Chapter 2 - Ethernet Networking and Data Encapsulation

Fiber Optic Cable

- Allows for very fast transmission of data, is made of glass (or even plastic), is very thin, and works as a waveguide to transmit light between two ends of the fiber - Has been used to go very long distances, as in intercontinental connections - Is becoming more apopular in Ethernet LAN networks due to the fast speeds available - Unlike UTP, immune to interference like cross-talk

Converting from Binary to Hex

- Binary number 01010101: 1. First, break it into nibbles—0101 and 0101—with the value of each nibble being 5 since the 1 and 4 bits are on 2. The hex answer 0x55 3. In decimal format, the number converts to 64 + 16 + 4 + 1 = 85 - Binary number 11001100: 1. Answer would be 1100 = 12 and 1100 = 12 2. Converted to CC in hex 3. The decimal conversion answer would be 128 + 64 + 8 + 4 = 204 - Binary number 10110101: 1. The hex answer would be 0xB5; 1011 converts to B and 0101 converts to 5 2. The decimal equivalent is 128 + 32 + 16 + 4 + 1 = 181

Console Emulation Program Configuration

- Bit Rate is set to 9600 - Data Bits to 8 - Parity to None - Flow Control is set to None Click Connect and press the Enter key to connect to Cisco device console port

Bytes Examples

- Byte decimal values can add up to a number that's significantly higher than 15 - If every bit is counted as a one (1), then the byte binary value would look like: 11111111; Then count up every bit spot because each is turned on; It would look like: 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255 - 10010110; The 128, 16, 4, and 2 bits are on, so we'll just add them up: 128 + 16 + 4 + 2 = 150 - 01101100; The 64, 32, 8, and 4 bits are on: 64 + 32 + 8 + 4 = 108 - 11101000; The 128, 64, 32, and 8 bits are on: 128 + 64 + 32 + 8 = 232

Crossover Cable

- Can be used to connect the following devices: Switch to switch Hub to hub Host to host Hub to switch Router direct to host Router to router - The same four wires used in the straight-through cable are used in this cable, just connect different pins together - Instead of connecting 1 to 1, 2 to 2, and so on, connect pins 1 to 3 and 2 to 6 on each side of the cable

Access Layer Functions

- Continued (from distribution layer) use of access control and policies - Creation of separate collision domains (segmentation) - Workgroup connectivity into the distribution layer

The Access Layer

- Controls user and workgroup access to internetwork resources - The network resources most needed will be available locally because the distribution layer handles any traffic for remote services - Technologies like Gigabit or Fast Ethernet switching are frequently seen here

Hexadecimal Addressing

- Converted by reading nibbles, not bytes - Uses only the characters 0 through 9 - uses the first six letters of the alphabet, A through F, to extend beyond the available 10 characters in the decimal system; used to represent 10, 11, 12, 13, 14, and 15, respectively - Cisco likes to put 0x in front of characters so you know that they are a hex value - Each hex character is one nibble and that two hex characters joined together make a byte - To figure out the binary value, put the hex characters into two nibbles and then join them together into a byte

1000Base-CX (IEEE 802.3z)

- Copper twisted-pair, called twinax, is a balanced coaxial pair that can run only up to 25 meters and uses a special 9-pin connector known as the High Speed Serial Data Connector (HSSDC) - Used in Cisco's new Data Center technologies

Effects of CSMA/CD Network Collisions

- Delay - Low Throughput - Congestion

Things to Achieve when Designing Core Layer

- Design the core for high reliability; Consider data-link technologies that facilitate both speed and redundancy, like Gigabit Ethernet with redundant links or even 10 Gigabit Ethernet. - Design with speed in mind. The core should have very little latency - Select routing protocols with lower convergence times; Fast and redundant data-link connectivity is no help if routing tables are shot

The Cisco Three-Layer Hierarchical Model

- Makes networks more predictable and helps define which areas should perform certain functions - Helps summarize a complex collection of details into an understandable model, then as specific configurations are needed, the model dictates the appropriate manner in which to apply them - Can help design, implement, and maintain a scalable, reliable, cost-effective hierarchical internetwork - Each layer has specific responsibilities - Definition of the layers is logical, not physical

