automatically detects the type of cable attached to the port and configures the interfaces accordingly. -Therefore, you can use either a crossover or a straight-through cable for connections to a copper 10/100/1000 port on the switch, regardless of the type of device on the other end of the connection. Command: mdix auto - enables mdix -The auto-MDIX feature is enabled by default on switches running Cisco IOS Release 12.2(18)SE or later. -DON'T ever rely on Auto-MDIX

Full-duplex communication

-Both devices can simultaneously transmit and receive on the shared media. -The data link layer assumes that the media is available for transmission for both nodes at any time. -Ethernet switches operate in full-duplex mode by default, but they can operate in half-duplex if connecting to a device such as an Ethernet hub.

Half-duplex communication

-Both devices can transmit and receive on the media but cannot do so simultaneously. -Half-duplex allows only one device to send or receive at a time on the shared medium. -WLANs and legacy bus topologies with Ethernet hubs use the half-duplex mode.

Contention-Based Access - CSMA/CD

-Carrier sense multiple access/Collision Detection -These networks operate in half-duplex mode, meaning only one device can send or receive at a time. -This requires a process to govern when a device can send and what happens when multiple devices send at the same time. -If two devices transmit at the same time, a collision will occur. -For legacy Ethernet LANs, both devices will detect the collision on the network. --This is the collision detection (CD) portion of CSMA/CD -The NIC compares data transmitted with data received, or by recognizing that the signal amplitude is higher than normal on the media. The data sent by both devices will be corrupted and will need to be resent. -When a hub broadcasts the frame from one PC to all others the receiving NICs will determine if the frame is for them if not it will ignore the frame. -provides a back-off algorithm for retransmission.

Latency

-Refers to the amount of time, including delays, for data to travel from one given point to another. -it will only take one segment in the path with low throughput to create a bottleneck in the throughput of the entire network.

Cabling Different Device Restrictions

-Connections between devices once required the use of either a crossover or straight-through cable. -The type of cable required depended on the type of interconnecting devices. For example, the figure identifies the correct cable type required to interconnect switch-to-switch, switch-to-router, switch-to-host, or router-to-host devices. A crossover cable is used when connecting like devices, and a straight-through cable is used for connecting unlike devices. Note: A direct connection between a router and a host requires a cross-over connection.

How is data transmitted on copper cables? And what is Attenuation?

-Data is encoded and transferred as electrical impulses. -Attenuation is the deterioration of the signal as it travels through the medium. -To prevent attenuation copper media must follow strict distance limitations specified by guiding standards.

Layer 2 Addresses

-Data link layer addressing is contained within the frame header and specifies the frame destination node on the local network. -It is typically at the beginning of the frame, so the NIC can quickly determine if it matches its own Layer 2 address before accepting the rest of the frame. The frame header may also contain the source address of the frame. -Layer 2 addresses are only used to connect devices within the same shared media, on the same IP network. What Routers Do: -Using the IP address, the router can determine the network location of the destination device and the best path to reach it. -When it knows where to forward the packet, the router then creates a new frame for the packet, and the new frame is sent on to the next network segment toward its final destination.

What is a trailer used for in a frame?

-Data link protocols add a trailer to the end of each frame. -In a process called error detection, the trailer determines if the framed arrived without error. -It places a logical or mathematical summary of the bits that comprise the frame in the trailer. -The data link layer adds error detection because the signals on the media could be subject to interference, distortion, or loss that would substantially change the bit values that those signals represent.

Shared memory buffering

-Deposits all frames into a common memory buffer shared by all switch ports and the amount of buffer memory required by a port is dynamically allocated. -The frames in the buffer are dynamically linked to the destination port enabling a packet to be received on one port and then transmitted on another port, without moving it to a different queue. ----- -Shared memory buffering also results in the ability to store larger frames with potentially fewer dropped frames. -This is important with asymmetric switching which allows for different data rates on different ports such as when connecting a server to a 10 Gbps switch port and PCs to 1 Gbps ports.

What are the two main cable types obtained by using specific wiring conventions?

-Different situations may require UTP cables to be wired according to different wiring conventions. This means that the individual wires in the cable have to be connected in different orders to different sets of pins in the RJ-45 connectors. Two Main Types: 1. Ethernet Straight-through - The most common type of networking cable. It is commonly used to interconnect a host to a switch and a switch to a router. 2. Ethernet Crossover - A cable used to interconnect similar devices. For example, to connect a switch to a switch, a host to a host, or a router to a router. However, crossover cables are now considered legacy as NICs use medium-dependent interface crossover (auto-MDIX) to automatically detect the cable type and make the internal connection. -------- Another type of cable is a rollover cable, which is Cisco proprietary. It is used to connect a workstation to a router or switch console port.

MAC Address Format

-Ethernet MAC address is 48-bits long -OR 6 Bytes long -It is 12 hexadecimal digits long -Each hexadecimal Number or Digit is 4 bits long

Fast-forward switching

-Fast-forward switching offers the lowest level of latency. -Fast-forward switching immediately forwards a packet after reading the destination address. -Because fast-forward switching starts forwarding before the entire packet has been received, there may be times when packets are relayed with errors. -Faulty frames occur infrequently, and the destination NIC discards the faulty packet upon receipt. -In fast-forward mode, latency is measured from the first bit received to the first bit transmitted. -Fast-forward switching is the typical cut-through method of switching.

