Standards
Standards are sets of rules that ensure hardware and software released from different companies work together.
International Organization for Standardization (ISO)
Federation of standards organizations from multiple nations.
American National Standards Institute (ANSI)
Responsible for coordinating and publishing computer and information technology standards in the United States.
International Electrical and Electronics Engineers (IEEE)
Professional organization for the electrical and electronics field.
Open Systems Interconnection (OSI)
The Open Systems Interconnection (OSI) reference model is used to define how data communication occurs between devices. The model is divided into 7 layers, each layer providing services to the layers above and below.
Physical Layer (Layer 1 )
Defines the physical and electrical medium for data transfer.
Unit of measurement: Bits
Physical layer components (Layer 1 )
cables, jacks, patch panels, punch blocks, hubs and MAUs.
Physical layer concepts (Layer 1 )
topologies, analog versus digital/encoding, bit synchronization, baseband versus broadband, multiplexing, and serial data transfer.
Communications Subnetwork
The communications subnetwork consists of layers 1 through 3:
-Physical
-Data Link
-Network
Regardless of what type of data transmission occurs in a computer network, the communication subnetwork is used.
Ethernet Standards
LAN standard providing a communication method for high speed data exchange among devices.
Defined Physical and Data Link Layer.
100BASE-T
100 for 100 Mbps;
BASE for baseband;
T for twisted-pair cabling.
Baseband
refers to the fact that devices on the network use digital signaling over a single frequency�
Broadband
systems use analog signaling over a range of frequencies enabling multiple channels over the same physical medium.
Data Link Layer (Layer 2)
Establishes, maintains, and decides how transfer is accomplished over the physical layer and ensures error-free transmission over the physical layer.
Physical addresses (the hexadecimal address that is burned into the ROM of the NIC), known as the MAC address uniquely identify each hardware device work at the Data Link Layer.
Data Link Layer components: network interface cards and bridges
Unit of measurement: frames
Data Link Layer components (Layer 2)
network interface cards and bridges
Communications Subnetwork
The communications subnetwork consists of layers 1 through 3:
- Physical
- Data Link
- Network
Regardless of what type of data transmission occurs in a computer network, the communication subnetwork is used.
Layer 2 Switches
Layer 2 switches are hardware-based and use the MAC address of each host computer's network adapter when deciding where to direct data frames.
Ports on the switch are mapped to the specific MAC address of the device attached.
Virtual LAN (VLAN)
Layer 2 switching can also allow for a virtual LAN (VLAN) to be implemented.
A VLAN is implemented to segment and organize the network, to reduce collisions, boost performance.
IEEE 802.1Q is the standard that supports VLANs.
A tag is added to the data frame to identify the VLAN.
Network Layer (Layer 3)
Controls the operations of routing and switching information to different networks.Translates logical addresses or names to physical addresses.
Internet Protocol (IP) is a Network Layer protocol.
Unit of measurement: packets.
Network Layer Devices and Components (Layer 3)
Devices that work at the network layer are routers and IP switches.
Network Layer components: IP addresses, subnets.
Layer 3 Switches
Switches can also reside on the network layer.
A layer 3 switch determines paths for data using logical addressing (IP addresses) instead of physical addressing (MAC addresses for a layer 2 switch).
Layer 3 switches forward packets, whereas layer 2 switches forward frames.
Transport Layer (Layer 4 )
This layer ensures messages are delivered error-free, in sequence and with no losses or duplications.
Unit of measurement used: segments or messages.
Transport Layer Protocols (Layer 4 )
Protocols that work at this layer segment messages, ensure correct reassembly at the receiving end, perform message acknowledgement and message traffic control.
The Transport Layer contains both connection-oriented and connectionless protocols.
Connection Oriented Communications
Require both devices involved in the communication establish an end-to-end logical connection before data can be sent. These communications are considered reliable network services. Packets not received by the destination device can be resent by the sender.
Connectionless Communications
End-to-end connection is not necessary before data is sent
Every packet that is sent has the destination address in the header. Sufficient to move independent packets, such as in streaming media. Datagram delivery is not guaranteed and lost packets cannot be resent.