Single-Mode Fiber

- More expensive - Has a tighter cladding - Can go much farther distances than multimode - The difference comes in the tightness of the cladding, which makes a smaller core, meaning that only one mode of light will propagate down the fiber

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

- Protocol used by ethernet networks which helps devices share bandwidth evenly while preventing two devices from transmitting simultaneously on the same network medium - Created to overcome the problem of the collisions that occur when packets are transmitted from different nodes at the same time - When a host wants to transmit over the network, it first checks for the presence of a digital signal on the wire; If all is clear and no other host is transmitting, the host will then proceed with its transmission - The transmitting host constantly monitors the wire to make sure no other hosts begin transmitting; If the host detects another signal on the wire, it sends out an extended jam signal that causes all nodes on the segment to stop sending data (think busy signal) - The nodes respond to that jam signal by waiting a bit before attempting to transmit again - Backoff algorithms determine when the colliding stations can retransmit; If collisions keep occurring after 15 tries, the nodes attempting to transmit will then time out

Ethernet at the Data Link Layer

- Responsible for Ethernet addressing, commonly referred to as MAC or hardware addressing - Also responsible for framing packets received from the Network Layer and preparing them for transmission on the local network through the Ethernet contention-based media access method

Distribution Layer Functions

- Routing - Implementing tools (such as access lists), packet filtering, and queuing - Implementing security and network policies, including address translation and firewalls - Redistributing between routing protocols, including static routing - Routing between VLANs and other workgroup support functions - Defining broadcast and multicast domains

Two Major types of Fiber Optics

- Single-mode - Multimode

The Distribution Layer

- Sometimes referred to as the workgroup layer and is the communication point between the access layer and the core - Primary functions of the distribution layer are to provide routing, filtering, and WAN access and to determine how packets can access the core, if needed - Must determine the fastest way that network service requests are handled—for example, how a file request is forwarded to a server - After the distribution layer determines the best path, it forwards the request to the core layer if necessary - The core layer then quickly transports the request to the correct service - Where network policies shold be implemented due to the amount of flexibility allowed in defining network operation

Ethernet Frames

- The Data Link Layer is responsible for combining bits into bytes and bytes into frames - Frames are used at the Data Link Layer to encapsulate packets handed down from the Network Layer for transmission on a type of media access - The function of Ethernet stations is to pass data frames between each other using a group of bits known as a MAC frame format - This provides error detection from a cyclic redundancy check (CRC); This is error detection, not error correction

Port Numbers at the Transport Layer

- The Transport Layer uses port numbers to define both the virtual circuit and the upper-layer processes - When using a connection-oriented protocol like TCP, the Transport layer takes the data stream, makes segments out of it, and establishes a reliable session by creating a virtual circuit - It then sequences (numbers) each segment and uses acknowledgments and flow control - If using TCP, the virtual circuit is defined by the source and destination port number plus the source and destination IP address and called a socket - The host makes these port numbers up, starting at port number 1024 because 0 through 1023 are reserved for well-known port numbers - The destination port number defines the upper-layer process or application that the data stream is handed to when the data stream is reliably rebuilt on the receiving host

Binary Numbering

- The digits used are limited to either a 1 or a 0, and each digit is called a bit, which is short for binary digit - Typically, you group either 4 or 8 bits together, with these being referred to as a nibble and a byte, respectively - The typical decimal format is the base-10 number scheme - The numbers are placed in a value spot, starting at the right and moving left, with each spot having double the value of the previous spot - If a one digit (1) is placed in a value spot, then the nibble or byte takes on that decimal value and adds it to any other value spots that have a 1 - If a zero (0) is placed in a bit spot, you don't count that value

Data Encapsulation

- The process in which data is wrapped with protocol information at each layer of the OSI model - Each layer communicates only with its peer layer on the receiving device - Also known as Packet Creation

Backoff on an Ethernet Network

- The retransmission delay that's enforced when a collision occurs - When that happens, a host will resume transmission only after the forced time delay has expired - After the backoff has elapsed, all stations have equal priority to transmit data

