• Physical & Data Link Layers
• Controls the use of a network

Ethernet 802.3

• Uses CSMA/CD
• Designed for sporadic traffic
• Defines a bus topology with 3 different cabling standards:
  • Thinnet (10Base2) – coax with segments up to 185 meters
  • Thicknet (10Base5) – coax with segments up to 500 meters
  • Unshielded Twisted Pair (UTP) – all devices connected to a hub or a switch

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ARCNet (802.5)

• Early LAN technologies
• Uses token passing in a Star topology on coax cable

Token Ring

• Second to Ethernet
• All end stations connected to a Multistation Access Unit (MSAU)
• One station is designated as the Active Monitor
• IF a transmitting station fails, the Active monitor will remove the token and generate a new one

Fiber Distributed Data Interface (FDDI)

• Dual token ring LAN at 100 MBps on Fiber
• Dual counter rotating rings only one active at a time
• Operates over long distances with minimal interference
• Predictable delays, deterministic
• Permits several tokens to be present at a time
• Expensive and requires special expertise
• Copper Distributed Data Interface – can be used with UTP cable, but subject to interference and length issues associated with copper

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Twisted Pair Cable

• Relatively slow speed
• Two insulated wires can be shielded (STP0 or unshielded (UTP)
• UTP is four-pair medium and comes in several categories
• UTP can be easily tapped by eavesdroppers than the other cable types
• Category based on how tightly wound the wires are, the tighter the wind the higher the rating and the higher the resistance to interference
• Cat 1 UTP – was used for telephone lines, not good for data
• Cat 2 UTP – up to 4 MBps
• Cat 3 UTP – Used for 10BaseT networks up to 10 MBps
• Cat 4 UTP – Used in Token Ring Networks up to 16 MBps
• Cat 5 – Current UTP standard for new installations up to 100MBps
• Cat 6 UTP – up to 155MBps
• Cat 7 UTP – up to 1 GBps

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Planning to take the CISSP Exam? Get a copy of my personal notes (300plus pages worth) that I used to pass the exam for only $25.00. Click the Add To Cart Button to Purchase Plus you will also get copies of notes from other CISSPs. Learn more about this package by visiting this blog entry: CISSP REVIEW NOTES I USED TO PASS THE EXAM. CLICK BELOW TO MAKE YOUR PURCHASE NOW. All Purchases are securely processed through Paypal. Once you click the button please check your shopping cart at the upper right hand side of the page to complete your order. IMPORTANT NOTICE: I MANUALLY REVIEW ALL ORDERS. SO ONCE YOU PURCHASE THE PRODUCT, THERE WILL BE SOME DELAY ON YOU RECEIVING AN E-MAIL FROM ME WITH THE LINK TO THE DOWNLOAD AREA OF THE PRODUCT. YOU WILL GET A RESPONSE FROM ME WITHIN 24-48 HOURS. You may also want to consider these CISSP resources from Amazon.com

Coaxial Cable

• Hollow outer conductor surrounds inner wire conductor
• Currently two types of LAN
  • 50-ohm Cable for digital signaling
  • 75-ohm Cable for analog signaling and high-speed digital signaling
• More expensive, but is more resistant to Electromagnetic Interference (EMI)
• Used rarely except in Broadband communications
• Comes in two types:
  • Thinnet – RG58
  • Thicknet RG8 and RG11
• Two common types of coaxial transmission methods:
  • Baseband – The cable carries a single channel
  • Broadband – Cable carries several channels

Fiber Optic Cable

• Conducts modulated light transmission
• Light waves are faster and travel greater distances
• Difficult to tap
• Resistant to EMI
• Usually connects backbones in larger networks
• Can be used to connect workstations to the network
• Expensive to install and to terminate

LAN Transmission Protocols

• Rules for communication between computers on a LAN
• Formatting of the data frame, the timing and sequencing of packet delivery, and resolution of error states

Carrier Sense Multiple Access (CSMA)

• Foundation of the Ethernet protocol
• Workstation continuously monitors the line waiting until it thinks it is free
• If the workstation doesn’t receive an acknowledgement from the destination to which it sent the packet, it assumes a collision has occurred and it resends the packet
  • Persistent Carrier Sense – Unless it receives an acknowledgement it will resend
  • Non-persistent Carrier Sense – Waits a random amount of time before it resends

CSMA/CA

• Carrier Sense Multiple Access / Collision Avoidance
• Workstations connected to two coax cables, one to send and one to receive data

CSMA/CD

• Carrier Sense Multiple Access / Collision Detection
• If the host detects another signal while transmitting it will send a jam signal causing all nodes to stop sending data
• Nodes will wait to resend
• Designed to avoid collisions

Polling

• A primary workstation polls another at a predetermined time to determine if it has data to transmit
• Primary must give permission to others to transmit

Token Passing

• Token Ring, FDDI and ARCnet
• Cannot transmit without the token
• Each station can hold token for maximum predetermined amount of time

LAN Transmission Methods

• Refer to the way packets are sent on the network
• Unicast – from single source to single destination
• Multicast – source copied and sent to multiple destinations
• Broadcast – source copied and sent to all nodes on the network

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• Slow transfer of data to back-up
  • Retrieval time to restore
  • Off-hour processing and monitoring
• Server disk space expands over time
• Loss of data between last back-up
• Physical security of tapes

Planning to take the CISSP Exam? Get a copy of my personal notes (300plus pages worth) that I used to pass the exam for only $25.00. Click the Add To Cart Button to Purchase Plus you will also get copies of notes from other CISSPs. Learn more about this package by visiting this blog entry: CISSP REVIEW NOTES I USED TO PASS THE EXAM. CLICK BELOW TO MAKE YOUR PURCHASE NOW. All Purchases are securely processed through Paypal. Once you click the button please check your shopping cart at the upper right hand side of the page to complete your order. IMPORTANT NOTICE: I MANUALLY REVIEW ALL ORDERS. SO ONCE YOU PURCHASE THE PRODUCT, THERE WILL BE SOME DELAY ON YOU RECEIVING AN E-MAIL FROM ME WITH THE LINK TO THE DOWNLOAD AREA OF THE PRODUCT. YOU WILL GET A RESPONSE FROM ME WITHIN 24-48 HOURS.

Single Points of Failure

• Cabling failures
  • Coaxial – many workstations or servers attached to the same segment of cable, which creates a single point of failure if it is broken
  • Exceeding cable length is a source failure
• Twisted Pair
  • CAT3 or CAT5 – difference the two has to do with the tightness of the copper wires that were wound
  • Tightness determines its resistance to interference
  • CAT3 is older and cable length is a common failure
• Fiber Optic
  • Immune to EMI
  • Longer usable length – up to 2kms
  • Expensive

Technology Failures

Ethernet

• Most popular
• Extremely resistant to failure, especially in a star-wired configuration

Token Ring

• Since token is passed by every station on the ring, NIC set at wrong speed or in error state can bring the network down

FDDI – Fiber Distributed Data Interface

• Dual rings fault tolerance (if first ring fails, the secondary ring takes over)
• Sometimes uses second ring for improved performance

Leased Lines

• T1 and ISDN – go with multiple vendors to reduce failures

Frame Relay

• Public switched WAN
• Highly fault tolerant
• Bad segments diverts packets
• Can use multiple vendors for high availability

Other Single Points of Failure

• Can be any device where all traffic goes through a single device – Router, firewall, hub or switch
• Power failure – surges, spikes (need for UPS)