Chapter 2: The OSI Model and Networking Protocols Flashcards
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
Scopes
A range of IP addresses
Leases
The predetermined amount of time of the address that the server assigns from the scope to the client
Reservations
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