Connection-based Protocols
The Transport Layer contains both connection-oriented and connectionless protocols. Transmission Control Protocol (TCP) provides a connection-based, reliable, byte-stream service to programs. User Datagram Protocol (UDP) provides a connectionless, unreliable transport service.
TPC
TCP transport is used for logging on, file and print sharing, replication of information between domain controllers, transfer of browse lists, and other common functions.
TCP can only be used for one-to-one communications.
PROTOCOL: Transmission Control Protocol (TCP)
TYPE: Connection-oriented
EXEMPLE: Web browser
UDP
UDP is often used for one-to-many communications, using broadcast or multicast IP datagrams
PROTOCOL:User Datagram Protocol (UDP)
TYPE: Connectionless
EXEMPLE: Streaming media
Ports
Ports are a Layer 4 protocol that a computer uses for data transmission.
Ports act as logical communications end point for specific program on computers for delivery of data sent.
PORT 21
File Transfer Protocol - FTP
PORT 22
Secure Shell - SSH
PORT 23
Terminal Network - Telnet
PORT 25
Simple Mail Transfer Protocol - SMTP
PORT 53
Domain Name System - DNS
PORT 80
Hypertext Transfer Protocol - HTTP
PORT 88
Kerberos
PORT 110
Post Office Protocol Version 3 - POP3
PORT 119
Network News Transfer Protocol - NNTP
PORT 137-139
NetBIOS Name, Datagram, and Session Services, respectively - NetBIOS
PORT 143
Internet Access Message Protocol - IMAP
PORT 161
Simple Network Management Protocol - SNMP
PORT 389
Lightweight Directory Access Procotol - LDAP
PORT 443
Hypertext Transfer Protocol Secure (uses TLS or SSL) - HTTPS
PORT 445
Server Message Block - SMB
PORT 1701
Layer 2 Tunneling Protocol - L2TP
PORT 1723
Point-to-Point Tunneling Protocol - PPTP
PORT 3389
Remote Desktop Protocol - RDP
Presentation Layer(Layer 6 )
This layer translates the data format from sender to receiver in the various OSes that may be used.
Presentation Layer concepts include: character code conversion, data compression, and data encryption.
Redirectors work on this layer, such as mapped network drives that enable a computer to access file shares on a remote computer.
Application Layer (Layer 7)
Serves as a the window for users and application processes to access network services. This layer is where message creation begins.
Application Layer protocols (Layer 7)
End-user protocols such as FTP, SMTP, Telnet, and RAS work at this layer.
This layer is not the application itself, but the protocols that are initiated by this layer.
OSI Model Revisited
(Layer: 7 ) Application - Protocol: FTP, HTTP, POP3, SMTP. Device: Gateway.
(Layer: 6) Presentation - Protocol: Compression, Encryption
(Layer: 5) Session - Protocol:Logon/Logoff
(Layer: 4) Transport -Protocol:TCP, UDP
OSI Model Revisited
(Layer: 3)Network - Protocol:IP, ICMP, ARP, RIP
Device:Routers
(Layer: 2) Data Link - Protocol: 802.3, 803.5
Device:NICs, Switches, Bridges, WAPs
(Layer: 1) Physical - Protocol:100BASE-T, 1000BASE-X
Device:Hubs, Patch Panels, RJ45 Jacks
TCP Model
The TCP/IP model is similar to the OSI model
This model is composed of only four layers
Layer: Network Interface
Description: Details how data is physically sent through the network
Protocols: Ethernet, Token Ring, Frame Relay
TCP Model - Application Layer
Layer: Application Layer
Description: Defines TCP/IP application protocols
Protocols: HTTP, Telnet, FTP, SMNP, DNS
TCP Model - Transport Layer
Layer: Transport Layer
Description: Provides communication session management
Protocols: TCP, UDP, RTP
TCP Model - Internet Layer
Packages and routes data
IP, ICMP, ARP, RARP
TCP Model - Transport Layer
...
OSI Model compared to TCP Model