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© 2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1
Chapter 10:
Application Layer
Network Basics
Presentation_ID 2© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Chapter 10 Objectives
 Explain how the functions of the application layer, session layer, and presentation
layer work together to provide network services to end user applications.
 Describe how common application layer protocols interact with end user
applications.
 Describe, at a high level, common application layer protocols that provide Internet
services to end-users, including WWW services and email.
 Describe application layer protocols that provide IP addressing services, including
DNS and DHCP.
 Describe the features and operation of well-known application layer protocols that
allow for file sharing services, including: FTP, File Sharing Services, SMB
protocol.
 Explain how data is moved across the network, from opening an application to
receiving data.
Presentation_ID 3© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Chapter 10
10.1 Application Layer Protocols
10.2 Well-Known Application Layer Protocols and Service
10.3 The Message Heard Around the World
10.4 Summary
Presentation_ID 4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
The Application Layer provides the interface to the network.
10.1 Application Layer Protocols
Presentation_ID 5© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application, Session and Presentation
OSI and TCP/IP Models Revisited
The key parallels are in the transport and network layer.
Presentation_ID 6© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application Session and Presentation
Application Layer
Presentation_ID 7© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application, Session and Presentation
Presentation and Session Layers
Presentation layer has three primary functions:
• Coding and conversion of application layer data
• Compression of the data
• Encryption of the data for transmission and the
decryption of data upon receipt by the destination
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
Presentation_ID 8© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application, Session and Presentation
Presentation and Session Layers
Presentation_ID 9© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application, Session and Presentation
TCP/IP Application Layer Protocols
Domain Name Service Protocol (DNS) - used to resolve
Internet names to IP addresses
Telnet - a terminal emulation protocol used to provide
remote access to servers and networking devices
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
server to a host
Hypertext Transfer Protocol (HTTP) - used to transfer files
that make up the Web pages of the World Wide Web
Presentation_ID 10© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application, Session and Presentation
TCP/IP Application Layer Protocols
File Transfer Protocol (FTP) - used for interactive file
transfer between systems
Trivial File Transfer Protocol (TFTP) - used for
connectionless active file transfer
Simple Mail Transfer Protocol (SMTP) - used for the
transfer of mail messages and attachments
Post Office Protocol (POP) - used by email clients to
retrieve email from a remote server
Internet Message Access Protocol (IMAP) – another
protocol for email retrieval
Presentation_ID 11© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
How Application Protocols Interact with End-User Applications
Peer-to-Peer Networks
Both devices are considered equal in the communication
The roles of client and server are set on a per request basis.
Presentation_ID 12© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
How Application Protocols Interact with End-User Applications
Peer-to-Peer Applications
Client and server in the same communication
Both can initiate a communication and are considered equal
in the communication process
Presentation_ID 13© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
How Application Protocols Interact with End-User Applications
Common P2P Applications
 With P2P applications, each computer in the network
running the application can act as a client or a server for
the other computers in the network running the application
 Common P2P applications include:
• eDonkey
• eMule
• Shareaza
• BitTorrent
• Bitcoin
• LionShare
 Some P2P applications are based on the Gnutella protocol
which enables people to share files on their hard disks with
others
Presentation_ID 14© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
How Application Protocols Interact with End-User Applications
Client-Server Model
Presentation_ID 15© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
How Application Protocols Interact with End-User Applications
Client-Server Model
Presentation_ID 16© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
10.2 Well-Known Application Layer
Protocols and Services
Presentation_ID 17© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
Application Layer Protocols Revisited
Three application layer protocols that are involved in everyday
work or play are:
 Hypertext Transfer Protocol (HTTP)
• browse the web
 Simple Mail Transfer Protocol (SMTP)
• used to enable users to send email
 Post Office Protocol (POP)
• used to enable users to receive email
Presentation_ID 18© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
Hypertext Transfer Protocol / Markup Language
Example
URL: http://www.cisco.com/index.html
 First, the browser interprets the three parts of the URL:
1. http (the protocol or scheme)
2. www.cisco.com (the server name)
3. index.html (the specific file name requested)
 Browser checks with a name server to convert
www.cisco.com into a numeric address
 Using the HTTP protocol requirements sends a GET request
to the server and asks for the file index.html
 Server sends the HTML code for this web page
 Browser deciphers the HTML code and formats the page
Presentation_ID 19© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
HTTP and HTTPS
• Developed to publish
and retrieve HTML
pages
• Used for data transfer
• Specifies a
request/response
protocol
• Three common
message types are
GET, POST, and PUT
• GET is a client
request for data
• POST and PUT are
used to send
messages that upload
data to the web
server
Presentation_ID 20© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
SMTP, POP, and IMAP
• Typically use an application
called a Mail User Agent
(email client)
• Allows messages to be sent
• Places received messages
into the client's mailbox
• SMTP - Send email from
either a client or a server
• POP - Receive email
messages from an email
server
• IMAP - Internet Message
Access Protocol
• Email client provides the
functionality of both
