5: Network Protocols

Peer-to-peer network

In small businesses and homes, many computers function as both the servers and clients on the network. This type of network is called a peer-to-peer network.

Small Home networks

Small home networks connect a few computers to each other and to the internet.

Small Office and Home Office (SOHO) networks

The SOHO network allows a home office or a remote office to connect to a corporate network, or access centralized, shared resources.

Medium to Large networks

These are used by corporations and schools and can have many locations with hundreds or thousands of interconnected hosts.

World Wide networks

The internet is a network of networks that connects hundreds of millions of computers world-wide.

Hosts

All computers that are connected to a network and that participate directly in network communication are classified as hosts. Hosts are also called end devices, endpoints, or nodes.

Servers

Servers are simply computers with specialized software that enables servers to provide information to other end devices on the network.

File Server

Stores corporate and user files in a central location. The client devices access these files with client software such as Windows Explorer.

Web Server

Runs web server software and clients use their browser software, such as Windows Internet Explorer, to access web pages on the server.

Email Server

Runs email server software and clients use their mail client software, such as Microsoft Outlook, to access email on the server.

Internet Exchange Point (IXP)

Global Tier 1 and Tier 2 ISPs connect portions of the internet together, usually through an Internet Exchange Point.

Point of Presence (PoP)

Larger networks connect to Tier 2 networks through a Point of Presence, which is usually a location in the building where physical connections to the ISP are made.

Protocols

Communication is governed by rules called protocols.

Network protocols

Network protocols provide the means for computers to communicate on networks.

Message Structure

Specifies how the message is formatted or structured.

Path Sharing

Specifies the process by which networking devices share information about pathways with other networks.

Information Sharing

Specifies how and when error and system messages are passed between devices.

Session Management

Manages the setup and termination of data transfer sessions.

Open standard protocol suite

This means it is freely available to the public and can be used by any vendor on their hardware or in their software.

Standards-based protocol suite

This means it has been endorsed by the networking industry and approved by a standards organization.

DNS (Domain Name System)

Translates domain names into IP addresses.

DHCPv4 (Dynamic Host Configuration Protocol for IPv4)

Dynamically assigns IPv4 addressing information to DHCPv4 clients at start-up and allows the addresses to be re-used when no longer needed.

DHCPv6 (Dynamic Host Configuration Protocol for IPv6)

It is similar to DHCPv4. Dynamically assigns IPv6 addressing information to DHCPv6 clients at start-up.

SLAAC (Stateless Address Autoconfiguration)

A method that allows a device to obtain its IPv6 addressing information without using a DHCPv6 server.

SMTP (Simple Mail Transfer Protocol)

Enables clients to send email to a mail server and enables servers to send email to other servers.

POP3 (Post Office Protocol version 3)

Enables clients to retrieve email from a mail server and download the email to the client's local mail application.

IMAP (Internet Message Access Protocol)

Enables clients to access email stored on a mail server as well as maintaining email on the server.

FTP (File Transfer Protocol)

Sets the rules that enable a user on one host to access and transfer files to and from another host over a network.

SFTP (SSH File Transfer Protocol)

Used to establish a secure file transfer session in which the file transfer is encrypted.

TFTP (Trivial File Transfer Protocol)

A simple and connectionless protocol with best-effort, unrecognized file delivery.

HTTP (Hypertext Transfer Protocol)

A set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web.

HTTPS (HTTP Secure)

A secure form of HTTP that encrypts the data that is exchanged over the World Wide Web.

REST (Representational State Transfer)

A web service that uses application programming interfaces (APIs) and HTTP requests to create web applications.

TCP (Transmission Control Protocol)

Enables reliable communication between processes running on separate hosts and provides reliable transmissions that confirm successful delivery.

UDP (User Datagram Protocol)

Enables a process running on one host to send packets to a process running on another host.

