Introduction to Data Communications
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The Frame Control (FC) field is used to:

• Indicate frame type (MAC or LLC)
• Provides communication at the MAC level between stations

The FC field consists of 8 bits:

	F F Z Z Z Z Z Z

Where:

• F = Frame Type (00 = MAC, 01 = LLC, 1x = not defined)
• Z = Control Bits

The Frame Type indicates whether it is a MAC layer addressed communication or an LLC layer addressed communication.

The Control bits indicate the type of MAC level communication:

• 00 - Normal Buffer
• 01 - Express Buffered
• 02 - Beacon
• 03 - Claim Token
• 04 - Ring Purge
• 05 - Active Monitor
• 06 - Standby Monitor

Destination Address (DA)

The Destination Address (DA) is use to indicate the destination address of the Token Frame (information frame). It consists of 48 address bits.

The first bit is the Individual/Group (I/G) bit - this is used to indicate an individual or broadcast (to everyone). The 2nd bit is used to indicate whether a Universal or Local naming convention. A Universal naming convention would use the MAC address burnt into the NIC's ROM. The Local naming convention would be set by the Lan Administrator. The remaining 46 bits are the stations unique address.

Introduction to Data Communications
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