Lesson 4—Networking BASICS1 Networking BASICS Network Architectures Unit 2 Lesson 4

1Lesson 4—Networking BASICS

Networking BASICS

Network Architectures

Unit 2

Lesson 4

Lesson 4—Networking BASICS 2

Objectives• Explain why standards were

developed for LANs.

• Give several examples of Ethernet architectures.

• List the features of a token ring network.


Objectives (continued)

• Tell how a wireless LAN functions.

• Provide guidelines for designing a network.


Standards• Different architectures could

restrict the growth of networking.

• The Institute of Electrical and Electronic Engineers (IEEE) developed computer network architecture standards.


Standards• The IEEE efforts were called

Project 802.• There are three dominant

standards: Ethernet (802.3), token ring (802.5), and wireless (802.11).


Ethernet• Ethernet is the most popular LAN architecture

today. • It is easy to install and inexpensive. • Data transmission is broken into packets. • The standard method of labeling different

versions is Maximum Speed-Transmission Mode-Segment Length or Media Type.


10Base2• It is a bus topology that uses contention

(CSMA/CD) and thin coax.

• Segments are connected together through a repeater.

• It can connect up to five 200-meter segments using four repeaters (5-4-3 rule).


10Base2


10Base-T• It runs 10 Mbps and uses

CSMA/CD.• It is a star-wired bus

topology. • It is still used today due to its

reliability and ease of use.


10Base-T


100Base-T• It uses CMSA/CD as a star-wired

bus.• There are three subcategories of

100Base-T networks with different cable requirements.

• The most common is 100Base-TX (Category 5 or higher UTP).


Switched Ethernet• A switch knows which segment

belongs to which device.

• It uses a table stored in memory to send a packet.

• It increases bandwidth by decreasing traffic and collisions.


Switched Ethernet


100VG-AnyLAN • It uses Category 3 or higher cabling or

fiber optic cable.• It is a true star network topology with

central hubs controlling the network.• It uses the demand priority channel

access method.• It supports other network architectures.


Gigabit Ethernet • 1000Base-T is a star topology

that uses Category 5 or higher cabling.

• It increases speed by sending more bits and using 4 pairs of wires simultaneously.


10G Ethernet

• It can be used in both LANs and WANs.

• It requires fiber optic cable.

• Networks do not encounter collisions.


Token Ring • It has the ability to diagnose and

avoid network problems.

• It does not slow down when more devices are added to the network.

• The packet size can be larger than on an Ethernet network.


Token Ring • IEEE Project 802.5• 16-Mbps speed• It uses twisted pair cable in a hybrid

star ring topology• The packets go to a central hub

called the Multistation Access Unit (MAU).


Token Ring


WLAN• Wireless local area network• It is used when mobility is needed,

but it still must remain connected to the network.

• 802.11b or Wi-Fi (11 Mbps)• 802.11a or Wi-Fi5 (108 Mbps)• 802.11g (54 Mbps)


WLAN• Only wireless network interface cards

and access points are needed.

• An access point acts as a link between wireless and wired networks.

• 802.11b uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).


WLAN


Network Design• Basic rules should be followed for a

good network design.

• The switches in an Ethernet network must be configured in a hierarchy.

• Smaller network segments are better than larger network segments.


Summary• In the early 1980s, the Institute of Electrical and Electronic

Engineers (IEEE) began work on developing computer network architecture standards. Known as Project 802, this work estab-lished the foundation for three network architecture standards that make up over 95 percent of the LANs in use today. These three dominant standards are Ethernet (802.3), token ring (802.5), and wireless (802.11).

• IEEE Project 802.3 set specifications for a type of local area network known as Ethernet. Several versions of Ethernet trans-mit at 10 Mbps, but these are rarely used today. 10Base5, also called Standard Ethernet, required the use of thick coaxial cable. Other versions of 10 Mbps Ethernet were designed to run over fiber optic cable in specific settings.


Summary (continued)• 10Base2 is a version of Ethernet that used to be very popular

and is still used today, although not as extensively. 10Base2 is a bus topology that uses contention (CSMA/CD) and requires thin coax cable as the transmission media. 10Base-T also runs at 10 Mbps, uses CSMA/CD, and can support a total of 1,024 devices on the network. 10Base-T is a star-wired bus topology, which means it functions like a bus (in that each packet makes a stop at every device), but is wired like a star (with one central controlling device).


Summary (continued)• As faster network architectures were needed beyond 10 Mbps,

the IEEE subcommittee began work on creating a new Ethernet standard called 100Base-T (or Fast Ethernet). 100Base-T has many of the same basic characteristics as 10Base-T. It uses CSMA/CD as its channel access method, the topology is a star-wired bus, and it continues to use the same basic equipment (such as hubs in distribution racks with patch panels). The only new items for 100Base-T networks were 100-Mbps NICs and 100-Mbps hubs. To increase the speed even more, a switch (or a switching hub) is used. A switch knows which segment goes to which network device. This dramatically increases the band-width on the network because it decreases the traffic and the number of collisions. Ethernet networks that use switching hubs are often called Switched Ethernet.


Summary (continued)• 100VG-AnyLAN also runs at 100 Mbps. The network topology is a true

star, with central hubs controlling the network. 100VG-AnyLAN uses the demand priority channel access method instead of CSMA/CD. This means that when a device needs to transmit a packet, it must first send a request to the hub and then wait for permission before transmitting. Unlike CSMA/CD, demand priority prevents collisions that slow down the network. Another advantage of 100VG-AnyLAN is its ability to support other network architectures.

• Gigabit Ethernet (or 1000Base-T) is the standard that most closely resembles 100Base-TX. 1000Base-T is a star topology that uses Category 5 or higher cabling. 1000Base-T achieves its higher speed by increasing the number of bits sent and sending data in over all four pairs of wires simultaneously. 10G Ethernet transmits at 10 billion bits per second.


Summary (continued)• IEEE Project 802.5 set specifications for a type of local area

network known as token ring. Token ring runs at 16 Mbps and uses twisted pair cable in a hybrid star ring topology. The packets in a star ring do not go directly to the next device on the ring; instead, they go to a central hub, which then sends the packet to the next device on the ring. At the center of a token ring network is a hub, called the Multistation Access Unit (MAU). Token ring also has the ability to diagnose and avoid network problems.


Summary (continued)• Wireless local area networks (WLANs) are found anywhere a

user needs mobility but still must remain connected to a net-work. The list of components necessary for a WLAN is short. Only wireless network interface cards and access points are needed for communication to take place. A wireless NIC per-forms the same functions as a wired NIC except an antenna is used to send and receive radio frequency signals. An access point (AP) is a device that contains a radio transceiver (to send and receive signals) along with an RJ-45 wired network inter-face, which allows it to connect by cable to a standard wired network.


Summary (continued)• Some basic rules should be followed for good network design. First,

switches in an Ethernet network must be configured in a hierarchy, sometimes known as an inverted tree. In a hierarchy, only one possible path exists between any two devices. Secondly, smaller network seg-ments are better than larger network segments. Smaller segments make managing a network easy to do. Segmenting can also be accom-plished by dividing the network into a hierarchy using switches. Core switches are those switches that are farther up in the hierarchy and carry traffic between switches. Workgroup switches are connected directly to the devices on the network. Lower-cost hubs can often be substituted for switches at the workgroup level. Segmenting can also be accomplished by grouping devices into logical groupings. This is known as creating a virtual LAN (VLAN).

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Lesson 4—Networking BASICS1 Networking BASICS Network Architectures Unit 2 Lesson 4