Chapter 2: The OSI Model and Networking Protocols Flashcards Preview

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Flashcards in Chapter 2: The OSI Model and Networking Protocols Deck (46)
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Physical (Layer 1)
Device: Hub

Physical (Layer 1): Defines the physical structure of the network and the topology


Data Link (Layer 2)
Device: Wireless Bridge, Switch, NIC, AP

Provides error detection and correction; Media Access Control (MAC) and Logical Link Control (LLC) layers; Identifies the method by which media are accessed; Defines hardware addressing through the MAC sublayer.


Network (Layer 3)
Device: Switch or Router

Handles the discovery of destination systems and addressing. Provides the mechanism by which data can be passed and routed from one network system to another.


Transport (Layer 4)

Provides connection services between the sending and receiving devices and ensures reliable data delivery. Manages flow control through buffering or windowing. Provides segmentation, error checking and service identification.


Session (Layer 5)

Synchronizes the data exchange between applications on separate devices


Presentation (Layer 6)

Translates data from the format used by applications into one that can be transmitted across the network. Handles encryption and decryption of data. Provides compression and decompression functionality. Formats data from the application layer into a format that can be sent over the network.


Application (Layer 7)

Provides access to the network for applications


Dynamic Host Configuration Protocol (DHCP)

Enables a range of IP addresses to be defined on a system running a DHCP server application; Protocol dependent NOT platform dependent; Can provide DNS suffixes to clients



A range of IP addresses



The predetermined amount of time of the address that the server assigns from the scope to the client



A specific address configured by DHCP to a client, as opposed to a random one from the scope; Guarantees the same IP address


DHCP Relays

An agent on the router that acts as a go-between for clients and the server; Useful when working with clients on different subnets since a client cannot communicate directly with the server until it has the IP configuration information assigned to it


Domain Name Service (DNS)

Resolves host names to IP addresses; Platform independent; Default port 53


Resolvers or DNS Clients (DDNS)

Systems that ask DNS servers for a hostname-to-IP address mapping


Dynamic DNS (DDNS)

A newer system that enables hosts to be dynamically registered with the DNS server


DNS namespace

Logical divisions hierarchically organized; Top levels are domains (e.g. .com and .edu) as well as domains for countries (e.g. .uk and .de); Below the top level are subdomains or second-level domains associated with organizations or commercial companies (e.g. Microsoft); Within these domains, hosts or other subdomains can be assigned


Fully Qualified Domain Name (FQDN)

The domain name, along with any subdomains, because it includes all the components from the top of the DNS namespace to the host


Reverse lookup

When DNS performs IP address-to-hostname resolution (as opposed to DNS resolving hostnames to IP addresses) using pointer (PTR) records


DNS Records - Pg. 61

IPv4 Address (A): Stores info for IPv4 (32-bit) addresses, most commonly used to map hostnames to an IP address for a host.

IPv6 Address (AAAA): Stores info for IPv6 (128-bit) addresses, most commonly sed to map hostnames to an IP address for a host.

Mail Exchange (MX): Stores info about where mail for the domain should be delivered

Canonical Name (CNAME): Stores additional hostnames, or aliases, for hosts in the domain. A CNAME specifies an alias or nickname for a canonical hostname record in a Domain Name Service (DNS) database. CNAME records give a single computer multiple names (aliases)

Pointer (PTR): A pointer to the canonical name, which is used to perform a reverse DNS lookup, in which case the name is returned when the query originates with an IP address.


Simple Network Management Protocol (SNMP)
Default Port 161

SNMP enables network devices to communicate information about their state to a central system (manager). It also enables the central system to pass configuration parameters to the devices.

SNMP is a protocol that facilitates network management functionality. It is not, in itself, a network management system (NMS), simply the protocol that makes NMS possible.


Network Management System (NMS)

Software run on a computer with SNMP management system; Can monitor all devices on a network, including switches, hubs, routers, servers, and printers, as well as any device that supports SNMP, from a single location.


SNMP Agent

Any device that can run a small software component that facilitates communication with an SNMP manager. SNMP agent functionality is supported by almost any device designed to be connected to a network.


Management Information Bases (MIBs)

Databases of information that SNMP uses to define what parameters are accessible, which of the parameters are read-only, and which can be set. MIB creation controlled by the International Organization for Standardization (ISO).


SNMP Communities

Logical groupings of systems



Support authentication and encryption unlike SNMPv1 and SNMPv2


Internet Protocol (IP)

Protocol used to transport data from one node on a network to another; Operates at the network layer of the OSI model; Performs fragmentation and reassembly tasks for network transmissions; Maximum transmission unit (MTU) size is limited in IP.


Transmission Control Protocol (TCP)

TCP provides reliability to IP communications; Adds features such as flow control, sequencing, and error detection and correction. Higher level applications that need guaranteed delivery use TCP rather than the connectionless UDP. TCP operates at the transport layer of the OSI model. Three way handshake (SYN -> SYN ACK -> ACK)


User Datagram Protocol (UDP)

"Fire-and-forget" protocol; UDP operates at the transport layer of the OSI model; No session established between sending and receiving hosts, but also much lower overhead


File Transfer Protocol (FTP)

Provides for the uploading and downloading of files from a remote host running FTP server software; Allows you to view the content of folders on an FTP server and rename and delete files and directories if you have the necessary permissions. Uses TCP as a transport protocol to guarantee delivery of packets. Application layer protocol


Secure File Transfer Protocol (SFTP)

Provides robust authentication between sender and receiver; Implemented through client and server software available for all commonly used computing platforms