The document discusses several IEEE 802 standards for local and metropolitan area networks. It describes the purpose of IEEE 802 standards to define physical network interfaces and the lowest three layers of the network architecture. It provides details on some famous IEEE 802 standards including 802.2 (LLC), 802.3 (Ethernet), 802.4 (Token Bus), 802.5 (Token Ring), 802.6 (DQDB), and 802.11 (Wireless LAN). It then focuses on explaining the Ethernet, Token Bus and Token Ring standards in more depth including their frame formats and other specifications.

1. IEEE 802 Standards for
LAN & MAN
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2. IEEE 802 Standards
 Define physical network interfaces such
as NICs, bridges, routers, connectors,
cables etc.
 Describe the three lowest layers of
network architecture: physical layer,
MAC sublayer & Data link layer.
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3. Famous IEEE Standards
 802.2 : LLC
 802.3 : Ethernet
 802.4 : Token Bus
 802.5 : Token Ring
 802.6 : DQDB (MAN standard)
 802.11 : Wireless LAN (CSMA)
 802.14 : Cable Modem
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4. 802.3 - Ethernet
 Modes of operation: half-duplex and full-duplex
 Four data rates defined for operation over optical fiber and
twisted-pair cables:
 10 Mbps - 10Base-T Ethernet (IEEE 802.3)
 100 Mbps - Fast Ethernet (IEEE 802.3u)
 1000 Mbps - Gigabit Ethernet (IEEE 802.3z)

10-Gigabit - 10 Gbps Ethernet (IEEE 802.3ae).
 Three basic elements:
 physical medium
 a set of medium access control rules, and
 an Ethernet frame that consists of a standardized set of bits used to
carry data over the system.
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5. Ethernet Frame
•Preamble (PRE)- 7 bytes. To synchronize the frame-reception portions of receiving
physical layers with the incoming bit stream.
•Start-of-frame delimiter (SFD)- 1 byte.
•Destination address (DA)- 6 bytes
•Source addresses (SA)- 6 bytes
•Length/Type- 2 bytes. This field indicates the number of data bytes that are contained in
the data field of the frame.
•Data- Is a sequence of n bytes (46=< n =<1500) of any value. (The total frame minimum is
64 bytes.)
•Frame check sequence (FCS)- 4 bytes. Contains a 32-bit cyclic redundancy check
(CRC) value to check for damaged frames.
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6. Ethernet Specifications
 10Base2 : thin wire coax cable
 10Base5 : thick wire coax cable
 10BaseF : Optical fiber cable
 10BaseT : Twisted pair cable
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7. 802.4 –
Token Bus
 It a network implementing the token ring protocol over a "virtual
ring" on a coaxial cable.
 A token is passed around the network nodes and only the node
possessing the token may transmit. If a node doesn't have
anything to send, the token is passed on to the next node on the
virtual ring.
 Token Bus suffered from two limitations:
 Any failure in the bus caused all the devices beyond the failure to
be unable to communicate with the rest of the network.
 Adding more stations to the bus was somewhat difficult.
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8. Token Bus Frame
Frame Control (FC):
This field is used to distinguish data frames from control
frames.
For data frames, it carries the frame's priority indicator
requiring destination to acknowledge the frame receipt.
For control frames, it is used to specify the frame type. The
allowed types include token passing, entrance of any new
station and various ring maintenance functions.
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9. 802.5 –
Token Ring
 The principle used in the token ring network is that a
token is circulating in the ring and whichever node grabs
that token will have right to transmit the data
 Each link is terminated with an active repeater that
detects a data packet on the in-bound link and re-
transmits it on the outbound link.
 At the end of the packet transmission, the data
equipment unit issues another idle token.
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10. Token Ring Frame
Token consists of –
Start delimiter - which alerts the stations of a token arrival.
Access control byte - which contains the priority and reservation
fields, a token bit to differentiate token from data/command frame and
a monitor bit checking whether a frame is circling the ring endlessly.
End delimiter - which signals the end of a frame, end of a logical
sequence and damaged frames.
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11. Things to do
 LAN transmission modes
 LLC, Hiper LAN
 Ethernet cables & connectors
 CSMA/CD, Frame Relay & X.25 protocol
 Comparison of various IEEE Standards
 Merits & demerits of IEEE Standards
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