Transcript Layer2 Technologies Power Point for Chapter #3

C.C.Chau
P.1
Chapter 7
Layer 2 - Technologies
C.C.Chau
P.2
Lecture Objective (Week 8)
• After finishing the lecture, student should
be able to:
– Describe the IEEE 802 standards
– Learn Token Ring technology (by your own)
– Understand FDDI architecture, cable type, &
signaling technique
– Explain how Ethernet works
– Explain the operation of Layer 2 devices
C.C.Chau
IEEE Standard
Title and Comments
802
Standards for Local and Metropolitan Area Networks
802.1
LAN and MAN Bridging and Management (including Spanning Tree Protocol)
802.2
Logical Link Control
802.3
Carrier Sense Multiple Access/ Collision Detect (CSMA/CD) Access Method
802.3u Fast Ethernet
802.3z Gigabit Ethernet
802.4
Token Passing Bus Access Method
802.5
Token Ring Access Method
802.6
Distributed Queue Dual Bus Access Method (for WANs)
802.7
Broadband Local Area Networks
802.8
Fiber-Optic Local and Metropolitan Area Networks
802.9
Integrated Services (internetworking between subnetworks)
802.10 LAN/MAN Security
802.11 Wireless LANs(1 baseband IR and 2 microwave signals in the 2.4-2.5kMHz
band)
802.12 High-speed LANs (100 Mbps signals using Demand Priority Access Method)
802.14 Cable TV Access Method
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C.C.Chau
P.4
Overview of Token Ring and its variants
• The term Token
Ring refers both
to IBM's Token
Ring and to
IEEE's 802.5
specification.
C.C.Chau
P.5
• Token:
Token Ring
Frame Format
– Start Delimiter: alerts each station to the arrival of a frame.
– Access Control Byte: contains the priority and reservation field, and a
token and monitor bit.
• token bit distinguishes a token from a data/command frame
• monitor bit determines whether a frame is continuously circling the ring.
– End Delimiter: signals the end of the token or data/command frame.
C.C.Chau
P.6
Data/Command Frames
•
•
•
•
vary in size depending on the size of the information field. Data frames
carry information for upper-layer protocols; command frames contain
control information and have no data for upper-layer protocols.
Frame Control Byte: indicates whether the frame contains data or
control information.
– In control frames, this byte specifies the type of control information.
Address Fields: that identify destination and source stations.
Data Field: length of this field is limited by the ring token that holds the
time, thus defining the maximum time a station may hold the token.
Frame Check Sequence (FCS) Field : The source station fills this field
with a calculated value dependent on the frame contents. The
destination station recalculates the value to determine whether the
frame has been damaged in transit. The frame is discarded if it has been
damaged. As with the token, the end delimiter completes the
data/command frame.
C.C.Chau
P.7
Token
Passing
• Token-passing networks move a small frame, called a token, around
the network. Possession of the token grants the right to transmit data.
If a node that receives a token has no information to send, it passes
the token to the next end station. Each station can hold the token for
a maximum period of time, depending on the specific technology that
has been implemented.
C.C.Chau
Token Passing
• When a token is passed to a host that has information to transmit, the
host seizes the token and alters 1 bit of it. The token becomes a startof-frame sequence.
• Next, the station appends the information to transmit to the token and
sends this data to the next station on the ring. There is no token on the
network while the information frame is circling the ring, unless the ring
supports early token releases. Other stations on the ring cannot
transmit at this time. They must wait for the token to become available.
Token Ring networks have no collisions. If early token release is
supported, a new token can be released when the frame transmission
has been completed.
• The information frame circulates around the ring until it reaches the
intended destination station, which copies the information for
processing. The information frame continues around the ring until it
reaches the sending station, where it is removed. The sending station
can verify whether the frame was received and copied by the
destination.
P.8
C.C.Chau
Token Passing
• Token-passing networks are deterministic.
– we can calculate the maximum time that will pass before any end station will
be able to transmit.
– ideal for applications where any delay must be predictable, and robust
network operation is important. Factory automation environments are
examples of predictable robust network operations.
• Priority System
– Token Ring frames have two fields that control priority - the priority field and
the reservation field.
– Only stations with a priority equal to, or higher than, the priority value
contained in a token can seize that token.
– Once the token has been seized and changed to an information frame, only
stations with a priority value higher than that of the transmitting station can
reserve the token for the next network pass. The next token generated
includes the higher priority of the reserving station. Stations that raise a
token's priority level must reinstate the previous priority when their
transmission has been completed.