protocols within one
application
Presentation_ID 21© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
SMTP, POP, and IMAP
Presentation_ID 22© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
SMTP, POP, and IMAP (Continued)
Simple Mail Transfer
Protocol (SMTP)
 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
Presentation_ID 23© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
SMTP, POP, and IMAP (Continued) Post Office Protocol
(POP)
 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
 POP does not store
messages
 POP3 is desirable for
an ISP, because it
alleviates their
responsibility for
managing large
amounts of storage
for their email servers
Presentation_ID 24© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Common Application Layer Protocols
SMTP, POP, and IMAP (Continued)
Simple Mail Transfer Protocol (SMTP)
• Transfers mail reliably and efficiently
Post Office Protocol (POP)
• Enables a workstation to retrieve mail from a mail server
• With POP, mail is downloaded from the server to the
client and then deleted on the server
Internet Message Access Protocol (IMAP)
• Another protocol that to retrieves email messages
• Unlike POP, when the user connects to an IMAP-capable
server, copies of the messages are downloaded to the
client application
• Original messages are kept on the server until manually
deleted
Presentation_ID 25© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
Domain Name Service
A human legible
name is resolved
to its numeric
network device
address by the
DNS protocol
Presentation_ID 26© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
Domain Name Service
A human legible
name is resolved
to its numeric
network device
address by the
DNS protocol
Presentation_ID 27© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
DNS Message Format
• DNS server stores different types of resource records used
to resolve names
• Contain the name, address, and type of record
• Record types are:
• A - an end device address
• NS - an authoritative name server
• 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
• MX - mail exchange record; maps a domain name to a
list of mail exchange servers
• 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
• Windows ipconfig /displaydns displays all cached DNS
Presentation_ID 28© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
DNS Hierarchy
Examples top-
level domains:
.au - Australia
.co - Colombia
.com - business
or industry
.jp - Japan
.org - non-profit
organization
Presentation_ID 29© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
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
Presentation_ID 30© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
Dynamic Host Configuration Protocol
 DHCP allows a host to
obtain an IP address
dynamically
 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 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
Presentation_ID 31© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing IP Addressing Services
DHCP Operation
Presentation_ID 32© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing File Sharing Services
File Transfer Protocol
• FTP allow data
transfers between a
client and a server
• FTP client is an
application that runs
on a computer that 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
Presentation_ID 33© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing File Sharing Services
Server Message Block
• Clients
establish a long
term connection
to servers
• After the
connection is
established, the
user can
access the
resources on
the server as if
the resource is
local to the
client host
Presentation_ID 34© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Providing File Sharing Services
Server Message Block
Presentation_ID 35© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
The Internet of Things
Presentation_ID 36© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Message Travels Through a Network
Presentation_ID 37© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Message Travels Through a Network
Presentation_ID 38© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Message Travels Through a Network
Presentation_ID 39© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Getting the Data to the End Device
Presentation_ID 40© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Getting the Data through the Internetwork
Presentation_ID 41© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Move It!
Getting the Data to the Right Application
Presentation_ID 42© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application Layer
Summary
 Applications are computer programs with which the user
interacts and which initiate the data transfer process at the
user’s request.
 Services are background programs that provide the
connection between the application layer and the lower layers
of the networking model.
 Protocols provide a structure of agreed-upon rules and
processes that ensure services running on one particular
device can send and receive data from a range of different
network devices.
Presentation_ID 43© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Application Layer
Summary
 HTTP supports the delivery of web pages to end devices
 SMTP, POP, and IMAP support sending and receiving email
 SMB and FTP enable users to share files
 P2P applications make it easier for consumers to seamlessly
share media
 DNS resolves the human legible names used to refer to
network resources into numeric addresses usable by the
network
 All of these elements work together, at the application layer.
 The application layer enables users to work and play over the
Internet.
Presentation_ID 44© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential

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Ccna v5-S1-Chapter 10

  • 1. © 2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1 Chapter 10: Application Layer Network Basics
  • 2. Presentation_ID 2© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Chapter 10 Objectives  Explain how the functions of the application layer, session layer, and presentation layer work together to provide network services to end user applications.  Describe how common application layer protocols interact with end user applications.  Describe, at a high level, common application layer protocols that provide Internet services to end-users, including WWW services and email.  Describe application layer protocols that provide IP addressing services, including DNS and DHCP.  Describe the features and operation of well-known application layer protocols that allow for file sharing services, including: FTP, File Sharing Services, SMB protocol.  Explain how data is moved across the network, from opening an application to receiving data.
