Network+ 1.1 Compare the layers of the OSI and TCP/IP models

Data Packets

Packets used to transport user data through the internetwork.

Routed Protocols

Protocols used to support data traffic.
Internet Protocol (IP) and Internet Protocol version 6 (IPv6) are two examples.

Route-update Packets

Packets used to update neighboring routers about the networks connected to all routers within the internetwork.
Used to help build and maintain routing tables on each router.

Routing Protocols

Protocols used to send route-update packets.
Routing Information Protocol (RIP), RIPv2, Enchanced Interior Gateway Routing Protocol (EIGRP), and Open Shortest Path First (OSPF) are examples.

Network Address

An identifier for a node or network interface of a telecommunications network.
A router must maintain a routing table with these identifiers due to needing individual routing protocols because each routing protocol keeps track of a network with a differen

Interface

The exit of a routing table taken when destined for a specific network.

Metric

This value equals the distance to the remote network.

Hop Count

The number of routers a packet passes through en route to a remote network.

Routing Table

Also known as a routing information base (RIB), is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes.
This data table conta

Router Characteristics

By default, won't forward any broadcast or multicast packets
Use the logical address in a Network layer header to determine the next-hop router to forward the packet to.
Can use access lists, created by an administrator, to control security on the types o

Logical Address

The address at which an item (memory cell, storage element, network host) appears to reside from the perspective of an executing application program.

Frame

A data unit transferred across a network. These consist of several parts, such as the sending and receiving MAC addresses, the data being sent, and the frame check sequence.

Packet

Basic component of communication over a network. Group of bits of fixed maximum size and well-defined format that is switched and transmitted as a single entity through a network. Contains source and destination address, data, and control information.

Header

A part of the data packet and contains transparent information about the file or the transmission.

Data Link (Layer 2)

Provides the physical transmission of the data and handles error notification, network topology and flow control. This means that this layer ensures that messages are delivered to the proper device on a LAN using hardware addresses and translates messages

Data Link Header

A customized header used by the Data Link layer that contains the destination and source hardware address.

Media Access Control (MAC)

Defines how packets are placed on the media.
One of two sublayers of the IEEE Ethernet Data Link layer.

Logical Link Control (LLC)

Responsible for identifying Network layer protocols and then encapsulating them. This type of header tells the Data Link layer what to do with a packet once a frame is received.

Physical (Layer 1)

This layer sends bits and receives bits. It communicates directly with the various types of actual communication media.
Specifies the electrical, mechanical, procedural, and functional requirements for activating, maintaining, and deactivating a physical

State Transition

A change in voltage from high to low and low to high.

Encoding

Allows the perceived item of use or interest to be converted into a construct that can be stored within the brain and recalled later from short term or long term memory.

Physical Topology

Describes how devices are connected to the network through the actual cables that transmit data, or the physical structure of the network.

Logical Topology

Describes the arrangement of devices on a computer network and how they communicate with one another.

Encapsulation

The process of encoding data as it goes down the OSI stack.
Order is data, segment, packet, frame, bits.

Protocol Data Unit (PDU)

A unit of data which is specified in a protocol of a given layer and which consists of protocol-control information and possibly user data of that layer.
Allows communication and the exchange of information between layers.
Usually attached to the header i

TCP/IP (DoD) Model

A condensed version of the OSI model that's composed of four layers:
1.) Process/Application Layer
2.) Host-to-Host Layer
3.) Internet Layer
4.) Network Access Layer

Process/Application Layer

Integrates the various activities of the OSI's top three layers (Application, Presentation and Session).
This layer defines protocols for node-to-node application communication and also controls user-interface specifications.

Host-to-Host Layer

Parallels the functions of the OSI's Transport Layer, defining protocols for setting up the level of transmission service for applications.
It tackles issues such a creating reliable end-to-end communication and ensuring the error-free delivery of data.
I

Internet Layer

Corresponds to the OSI's Network layer, designating the protocols relating to the logical transmission of packets over the entire network.
It takes care of logical addressing of hosts by giving them an IP address, and it handles the routing of packets amo

Network Access Layer

Monitors the data exchange between the host and the network.
The equivalent of the Data Link and Physical layers of the OSI Model, this layer oversees hardware addressing and defines protocols for the physical transmission of data.

Datagram

A basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order of arrival are not guaranteed by the network.

Cyclic Redundancy Check (CRC)

An error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial division of their conten

Frame Check Sequence (FCS)

Refers to the extra error-detecting code added to a frame in a communications protocol. Frames are used to send upper-layer data and ultimately the application data from a source to a destination.

De-encapsulation

The process of pulling a packet from the frame and discarding what is left of the frame. The packet is then handed to the Network layer, where the address is checked. If the address matches, the segment is pulled from the packet and what's left of the pac

TCP Segment

Consists of a segment header and a data section.

Application Layer Basic Functions

File, print, message, database and application services.

Presentation Layer Basic Functions

Data encryption, compression, and translation services.

Session Layer Basic Functions

Dialog control

Transport Layer Basic Functions

End-to-end connection

Network Layer Basic Functions

Routing

Data Link Layer Basic Functions

Framing

Physical Layer Basic Functions

Physical topology

OSI Model Mnemonic

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