Virtual LANs (VLANs)

- Used to create small broadcast domains in modern switched networks - Employed to increase bandwidth available to individual users - Can be used to easily control both collision and broadcast domains

Half-Duplex Ethernet

- Uses only one wire pair with a digital signal running in both directions on the wire - Uses the CSMA/CD protocol to help prevent collisions and to permit retransmitting if one occurs - If a hub is attached to a switch, it must operate in half-duplex mode because the end stations must be able to detect collisions - The network can only run half-duplex, and if two hosts communicate at the same time there will be a collision - Half-duplex Ethernet is only about 30 to 40 percent efficient because a large 100Base-T network will usually only give you 30 to 40 Mbps, at most, due to overhead

Ethernet Addressing

- Uses the Media Access Control (MAC) address burned into each and every Ethernet network interface card (NIC) - The MAC, or hardware, address is a 48-bit (6-byte) address written in a hexadecimal format

Steps in CSMA/CD Operation

1. A jam signal informs all devices that a collision occurred 2. The collision invokes a random backoff algorithm 3. Each device on the Ethernet segment stops transmitting for a short time until its backoff timer expires 4. All hosts have equal priority to transmit after the timers have expired

Data De-Encapsulation Process

1. After the receiving devices synchronize on the digital signal and extract (decode) the 1s and 0s from the digital signal, the devices reconstruct the frames, run a CRC, and then check their answer against the answer in the frame's FCS field 2. If it matches, the packet is pulled from the frame and what's left of the frame is discarded 3. The packet is handed to the Network layer, where the address is checked 4. If the address matches, the segment is pulled from the packet and what's left of the packet is discarded 5. The segment is processed at the Transport layer, which rebuilds the data stream and acknowledges to the transmitting station that it received each piece 6. It then hands the data stream to the upper-layer application

MAC Address Composition

1. Organizationally Unique Identifier (OUI) - assigned by the IEEE to an organization; composed of 24 bits, or 3 bytes, and it in turn assigns a globally administered address also made up of 24 bits, or 3 bytes, that's supposedly unique to each and every adapter an organization manufactures 2. Individual/Group (I/G) bit - high-order bit; when it has a value of 0, we can assume that the address is the MAC address of a device and that it may well appear in the source portion of the MAC header; when it's a 1, the address represents either a broadcast or multicast address in Ethernet 3. Global/Local (G/L) bit - next bit; when set to 0, this bit represents a globally administered address, as assigned by the IEEE, but when it's a 1, it represents a locally governed and administered address 4. Locally Administered or Manufacturer-Assigned Code - low-order 24 bits of an Ethernet address; commonly starts with 24 0s for the first card made and continues in order until there are 24 1s for the last (16,777,216th) card made

10Base-T (IEEE 802.3)

- 10 Mbps using category 3 unshielded twisted pair (UTP) wiring for runs up to 100 meters - Each device must connect into a hub or switch, and allows only one host per segment or wire - Uses an RJ45 connector (8-pin modular connector) with a physical star topology and a logical bus

Most Common IEEE Ethernet Standards

- 10Base-T (IEEE 802.3) - 100Base-TX (IEEE 802.3u) - 100Base-FX (IEEE 802.3u) - 1000Base-CX (IEEE 802.3z) - 1000Base-T (IEEE 802.3ab) - 1000Base-SX (IEEE 802.3z) - 1000Base-LX (IEEE 802.3z) - 1000Base-ZX (Cisco standard) - 10GBase-T (802.3.an)

1000Base-ZX (Cisco standard)

- A Cisco specified standard for Gigabit Ethernet communication - Operates on ordinary single-mode fiber-optic links with spans up to 43.5 miles (70 km)

Ethernet

- A contention based media access method that allows all hosts on a network to share the same link's bandwidth - Simple to implement and makes troubleshooting straightforward - Readily scalable: eases the process of integrating new technologies into an existing network infrastructure - Uses both Data Link and Physical Layer specifications

Wireless Access Point

- A wireless device that allows hosts to connect wirelessly using the IEEE 802.11 specification - Don't actually segment the network, only extend them

