Repeaters (Layer 1) – amplify signal, no added intelligence, no filtering

Hubs (Layer 1) – used to connect multiple LAN devices, no added intelligence

Bridges (Layer 2)

• Amplifies signal and adds some intelligence
• Forwards the data to all network segments if the Media Access Control (MAC) or hardware address of the destination computer is not on the local network segment
• Automatically forwards all broadcast traffic

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

Switches (Layer 2) – Will only send data to the port where the destination MAC address is, not to all ports

Routers (Layer 3) – opens packet and looks at either MAC or IP address and forwards the packet to the destination network

Gateways – primarily software, can be multi-protocol and can examine the entire packet

Asynchronous Transfer Mode (ATM) Switches – use relay technology and typically used in WANs and CANs.

LAN Extenders

• Remote access multi-layer switch connected to a host router
• Filters based on MAC address, but not capable of firewalling

WAN Technologies

• Rules for communicating between computers on a WAN
• Communications between large disparate networks

Private Circuit Technologies

• Evolved before packet switching networks
• Dedicated analog or digital point-to-point connection
• Serial Line Internet Protocol (SLIP), Point-to-Pont Protocol (PPP), ISDN and xDSL
• Dedicated Line – indefinitely and continuously reserved for transmissions
• Leased Line – type of dedicated line leased from a carrier

Types and Speeds of Leased Lines

Digital Signal Level 0 (DS0) – single channel at 64KBps on a T1

Digital Signal Level 1 (DS1) – 1.544 MBps in US on a T1 and 2.108 MBps in Europe on an E1

Digital Signal Level 3 (DS3) – 44.736 MBps on a T3

T1 – transmits DS-1 data at 1.544 MBps on telephone switching network

T3 – transmits DS-3 data at 44.736 MBps on telephone switching network

E1 – predominantly used in Europe and carries data at 2.108 MBps

E3 – predominantly used in Europe and carries data at 34.368 MBps

SLIP (Serial Line Internet Protocol)

• Developed in 1984 to support TCP/IP over low speed serial interfaces
• Using Windows NT RAS, NT computers can use TCP/IP and SLIP to communicate to remote hosts

PPP (Point to Point Protocol)

• Used over dial-up and dedicated links
• Includes login, password and error correction
• Operates at Layer 2 and uses CHAP and PAP

ISDN (Integrated Services Digital Network)

• Integration of digital telephony and data transport
• Digitization of the telephone network, allowing voice, data, etc.
• Overtaken by DSL

xDSL (Digital Subscriber Line)

• Uses existing twisted pair telephone lines
• ADSL (Asymmetric DSL)
  • More bandwidth downstream (1.5 to 9 MBps) than upstream (16 to 640 KBps)
  • Works at 18000 ft theoretical lengths and 14400 ft practical lengths over copper twisted pair
• SDSL (Single-line DSL)
  • Provides from 144 KBps up to 1.544 MBps in both downstream and upstream traffic, depending on the distance from the carriers point of presence (POP) over copper twisted pair
  • Works at 10000 ft lengths
• HDSL (High-rate DSL)
  • 1.544 MBps both up and down over two copper twisted pair (T1 speed)
  • Can do 2.048 MBps on three copper twisted pair
• VDSL – (Very High-rate DSL)
  • 13-52 MBps down and 1.5 MB to 2.3 MBps upstream over single copper twisted pair operating range 1,000 – 4,500 feet

You may also want to consider these CISSP resources from Amazon.com

Layered architecture

• Shows how communication should take place
• Clarify the general functions of a communication process
• To break down complex networking processes into more manageable sub-layers
• Using industry standard interfaces enables interoperability
• To change the features of one layer without changing the code in every layer
• Easier troubleshooting

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.

Open Systems Interconnect (OSI) Model

Layer 7 – Application

• Responsible for all application-to-application communications
• User information maintained at this layer is user data
• Security: Confidentiality, Authentication, Data Integrity, Non-repudiation
• Technology: Gateways
• Protocols: FTP, SMB, Telnet, TFTP, SMTP, HTTP, NNTP, CDP, GOPHER, SNMP, NDS, AFP, SAP, NCP, SET

Layer 6 – Presentation

• Responsible for the formatting of the data so that it is suitable for presentation
• Responsible for character conversion (ASCII/EBCDIC)
• Encryption/Decryption, Compressions and Virtual Terminal Emulation
• User information maintained at this layer is called messages
• Security: Confidentiality, Authentication, Encryption
• Technology: Gateway
• Protocols: ASCII, EBCDIC, Postscript, JPEG, MPEG, GIF

Layer 5 – Session

• Responsible for the setup of the links, maintaining of the link and the link tear-down between applications
• Security: None
• Technology: Gateway
• Protocols: Remote Procedure Calls (RPC), SQL, RADIUS, DNS, ASP

Layer 4 – Transport

• Responsible for the guaranteed delivery of user information
• Also responsible for error detection, correction and flow control
• User information at this layer is called datagram
• Security: Confidentiality, Authentication, Integrity
• Technology: Gateway
• Protocols: TCP, UDP, SSL, SSH-2, SPX, NetBIOS, ATP

Layer 3 – Network

• Responsible for the routing of user data from one node to another through the network including the path selection
• Logical addresses are used at this layer
• User information maintained at this layer is called packets
• Security: Confidentiality, Authentication, Data Integrity
• Technology: Virtual Circuits (ATM), routers
• Protocols: IP, IPX, ICMP, OSPF, IGRP, EIGRP, RIP, BOOTP, DHCP, ISIS, ZIP, DDP, X.25

Layer 2 – Data Link

• Responsible for the physical addressing of the network via MAC addresses
• There are two sublevels: MAC & LLC
• Has error detection, frame ordering and flow control
• User information maintained at this layer is called frames
• Security: Confidentiality
• Technology: Bridges, switches
• Protocols: L2F, PPTP, L2TP, PPP, SLIP, ARP, RARP, SLARP, IARP, SNAP, BAP, CHAP, LCP, LZS, MLP, Frame Relay, Annex A, Annex D, HDLC, BPDU, LAPD, ISL, ,MAC, Ethernet, Token Ring, FDDI

Layer 1 – Physical

• Responsible for the physical transmission of the binary digits through the physical medium
• Includes things such as the physical cables, interfaces and data rate specifications
• User information maintained at this layer is called bits
• Security: Confidentiality
• Technology: ISDN, Hubs, Repeaters, Cables

• 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)