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CHAPTER 10: APPLICATION LAYER - Coggle Diagram
CHAPTER 10: APPLICATION LAYER
Application Layer Protocols
The Application Layer provides the interface to the network.
OSI Model
Transport
Network
Session
Presentation
Application
Data Link
1.Physical
Presentation and Session Layer
Presentation Layer
Compression of the data
Encryption of the data for transmission and the decryption of data upon receipt by the destination
Coding and conversion of application layer data
Session Layer
Functions create and maintain dialogs between source and destination applications
Handles the exchange of information to initiate dialogs, keep them active, and to restart sessions
TCP/IP Application Layer Protocols
Bootstrap Protocol (BOOTP)
- a precursor to the DHCP
protocol, a network protocol used to obtain IP address information during bootup
Dynamic Host Control Protocol (DHCP)
- used to assign
an IP address, subnet mask, default gateway and DNS
Telnet
- a terminal emulation protocol used to provide
remote access to servers and networking devices
Hypertext Transfer Protocol (HTTP)
- used to transfer files
that make up the Web pages of the World Wide Web
Domain Name Service Protocol (DNS)
- used to resolve internet names to IP addresses
Simple Mail Transfer Protocol (SMTP)
- used for the transfer of mail messages and attachments
Trivial File Transfer Protocol (TFTP)
- used for connectionless active file transfer
Post Office Protocol (POP)
- used by email clients to retrieve email from a remote server
File Transfer Protocol (FTP)
- used for interactive file transfer between systems
Internet Message Access Protocol (IMAP)
– another
protocol for email retrieval
HTTP and HTTPs
Specifies a request/response protocol
Three common message types are
GET, POST and PUT
Used for data transfer
GET
is a client request for data
Developed to publish and retrieve HTML pages
POST and PUT
are used to send messages that upload
data to the web server
SMTP, POP & IMAP
Places received messages into the client's mailbox
SMTP
- Send email from either a client or a server
transfers mail
message must be formatted properly
SMTP processes must be running on both the client and
server
message header must have a properly formatted recipient
email address and a sender
uses
port 25
Allows messages to be sent
POP
- Receive email messages from an email server
POP3
is desirable for an ISP, because it alleviates their
responsibility for managing large amounts of storage for their email servers
POP does not store messages
uses
port 110
mail is downloaded from the server to the client and then
deleted on the server
enables a workstation to retrieve mail from a mail server
Typically use an application called a Mail User Agent (email client)
IMAP
- Internet Message Access Protocol
Email client provides the functionality of both protocols within one application
Domain Name Service
A human legible name is resolved to its numeric network device address by the DNS protocol
DNS Hierarchy
.co
-Colombia
.com
-business or industry
.jp
- Japan
.au
-Australia
.org-non
-profit organization
DNS Message Format
Unable to resolve the name using its stored records, contacts other servers
Server temporarily stores the numbered address that matches the name in cache memory
Contain the name, address, and type of record
Windows ipconfig /displaydns displays all cached DNS
DNS server stores different types of resource records used to resolve names
Record types are:
A
- an end device address
NS
- an authoritative name server
MX
- mail exchange record; maps a domain name to a list of mail exchange servers
CNAME
- the canonical name for an alias; used when multiple services have the single network address but each service has its own entry in DNS
nslookup
Operating system utility called
nslookup
allows the user to manually query the name servers to resolve a given host name
Utility can be used to troubleshoot name resolution issues and to verify the current status of the name servers
Dynamic Host Configuration Protocol (DHCP)
DHCP used for general purpose hosts such as end user devices and static addressing is used for network devices such as gateways , switches servers and printers
DHCP server is contacted and address requested - chooses
address from a configured range of
addresses called a pool and "leases" it to the host for a set period
DHCP Operation
DCHP Client
-DHCP DISCOVER>
DHCP Server
DCHP Client
< DHCP OFFER-
DHCP Server
DCHP Client
-DHCP REQUEST>
DHCP Server
DCHP Client
< DHCP ACk -
DHCP Serve
DHCP allows a host to obtain an IP address dynamically
File Transfer Protocol
FTP client is an application that runs on a computer tat is used to push and pull data from a server running an FTP daemon
To successfully transfer data, FTP requires two connections between the client and the server, one for commands and replies, the other for the actual file transfer
FTP allow data transfers between a client and a server
Message Travels Through a Network
Application -> Stream ->Transport ->Segment ->Internet ->Network Access
Getting the Data through the Internetwork
Application > Stream > Transport> Internet> Packet> Network Access