Network+

Resources a network makes available to its users including applications and the data provided by these applications.

Methods and rules of communication.

Using the same network to deliver multiple types of communication services, such as video, voice and fax.

The centralized management of multiple network-based communications.  E.g. intraoffice phone, long distance phone, cell phone, voice mail, fax, text messages.

• Allow people to communicate with video and voice.
• Primarily uses point-to-point model
• Skype and Google Talk are examples.

• You don't want to hear breaks or buffering in A/V in a movie, this is delay sensitivity
• Video transmissions are Loss Tolerant.

• Not scalable
• Not secure
• Not practical

• Managing data and other resources for a number of clients.
• Ensuring that only authorized users access the network.
• Control which types of files a user can open and read.
• Restricting when and from where users can access the network.
• Dictating which rules computers will use to communicate.
• Sometimes supplying applications and data files to clients.

• User accounts and passwords to network are assigned in one place.
• Access to multiple shared resources can be centrally granted to a user or group.
• Problems on the network can be monitored, diagnosed and often fixed from one location.
• More scalable.

• Switch belongs to one network.
• Router belongs to more than one.

• Layer 7: Application Layer
• Layer 6: Presentation Layer
• Layer 5: Session Layer
• Layer 4: Transport Layer
• Layer 3: Network Layer
• Layer 2: Data Link Layer
• Layer 1: Physical Layer

• A group of bits moving from one layer of the OSI to another.
• Layer 7-5: L7PDU: Payload or Data
• Layer 4: L4PDU: Segment (TCP) or Datagram (UDP)
• Layer 3: L3PDU: Packet
• Layer 2: L2PDU: Frame
• Layer 1: L1PDU: Bit

• Describes the interface between two applications on separate computers.
• Application programs that provide services to a user.  E.g. browser and web server using HTTP
• Utility Programs that provide services to the system.  E.g. SNMP that monitors and gathers information about network traffic.

Responsible for reformatting, compressing, and encrypting data for an application to be able to read it.

Describes how data between applications is synced and recovered if messages don't arrive intact.

• Responsible for transporting Application layer payloads from one application to another.
• Transmission Control Protocol (TCP)
• User Datagram protocol (UDP)
• Uses the port number
• Divides messages into smaller segments if they are too large.
• Adds header information to Segments or Datagrams.

• Transmission Control protocol
• Connection oriented protocol
• Guaranteed delivery
• Makes a connection, checks whether data was received, resends if not.

• User Datagram Protocol
• Connectionless protocol / Best effort protocol
• Not guaranteed delivery
• used for broadcasting, streaming, network traffic monitoring

• Adding header information to PDUs
• Transport Layer 4
• Network Layer 3
• Data Link Layer 2

• Responsible for moving messages from one note to another until they reach their destination.
• IP (Internet Protocol) is the principle protocol used.
• Identifies sending and receiving hosts by IP address.
• Routing protocols include...
• ICMP (Internet Control Message protocol)
• ARP (Address Resolution Protocol)
• Adds header information to packets.

• Applies to Layer 3: Network Layer
• If a packet is larger than the maximum size for the network, the Network Layer will divide it into smaller packets.

• Protocols used here are programmed into the firmware of the NIC or other hardware.
• Example protocols used are...
• Ethernet
• Wi-fi
• Adds Header and trailer information to frames.
• header information contains the MAC address of the source and destination NICs.

• Media Access Control
• Unique address on ever NIC

• Responsible for sending bits via wired or wireless transmission.
• Wi-fi: Wavelengths in the air
• Ethernet with Twisted Pair: Voltage on copper wire
• Ethernet with Fiber Optic Cable: Light

• Similar to OSI model but with only 4 layers.
• Application, presentation, and Session Layers are combined into Application Layer.
• Physical Layer is ignored.

Explains how to properly handle substances such as chemical solvelts and how to dispose of them.

• Identify problem and symptoms
• Establish a theory of probably cause
• Test your theory to determine cause
• Establish a plan to resolve the problem
• Implement the solution or escalate the problem
• Verify functionality and implement preventive measures
• Document findings, actions, and outcomes

• First 24 bits (6 hex characters) of a MAC address that identifies the manufacturer of the NIC.
• Assigned by IEEE.

• Last 24 bits (6 hex characters) of a MAC address that identifies the NIC.
• Based on model and manufacture date.

• A computer, router, or other device that a host uses to access another network.
• The default gateway is the gateway that nodes turn to first for access to the outside world.

• 32 bit number that helps computers find each other.
• The bits are used to indicate what portion of an IP address is the network portion and what part if the host portion.
• Using this information, a computer can know if a remote computer with a given IP address is on its own or a different network.

Responsible for tracking computer names and their IP addresses.

• The IP Address plus port number.
• E.g.
• 192.168.1.1:80

• 0-1023
• Assigned by IANA to well known protocols and programs.
• 20: FTP-DATA / TCP / File transfer 
• 21: FTP / TCP / File transfer control
• 22: SSH / TCP / Secure shell
• 23: TELNET / TCP
• 25: SMTP / TCP
• 53: DNS / TCP & UDP
• 67: DHCPv4 / UDP / Client to Server
• 68: DHCPv4 / UDP / Server to Client
• 69: TFTP / UDP / Trivial FTP
• 80: HTTP / TCP & UDP
• 110: POP3 / TCP
• 123: NTP / UDP / Network Time Protocol
• 137-139: NetBIOS / TCP & UDP / Legacy support
• 143: IMAP / TCP
• 161: SNTP / TCP & UDP
• 443: HTTPS / TCP
• 445: SMB / TCB / Server message Block
• 546: DHCPv6 / UDP / Client to Server
• 547: DHCPv6 / UDP / Server to Client
• 1720: H.323 / TCP / Packet-based Multimedia Communications Systems
• 2427/2727: MGCP / TCP & UDP / Media Gateway Control Protocol
• 3389: RDP / TCP / Remote Desktop
• 5004: RTP / UDP / Real-time Transport Protocol
• 5005: RTCP / UDP / Real-time Transport Control Protocol
• 5060: SIP / UDP / Session Initiaion Protocol, not encrypted
• 5061: SIP / UDP / Encrypted SIP

• 1024-49151
• Used by network users and processes that are not considered standard.
• Must be registered with IANA.

• 49152-65535
• Can be used without restriction.

• 1.x.y.z to 126.x.y.z
• 126 possible networks or licences
• 16 million possible IP addresses in each network

• 128.0.x.y to 191.255.x.y
• 16,000 possible networks or licenses
• 65,000 possible IP addresses in each network

• 192.0.0.x to 223.255.255.x
• 2 million possible networks or licenses
• 254 possible IP addresses in each network

• 255.255.255.255: Used for broadcast messages by TCP/IP sent to every node ont he network
• 0.0.0.0: Currently unassigned
• 127.0.0.1: Loopback address