Ethernet at the Physical Layer

- Ethernet was first implemented by a group called DIX, which stands for Digital, Intel, and Xerox - They created and implemented the first Ethernet LAN specification, which the IEEE used to create the IEEE 802.3 committee - This was a 10 Mbps network that ran on coax and then eventually twisted-pair and fiber physical media - The IEEE extended the 802.3 committee to three new committees known as 802.3u (Fast Ethernet), 802.3ab (Gigabit Ethernet on category 5) and then finally one more, 802.3ae (10 Gbps over fiber and coax)

Half-Duplex and Full-Duplex Points to Remember

- Full-duplex Ethernet requires a point-to-point connection when only two nodes are present - Half-duplex Ethernet shares a collision domain and provides a lower effective throughput than full-duplex Ethernet, which typically has a private per-port collision domain plus a higher effective throughput - There are no collisions in full-duplex mode - A dedicated switch port is required for each full-duplex node - The host network card and the switch port must be capable of operating in fullduplex mode - The default behavior of 10Base-T and 100Base-T hosts is 10 Mbps half-duplex if the autodetect mechanism fails, so it is always good practice to set the speed and duplex of each port on a switch if you can

Nibble Examples

- If a 1 is placed in each spot of a nibble, add up 8 + 4 + 2 + 1 to get a maximum value of 15 - A nibble binary value of 1001 means that the 8 bit and the 1 bit are turned on, which equals a decimal value of 9 - A nibble binary value of 0110 means that the decimal value would be 6, because the 4 and 2 bits are turned on

The Core Layer

- Literally the core of the network - At the top of the hierarchy, responsible for transporting large amounts of traffic both reliably and quickly - The only purpose is to switch traffic as fast as possible - The traffic transported across the core is common to a majority of users - User data is processed at the distribution layer, which forwards the requests to the core if needed - If there's a failure, every single user can be affected, making fault tolerance very important - Likely to see large volumes of traffic, so speed and latency are driving concerns

Multimode Fiber

- Looser and has a larger core so it allows multiple light particles to travel down the glass - Particles have to be put back together at the receiving end - Distance is less than that with singlemode fiber, which allows only very few light particles to travel down the fiber

Fiber Optic Cable Components

- Main components are the core and the cladding - The core holds the light - The cladding confines the light in the core - The tighter the cladding, the smaller the core - When the core is small, less light will be sent, but can go faster and farther - Typical core dimension is 9 microns (um) - Typical cladding is 125 microns, which is actually a fiber standard that allows manufacturers to make connectors for all fiber cables - The last piece of the cable is the buffer, which is there to protect the glass

100Base-TX (IEEE 802.3u)

- Most commonly known as Fast Ethernet, uses EIA/TIA category 5, 5E, or 6 UTP two-pair wiring - One user per segment - Up to 100 meters long - Uses an RJ45 connector with a physical star topology and a logical bus

Things NOT to do at Core Layer

- Never do anything to slow down traffic; This includes using access lists, routing between virtual local area networks and implementing packet filtering - Don't support workgroup access here - Avoid expanding the core (e.g., adding routers when the internetwork grows); If performance becomes an issue in the core, give preference to upgrades over expansion