What are Fiber Optic connectors and what are the main differences of the Fiber optic connectors?

-Fiber optic connectors are what terminate the end of an optical fiber. The main differences in connectors: 1. Dimensions 2. Coupling -Businesses decide on the types of connectors that will be used, based on their equipment. -Some switches and routers have ports that support fiber-optic connectors through a small form-factor pluggable (SFP) transceiver. Search the internet for various types of SFPs.

Generic Frame Fields and their definitions

-Frame start and stop indicator flags - Used to identify the beginning and end limits of the frame. -Addressing - Indicates the source and destination nodes on the media -Type - Identifies the Layer 3 protocol in the data field. - Control - Identifies special flow control services such as quality of service (QoS) -- QoS gives fowarding priority to certain types of messages. -- for example VoIP frames normaly receive priority because they are sensitive to delay. - Data - Contains the frame payload (i.e., packet header, segment header, and the data) - Error Detection - Included after the data to form the trailer

Port-based memory buffering

-Frames are stored in queues that are linked to specific incoming and outgoing ports. -A frame is transmitted to the outgoing port only when all the frames ahead in the queue have been successfully transmitted. -It is possible for a single frame to delay the transmission of all the frames in memory because of a busy destination port. -This delay occurs even if the other frames could be transmitted to open destination ports.

What does framing do?

-Framing breaks the stream into decipherable groupings, with control information inserted in the header and trailer as values in different fields. -This format gives the physical signals a structure that are by recognized by nodes and decoded into packets at the destination.

Shielded twisted-pair (STP)

-Provides better noise protection than UTP cabling. -This is more expensive and difficult to install. -STP uses an RJ-45 -- just like UTP -STP combine the techniques to counter EMI and RFI, and wire twisting to counter crosstalk. -STP cables are terminated with special shielded STP data connectors. - if improperly grounded, the shield may act as an antenna and pick up unwanted signals.

Coaxial cable (Coax)

-Gets its name from the fact that there are two conductors that share the same acis. Coax consists of the following: 1. A copper conductor is used to transmit the electronic signals. 2. A layer of flexible plastic insulation surrounds a copper conductor. 3. The insulating material is surrounded in a woven copper braid, or metallic foil, that acts as the second wire in the circuit and as a shield for the inner conductor. This second layer, or shield, also reduces the amount of outside electromagnetic interference. 4. The entire cable is covered with a cable jacket to prevent minor physical damage. -There are different type of connectors used with coax cable. -The Bayonet Neill-Concelman (BNC), N type, and F type are shown in pick.

IEEE 802 LAN/MAN Data Link Sublayers

-IEEE 802 LAN/MAN standards are specific to Ethernet LANs, wireless LANs (WLAN), wireless personal area networks (WPAN) and other types of local and metropolitan area networks. IEEE 802 LAN/MAN data link layer Sublayers: 1. Logical Link Control (LLC) - This IEEE 802.2 sublayer communicates between the networking software at the upper layers and the device hardware at the lower layers. -It places information in the frame that identifies which network layer protocol is being used for the frame. -This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to use the same network interface and media. 2. Media Access Control (MAC) - Implements this sublayer (IEEE 802.3, 802.11, or 802.15) in hardware. -It is responsible for data encapsulation and media access control. -It provides data link layer addressing and it is integrated with various physical layer technologies.

Throughput

-IS the measure of the transfer of bits across the media over a given period of time. -Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations. -Throughput is usually lower than bandwidth Factors that influence throughput: 1. The amount of traffic 2. Type of traffic 3. The latency created by the number of network devices encountered between source and destination Can see Throughput by using a speed test like the one in the pic.

Layer 2 Switch Forwarding

-If the destination MAC address is a unicast address, the switch will look for a match between the destination MAC address of the frame and an entry in its MAC address table. -If the destination MAC address is in the table, it will forward the frame out the specified port. -If the destination MAC address is not in the table, the switch will forward the frame out all ports except the incoming port. -- This is called an unknown unicast. -If the destination MAC address is a broadcast or a multicast, the frame is also flooded out all ports except the incoming port. As shown in the figure, the switch does not have the destination MAC address in its table for PC-D, so it sends the frame out all ports except port 1.

Who defines the electrical characteristics of copper cabling?

-Institute of Electrical and Electronics Engineers (IEEE) -IEEE Rates UTP cabling according to its performance -Cables are placed into categories based on their ability to carry higher bandwidth rates.

Encoding (line-encoding)

-Is a method of converting a stream of data bits into a predefined "code." -Codes are groupings of bits used to provide a predictable pattern that can be recognized by both the sender and the receiver. (it is the method or pattern used to represent digital information) -This is similar to how Morse code encodes a message using a series of dots and dashes. IE: -Manchester encoding represents a 0 bit by a high to low voltage transition, and a 1 bit is represented as a low to high voltage transition. -See pic for illustration -This type of encoding is used in 10 Mbps Ethernet. -Faster data rates require more complex encoding. -Manchester encoding is used in older Ethernet standards such as 10BASE-T. -Ethernet 100BASE-TX uses 4B/5B encoding and 1000BASE-T uses 8B/10B encoding.

