ccna course-2 aitso ccna course -2 class-3 (22-04-2014)

CCNA Course-2

AITSOCCNA Course -2

Class-3 (22-04-2014)

jjRA

Ethernet Networking & Data Encapsulation Chapter-2 (Page 41-75)

Collision Domain

A collision domain is a group of Ethernet or fast Ethernet devices that are directly connected by repeaters or hubs. At any time only one node/device may transmit inside of this collision domain. Repeaters and hubs are physical layer devices and do not understand Ethernet frames or protocols. Their role is to simply extend distance and to facilitate star topology.

Collisions are often in a hub environment, because each port on a hub is in the same collision domain

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Ethernet Networking & Data Encapsulation

Broadcast Domain

A broadcast domain is a domain in which a broadcast is forwarded. A broadcast domain contains all devices that can reach each other at the data link layer (OSI layer 2) by using broadcast. All ports on a hub or a switch are by default in the same broadcast domain. All ports on a router are in the different broadcast domains and routers don't forward broadcasts from one broadcast domain to another.

In the picture above we have three broadcast domains

Ethernet Networking & Data EncapsulationCSMA/CD

Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is the protocol for carrier transmission access in Ethernet networks.

CSMA/CD is a Media Access Control mechanism, whenever any PC wants to send a data, it first sends out a dummy electrical signal into the channel to check whether any incoming data traffic is coming down or the line is free. If the traffic is already coming down, then the dummy signal collides with the incoming traffic and sends back a jam signal to the PC so that, the PC is notified to hold its traffic for a random amount of time before attempting to send the data again. This process will continue until the line/channel becomes free. The moment line is free, the PC immediately initiates/send it's data to the intended destination. This is how the data collision is avoided in a half-duplex channels.

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The Half-duplex transmission is capable of sending signal in both directions, but in only one direction at a time.

Full-duplex It allows signal transmission in both directions simultaneously.

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Advantage-Disadvantage of Half Duplex and Full Duplex.

Half duplex uses the same medium to receive and transmit data, but that data is received and transmitted at different times.A full duplex network, on the other hand, can receive and transmit data simultaneously.

Speed

Speed is a big advantage of a full duplex network infrastructure. That can result in faster throughput speeds

Homogeneous Environment

It can be much easier for network administrators to work with a single homogeneous environment. Troubleshooting is easier when every piece of network equipment, from the servers, switches and hubs in the data room to the terminals and computers on the floor, are set to full duplex or Half Duplex

Compatibility & Stability


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Ethernet at the Data Link Layer

Ethernet provides services corresponding to Layers 1 and 2 of the OSI reference model, and IEEE 802.3 specifies the physical layer (Layer 1) and the channel-access portion of the Data Link (Layer 2)

The IEEE defines the format and assignment of LAN addresses. To ensure a unique MAC address, the first half of the address identifies the manufacturer of the card. This code is called the organizationally unique identifier (OUI).Each manufacturer assigns a MAC address with its own OUI as the first half of the address. The second half of the address is assigned by the manufacturer and is never used on another card or network interface with the same OUI.

Ethernet AddressingEvery network device has a unique physical identity that is assigned by the manufacturing vendor is called MAC address or Ethernet address.

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The IEEE defines two general categories of group addresses for Ethernet:Broadcast addresses: The broadcast address implies that all devices on the LAN should process the frame and has a value of FFFF.FFFF.FFFF.Multicast addresses: Multicast addresses are used to allow a subset of devices on a LAN to communicate. When IP multicasts over an Ethernet, the multicast MAC addresses used by IP follow this format: 0100.5exx.xxxx, where any value can be used in the last half of the address.


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Ethernet frameAn Ethernet frame is a way of arranging sections of data for transfer over a computer network. There are various types of data frames such as Ethernet frames, Ethernet jumbo frames and snap frames etc.

64 bit preamble is 7 bytes for synchronization and 1 byte for SFD, which basically says here comes a new frame.

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The destination address (DA) and source address (SA) fields contain the 6-octet (48-bit) MAC addresses for the destination and source ports on the network. These Layer 2 addresses uniquely identify the devices on the LAN.


The length/type field is a 2-octet field that either indicates the length of the frame's data field or identifies the protocol stack associated with the frame. Following are some common frame types: AppleTalk—0x809B AppleTalk ARP—0x80F3 DECnet—0x6003 IP—0x0800 IPX—0x8137 Loopback—0x9000 XNS—0x0600

The frame check sequence (FCS) field is a 4-octet field that contains the calculated CRC value. This value is calculated by the originating host and appended to the frame. When it receives the frames, the receiving host calculates the CRC and checks it against this appended value to verify the integrity of the received frame.

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Common Name Speed Alternative Name

Name of IEEE Standard

Cable Type, Maximum Length

Ethernet 10 Mbps 10BASE-T IEEE 802.3 Copper, 100 m

Fast Ethernet 100 Mbps 100BASE-TX IEEE 802.3u Copper, 100 m

Gigabit Ethernet 1000 Mbps 1000BASE-LX, 1000BASE-SX

IEEE 802.3z Fiber, 550 m (SX) 5 km (LX)

Gigabit Ethernet 1000 Mbps 1000BASE-T IEEE 802.3ab Copper, 100 m

10GigE (Gigabit Ethernet)

10 Gbps 10GBASE-SR, 10GBASE-LR

IEEE 802.3ae Fiber, up to 300 m (SR), up to 25 km (LR)

10GigE (Gigabit Ethernet)

10 Gbps 10GBASE-T IEEE 802.3an Copper, 100 m

Common IEEE Ethernet Standard

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Ethernet Cabling

An Ethernet cable is one of the most popular forms of network cable used on wired networks. Ethernet cables connect devices on local area networks such as PCs, routers and switches.Ethernet cables are grouped into sequentially numbered categories (CAT)


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Physical DifferencesThere are two main physical differences between Cat-5 and Cat-6 cables, the number of twists per cm in the wire, and sheath thickness. Cable twisting length is not standardized, but typically there are 1.5-2 twists per cm in Cat-5(e) and 2+ twists per cm in Cat-6. Within a single cable

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Solid cable uses a single piece of copper for the electrical conductor while stranded uses a series of copper cables twisted together.


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Three types of Ethernet cables are available:

• Straight-through cable• Crossover cable• Rolled cable

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An optical fiber cable is a cable containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed.

Types of Optical FiberThere are two basic types of fiber: multimode fiber and single-mode fiber.

Multimode fiber is best designed for short transmission distances, and is suited for use in LAN systems and video surveillance.

Single-mode fiber is best designed for longer transmission distances, making it suitable for long-distance telephony and multichannel television broadcast systems


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LC

This interface was developed by Lucent Technologies (hence, Lucent Connector). It uses a retaining tab mechanism, similar to a phone or RJ45 connector, and the connector body resembles the squarish shape of SC connector. LC connectors are normally held together in a duplex configuration with a plastic clip. The ferrule of an LC connector is 1.25mm. SC

SC connectors also use a round 2.5mm ferrule to hold a single fiber. They use a push-on/pull-off mating mechanism which is generally easier to use than the twist-style ST connector when in tight spaces. The connector body of an SC connector is square shaped, and two SC connectors are usually heldST ST (Straight Tip an AT&T Trademark) is probably still the most popular connector for multimode networks

FC (Fixed Connection)FC was one of the most popular singlemode connectors for many years


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Data Encapsulation


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THANK YOU

ccna course-2 aitso ccna course -2 class-3 (22-04-2014)

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