Binary Values

- Nibble Values: 8 4 2 1 - Byte Values: 128 64 32 16 8 4 2 1

PDU and Layer Addressing

- Once the Transport Layer header information is added to the piece of data, it becomes a segment that's handed down to the Network Layer along with the destination IP address - The destination IP address was handed down from the upper layers to the Transport Layer with the data stream and was identified via name resolution at the upper layers—probably with DNS - The Network Layer adds a header and adds the logical addressing such as IP addresses to the front of each segment - Once the header is added to the segment, the PDU is called a packet - The packet has a protocol field that describes where the segment came from (either UDP or TCP) so it can hand the segment to the correct protocol at the Transport Layer when it reaches the receiving host - The Network Layer finds the destination hardware address that dictates where the packet should be sent on the local network by using the Address Resolution Protocol (ARP) - IP at the Network Layer looks at the destination IP address and compares that address to its own source IP address and subnet mask - If it turns out to be a local network request, the hardware address of the local host is requested via an ARP request - If the packet is destined for a remote host, IP will look for the IP address of the default gateway (router) instead - The packet, along with the destination hardware address of either the local host or default gateway, is then handed down to the Data Link Layer - The Data Link Layer will add a header to the front of the packet and the piece of data then becomes a frame; It's called a frame because both a header and a trailer are added to the packet, which makes it look like it's within bookends—a frame - The frame uses an Ether-Type field to describe which protocol the packet came from at the Network layer - Now a cyclic redundancy check is run on the frame, and the answer to the CRC is placed in the Frame Check Sequence field found in the trailer of the frame - The frame is now ready to be handed down, one bit at a time, to the Physical layer, which will use bit-timing rules to encode the data in a digital signal - Every device on the network segment will receive the digital signal and synchronize with the clock and extract the 1s and 0s from the digital signal to build a frame - After the frame is rebuilt, a CRC is run to make sure the frame is in proper order - If everything turns out to be all good, the hosts will check the destination MAC and IP addresses to see if the frame is for them

UTP Gigabit Wiring (1000Base-T)

- Requires four wire pairs and uses more advance delectronics so that each and every pair in the cable can transmit simultaneously - Almost identical to 10/100 cabling, except that it uses the other two pairs in the cable - For a gigabit straight-through cable it's still 1 to 1, 2 to 2, and so on up to pin 8 - For a gigabit crossover cable, still cross 1 to 3 and 2 to 6, but add 4 to 7 and 5 to 8

EIA/TIA (Electronic Industries Alliance and the newer Telecommunications Industry Association)

- The standards body that creates the Physical layer specifications for Ethernet - Specifies that Ethernet use a registered jack (RJ) connector on unshielded twisted-pair (UTP) cabling (RJ45) - Every Ethernet cable type that's specified has inherent attenuation - The cabling used in corporate and home markets is measured in categories; A higher-quality cable will have a higher-rated category and lower attenuation

Cisco 2960 Console Connections

- There are two console connections: 1. A typical original RJ45 connection 2. The newer mini type-B USB console - The new USB port supersedes the RJ45 port if both are plugged into both at the same time, and the USB port can have speeds up to 115,200 Kbps - The two bottom ports are referred to as Small Form-Factor Pluggable, or SFPs

Protocol Data Units (PDUs)

- Used by each layer of the OSI model to communicate and exchange information - Hold the control information attached to the data at each layer - Usually attached to the header in front of the data field but can also be at the trailer, or end, of it - Each attaches to the data by encapsulating it at each layer of the OSI model, and each has a specific name depending on the information provided in each header - Information is read-only by the peer layer on the receiving device - After its read, the information stripped off and the data is then handed to the next layer up

Rolled Cable

- Used to connect a host EIA-TIA 232 interface (RS-232 Port) to a router console serial communication (COM) port - Used to connect PC, Mac, or a device like an iPad to Cisco hardware - Eight wires are used to connect serial devices, although not all eight are used to send information - To make cut the end off on one side of a straight-through cable, turn it over, and put it back on with a new connector - Once the correct cable is connected from the PC to the Cisco router or switch console port, start an emulation program such as putty or SecureCRT to create a console connection and configure the device

100Base-FX (IEEE 802.3u)

- Uses fiber cabling 62.5/125-micron multimode fiber - Point-to-point topology - Up to 412 meters long - Uses ST and SC connectors, which are media-interface connectors *Fiber-optic cable provides a more secure, long-distance cable that is not susceptible to EMI (Electromagnetic Interference) at high speeds*