Bandwidth

-Is the capacity at which a medium can carry data -Digital bandwidth - measures the amount of data that can flow from one place to another in a given amount of time. -Typically measured in kbps, Mbps, Gbps

Good put

-Is the measure of usable data transferred over a given period of time. -Goodput is throughput minus (-) overhead for establishing sessions, acknowledgements, encapsulation, and retransmitted bits. -Goodput is always lower than throughput, which is generally lower than the bandwidth

Switch Duplex and Speed Settings (Autonegotiation)

-It is critical that the duplex and bandwidth settings match between the switch port and the connected devices, such as a computer or another switch. Autonegotiation: -is an optional function found on most Ethernet switches and NICs. -It enables two devices to automatically negotiate the best speed and duplex capabilities. -Full-duplex is chosen if both devices have the capability along with their highest common bandwidth.

Lucent Connector (LC) Simplex Connectors - FIBER

-LC simplex connectors are a smaller version of the SC connector. -These are sometimes called little or local connectors and are quickly growing in popularity due to their smaller size.

Fiber Optic Cable

-Optical fiber cable transmits data over longer distances and at higher bandwidths than any other networking media. -Unlike copper wires, fiber-optic cable can transmit signals with less attenuation and is completely immune to EMI and RFI. -Optical fiber is a flexible, but extremely thin, transparent strand of very pure glass, not much bigger than a human hair. -Bits are encoded on the fiber as light impulses. -The fiber-optic cable acts as a waveguide, or "light pipe," to transmit light between the two ends with minimal loss of signal. -Optical fiber is commonly used to interconnect network devices.

Point-to-Point Topology

-Physical point-to-point topologies directly connect two nodes, as shown in the figure. -PPP topologies are limited to two nodes -A point-to-point connection over Ethernet requires the device to determine if the incoming frame is destined for this node. -when using a serial communications protocol such as Point-to-Point Protocol (PPP), a node does not have to make any determination about whether an incoming frame is destined for it or another node. -he logical data link protocols can be very simple, as all frames on the media can only travel to or from the two nodes. -The node places the frames on the media at one end and those frames are taken from the media by the node at the other end of the point-to-point circuit. --------------- -A source and destination node may be indirectly connected to each other over some geographical distance using multiple intermediary devices. -However, the use of physical devices in the network does not affect the logical topology, as illustrated in the figure. -In the figure, adding intermediary physical connections may not change the logical topology. The logical point-to-point connection is the same.

Subscriber Connector (SC) Connectors - FIBER

-SC connectors are sometimes referred to as square connector or standard connector. -They are a widely-adopted LAN and WAN connector that uses a push-pull mechanism to ensure positive insertion. -This connector type is used with multimode and single-mode fiber.

Straight-Tip (ST) connectors - FIBER

-ST connectors were one of the first connector types used. -The connector locks securely with a "Twist-on/twist-off" bayonet-style mechanism.

LAN Star and extended star Topology

-Star topology end devices are connected to a central intermediary device, such as a Ethernet switch. -Extended Star it takes the start topology and interconnection multiple ethernet switches -These topologies are easy to install, very scalable (easy to add and remove end devices), and easy to troubleshoot. -Early start topologies interconnected end devices using Ethernet hubs. At times there may be only two devices connected on the Ethernet LAN. An example is two interconnected routers. This would be an example of Ethernet used on a point-to-point topology.

Who establishes standards for UTP cabling?

-TIA/EIA -TIA/EIA - 568 stipulates the commercial cabling standard and is the standard most commonly used in LAN cabling environments. Common standard elements: 1. Cable types 2. Cable lengths 3. Connectors 4. Cable termination 5. Methods of testing cable -describes the wire color codes to pin assignments (pinouts) for Ethernet cables

LAN and WAN Frames

-The Layer 2 protocol that is used for a particular network topology is determined by the technology used to implement that topology. -The technology used is determined by the size of the network, in terms of the number of hosts and the geographic scope, and the services to be provided over the network. -A LAN typically uses a high bandwidth technology capable of supporting large numbers of hosts. The relatively small geographic area of a LAN (a single building or a multi-building campus) and its high density of users make this technology cost-effective. -However, using a high bandwidth technology is usually not cost-effective for WANs that cover large geographic areas (cities or multiple cities, for example). The cost of the long-distance physical links and the technology used to carry the signals over those distances typically results in lower bandwidth capacity. -The difference in bandwidth normally results in the use of different protocols for LANs and WANs.

RJ-45 UTP Sockets

-The socket, shown in the figure, is the female component of a network device, wall, cubicle partition outlet, or patch panel. -When terminated improperly, each cable is a potential source of physical layer performance degradation.

Layer 2 Switch Learning

-The switch dynamically builds the MAC address table by examining the source MAC address of the frames received on a port. -The switch forwards frames by searching for a match between the destination MAC address in the frame and an entry in the MAC address table. Learn: -Switch learns by examining the source MAC address of the frame and the port number where the frame entered the switch. -If the source MAC address does not exist, it is added to the table along with the incoming port number. -If the source MAC address does exist, the switch updates the refresh timer for that entry -By default, most Ethernet switches keep an entry in the table for 5 minutes -If the source MAC address does exist in the table but on a different port, the switch treats this as a new entry. -The entry is replaced using the same MAC address but with the more current port number.

Poorly Terminated UTP Cable

-This figure shows an example of a badly terminated UTP cable. -This bad connector has wires that are exposed, untwisted, and not entirely covered by the sheath.

