• Defines and verifies IP addresses
• Routes packets through an internetwork
• Resolves MAC addresses from IP addresses
• Delivers packets efficiently

• IPv4
• IPv6
• ICMP
• ARP
• IPSec

• Transmission Control Protocol (TCP)
• User Datagram Protocol (UDP)

• Work with segments
• Provide a means to identify the source and destination applications involved in a communication
• Protect data in the segment with a checksum

• Provides network services to user applications that access network resources.

• Access by applications to network services
• Client/server data access
• Name resolution
• Dynamic address assignment
• Authentication/user logon
• Data formatting and translation

• Provides a physical (MAC) address for the network interface.
• Verifies that incoming frames have the correct destination MAC address.
• Defines and follows media access rules
• Receives packets from the Internetwork layer and encapsulates them to create frames.
• De-encapsulates received frames and sends the resulting packets to the internetwork layer.

• Is where administrators usually do the most network configuration.
• This is where the IP protocol operates and is the heart of the TCP/IP protocol suite.
• Responsible for four main tasks: Defines and verifies IP addresses, Routes packets throught an internetwork, Resolves MAC addresses from IP addresses, and Delivers packets efficiently.

• IPv4
• IPv6
• Address Resolution Protocol (ARP)
• Internet Control Message Protocol (ICMP)
• Internet Protocol Security (IPSec)

• Physical
• Data Link
• Network
• Transport
• Session
• Presentation
• Application

• Data            Application
• Data            Presentation
• Data            Session
• Segments     Transport
• Network       Packets
• Frames         Data Link
• Bits             Physical

• PDU is Data
• Jobs include File Transfer, email, telnet...closest to user

• PDU is Data
• Job is Data syntax, jp, txt

• PDU is Data
• Job is to Establish, Manage, and End Connection

• PDU is Segments
• Job is reliability and flow control, windowing.

• PDU is Packets
• Job is Path Determination and Switching, puts header on each segment (IP Addresses)

What is the PDU and Job of the Data Link Layer?

• PDU is Frames
• Job is to put a Header and Trailer on each packet.

• PDU is Bits
• Job is to convert frames to bits. Defines electrical and functional specifications.

• Equipment used is computers
• Used to combine networks using different protocols.
• Words to remember are: Browsers for Application Layer, Common Data Format for Presentation Layer, Dialogues and Conversations for Session Layer and Quality of Service and Reliability for the Transport Layer.
• Protocols: Redirector, FTP, Telnet, SMTP, SNMP, Netware Core are used at the Application and Presentation Layer.
• Protocols NFS, SQL, RPC, X-Win for the Session Layer.
• Protocols TCP and UDP for the Transport Layer.

• Equipment used is Router.
• Purpose of equipment is to Segment Network into Smaller Broadcast Domains.
• Protocols used are Routable Protocols such as IP, IPX, and Apple Talk.
• Words to remember are Path Selection, Routing, and Addressing.

• Equipment used is Bridge (2 ports) or Switch (Multi-port) and NIC
• The purpose of the equipment is to Segment Network into Smaller Collision Domains.
• Protocols used are NDIS, ODI, MAC Address, and Ether Talk.
• Words to Remember are Frames and Media Access Control (MAC)

• Equipment used are Repeater (2 Ports), Hubs (multi-port), Cabling.
• Equipment purpose is One Collision and One Broadcast Domain.
• Protocols used are Physical.
• Words to remember are Signals and Media

• OSI                                 TCP/IP
• Application                Application
• Presentation              Application
• Session                     Application
• Transport                  Transport
• Network                    Internet
• Data Link                  Network Access
• Physical                    Network Access

• Missing or Misconfigured client software and incompatible or obsolete commands used to communicate between a client and server.

• Logical Link Control (LLC)
• Media Access Control (MAC)

• Application: Provides access to network resources.
• Presentation: Handles data formatting and translation.
• Session: Manages ongoing conversations between two computers.
• Transport: Breaks long data streams into smaller chunks (segments).
• Network: Provides best path selection and IP addressing
• Data Link: Defines how computers access the media.
• Physical: Converts bits into signals and defines media and connectors.

• Privacy policy
• Acceptable Use Policy
• Authentication Policy
• Internet use policy
• Access policy
• Auditing Policy
• Data Protection

• What must be protected
• From whom should data be protected
• What costs are associated with security being breached and data being lost or stolen
• How likely is it that a threat will occur
• Are the costs to implement security and train personnel to use a secure network outweighed by the need to create an efficient, user friendly environment.

• Highly Restrictive Security Policies
• Moderately Restrictive Security Policices
• Open Security Policies

• Authentication and Authorization
• Encryption
• Virtual Private Network (VPN)
• Firewalls
• Virus and Worm Protection
• Spyware Protection
• Wireless Security

• Enable mobile users to connect with corporate networks securely wherever an Internet connection is available.
• Allow multiple sites to maintain permanent secure connections via the Internet instead of using expensive WAN links.
• Can reduce costs by using the ISP's support services instead of paying for more expensive WAN support
• Eliminate the need to support dial-up remote access.

• Usually works with a firewall or router
• Detects an attempted security breach and notifies the administrator.
• In some cases IDS takes countermeasures like resetting the connection between source and destination devices.

• Service Set Identifier (SSID)
• MAC address  filtering
• Wired Equivalency Protocol (WEP)
• Wi-Fi Protected Access (WPA)
• 802.11i (WPA 2)