Ethernet Frame Format

1. Preamble: 7 Bytes; An alternating 1,0 pattern provides a 5 MHz clock at the start of each packet, which allows the receiving devices to lock the incoming bit stream 2. Start Frame Delimiter (SFD)/Synch: 1 Byte; The preamble is seven octets and the SFD is one octet (synch); The SFD is 10101011, where the last pair of 1s allows the receiver to come into the alternating 1,0 pattern somewhere in the middle and still sync up to detect the beginning of the data 3. Destination Address (DA): 6 Bytes; This transmits a 48-bit value using the least significant bit (LSB) first; Used by receiving stations to determine whether an incoming packet is addressed to a particular node; Can be an individual address or a broadcast or multicast MAC address; A broadcast is all 1s—all Fs in hex— and is sent to all devices; A multicast is sent only to a similar subset of nodes on a network 4. Source Address (SA): 6 Bytes; a 48-bit MAC address used to identify the transmitting device, and it uses the least significant bit first; Broadcast and multicast address formats are illegal within the SA field 5. Length or Type: 2 Bytes; 802.3 uses a Length field, but an Ethernet_II frame uses a Type field to identify the Network layer protocol; The old, original 802.3 cannot identify the upper-layer protocol and must be used with a proprietary LAN—IPX, for example 6. Data: 46 - 1500 Bytes (Packet); A packet sent down to the Data Link layer from the Network layer; The size can vary from 46 to 1,500 bytes 7. Frame Check Sequence (FCS): 4 Bytes; A field at the end of the frame that's used to store the cyclic redundancy check (CRC) answer; When a receiving host receives the frame and runs the CRC, the answer should be the same; If not, the frame is discarded, assuming errors have occurred

Ethernet_II Frame Examples

1. The frame below has only three fields: Destination, Source,and Type, which is shown as Protocol Type - Destination: 00:60:f5:00:1f:27 Source: 00:60:f5:00:1f:2c Protocol Type: 08-00 IP The Type field is IP, or 08-00, mostly just referred to as 0x800 in hexadecimal 2. The next frame has the same fields, so it must be an Ethernet_II frame as well - Destination: ff:ff:ff:ff:ff:ff Ethernet Broadcast Source: 02:07:01:22:de:a4 Protocol Type: 08-00 IP This frame was a broadcastbecause the destination hardware address is all 1s in binary, or all Fs in hexadecimal 3. In the next example, the Ethernet frame is the same Ethernet_II frame used with the IPv4 routed protocol - Destination: IPv6-Neighbor-Discovery_00:01:00:03 (33:33:00:01:00:03) Source: Aopen_3e:7f:dd (00:01:80:3e:7f:dd) Type: IPv6 (0x86dd) The Type field has 0x86dd when the frame is carrying IPv6 data, and when we have IPv4 data, the frame uses 0x0800 in the protocol field Because of the Type field, we can run any Network Layer routed protocol and the frame will carry the data because it can identify the Network Layer protocol

Data Encapsulation Process

1. The upper-layer user data is converted for transmission on the network 2. The data stream is then handed down to the Transport layer, which sets up a virtual circuit to the receiving device by sending over a synch packet 3. Next, the data stream is broken up into smaller pieces, and a Transport layer header is created and attached to the header of the data field - The piece of data is called a segment (a PDU); Each segment can be sequenced so the data stream can be put back together on the receiving side exactly as it was transmitted 4. Each segment is then handed to the Network layer for network addressing and routing through the internetwork - Logical addressing (for example, IP and IPv6) is used to get each segment to the correct network; The Network layer protocol adds a control header to the segment handed down from the Transport layer, and what we have now is called a packet or datagram *The Transport and Network layers work together to rebuild a data stream on a receiving host; the Data Link layer that's responsible for taking packets from the Network layer and placing them on the network medium (cable or wireless)* 5. The Data Link layer encapsulates each packet in a frame, and the frame's header carries the hardware addresses of the source and destination hosts - If the destination device is on a remote network, then the frame is sent to a router to be routed through an internetwork; Once it gets to the destination network, a new frame is used to get the packet to the destination host - To put this frame on the network, it must first be put into a digital signal 6. Since a frame is really a logical group of 1s and 0s, the physical layer is responsible for encoding these digits into a digital signal, which is read by devices on the same local network; The receiving devices will synchronize on the digital signal and extract (decode) the 1s and 0s from the digital signal