Contention-based access control

-all notes are operating in half-duplex, competing for use of the medium. --only 1 devices can send at a time -there is a process if more than one device transmits at the same time. -Examples contention-based access methods include the following: 1. Carrier sense multiple access with collision detection (CSMA/CD) used on legacy bus-topology Ethernet LANs 2. Carrier sense multiple access with collision avoidance (CSMA/CA) used on Wireless LANs -Whether it is an Ethernet LAN using hubs, or a WLAN, contention-based systems do not scale well under heavy media use. -Ethernet LANs using switches do not use a contention-based system because the switch and the host NIC operate in full-duplex mode.

Contention-Based Access - CSMA/CA

-carrier sense multiple access/collision avoidance -Used by IEEE 802.111 WLANs -CMSA/CA does not detect collisions but attempts to avoid them by waiting before transmitting. -Each device that transmits includes the time duration that it needs for the transmission. All other wireless devices receive this information and know how long the medium will be unavailable. -After a wireless device sends an 802.11 frame, the receiver returns an acknowledgment so that the sender knows the frame arrived. In the figure, if host A is receiving a wireless frame from the access point, hosts B, and C will also see the frame and how long the medium will be unavailable.

Unicast MAC Address

-different MAC addresses are used for Layer 2 unicast, broadcast, and multicast communications. -Unicast MAC address is the unique address that is used when a frame is sent from a single transmitting device to a single destination device. -For a unicast packet to be sent and received, a destination IP address must be in the IP packet header. -A corresponding destination MAC address must also be present in the Ethernet frame header. -The IP address and MAC address combine to deliver data to one specific destination host. Note: The source MAC address must always be a unicast.

Controlled Access

-each node has its own time to use the medium -These deterministic types of legacy networks are inefficient because a device must wait its turn to access the medium. Examples of multiaccess networks that use controlled access include the following: 1. Legacy Token Ring 2. Legacy ARCNET

Duplex mismatch

-is one of the most common causes of performance issues on 10/100 Mbps Ethernet links. -It occurs when one port on the link operates at half-duplex while the other port operates at full-duplex, as shown in the figure. -Duplex mismatch occurs when one or both ports on a link are reset, and the autonegotiation process does not result in both link partners having the same configuration. !!!Best practice is to configure both Ethernet switch ports as full-duplex. -Figure: S2 will continually experience collisions because S1 keeps sending frames any time it has something to send.

Unshielded twisted-pair (UTP)

-is the most common networking media. -UTP cabling, terminated with RJ-45 connectors, is used for interconnecting network hosts with inermediary devices, such as switches and routers. -In LANs, UTP cable consists of four pairs of color-coded wires that have been twisted together and then encased in a flexible plastic sheath that protects from minor physical damage. -The twisting of wires helps protect against signal interference from other wires.

Fiber Versus Copper

-most enterprise environments optical fiber is primarily used as backbone cabling for high-traffic, point-to-point connections between data distribution facilities. -Fiber is also used for interconnection of building in multi-building campuses -Fiber optic cable do not conduct electricity and have a low signal loss. See picture for comparison of Fiber/Copper

Fragment-free switching

-the switch stores the first 64 bytes of the frame before forwarding. -The reason fragment-free switching stores only the first 64 bytes of the frame is that most network errors and collisions occur during the first 64 bytes. -Fragment-free switching tries to enhance fast-forward switching by performing a small error check on the first 64 bytes of the frame to ensure that a collision has not occurred before forwarding the frame. -Fragment-free switching is a compromise between the high latency and high integrity of store-and-forward switching, and the low latency and reduced integrity of fast-forward switching.

What is the special value assigned to the first 24 bits of a multicast MAC address transporting an IPv4 packet?

01-00-5E Topic 7.2.0 - Just as with multicast IP addresses, there is a special assigned value for multicast MAC addresses. The first 24 bits are set in hex to: 01-00-5E. The remaining 6 hex digits are derived from the lower 23 bits of the IP multicast.

At each hop along the path, what layer 2 functions does a router perform?

1. Accepts a frame from a medium 2. De-encapsulates the frame 3. Re-encapsulates the packet into a new frame 4. Forwards the new frame appropriate to the medium of that segment of the physical network

Units of Bandwidth

1. Bits per second (bps), 1 bps = fundamental unit of bandwidth 2. Kilobits per second (Kbps), 1 Kbps = 1,000 bps = 10^3 bps 3. Megabits per second (Mbps), 1 Mbps = 1,000,000 bps = 10^6 bps 4. Gigabits per second (Gbps), 1 Gbps = 1,000,000,000 bps = 10^9 bps 5. Terabits per second (Tbps), 1 Tbps = 1,000,000,000,000 bps = 10^12 bps

Legacy LAN Topologies

1. Bus - All end systems are chained to each other and terminated in some form on each end. -Infrastructure devices such as switches are not required to interconnect the end devices. -Legacy Ethernet networks were often bus topologies using coax cables because it was inexpensive and easy to set up. 2. Ring - End systems are connected to their respective neighbor forming a ring. The ring does not need to be terminated, unlike in the bus topology. -Legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks used ring topologies.

What are other ways that UTP cancels out EMI and RFI?