P.9
C.C.Chau
Token Ring Management Mechanisms
• one station act as the active monitor which performs a variety of ring
maintenance functions such as
– remove continuously circulating frames from the ring.
• active MSAUs (multi-station access units) can see all information in a
Token Ring network, thus enabling them to check for problems, and to
selectively remove stations from the ring whenever necessary.
• Beaconing - detects and tries to repair network faults.
– When a station detects a serious problem with the network (e.g. a cable
break) it sends a beacon frame. The beacon frame defines a failure
domain which includes the station that is reporting the failure, its nearest
active upstream neighbor (NAUN), and everything in between.
– Beaconing initiates a process called autoreconfiguration, where nodes
within the failure domain automatically perform diagnostics. This is an
attempt to reconfigure the network around the failed areas. Physically,
MSAUs can accomplish this through electrical reconfiguration.
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C.C.Chau
P.11
Token Ring
Signaling
• Signal encoding is a way of combining both clock and data information into a
stream of signals that is sent over a medium. Manchester encoding
combines data and clock into bit symbols, which are split into two halves,
the polarity of the second half always being the reverse of the first half.
Because both 0's and 1's result in a transition to the signal, the clock can be
effectively recovered at the receiver.
• Token-Ring uses the differential Manchester encoding method
C.C.Chau
P.12
Token Ring
Media and
Physical
Topologies
• IBM Token Ring network stations (often using STP and UTP as the media)
are directly connected to MSAUs, and can be wired together to form one
large ring.
• Patch cables connect MSAUs to other MSAUs that are adjacent to it. Lobe
cables connect MSAUs to stations. MSAUs include bypass relays for
removing stations from the ring
C.C.Chau
P.13
Token Ring Media and Physical Topologies
C.C.Chau
P.14
Fiber Distributed Data Interface (FDDI)
specifications
• Media Access Control (MAC) - defines how the medium is
accessed, including:
–
–
–
–
frame format
token handling
addressing
algorithm for calculating a cyclic redundancy check and error recovery
mechanisms
• Physical Layer Protocol (PHY) - defines data
encoding/decoding procedures, including:
– clocking requirements
– framing
– other functions
C.C.Chau
FDDI Specifications
• Physical Layer Medium (PMD) - defines the characteristics of the
transmission medium, including:
–
–
–
–
–
fiber optic link
power levels
bit error rates
optical components
connectors
• Station Management (SMT) - defines the FDDI station configuration,
including:
–
–
–
–
–
–
–
ring configuration
ring control features
station insertion and removal
initialization
fault isolation and recovery
scheduling
collection of statistics
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C.C.Chau
P.16
FDDI Format
• preamble - prepares each station for the upcoming frame
• start delimiter - indicates the beginning of the frame, and consists of
signaling patterns that differentiate it from the rest of the frame
• frame control - indicates the size of the address fields, whether the
frame contains asynchronous or synchronous data, and other control
information
C.C.Chau
P.17
FDDI Format
• destination address - contains a unicast (singular), multicast (group), or
broadcast (every station) address; destination addresses are 6 bytes
• source address - identifies the single station that sent the frame;
source addresses are 6 bytes
• data - control information, or information destined for an upper-layer
protocol
• frame check sequence (FCS) - filled by the source station with a
calculated cyclic redundancy check (CRC), value dependent on the
frame contents (as with Token Ring and Ethernet). The destination
station recalculates the value to determine whether the frame may
have been damaged in transit. If it has been, the frame is discarded.
• end delimiter - contains non-data symbols that indicate the end of the
frame
• frame status - allows the source station to determine if an error
occurred and if the frame was recognized and copied by a receiving
station
C.C.Chau
P.18
FDDI MAC
• FDDI uses a token passing strategy similar to Token Ring.
• FDDI are deterministic.
• FDDI's dual ring assures that not only are stations
guaranteed their turn to transmit, but if one part of one
ring is damaged or disabled for any reason, the second
ring can be used. This makes FDDI very reliable.
• FDDI supports real-time allocation of network bandwidth
by defining two types of traffic - synchronous and
asynchronous.
C.C.Chau
P.19
FDDI
Signaling
• FDDI uses an encoding scheme called 4B/5B. Every 4 bits of
data are sent as a 5 bit code.
• The signal sources in FDDI transceivers are LEDs or lasers.
