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ARP
- ○Address Resolution Protocol
- ○ Data traffic is routed using the network addresses
- ○ Data traffic is forwarded over a physical network using MAC addresses
- ○ ARP is a method used in TCP/IP suite to map network addresses to MAC addresses
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Transmission methods
- unicast
- multicast
- broadcast
- connection oriented
- connectionless oriented
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Unicast
§ Single packet from source to destination
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Multicast
§ Single packet that is sent to a specific subset of nodes
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Broadcast
§ Single packet that is sent to all nodes
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Connection oriented
- -must first establish a connection before sending data
- § Connection Establishment, data transfer, and connection termination
- § Method used for TCP
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Connectionless service
- - can send the data without the need to establish a connection
- § Transfer can simply send the data without the added overhead
- § Method used for UDP
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Local Area Network (LAN)
- ○ A high-speed network that is bounded by a small geographic area
- □ Tends to encompass one broadcast domain
- □ Usually restricted to a building or floor
- □ Operates at the layer 1 and 2 of the OSI model
- □ Interconnected using a hub or switch
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Ethernet
- ® Most commonly used
- ® Duplex – full/half
- ® Speed – 10/100/auto
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Data Identification at OSI Layers
- ○ Segment – Transport layer (Layer 4)
- ○ Packet – Network Layer (Layer 3)
- ○ Frame – Data Link Layer (Layer 2)
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Switching layers
- access layer
- distribution layer
- core layer
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Access Layer
- ○ This is the bottom layer of the 3 layer network design
- ○ Users are connected at this layer
- ○ Collision domains can be limited through VLANs
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Distribution Layer
- ○ Routing (or at the Core Layer)
- ○ Packet Filtering
- ○ QOS
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Core Layer
○ High speed data transfers and reliability
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Cisco Switches
- ○ Cisco switches can be modular in the number of ports they allow or non-modular
- § Non-Modular come in different sizes but the sizes are fixed and cannot be expanded
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Virtual Area LAN Network (VLAN)
- ○ A LAN not restricted by physical location
- § Can be developed based on more than physical location
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○ Benefits of VLAN
- § Performance
- § Formation of virtual workgroups
- § Easy Administration
- § Cost
- § Security
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Dynamic VLANs
- § Switch ports are joined to a VLAN based on the workstation’s MAC address
- § Cisco Works 2000 or VLAN Management Policy Server (VMPS) can be used to associate MAC addresses to VLANS
- § Management is a headache in large networks
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Static VLANs
- § Membership is based on the VLAN that a switch port belongs to
- □ Every port is configured to be belong to a VLAN
- § Static VLANs allow for tighter control of resources and user movement
- § Easy management
- □ No need to maintain large MAC address tables
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CatOS
- § OS loaded on Switches
- § Older OS and Cisco is working to move away from CatOS and to IOS
- □ IOS is used on routers
- § New equipment shipped comes with IOS
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Communication Closets
- ○ Ethernet has limits of 100 meters
- § Wiring runs longer than 100 meters could cause service failures
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Trunking
- ○ A method to support multiple VLANs that have members on more than one switch
- ○ Switches tag each frame so that the receiving switch knows which VLAN the frame belongs to
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○ Two trunking methods
- § Cisco Inter-Switch Link (ISL)
- § IEEE 802.1q
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○ Cisco ISL
- § ISL created before IEEE standardized a trunking protocol
- § ISL is a Cisco proprietary so it can only be used between Cisco switches
- § ISL encapsulates each Ethernet frame with an ISL header and trailer
- □ ISL header is 26 bytes
- ® VLAN number is encoded in header
- □ ISL trailer is 4 bytes CRC
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○ 802.1q
- § Developed in 1998
- § Actual frame is modified or tagged
- □ 4 bytes are added to the original Ethernet header
- ® A field within this header identifies the VLAN number
- § FCS is recalculated
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DTP
- Dynamic Trunk Protocol (DTP)
- ○ DTP is the process that takes place to determine whether tow connecting devices can create a trunk connection
- § Supports auto-negotiations for both ISL and 802.1q
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VTP
- • VLAN Trunking Protocol (VTP)
- ○ VTP is a Cisco proprietary messaging protocol that occurs between devices on trunk ports
- § Allows VLAN information to be propagated across your switched network so you have a consistent VLAN configuration
- § Makes management easy
- □ Propagates across mixed media
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VTP Domain
□ A management domain is a grouping of switches that will be sharing information about VLANs
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VTP Modes
- □ Server- Responsible for making all VLAN configurations (adds/changes/deletions)
- □ Client- Accepts VTP messages
- □ Transparent- Do not participate in management domain but do forward messages
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VTP Messages
- § Summary- Generated every 300 seconds to ensure all switches are in sync; -Contains a revision number
- § Request- Generated to acquire VLAN information
- § Subset- Generated in response to a request
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VTP Pruning
- § Allows a switch to make intelligent decisions concerning the forwarding of multicast, broadcast, and unknown destinations across trunk ports
- § Turned off by default
- § Switch must be in Server mode
- § Pruning can be done manually
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STP
- • Spanning Tree Protocol (STP)
- ○ A protocol developed to prevent loops
- § Places a port in either blocking or forwarding state
- □ Ports that are in forwarding state can send and receive frames
- § Traffic has to take longer paths
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How does STP Work
- ○ STP selects a root bridge
- § All interfaces on the root bridge in forwarding state
- ○ All other bridges select a port that has the least administrative cost between itself and the root bridge.