1. Cancellation - Designers now pair wires in a circuit. When two wires in an electrical circuit are placed close together, their magnetic fields are the exact opposite of each other. Therefore, the two magnetic fields cancel each other and also cancel out any outside EMI and RFI signals. 2. Varying the number of twists per wire pair - To further enhance the cancellation effect of paired circuit wires, designers vary the number of twists of each wire pair in a cable. UTP cable must follow precise specifications governing how many twists or braids are permitted per meter (3.28 feet) of cable. Notice in the figure that the orange/orange white pair is twisted less than the blue/blue white pair. Each colored pair is twisted a different number of times.

What are 3 categories of UTP cable?

1. Category 3 was originally used for voice communication over voice lines, but later used for data transmission. 2. Category 5 and 5e is used for data transmission. Category 5 supports 100Mbps and Category 5e supports 1000 Mbps 4. Category 6 has an added separator between each wire pair to support higher speeds. Category 6 supports up to 10 Gbps. 5. Category 7 also supports 10 Gbps. 6. Category 8 supports 40 Gbps.

What are the areas of wireless standards? And who manages them?

1. Data to radio signal encoding 2. Frequency and power of transmission 3. Signal reception and decoding requirements 4. Antenna design and construction -The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers.

What are the two sources of timing and voltage impulse interference?

1. Electromagnetic interference (EMI) or radio frequency interference (RFI) - EMI and RFI signals can distort and corrupt the data signals being carried by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic devices, such as fluorescent lights or electric motors. 2. Crosstalk - Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire. In telephone circuits, crosstalk can result in hearing part of another voice conversation from an adjacent circuit. Specifically, when an electrical current flows through a wire, it creates a small, circular magnetic field around the wire, which can be picked up by an adjacent wire. -To counter negative affects of EMI and RFI, some types of copper cables are wrapped in metallic shielding and require proper grounding connections -To counter the negative effects of crosstalk, some types of copper cables have opposing circuit wire pairs twisted together, which effectively cancels crosstalk.

What are the 4 types of industry where Fiber-Optics are used?

1. Enterprise Networks - Used for backbone cabling applications and interconnecting infrastructure devices 2. Fiber-to-the-Home (FTTH) - Used to provide always-on broadband services to homes and small businesses 3. Long-Haul Networks - Used by service providers to connect countries and cities 4. Submarine Cable Networks - Used to provide reliable high-speed, high-capacity solutions capable of surviving in harsh undersea environments at up to transoceanic distances. Search the internet for "submarine cables telegeography map" to view various maps online.

What the data link layer protocols?

1. Ethernet 2. 802.11 Wireless 3. Point-to-Point Protocol (PPP) 4. High-Level Data Link Control (HDLC) 5. Frame Relay

Cable Types and Standards

1. Ethernet Straight-through: -Both ends T568A or both ends T568B -Connects a network host to a network device such as a switch or hub 2. Ethernet Crossover: -One end T568A, other end T568B -Connects two network hosts Connects two network intermediary devices (switch to switch or router to router) 3. Rollover: -Cisco proprietary -Connects a workstation serial port to a router console port, using an adapter

What are the 2 variants of Cut-Through Switching

1. Fast-forward switching 2. Fragment-free switching

What is involved in MAC sublayer encapsulation?

1. Frame delimiting - The framing process provides important delimiters to identify fields within a frame. These delimiting bits provide synchronization between the transmitting and receiving nodes. 2. Addressing - Provides source and destination addressing for transporting the Layer 2 frame between devices on the same shared medium. 3. Error detection - Includes a trailer used to detect transmission errors.

What are 3 basic parts of a data link layer frame? And what is the data link protocol responsible for?

1. Header 2. Data 3. Trailer -Data link protocol is responsible for NIC-to-NIC communications within the same network. -Data link layer prepares encapsulated data (usually IPv4 or IPv6 packet) for transport across the local media by encapsulating it with a header and a trailer to create a frame. -the structure of the frame and the fields contained in the header and trailer vary according to the protocol. -There is no one frame structure that meets the needs of all data transportation across all types of media.

What are the organizations that define open standards and protocols that apply to the network access layer (OSI-Data link/Physical)?

1. Institute of Electrical and Electronics Engineers (IEEE) 2. International Telecommunication Union (ITU) 3. International Organization for Standardization (ISO) 4. American National Standards Institute (ANSI)

What are the standard organizations involved in establishing and maintaining physical layer standards?

1. International Organization for Standardization (ISO) 2. Telecommunications Industry Association/Electronic Industries Association (TIA/EIA) 3.International Telecommunication Union (ITU) 4, American National Standards Institute (ANSI) 5. Institute of Electrical and Electronics Engineers (IEEE) 6. National telecommunications regulatory authorities including the Federal Communication Commission (FCC) in the USA and the European Telecommunications Standards Institute (ETSI)

What are the two sublayers of the datalink layer

1. LLC (Logical Link Control) 2. MAC (Media Access Control)

What are the functional areas of physical layer standards?

1. Physical Components 2. Encoding 3. Signaling

What are the two topologies used to describe LAN and WAN networks? And what are their definitions?

1. Physical topology - Identifies the physical connections and how end devices and intermediary devices (i.e, routers, switches, and wireless access points) are interconnected. -The topology may also include specific device location such as room number and location on the equipment rack. -Physical topologies are usually point-to-point or star. 2. Logical topology - Refers to the way a network transfers frames from one node to the next. -This topology identifies virtual connections using device interfaces and Layer 3 IP addressing schemes. ------------- -The data link layer "sees" the logical topology of a network when controlling data access to the media. -It is the logical topology that influences the type of network framing and media access control used.

