Lesson 9

Quick Lesson 8 Re-cap – HOT TIP


Ethernet Frames can have a total size of 1526 bytes – the data at a maximum or 1500 bytes

The minimum can be 72 bytes where the data is at the minimum of 46 bytes

Lesson 9

IEEE Standards

• A family of Networking standards developed by the IEEEE in 1980 to address the rapid changes in networking technology. The 802.x standards are divided into several sub-categories to address the different requirements.

We work with 3 main standards:

1. 802.3 – Ethernet (CSMA/CD)

2. 802.5 – Ring

3. 802.11 - Wireless

802.3 Standard

• IN addition to the media type (cable) 802.3 also defines the transmission speed and signal method.

10 Base standard

• This describes the type of media used and the speeds at which each type of media operates. The cable specification contains three components

• A number indicating the speed

• The signal type in baseband or broadband

• The code for either copper or fiber

The codes and physical media are as follows:

T – UTP or STP (cat3,4,5,5e)

F – Fiber optic

FL – Fiber optic link

FX – Fiber optic using 2 pairs of multimode fiber



10Mbps table below:

10Base-2

Standard Specification Medium Distance

10Base-2 IEEE 802.3a Thinnet Coax 185 metres

10Base-5 IEEE 802.3 ThickNet 500 metres



Fast Ethernet

Standard Specification Medium Distance

100Base-T IEEE 802.3u Cat 5 UTP 100 metres



Gigabit Ethernet (1000 Mbps)

Standard Specification Medium Distance

1000Base-T IEEE 802.3ab Cat 5e or Cat 6 UTP 100 metres



Token Ring Networks

Token-based Media Access

• Media access method in which computers pass a special sequence of bits called a token between them. Only the node holding the token can transmit on the network.

Token Ring Standards – these use a MAU NOT a Hub

• There are two token ring standards that are very similar. IBM Token Ring and IEEE 802.5

Token Ring Characteristics IBM Token Ring IEEE 802.5

Transmission Speed 4/16 Mbps 4/16Mbps

Media Type Star Not Specified

Signalling Baseband Baseband

Access Method Token Passing CSMA/CA Token Passing



Token States

Token State Description

Available There is no data in the payload and the token may be captured for use

Captured There is a valid data payload

Acknowledged Notification of either ACK or NACK positive or negative

Reserved A priority system, in which the token can be reserved



Token ring Access Priority

• Token ring networks use a priority system that permits certain user designated high priority stations to use the network more frequently. They have a priority and reservation field.

MAU (Multi-station Access Unit) – sometimes called a MSAU

• MAU’s can be wired together to form a ring using patch cables and lobe cables for connections.

• A MAU has the same function as a switch.

Token Ring Failure Recovery

• Token ring networks take on a star configuration when a device is turned off or disconnected from the network. IN this situation the MAU simply bypasses the disconnected device, when the device is online but not responsive the MAU will keep the connection live but breaks the ring because the device is not passing data.

Fiber Distributed Data Interface (FDDI) – 802.5 (ring)

Ring 802.5 has an IN and OUT port on the NIC, for FDDI has 2X IN and 2X OUT

This is not very important but nice to know.

It is a networking ring technology that uses double single mode or multimode fiber that operate at 100Mbps.

• Dual Ring

o FDDI ring does not have a device such as a MAU to remove stations when they are turned off. Second fiber transceivers cannot be configured to reverse, there is receive hardware and transmit hardware.

• FDDI Connection Devices

o Nodes are connected to the FDDI in one of two ways.

 In dual attached stations (DAS) nodes are connected directly to both the primary and secondary rings

 IN single attached stations (SAS) node are connected to a concentrator which is connected to both rings. – Here the concentrator gives the SAS access to the primary ring.

FDDI Failure recovery

• DAS nodes provide fault tolerance measure that detects loss if connectivity and then loop back the signal.