C.C.Chau
FDDI
Media
• FDDI specifies a 100 Mbps, token-passing, dual-ring LAN that uses a
fiber-optic transmission medium. It defines the physical layer and
media access portion of the link layer, which is similar to IEEE 802.3 and
IEEE 802.5 in its relationship to the OSI Model. Although it operates at
faster speeds, FDDI is similar to Token Ring. The two networks share a
few features, such as topology (ring) and media access technique
(token-passing). A characteristic of FDDI is its use of optical fiber as a
transmission medium.
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C.C.Chau
P.21
FDDI Media
• Optical fiber offers several advantages over traditional
copper wiring, including such advantages as:
– security - Fiber does not emit electrical signals that can be tapped.
– reliability - Fiber is immune to electrical interference.
– speed - Optical fiber has much higher throughput potential than
copper cable.
• FDDI defines the two specified types of fiber: single-mode
(also mono-mode); and multi-mode.
– Single-mode fiber allows only one mode of light to propagate
through the fiber => higher bandwidth, and greater cable run
distances => used for inter-building connectivity
– multi-mode fiber allows multiple modes of light to propagate
through the fiber => modal dispersion => slower bandwidth, and
shorter cable run distances => used for intra-building connectivity
– Multi-mode fiber uses LEDs as the light-generating devices, while
single-mode fiber generally uses lasers.
C.C.Chau
FDDI
Media
• FDDI specifies the use of dual rings for physical connections. Traffic on
each ring travels in opposite directions. Physically, the rings consist of
two or more point-to-point connections between adjacent stations.
• The primary ring is used for data transmission; the secondary ring is
generally used as a back up.
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C.C.Chau
P.23
FDDI
Media
• Class A, or dual attachment stations (DAS), attach to both rings.
– SASs are attached to the primary ring through a concentrator, which
provides connections for multiple SASs. The concentrator ensures that a
failure, or power down, of any given SAS, does not interrupt the ring. This
is particularly useful when PCs, or similar devices that frequently power
on and off, connect to the ring.
• Class B, or single-attachment stations (SAS), attach to one ring
– DAS has two ports - designated A and B. These ports connect the station
to the dual FDDI ring, therefore, each port provides a connection for both
the primary and the secondary ring.
C.C.Chau
Comparing Ethernet and IEEE 802.3
• is well suited to applications where a local communication medium must
carry sporadic, occasionally heavy traffic at high peak data rates.
• shortly after the 1980 IEEE 802.3 specification, Digital Equipment
Corporation, Intel Corporation, and Xerox Corporation jointly developed
and released an Ethernet specification, Version 2.0, that was
substantially compatible with IEEE 802.3. Today, the term Ethernet is
often used to refer to all CSMA/CD LAN’s that generally conform to
Ethernet specifications, including IEEE 802.3.
• differences between Ethernet and IEEE 802.3 LANs are subtle.
– Ethernet provides services corresponding to Layer 1 and Layer 2 of the OSI
reference model.
– IEEE 802.3 specifies the physical layer, Layer 1, and the channel-access
portion of the data link layer, Layer 2, but does not define a Logical Link
Control protocol.
– Both Ethernet and IEEE 802.3 are implemented through hardware. Typically,
the physical part of these protocols is either an interface card in a host
computer or circuitry on a primary circuit board within a host computer.
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C.C.Chau
P.25
Ethernet Family Tree
C.C.Chau
P.26
10BASE-T
C.C.Chau
P.27
100BASE-TX
• 100BASE-TX (Fast Ethernet using Twisted Pair Cables)
• 100BASE-FX (Fast Ethernet using Optical Fiber)
C.C.Chau
P.28
1000BASE-T
• 1000BASE-T
– Gigabit Ethernet over UTP
C.C.Chau
P.29
1000BASE-SX and
1000BASE-LX
• 1000BASE-SX
– Gigabit Ethernet over
optical fiber with
short-wavelength laser
source
• 1000BASE-LX
– Gigabit Ethernet over
optical fiber with longwavelength laser
source
C.C.Chau
P.30
Ethernet Frame Format
C.C.Chau
P.31
Ethernet Frame Format
• preamble - The alternating pattern of 1's and 0's tells
receiving stations that a frame is Ethernet or IEEE 802.3.
• start-of-frame (SOF) - The IEEE 802.3 delimiter byte ends with
two consecutive 1 bits, which serve to synchronize the framereception portions of all stations on the LAN. SOF is explicitly
specified in Ethernet.