What are are the 3 different WAN topologies?

1. Point-to-point (PPP) - permanent link btw 2 endpoints 2. Hub and Spoke - This is a WAN version of the star topology in which a central site interconnects branch sites through the use of point-to-point links. Branch sites cannot exchange data with other branch sites without going through the central site. 3. Mesh - This topology provides high availability but requires that every end system is interconnected to every other system. Therefore, the administrative and physical costs can be significant. Each link is essentially a point-to-point link to the other node. (looks like a star)

What are the Ethernet Frame Fields and their definitions?

1. Preamble and Start Frame Delimiter Fields -The Preamble (7 bytes) and Start Frame Delimiter (SFD), also called the Start of Frame (1 byte), fields are used for synchronization between the sending and receiving devices. -These first eight bytes of the frame are used to get the attention of the receiving nodes. -Essentially, the first few bytes tell the receivers to get ready to receive a new frame. (PREAMBLE) 2. Destination MAC Address Field -This 6-byte field is the identifier for the intended recipient. -this address is used by Layer 2 to assist devices in determining if a frame is addressed to them. -The address in the frame is compared to the MAC address in the device. If there is a match, the device accepts the frame. Can be a unicast, multicast or broadcast address. 3. Source MAC Address Field -This 6-byte field identifies the originating NIC or interface of the frame. 4. Type / Length -This 2-byte field identifies the upper layer protocol encapsulated in the Ethernet frame. -Common values are, in hexadecimal, 0x800 for IPv4, 0x86DD for IPv6 and 0x806 for ARP. -Note: You may also see this field referred to as EtherType, Type, or Length. 5. Data Field -This field (46 - 1500 bytes) contains the encapsulated data from a higher layer, which is a generic Layer 3 PDU, or more commonly, an IPv4 packet. -All frames must be at least 64 bytes long. If a small packet is encapsulated, additional bits called a pad are used to increase the size of the frame to this minimum size. 6. Frame Check Sequence Field -The Frame Check Sequence (FCS) field (4 bytes) is used to detect errors in a frame. -It uses a cyclic redundancy check (CRC). -The sending device includes the results of a CRC in the FCS field of the frame. -The receiving device receives the frame and generates a CRC to look for errors. -If the calculations match, no error occurred. -Calculations that do not match are an indication that the data has changed; therefore, the frame is dropped. -A change in the data could be the result of a disruption of the electrical signals that represent the bits.

What can be done limit the copper cables electronic noise?

1. Selecting the cable type or category most suited to a given networking environment 2. Designing a cable infrastructure to avoid known and potential sources of interference in the building structure 3. Using cabling techniques that include the proper handling and termination of the cables

What are 2 types of Fiber-Optic cables?

1. Single-mode fiber (SMF) -SMF consists of a very small core and uses expensive laser technology to send a single ray of light. -SMF is popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications. 2. Multimode fiber (MMF) -MMF consists of a larger core and uses LED emitters to send light pulses. -Specifically, light from an LED enters the multimode fiber at different angles, as shown in the figure. -Popular in LANs because they can be powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters.

Methods for switch data between network ports on Cisco Switches

1. Store-and-forward switching 2. Cut-through switching

Properly Terminated UTP Cable

1. The next figure shows a properly terminated UTP cable. 2. It is a good connector with wires that are untwisted only to the extent necessary to attach the connector.

What are the combination factors that determine the practical bandwidth of a network?

1. The properties of the physical media 2. The technologies chosen for signaling and detecting network signals

What are the wireless standards?

1. Wi-Fi (IEEE 802.11) - Wireless LAN (WLAN) technology, commonly referred to as Wi-Fi. WLAN uses a contention-based protocol known as carrier sense multiple access/collision avoidance (CSMA/CA). The wireless NIC must first listen before transmitting to determine if the radio channel is clear. If another wireless device is transmitting, then the NIC must wait until the channel is clear. Wi-Fi is a trademark of the Wi-Fi Alliance. Wi-Fi is used with certified WLAN devices based on the IEEE 802.11 standards. 2. Bluetooth (IEEE 802.15) - This is a wireless personal area network (WPAN) standard, commonly known as "Bluetooth." It uses a device pairing process to communicate over distances from 1 to 100 meters. 3. WiMAX (IEEE 802:16) - Commonly known as Worldwide Interoperability for Microware Access (WiMAX), this wireless standard uses a point-to-multipoint topology to provide wireless broadband access. 4. Zigbee (IEEE 802.15.4) - Zigbee is a specification used for low-data rate, low-power communications. It is intended for applications that require short-range, low data-rates and long battery life. Zigbee is typically used for industrial and Internet of Things (IoT) environments such as wireless light switches and medical device data collection.

What devices are required in a WLAN?

1. Wireless Access Point (AP) - These concentrate the wireless signals from users and connect to the existing copper-based network infrastructure, such as Ethernet. Home and small business wireless routers integrate the functions of a router, switch, and access point into one device, as shown in the figure. 2. Wireless NIC adapters - These provide wireless communication capability to network hosts.

What situations are coax cable installed?

1. Wireless installations - Coaxial cables attach antennas to wireless devices. The coaxial cable carries radio frequency (RF) energy between the antennas and the radio equipment. 2. Cable internet installations - Cable service providers provide internet connectivity to their customers by replacing portions of the coaxial cable and supporting amplification elements with fiber-optic cable. However, the wiring inside the customer's premises is still coax cable.

