Chapter 10 - Network Protocols Flashcards
Network Protocols
Network Protocols are the standards by which network messages are constructed.
The protocols themselves are complicated enough that layered models have been developed to describe them.
The two most common models are the OSI network model and the TCP/IP network model. These two models are described in detail in this section.
The OSI Network Model
Open System interconnect is a seven-layer model whose layers represent various abstractions of communication.
Each layer provides services to the layer above it and receives services from the layer beneath.
The common terminology for these layers is a protocol stack.
The layers of the OSI Model
- Physical
- Data Link
- Network
- Transport
- Session
- Presentation
- Application
Physical Layer
This is the lowest layer of the OSI model. It deals with the physical connection between devices. It defines the hardware elements involved, such as cables, switches, and network interface cards.
Functions: Bit transmission over a medium, defining voltage levels, data rates, physical connectors, etc
Data Link Layer
This layer is responsible for creating a reliable link between two directly connected nodes, managing errors in the physical layer, and controlling the flow of data.
Functions: Error detection and correction, frame synchronization, logical link control, and MAC addressing.
Network Layer
Determines the best path to route data packets from the source to the destination across the network.
Functions: Packet forwarding, routing, logical addressing (like IP addresses), and error handling and packet sequence control.
Transport Layer
Ensures the reliable arrival of messages and provides error-checking mechanisms and data flow controls.
Functions: Segmenting data and reassembling it into complete messages, ensuring data integrity, and establishing, maintaining, and terminating connections.
Session Layer
Manages sessions or connections between applications on different devices. It establishes, maintains, and terminates connections.
Functions: Dialog control (keeping data in sync), session establishment, maintenance, and termination.
Presentation Layer
Acts as a translator between the application and the lower layers. It converts the data format from one presentation to another (for example, EBCDIC to ASCII).
Functions: Data translation, encryption, compression, and interpretation of data between application and transport layers.
Application Layer
The topmost layer, it provides network services to end-users. It facilitates end-user processes and network services like email and file transfer.
Functions: End-user interface, email, file transfer, remote login, and management services.
TCP/IP
The TCP/IP network protocol is built on a four-layer model:
- Link
- Internet
- Transport
- Application
TCP/IP Link Layer
The link layer is layer 1 in the TCP/IP model. The link layer is concerned with node-to-node delivery of bits or frames. Examples of link layer technologies include:
- WiFi
- Ethernet
- Token ring
TCP/IP Internet Layer
The Internet layer is layer 2 in the four-layer TCP/IP model.
The Internet layer is the layer that is concerned with end-to-end packet delivery, whereas layer 1 is concerned with node-to-node delivery. End-to-end delivery means that a packet can originate at one node and pass through several intermediate nodes (usually routers) before arriving at the destination node
Internet Layer Protocols
- Internet Protocol Version 4 (IPv4)
- Internet Protocol version 6 (IPv6)
- Address Resolution Protocol (ARP)
- Reverse Address Resolution Protocol (RARP)
- Internet Control Message Protocol (ICMP)
- Internet Group Management Protocol (IGMP)
- IP security (IPsec)
Internet Layer Routing Protocols
Routing protocols are used by network routers to determine how to send network packets to nodes on destination networks. Some network routing protocols exist in the Internet layer, including:
- RIP
- OSPF
- IS-IS
- BGP
Internet Layer Addressing
TCP/IP’s Internet layer addressing is designed to uniquely identify nodes on networks including the global Internet. Network addresses in IPv4 are 32 bits in length and are expressed as a dot-decimal notation, xx.xx.xx.xx, where the range of each ‘xx’ is 0–255 decimal. A typical network address is 141.204.13.200.
The TCP/IP Internet layer addressing scheme has several characteristics, including:
- Subnets
- Gateways
- Address allocation
- reserved address blocks
- Network Address Translation
- Classful networks
- Classless Inter-Domain Routing
- Addressing
TCP/IP Transport Layer
The transport layer is layer 3 in the four-layer TCP/IP model.
The two protocols that are principally used in the transport layer are TCP and UCP
TCP Transport Protocol
Transmission Control Protocol (TCP) is a connection-oriented transport protocol used to carry messages within a session between two nodes. In TCP, two nodes can establish a persistent connection, over which messages can be sent back and forth.
Protocols in the application layer (layer 4) that use TCP include FTP, HTTP, and Telnet.
UDP Transport Protocol
The User Datagram Protocol (UDP) (sometimes coined the unreliable datagram protocol) is a connectionless protocol used to carry messages between nodes. UDP is very lightweight in comparison to TCP—it’s a low-overhead protocol that is
suitable for some types of connections. Some of the protocols that use UDP include DNS, VoIP, and TFTP.
TCP/IP Application Layer
The application layer is layer 4—the topmost layer—of the TCP/IP model. The protocols in the application layer provide application functions for application programs, some of which are used directly by computer users.
TCP/IP Routing Protocols
A routing protocol is a router-to-router communication protocol used by routers to help determine the most efficient network routes between two nodes on different networks.
In a routing protocol, routers communicate information about network destinations to neighboring routers. This sharing of routing information gives each router greater visibility of the greater network, which makes it more capable of making good routing decisions.
Remote Access/Tunneling Protocols
Several TCP/IP-based protocols have been developed that permit the tunneling of network traffic between computers, networks, and between a computer and a network.
Network Authentication Protocols
There are several network-based protocols that are used for authentication, which is the verified identification of an individual who desires to access a resource.
There are two types of protocols used in network authentication: those that interact between a
user and an access point or gateway and those that occur between an access point or gateway
and an authentication/authorisation/accounting (AAA) server. Both types of protocols are often used in environments in which users are required to authenticate to a system or network
Examples of Network Authentication Protocols
- RADIUS
- Diameter
- TACACS
- 802.1X
- NAC
- CHAP
- EAP
- PEAP
- PAP