• destination and source addresses - The source address is
always a unicast (single-node) address. The destination
address can be unicast, multicast (group), or broadcast (all
nodes).
• type (Ethernet) - specifies the upper-layer protocol to receive
the data after Ethernet processing is completed.
• length (IEEE 802.3) - indicates the number of bytes of data
that follows this field.
C.C.Chau
P.32
Ethernet Frame Format
• data (Ethernet) - After physical-layer and link-layer processing is
complete, the data contained in the frame is sent to an upperlayer protocol, which is identified in the type field. Although
Ethernet version 2 does not specify any padding, in contrast to
IEEE 802.3, Ethernet expects at least 46 bytes of data.
• data (IEEE 802.3) - After physical-layer and link-layer processing
is complete, the data is sent to an upper-layer protocol, which
must be defined within the data portion of the frame. If data in
the frame is insufficient to fill the frame to its minimum 64-byte
size, padding bytes are inserted to ensure at least a 64-byte
frame.
• frame check sequence (FCS) - This sequence contains a 4 byte
CRC value that is created by the sending device and is
recalculated by the receiving device to check for damaged
frames.
C.C.Chau
P.33
Ethernet MAC
• Ethernet is a shared-media broadcast technology. The
access method CSMA/CD used in Ethernet performs three
functions:
– transmitting and receiving data packets
– decoding data packets and checking them for valid addresses
before passing them to the upper layers of the OSI model
– detecting errors within data packets or on the network
• In the CSMA/CD access method, networking devices with
data to transmit over the networking media work in a
listen-before-transmit mode. This means when a device
wants to send data, it must first check to see whether the
networking media is busy. The device must check if there
are any signals on the networking media.
C.C.Chau
Ethernet MAC
• After the device determines the networking media is not
busy, the device will begin to transmit its data. While
transmitting its data in the form of signals, the device also
listens. It does this to ensure no other stations are
transmitting data to the networking media at the same time.
After it completes transmitting its data, the device will
return to listening mode.
• Networking devices are able to tell when a collision has
occurred because the amplitude of the signal on the
networking media will increase.
• When a collision occurs, each device that is transmitting will
continue to transmit data for a short time. This is done to
ensure that all devices see the collision.
P.34
C.C.Chau
Ethernet MAC
• all devices on the network have backed off for a certain
period of time (different for each device), any device can
attempt to gain access to the networking media once again.
• When data transmission resumes on the network, the
devices that were involved in the collision do not have
priority to transmit data.
• Ethernet is a broadcast transmission medium. This means
that all devices on a network can see all data that passes
along the networking media.
• not all the devices on the network will process the data.
Only the device whose MAC address and IP address matches
the destination MAC address and destination IP address
carried by the data will copy the data.
P.35
C.C.Chau
Ethernet MAC
• Once a device has verified the destination MAC and IP
addresses carried by the data, it then checks the data
packet for errors. If the device detects errors, the data
packet is discarded.
• The destination device will not notify the source device
regardless of whether the packet arrived successfully or
not.
• Ethernet is a connectionless network architecture and is
referred to as a best-effort delivery system.
• Signal encoding is Manchester encoding
• 10BASE-T transceivers are designed to send and receive
signals over a segment that consists of 4 wires - 1 pair of
wires for transmitting data, and 1 pair of wires for
receiving data.
P.36
C.C.Chau
P.37
Ethernet 10BASE-T Media and Topologies
• Star topology is used;
communication between
devices attached to the
local area network is via
point-to-point wiring to
the central link or hub. All
network traffic in a star
topology passes through
the hub.
• The hub receives frames
on a port, then copies and
transmits (repeats) the
frame to all of the other
ports.
• In Ethernet where hubs act
as multiport repeaters,
they are sometimes
referred to as
concentrators.
C.C.Chau
P.38
Ethernet 10BASE-T Media and Topologies
• star topology’s advantages
– is that it is considered the easiest to design and install
– is its ease of maintenance since the only area of
concentration is located at the hub.
– is easy to modify and troubleshoot
• Workstations can be easily added to a network employing a star
topology.
• If one run of networking media is broken or shorted, then only the
device attached at that point is out of commission, the rest of the
LAN will remain functional.
• star topology's disadvantages
– while limiting one device per run of networking media
increases the amount of networking media required,
which adds to the setup costs.