What are the limitations of wireless?

2. Coverage area - Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage. 2. Interference - Wireless is susceptible to interference and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications. 3. Security - Wireless communication coverage requires no access to a physical strand of media. Therefore, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is a major component of wireless network administration. 4. Shared medium - WLANs operate in half-duplex, which means only one device can send or receive at a time. The wireless medium is shared amongst all wireless users. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user.

What does the data link layer do?

2. Enables upper layers to access the media. The upper layer protocol is completely unaware of the type of media that is used to forward the data. 2. Accepts data, usually Layer 3 packets (i.e., IPv4 or IPv6), and encapsulates them into Layer 2 frames. 3. Controls how data is placed and received on the media. 4. Exchanges frames between endpoints over the network media. 5. Receives encapsulated data, usually Layer 3 packets, and directs them to the proper upper-layer protocol. 6. Performs error detection and rejects any corrupt frame.

Broadcast MAC Address

A MAC address in which all bits are set to 1 (FF:FF:FF:FF:FF:FF). The features of an Ethernet broadcast are as follows: -It has a destination MAC address of FF-FF-FF-FF-FF-FF in hexadecimal (48 ones in binary). -It is flooded out all Ethernet switch ports except the incoming port. -It is not forwarded by a router. ----------- If the encapsulated data is an IPv4 broadcast packet, this means the packet contains a destination IPv4 address that has all ones (1s) in the host portion. -This numbering in the address means that all hosts on that local network (broadcast domain) will receive and process the packet. Example broadcast IP: 192.168.1.255 (255 meaning all positions set to 1)

Duplex Multimode LC Connectors - FIBER

A duplex multimode LC connector is similar to a LC simplex connector, but uses a duplex connector.

Which lists the Layer 2 and Layer 3 address fields in the correct order? A: Destination NIC address, source NIC address, Source IP address, destination IP address B: source NIC address, destination NIC address, source IP address, destination IP address C: destination NIC address, source NIC address, destination IP address, source IP address D: source NIC address, destination NIC address, destination IP address, source IP address

A: Destination NIC address, source NIC address, Source IP address, destination IP address

Which two functions or operations are performed by the MAC sublayer? (Choose two.) A: It is responsible for Media Access Control B: It performs the function of the NIC driver software C: It adds a header and trailer to form an OSI Layer 2 PDU D: It handles communication between upper and lower layers E: It adds control information to network protocol layer data

A: It is responsible for Media Access Control E: It adds control information to network protocol layer data Topic 7.1.0 - The MAC sublayer is the lower of the two data link sublayers and is closest to the physical layer. The two primary functions of the MAC sublayer are to encapsulate the data from the upper layer protocols and to control access to the media.

A wireless LAN is being deployed inside the new one room office that is occupied by the park ranger. The office is located at the highest part of the national park. After network testing is complete, the technicians report that the wireless LAN signal is occasionally affected by some type of interference. What is a possible cause of the signal distortion? A: The microwave oven B: The large number of trees that surround the office C: The elevated location where the wireless LAN was installed D: The number of wireless devices that are used in the wireless LAN

A: The microwave oven Topic 4.6.0 - Wireless LAN connectivity is not affected by trees or the elevation of the equipment. Because this is a one room office in an isolated area, there will not be a large number of wireless devices or source of interference operating in the immediate vicinity. The use of a microwave oven could result in signal interference.

What is the process that a source host uses to determine the destination MAC address associated with an IPv4 address?

Address Resolution Protocol (ARP)

Memory Buffering on Switches

An Ethernet switch may use a buffering technique to store frames before forwarding them. -Buffering may also be used when the destination port is busy because of congestion. The switch stores the frame until it can be transmitted. Two methods of buffering: 1. Port-based memory 2. Shared memory

Filtering Frames

As a switch receives frames from different devices, it is able to populate its MAC address table by examining the source MAC address of every frame. When the MAC address table of the switch contains the destination MAC address, it is able to filter the frame and forward out a single port.

The media access control method used depends on which two criteria? (Choose all that apply.) A: Layer 3 IP protocol B: Media Sharing C: Topology D: Transport layer protocol E: Type of data

B: Media Sharing C: Topology

What is another name for a MAC Address?

Burned in Address OR Physical Address Burned in Address - because the address is hard coded into read-only memory (ROM) on the NIC - this means that the address is encoded into the ROM chip permanently.

What are two services performed by the data link layer of the OSI model? (Choose two.) A: it fragments data packets into the MTU size B: It determines the path to forward packets C: It accepts layer 3 packets and encapsulates them into frames D: It provides media access control and performs error detection. E: It monitors the Layer 2 communication by building a MAC address table

C: It accepts layer 3 packets and encapsulates them into frames D: It provides media access control and performs error detection. The data link layer is responsible for the exchange of frames between nodes over a physical network media. Specifically the data link layer performs two basic services: 1. It accepts Layer 3 packets and encapsulates them into frames. 2. It provides media access control and performs error detection. Path determination is a service provided at Layer 3. A Layer 2 switch builds a MAC address table as part of its operation, but path determination is not the service that is provided by the data link layer.