Data Encapsulation Method

1. User information is converted to data for transmission on the network 2. Data is converted to segments, and a reliable connection is set up between the transmitting and receiving hosts 3. Segments are converted to packets or datagrams, and a logical address is placed in the header so each packet can be routed through an internetwork 4. Packets or datagrams are converted to frames for transmission on the local network; Hardware (Ethernet) addresses are used to uniquely identify hosts on a local network segment 5. Frames are converted to bits, and a digital encoding and clocking scheme is used

Ethernet Cabling

3 Types: - Straight-through cable - Crossover cable - Rolled cable

Cyclic Redundancy Check (CRC)

A mathematical algorithm that's run when each frame is built based on the data in the frame

Category 5 Enhanced Unshielded Twisted Pair (UTP) Cable

Can handle speeds up to a gigabit with a distance of up to 100 meters

1000Base-T (IEEE 802.3ab)

Category 5, four-pair UTP wiring up to 100 meters long and up to 1 Gbps

Tunneling

Encapsulating a frame within a different type of frame

Crossover Cable

RJ45 UTP Cable Question #1: What type of cable is used between the switches?

Crossover cable between the switches Rolled cable between the router and the console Straight-through cable between the router and the switch Straight-through cable between the switches and the hosts

RJ45 UTP cable question #2: What types of cables are used in the network example?

Collision Domain

Refers to a network scenario wherein one device sends a frame out on a physical network segment forcing every other device on the same segment to pay attention to it

1000Base-LX (IEEE 802.3z)

Single-mode fiber that uses a 9-micron core and 1300 nm laser and can go from 3 kilometers up to 10 kilometers

Attenuation

The loss of signal strength as it travels the length of a cable and is measured in decibels (dB)

Crosstalk

The unwanted signal interference from adjacent pairs in the cable

10GBase-T (802.3.an)

- A standard proposed by the IEEE 802.3an committee to provide 10 Gbps connections over conventional UTP cables, (category 5e, 6, or 7 cables) - Allows the conventional RJ45 used for Ethernet LANs and can support signal transmission at the full 100-meter distance specified for LAN wiring

Collision Event

- If two devices on a single physical segment just happen to transmit simultaneously, it will cause a collision and require these devices to retransmit - A situation where each device's digital signals totally interfere with one another on the wire

Broadcast Domain

- Refers to a group of devices on a specific network segment that hear all the broadcasts sent out on that specific network segment - Usually a boundary delimited by physical media like switches and routers - Can also refer to a logical division of a network segment, where all hosts can communicate via a Data Link Layer, hardware address broadcast

1000Base-SX (IEEE 802.3z)

- The implementation of 1 Gigabit Ethernet running over multimode fiber-optic cable instead of copper twisted-pair cable, using short wavelength laser - Multimode fiber (MMF) using 62.5- and 50-micron core - Uses an 850 nanometer (nm) laser and can go up to 220 meters with 62.5-micron, 550 meters with 50-micron

Straight-Through Cable

- Used to connect the following devices: Host to switch or hub Router to switch or hub - Four wires (2 wire pairs) are used to connect Ethernet devices; Only pins 1, 2, 3, and 6 are used - 10/100 Mbps Ethernet-only cable

Full-Duplex Ethernet

- Uses two pairs of wires at the same time instead of a single wire pair like half-duplex - Uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device - Transfers happen a lot faster when compared to half-duplex transfers - Because the transmitted data is sent on a different set of wires than the received data, collisions won't happen - Can be used with any device except a hub - Supposed to offer 100-percent efficiency in both directions; Rate is known as an aggregate rate (not guaranteed)

Auto-Detect Mechanism

- When a full-duplex Ethernet port is powered on, it first connects to the remote end and then negotiates with the other end of the Fast Ethernet link - The mechanism first decides on the exchange capability, which means it checks to see if it can run at 10, 100, or even 1000 Mbps - It then checks to see if it can run full-duplex, and if it can't, it will run half-duplex

Six Situations in which Full-Duplex Ethernet can be used

- With a connection from a switch to a host - With a connection from a switch to a switch - With a connection from a host to a host - With a connection from a switch to a router - With a connection from a router to a router - With a connection from a router to a host