- § This port is called the root port
- ○ Every port is configured to be belong to a VLAN
- ○ All switches send out bridge protocol data units (BPDU) with the following information
- § Root bridge’s ID ID (MAC address+priority)
- □ Default priority is 32768
- § Cost to reach the root
- § Bridge ID of the sender
- ○ Bridge with the lowest ID becomes the root bridge
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Hello Time
- § How long a root waits before sending periodic hello BPDUs.
- □ Default is 2 seconds
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MaxAge
- § How long a bridge should wait, after beginning to not hear hellos, before trying to change the STP topology
- □ Default is 20 seconds
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Forward Delay
§ Delay that affects the time involved when an interface changes from blocking state to forwarding state
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“Portfast” Command
§ When configured it skips the STP port states and places the port into forwarding state immediately
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ARP
- ARP (Address Resolution Protocol)
- 1. Host A want to send data to host B
- 2. Host A checks to see if it has the ARP entry for Host B - NO.
- 3. • Host A places the original packet in buffer
- • Host A creates the ARP Broadcast and sends it
- 4. • Host B now processes the ARP request
- ○ Host B first saves the MAC address and IP for Host A in its own ARP table
- 5. Host B now can respond to the ARP request
- 6. • Host A receives the ARP reply and can now complete the original packet
- ○ Host A will save the MAC and IP for Host B in its ARP Table
- 7. Host A now builds the packet with Layer 3 and 2 information to transmit
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Switch MAC-Address Table
- • MAC-Address Table
- ○ When this request is sent, the switch saves the MAC Address for Host A and assigns it to Port 1
- ○ When this reply is sent, the switch saves the MAC address for Host B and assigns it to Port 2
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Category 5e copper
- -Cheap and Ubiquitous
- ○ Successor to Category 5, which itself is a successor to Category 3
- ○ Speeds up to 1 Gbps
- ○ Requires 2 pair for 10/100, 4 pair for 1Gb
- ○ Maximum segment length of 100m
- ○ Also used for voice communications in newer building installations
- ○ Power over Ethernet is possible
- ○ Small cable diameter, easy to field terminate
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Category 6a cable: copper
- § Speeds up to 10Gbps
- § Requires 4 pairs
- § Maximum segment length of 100m
- § Much tighter controls on installation standards make field terminations significantly harder
- § More attention is paid to eliminate NEXT (near-end crosstalk), ANEXT (alien near-end crosstalk) and PSNEXT (power-sum near-end crosstalk)
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Category 7a cable (proposed): copper
- § Speeds up to 100Gbps at 15 meters, potentially 100 meters as electronics improve
- § Bandwidth up to 1GHz means potential for broadband cable television
- § Individually shielded pairs, as well as shielded cable
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Single Mode Fiber (SMF): Fiber Optics
- Ride the Light
- ○ Speeds of 10, 40, 100Gbps and higher
- ○ Distances of hundreds of miles or more
- ○ Use highly tuned, single-mode laser optics
- ○ Smaller core size greatly reduces modal dispersion
- ○ Typically used for connections between buildings, and even further distances
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Multi Mode Fiber (MMF): Fiber Optics
- Ride the Light
- ○ Speeds up to 10Gbps
- ○ Distances up to 2km
- ○ Can be used with LEDs instead of lasers, making optics much cheaper
- ○ Larger core size enhances modal dispersion; the signal can become spread in time
- ○ Typically used for connections within a building
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IEEE 802.11
- Wireless
- The Standard We All Know and Love
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802.11b
- § Introduced in 1999
- § Bit rates of 1-11 Mbps
- § 11 20MHz channels in the 2.4GHz band
- § Three non-overlapping channels (1, 6, 11)