A technician has been asked to develop a physical topology for a network that provides a high level of redundancy. Which physical topology requires that every node is attached to every other node on the network? A: Bus B: Hierarchical C: Mesh D: Ring E: Star

C: Mesh The mesh topology provides high availability because every node is connected to all other nodes. Mesh topologies can be found in WANs. A partial mesh topology can also be used where some, but not all, end points connect to one another.

Which is a function of the Logical Link Control (LLC) sublayer? A: to define the media access processes that are performed by the hardware B: to provide data link layer addressing C: to identify which network layer protocol is being used D: to accept segments and package them into data units that are called packets

C: to identify which network layer protocol is being used Defining the media access processes that are performed by the hardware and providing data link layer addressing are functions of the MAC sublayer. The data link layer accepts Layer 3 packets and packages them into data units that are called frames.

What does they physical layer consist of?

Consists of electronic circuitry, media, and connectors developed by engineers. The standards governing this hardware are defined by electrical and communications engineering organizations.

What are the regional cabling standard groups?

CSA (Canadian Standards Association) 3. CENELEC (European Committee for Electrotechnical Standardization) 3. JSA/JIS (Japanese Standards Association), which develop local specifications. ------ -The TCP/IP standards are implemented in software and governed by the IETF -The physical layer standards are implemented in hardware and are governed by many organizations including: -ISO -EIA/TIA -ITU-T -ANSI -IEEE

What is the logical summary of contents of a frame called?

Cyclic redundancy check (CRC) value -This value is placed in the frame check sequence (FCS) field to represent the contents of the frame. -In the Ethernet trailer, the FCS provides a method for the receiving node to determine whether the frame experienced transmission errors.

Which media access control method is used in legacy Ethernet LANs? A: Carrier sense multiple access/collision annoyance B: Carrier sense multiple access/collision avoidance C: Carrier sense multiple access/collision destruction D: Carrier sense multiple access/collision detection

D: Carrier sense multiple access/collision detection

Which statement correctly describes frame encoding? A: It uses the characteristic of one wave to modify another wave? B: It transmits data along wit ha clock signal which occurs at evenly spaced time durations. C: It generates the electrical, optical, or wireless signals that present the binary number of the frame. D: It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control units.

D: It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control units. Topic 4.2.0 - Frame encoding converts a stream of data bits into a predefined code that is recognized by both the sender and receiver. These codes are used for a variety of purposes, such as distinguishing data bits from control bits, and identifying the beginning and end of a frame.

Which type of UTP cable is used to connect a PC to a switch port? A: Console B: Rollover: C: Crossover D: Straight - Through

D: Straight - Through Topic 4.4.0 - A rollover cable is a Cisco proprietary cable used to connect to a router or switch console port. A straight-through (also called patch) cable is usually used to interconnect a host to a switch and a switch to a router. A crossover cable is used to interconnect similar devices together, for example, between two switches, two routers, and two hosts.

What does duplex mean?

It refers to the direction of data transmission between two devices. There are two common modes of duplex: 1. Half-duplex 2. Full-duplex -In a nutshell, half-duplex communications restrict the exchange of data to one direction at a time. Full-duplex allows the sending and receiving of data to happen simultaneously. -It is important that two interconnected interfaces, such as a host NIC and an interface on an Ethernet switch, operate using the same duplex mode. Otherwise, there will be a duplex mismatch creating inefficiency and latency on the link.

What does the LLC layer do?

LLC- Logical Link Control -takes the network protocol data, which is typically an IPv4 or IPv6 packet, and adds Layer 2 control information to help deliver the packet to the destination node.

MMF (multimode fiber)

MMF Picture

What is the minimum and maximum Ethernet frame size? -include details.

Min: 64 bytes Max: 1518 bytes -This includes all bytes from the destination MAC address field through the frame check sequence (FCS) field. -The preamble field is not included when describing the size of the frame. -Any frame less than 64 bytes in length is considered a "collision fragment" or "runt frame" and is automatically discarded by receiving stations. -Frames with more than 1500 bytes of data are considered "jumbo" or "baby giant frames". -If the size of a transmitted frame is less than the minimum, or greater than the maximum, the receiving device drops the frame. -Dropped frames are likely to be the result of collisions or other unwanted signals. They are considered invalid. -Jumbo frames are usually supported by most Fast Ethernet and Gigabit Ethernet switches and NICs.

SMF (single-mode fiber)

SMF Picture

LC-LC Single-mode Patch Cord

See Pic

SC-SC Multimode Patch Cord

See Pic

SC-ST Single-mode Patch Cord

See Pic

ST-LC Multimode Patch Cord

See Pic

T568A and T568B Standards Color Wiring Diagram

See figure

Which of the following fiber-optic cable types can travel approximately 100 km? Single-mode OR Multimode

Single-mode

What are some common Layer 2 WAN protocols?

Some WAN Protocols: 1. Point-to-Point Protocol (PPP) 2. High-Level Data Link Control (HDLC) 3. Frame Relay 4. Asynchronous Transfer Mode (ATM) 5. X.25 -These Layer 2 protocols are now being replaced in the WAN by Ethernet -WANs traditionally used other types of protocols for various types of point-to-point, hub-spoke, and full-mesh topologies.

What protocol standard do wireless communications fall under?

WLAN IEEE 802.11 protocols

What type of address is 01-00-5E-0A-00-02?

an address that reaches a specific group of hosts Topic 7.2.0 - The multicast MAC address is a special value that begins with 01-00-5E in hexadecimal. It allows a source device to send a packet to a group of devices.