– the hub represents a single point of failure
C.C.Chau
P.39
TIA/EIA568-A
Horizontal
Cabling
Standards
• TIA/EIA-568-A specifies that the physical layout, or topology that is to be
used for horizontal cabling, must be a star topology.
• This means the mechanical termination for each telecommunications
outlet/connector is located at the patch panel in the wiring closet. Every
outlet is independently and directly wired to the patch panel.
C.C.Chau
P.40
TIA/EIA-568-A Horizontal Cabling Standards
•
•
•
•
•
horizontal cabling for UTP < 90 m.
patch cords at the telecommunications outlet/connector < 3 m
patch cords/jumpers at the horizontal cross-connect I< 6 m.
horizontal cabling from the hub to any workstation < 100 (99)m
LAN that uses a star topology could cover the area of a circle with a radius
of 100 m.
C.C.Chau
Extend the TIA/EIA-568-A specified maximum
length
P.41
C.C.Chau
Layer 2 Devices
P.42
• A network interface card (NIC) plugs into a motherboard and provides ports
for network connection.
• Network cards communicate with the network through serial connections,
and with the computer through parallel connections.
• Network cards all require an IRQ, an I/O address, and upper memory
addresses for DOS and Windows 95/98. When selecting a network card,
consider the following three factors:
– type of network (e.g. Ethernet, Token Ring, FDDI, or other)
– type of media (e.g. twisted-pair, coaxial, or fiber-optic cable)
– type of system bus (e.g. PCI and ISA)
• NICs perform Layer 2 & 1 functions:
–
–
–
–
–
logical link control - communicates with upper layers in the computer
naming - provides a unique MAC address identifier
framing - part of the encapsulation process, packaging the bits for transport
Media Access Control (MAC) - provides structured access to shared access media
signaling - creates signals and interface with the media by using built-in
transceivers
C.C.Chau
P.43
Bridges
•
•
•
A bridge connects network segments and must make intelligent decisions about
whether to pass signals on to the next segment based on the station or MAC address.
A bridge can improve network performance by eliminating unnecessary traffic and
minimizing the chances of collisions.
Bridges often pass packets between networks operating under different Layer 2
protocols.
C.C.Chau
P.44
Bridge Layer 2 Operations
• Data packets originated from V and destined for Hh
C.C.Chau
P.45
Bridge Layer 2 Operations
• Bridges are not required to examine upper-layer information =>
Upper-layer protocol transparency
• Because bridges only look at MAC addresses, they can rapidly
forward traffic representing any network-layer protocol. To
filter or selectively deliver network traffic, a bridge builds tables
of all MAC addresses located on their directly connected
network segments.
• bridges can significantly reduce the amount of traffic between
network segments by eliminating unnecessary traffic.
• Bridges are internetworking devices that can be used to reduce
large collision domains. Collision domains are areas where
packets are likely to interfere with each other. They do this by
dividing the network into smaller segments and reducing the
amount of traffic that must be passed between the segments.
C.C.Chau
P.46
Bridge Layer 2 Operations
• Bridges work best where traffic is low from one segment of a network
to other segments. When traffic between network segments becomes
heavy, bridges can become a bottleneck and slow down
communication.
• Bridges always spread and multiply a special kind of data packet;
broadcasting packets. If too many broadcasts are sent out over the
network a broadcast storm can result. A broadcast storm can cause
network time-outs, traffic slowdowns, and the network to operate at
less than acceptable performance.
• Bridges increase the latency (delay) in a network by 10-30%. This
latency is due to the decision making that is required of the bridge, or
bridges, when transmitting data to the correct segment.
• A bridge is considered a store-and-forward device because it must
receive the entire frame and compute the cyclic redundancy check
(CRC) before forwarding can take place. The time it takes to perform
these tasks can slow network transmissions, thus causing delay.
C.C.Chau
P.47
Switches
• Switching is a technology that alleviates congestion in Ethernet LANs by reducing
traffic and increasing bandwidth. Switches, also referred to as LAN switches, often
replace shared hubs and work with existing cable infrastructures to ensure they are
installed with minimal disruption of existing networks.
C.C.Chau
Switches
P.48
• switching and routing equipment perform two basic operations:
– switching data frames -- The process by which a frame is received on an input
medium and then transmitted to an output medium.
– maintenance of switching operations -- Switches build and maintain switching
tables (based on MAC addresses) and search for loops. Routers build and
maintain both routing tables and service tables.
• Benefits:
– switches operate at much higher speeds than bridges, and can support new
functionality, such as virtual LANs.