IPv4 (Internet Protocol version 4)

Receives message segments from the transport layer, packages messages into packets, and addresses packets for end-to-end delivery over a network. IPv4 uses a 32-bit address.

IPv6 (IP version 6)

Similar to IPv4 but uses a 128-bit address.

NAT (Network Address Translation)

Translates IPv4 addresses from a private network into globally unique public IPv4 addresses.

ICMPv4 (Internet Control Message Protocol for IPv4)

Provides feedback from a destination host to a source host about errors in packet delivery.

ICMPv6 (ICMP for IPv6)

Similar functionality to ICMPv4 but is used for IPv6 packets.

ICMPv6 ND (ICMPv6 Neighbor Discovery)

Includes four protocol messages that are used for address resolution and duplicate address detection.

OSPF (Open Shortest Path First)

Link-state routing protocol that uses a hierarchical design based on areas. OSPF is an open standard interior routing protocol.

EIGRP (Enhanced Interior Gateway Routing Protocol)

A Cisco proprietary routing protocol that uses a composite metric based on bandwidth, delay, load and reliability.

BGP (Border Gateway Protocol)

An open standard exterior gateway routing protocol used between Internet Service Providers (ISPs).

ARP (Address Resolution Protocol)

Provides dynamic address mapping between an IPv4 address and a hardware address.

Ethernet

Defines the rules for wiring and signaling standards of the network access layer.

WLAN (Wireless Local Area Network)

Defines the rules for wireless signaling across the 2.4 GHz and 5 GHz radio frequencies.

Encapsulation

The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation.

De-encapsulation

De-encapsulation occurs when the process is reversed by the recipient and the letter is removed from the envelope.

Flow Control

Flow control defines how much information can be sent and the speed at which it can be delivered.

Response Timeout

Hosts on the network use network protocols that specify how long to wait for responses and what action to take if a response timeout occurs.

Access method

This determines when someone can send a message. When a device wants to transmit on a wireless LAN, it is necessary for the WLAN NIC to determine whether the wireless medium is available.

Unicast

A one-to-one delivery option means there is only a single destination for the message.

Multicast

When a host needs to send messages using a one-to many delivery option.

Broadcast

If all hosts on the network need to receive the message at the same time, a broadcast may be used. Broadcasting represents a one-to-all message delivery option.

Layered model

A layered model is used to modularize the operations of a network into manageable layers.

OSI Model Layer 7 - Application

Contains protocols used for process-to-process communications.

OSI Model Layer 6 - Presentation

Provides representation of the data transferred between application layer services.

OSI Model Layer 5 - Session

Provides services to the presentation layer to organize its dialogue and to manage data exchange.

OSI Model Layer 4 - Transport

Defines services to segment, transfer, and reassemble the data for individual communications between the end devices.

OSI Model Layer 3 - Network

Provides services to exchange the individual pieces of data over the network.

OSI Model Layer 2 - Data Link

Describe methods for exchanging data frames between devices over a common media.

OSI Model Layer 1 - Physical

Describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical connections for a bit transmission between devices.

TCP/IP Model Layer 4 - Application

Represents data to the user, plus encoding and dialog control.

TCP/IP Model Layer 3 - Transport

Supports communication between various devices across diverse networks.

TCP/IP Model Layer 2 - Internet

Determines the best path through the network.

TCP/IP Model Layer 1 - Network Access

Controls the hardware devices and media that make up the network.

Segmentation

The process of dividing a stream of data into smaller units for transmissions over the network.

Multiplexing

As a large data stream is segmented into packets, more data can be sent over the network without tying up a communications link. This allows many different conversations to be interleaved on the network called multiplexing.

Protocol Data Unit (PDU)

The form that a piece of data takes at any layer is called a Protocol Data Unit.

Data

The general term for the PDU used at the application layer.

Segment

Transport layer PDU.

Packet

Network layer PDU.

Frame

Data Link layer PDU.

Bits

Physical layer PDU used when physically transmitting data over the medium