week 11 Flashcards
what is the application layer
- -> The application layer is the closest to the user
- -> Provides interface between the applications we use to communicate and underlying network over which our messages are transmitted
- -> application layer protocols are used to exchange data between source and destination hosts
what are the 3 functions of the presentation layer
–> formats data from the source device into a compatible form for receipt by the destination device
–> compression of data in a way that can be decompressed by the destination device
–> Encryption of the data for transmission and the decryption of data upon receipt by the destination
what are the functions of the session layer
- -> creates and maintains dialogs between source and destination applications
- -> Handles the exchange of information to initiate dialogs, keep them active and to restart the session s
what is DNS
used to resolve internet names to ip addresses
what is telnet
a terminal emulation protocol used to provide remote access to servers and networking devices
what is DHCP
used to assign ip address, subnet mask, default gateway and DNS server to a host
what is HTTP used for
used to transfer flies that make up webpages of the world wide web
what is FTP
used for interactive file transfer between systems
what is trivial file transfer protocol (TFTP)
used for connectionless active file transfer
what is simple mail transfer protocol
used for transfer of mail messages and attachments
what is post office protocol (POP)
used by email clients to retrieve mail from a remote server
what is internet message access protocol (IMAP)
another protocol for email retrieval
every connected end device are considered _________ in the p2p network
equal
what is a peer in peer to peer networks
it is the end devices
what do peer networks do with the resources on the network
peer to peer networks decentralize the resources on a network
instead of locating the data to be shared on dedicated servers, data can be located anywhere and on any connected device
what do p2p applications do instead of using a central database
The devices on the network each tell the others what files are available when queried, and use the file sharing protocol and services to support locating resources
what are some common p2p applications
- -> edonkey
- -> eMule
- -> BitTorrent
- -> Bitcoin
- -> LionShare
in a client server architecture in addition to actual data transfer what else is required
user authentication
identification of file data
what protocols does HTTP specify
request and response protocol
what are 3 common request message types in HTTP
GET
POST
PUT
SMTP used to __________
send mails
_________ and __________ used to retrive mail
POP and IMAP
SMTP transfers mail reliably and efficiently to ___________–
destination email server
describe how SMTP works
- -> transfers mail
- -> SMTP processes must be running on both client and server
- -> message and message header must have a properly formatted recipient email address and a sender
- -> uses port 25
what is post office protocol
- -> enables a workstation to retrieve mail from a mail server
- -> mail is downloaded from the server to the client and then deleted on the server
- -> uses port 110
what is Internet Message Access Protocol
- -> another protocol that is used to retrieve email messages
- -> unlike POP, when the user connects to an IMAP capable server copies of the message are downloaded to the client application
- -> original messages are kept on the server until manually deleted
- -> port 143
why were domain names created
domain names were created to convert the numeric IP addresses into a simple, recognisable, and easy to remember name
the domain name system was created for ________________-
domain name to address resolution
what does DNS use to resolve the names associated with these numbered IP addresses
distributed set of servers
what system does a DNS protocol use and why
Hierarchical system is used to create a database to provide name resolutino
this system looks like inverted tree
DNS relies _________ to store and maintain records
decentralised servers
what is EACH DNS server responsible for
–>maintains a specific database file and is responsible for managing name to IP mappings for that small portion of the entire DNS structure
give some examples of top level domains
.au
.com
.jp
what is Dynamic Host Configuration Protocol
–> automatically assigns IP addresses, subnet masks, gateway and other IP networking parameters to network devices
–>When the DHCP server is contacted and an address is requested, the DHCP server chooses an address from a configured range of addresses called a pool and assigns it to the host for a set period. This is why DHCP assigned addresses are not permanent
–> DHCP can pose a security risk because any device connected to the network can receive an address
what are the 4 DHCP steps
DHCP discover
DHCP offer
DHCP request
DHCP Ack
how does an FTP client applicaiton push and pull data from a server
by running FTP daemon
what are the 2 connections that the client establishes in FTP
–> the client establishes the first connection to the server for control traffic, consisting of client commands and server replies
–> The client establishes the second connection to the server for the actual data transfer `