– allowing many users to communicate in parallel through the use of virtual
circuits and dedicated network segments in a collision-free environment. This
maximizes the bandwidth available on the shared medium.
– moving to a switched LAN environment is very cost effective because existing
hardware and cabling can be reused
– network administrators have great flexibility in managing the network
through the power of the switch and the software to configure the LAN.
C.C.Chau
Switch
Layer 2
Operations
• LAN switches are considered multi-port bridges with no collision domain,
because of microsegmentation.
• By reading the destination MAC address Layer 2 information, switches can
achieve high-speed data transfers, much like a bridge does.
• Frame is sent to the port of the receiving station prior to the entire frame
entering the switch. This leads to low latency levels and a high rate of
speed for frame forwarding.
P.49
C.C.Chau
P.50
Switch Layer 2 Operations
• Ethernet switching increases the bandwidth available on a network. It
does this by creating dedicated network segments, or point-to-point
connections, and connecting these segments in a virtual network
within the switch. This virtual network circuit exists only when two
nodes need to communicate. This is called a virtual circuit because it
exists only when needed, and is established within the switch.
• Even though the LAN switch reduces the size of collision domains, all
hosts connected to the switch are still in the same broadcast domain.
Therefore, a broadcast from one node will still be seen by all other
nodes connected through the LAN switch.
• Similar to bridges, switches forward and flood traffic based on MAC
addresses. Because switching is performed in hardware instead of in
software, it is significantly faster. You can think of each switch port as a
micro-bridge; this process is called microsegmentation. Thus each
switch port acts as a separate bridge and gives the full bandwidth of
the medium to each host.
C.C.Chau
P.51
Ethernet LAN Segmentation
C.C.Chau
P.52
Reasons for Segmenting a LAN
• A bridge, or switch, diminishes the traffic experienced by
devices on all connected segments, because only a certain
percentage of traffic is forwarded. Both devices act as a
firewall for some potentially damaging network errors.
• They also accommodate communication between a larger
number of devices than would be supported on any single
LAN connected to the bridge.
• Bridges and switches extend the effective length of a LAN,
permitting the attachment of distant stations that were not
previously permitted.
C.C.Chau
P.53
Ethernet LAN Segmentation
• Distinctions between bridges and switches :
– Switches are significantly faster because they switch in
hardware, while bridges switch in software
– Switches can interconnect LANs of unlike bandwidth. A 10
Mbps Ethernet LAN and a 100 Mbps Ethernet LAN can be
connected by using a switch.
– Switches can support higher port densities than bridges.
– Some switches support cut-through switching, which
reduces latency and delays in the network, while bridges
support only store-and-forward traffic switching.
– Finally, switches reduce collisions and increase bandwidth
on network segments because they provide dedicated
bandwidth to each network segment.
C.C.Chau
P.54
Ethernet LAN Segmentation
• Segmentation by routers has all of above
advantages and more
– routers do not forward broadcasts unless programmed to
do so => creates smaller collision domains and smaller
broadcast domains
– routers can perform best path selection.
– routers can be used to connect different networking
media, and different LAN technologies.
C.C.Chau
P.55
Switch Segmentation of a Collision Domain
• A LAN that uses a switched Ethernet topology creates a network
that performs as though it had only two nodes – the sending
node and the receiving node. => the available bandwidth can
reach close to 100%.
• Ethernet networks perform best when kept under 30-40% of full
capacity. This limitation is due to Ethernet’s media access
method (CSMA/CD). Bandwidth usage that exceeds the
recommended limitation results in increased collisions. A switch
segments a LAN into micro-segments, thereby creating collision
free domains from one formerly larger collision domain.
• Switched Ethernet is based on standard Ethernet. Each node is
directly connected to one of its ports, or to a segment that is
connected to one of the switch's ports. This creates a 10 Mbps
connection between each node and each segment on the switch.
A computer connected directly to an Ethernet switch is its own
collision domain and accesses the full 10Mbps.
C.C.Chau
Router
Segmentation
of a Collision
Domain
• A router operates at the network layer, and bases all of its forwarding
decisions on the Layer 3 protocol address.
• Routers create the highest level of segmentation because of their ability to
make exact determinations of where to send the data packet.
• Routers operate with a higher rate of latency as they must examine
packets to determine the best path for forwarding them to their
destinations.
P.56
C.C.Chau
Segmentation by Bridges, Switches, & RoutersP.57