- § Lower frequency means greater range, can traverse solid objects easier
- § Interference issues (microwave ovens, Bluetooth devices, wireless keyboards/mice)
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802.11a
- § Introduced in 1999
- § Bit rates of 6-54 Mbps
- § 21 20MHz channels in the 5GHz band
- § 21 non-overlapping channels
- § Higher frequency is more susceptible to absorption by surrounding objects
- § Fewer interference issues
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802.11g
- § Introduced in 2003
- § Bit rates of 6-54 Mbps
- § 11 20MHz channels in the 2.4GHz band
- § 3 non-overlapping channels
- § Same strengths and weaknesses as 802.11b
- § Cheaper manufacturing costs make this standard a commodity
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802.11n
- § Drafted in 2007, ratified 2009
- § Bit rates of 300Mbps and higher with channel bonding
- § 3 20MHz channels in the 2.4GHz band, 21 20MHz channels in the 5GHz band
- § 24 non-overlapping 20MHz channels
- § MIMO (multiple in-multiple out) uses multiple antennas for higher bandwidth and more recently beamforming
- § Multiple antennas cost more, and many manufacturers only implement the 2.4GHz standard, keeping the same limitations as 802.11b and 802.11g.
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802.11ac
- § Still in draft status, anticipated ratification in 2014
- § Single stream bit rates of up to 866Mbps
- § Up to 8 spatial streams instead of 4 in 802.11n
- § 3 20MHz channels in the 2.4GHz band, 21 20MHz channels in the 5GHz band
- § 24 non-overlapping 20MHz channels
- § MIMO (multiple in-multiple out) uses multiple antennas for higher bandwidth
- § Uses more dense 256-QAM modulation, over 64-QAM used in 802.11n
- § Gigabit wireless to multiple users possible
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Microwave: Wireless Methods
- § Very high frequencies, very high potential bandwidth
- § Expensive to deploy, frequency licensing may be an issue
- § Limited to point-to-point links
- § Links can be dozens of miles apart
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Free-space optical wireless: Wireless Methods
- § Uses lasers to transmit data, very high (up to 10Gb) bandwidth
- § Expensive to deploy, costly equipment
- § Limited to point-to-point links, can be affected by weather
- § Links can be miles apart
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Infrared: Wireless Methods
- § Also uses light to transmit data, but bandwidth is not as high
- § Cheaper to deploy
- § Limited to point-to-point links
- § Links have limited distance
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Cellular: Wireless Methods
- § HSPA+ (most commonly used by AT&T and T-Mobile)
- □ Theoretical throughput capacity of 672 Mbps
- § LTE (most commonly used by Verizon, and now by Sprint Nextel and AT&T)
- □ Theoretical throughput capacity (with LTE-Advanced update) of 1Gbps
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Bluetooth: Wireless Methods
- § Primarily used to create (relatively) low data speed personal area networks
- § Also used for wireless keyboards, mice, headsets
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802.16
- -Other IEEE Standards; What’s to Come
- ○ Drafted in 2001, ratified in 2004, currently in use as 802.16-2009
- ○ Also known as WiMAX or WirelessMAN, it is meant to operate at microwave frequencies (10-63GHz)
- ○ Speeds up to 128Mbps for mobile and 1Gbps for fixed stations but at a much greater range, up to 50 miles
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802.20
- -Other IEEE Standards; What’s to Come
- ○ Published in 2008
- ○ Also known as MBWA (mobile broadband wireless access), it is meant to provide up to 80Mbps access to clients moving up to 250km/h
- ○ Operates in licensed frequencies below 3.5GHz
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802.22
- -Other IEEE Standards; What’s to Come
- ○ Published in July, 2011
- ○ Also known as WRAN (wireless regional area network), aims to use white spaces in current television broadcast spectrum
- ○ Can be used to help get access to people still too far from traditional broadband technologies (DSL, cable, etc.)
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