  • 3. Presentation_ID 3© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Chapter 10 10.1 Application Layer Protocols 10.2 Well-Known Application Layer Protocols and Service 10.3 The Message Heard Around the World 10.4 Summary
  • 4. Presentation_ID 4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential The Application Layer provides the interface to the network. 10.1 Application Layer Protocols
  • 5. Presentation_ID 5© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application, Session and Presentation OSI and TCP/IP Models Revisited The key parallels are in the transport and network layer.
  • 6. Presentation_ID 6© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application Session and Presentation Application Layer
  • 7. Presentation_ID 7© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application, Session and Presentation Presentation and Session Layers Presentation layer has three primary functions: • Coding and conversion of application layer data • Compression of the data • Encryption of the data for transmission and the decryption of data upon receipt by the destination 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
  • 8. Presentation_ID 8© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application, Session and Presentation Presentation and Session Layers
  • 9. Presentation_ID 9© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application, Session and Presentation TCP/IP Application Layer Protocols Domain Name Service Protocol (DNS) - used to resolve Internet names to IP addresses Telnet - a terminal emulation protocol used to provide remote access to servers and networking devices 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 server to a host Hypertext Transfer Protocol (HTTP) - used to transfer files that make up the Web pages of the World Wide Web
  • 10. Presentation_ID 10© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application, Session and Presentation TCP/IP Application Layer Protocols File Transfer Protocol (FTP) - used for interactive file transfer between systems Trivial File Transfer Protocol (TFTP) - used for connectionless active file transfer Simple Mail Transfer Protocol (SMTP) - used for the transfer of mail messages and attachments Post Office Protocol (POP) - used by email clients to retrieve email from a remote server Internet Message Access Protocol (IMAP) – another protocol for email retrieval
  • 11. Presentation_ID 11© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential How Application Protocols Interact with End-User Applications Peer-to-Peer Networks Both devices are considered equal in the communication The roles of client and server are set on a per request basis.
  • 12. Presentation_ID 12© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential How Application Protocols Interact with End-User Applications Peer-to-Peer Applications Client and server in the same communication Both can initiate a communication and are considered equal in the communication process
  • 13. Presentation_ID 13© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential How Application Protocols Interact with End-User Applications Common P2P Applications  With P2P applications, each computer in the network running the application can act as a client or a server for the other computers in the network running the application  Common P2P applications include: • eDonkey • eMule • Shareaza • BitTorrent • Bitcoin • LionShare  Some P2P applications are based on the Gnutella protocol which enables people to share files on their hard disks with others
  • 14. Presentation_ID 14© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential How Application Protocols Interact with End-User Applications Client-Server Model
  • 15. Presentation_ID 15© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential How Application Protocols Interact with End-User Applications Client-Server Model
  • 16. Presentation_ID 16© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential 10.2 Well-Known Application Layer Protocols and Services
  • 17. Presentation_ID 17© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols Application Layer Protocols Revisited Three application layer protocols that are involved in everyday work or play are:  Hypertext Transfer Protocol (HTTP) • browse the web  Simple Mail Transfer Protocol (SMTP) • used to enable users to send email  Post Office Protocol (POP) • used to enable users to receive email
  • 18. Presentation_ID 18© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols Hypertext Transfer Protocol / Markup Language Example URL: http://www.cisco.com/index.html  First, the browser interprets the three parts of the URL: 1. http (the protocol or scheme) 2. www.cisco.com (the server name) 3. index.html (the specific file name requested)  Browser checks with a name server to convert www.cisco.com into a numeric address  Using the HTTP protocol requirements sends a GET request to the server and asks for the file index.html  Server sends the HTML code for this web page  Browser deciphers the HTML code and formats the page
  • 19. Presentation_ID 19© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols HTTP and HTTPS • Developed to publish and retrieve HTML pages • Used for data transfer • Specifies a request/response protocol • Three common message types are GET, POST, and PUT • GET is a client request for data • POST and PUT are used to send messages that upload data to the web server
  • 20. Presentation_ID 20© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols SMTP, POP, and IMAP • Typically use an application called a Mail User Agent (email client) • Allows messages to be sent • Places received messages into the client's mailbox • SMTP - Send email from either a client or a server • POP - Receive email messages from an email server • IMAP - Internet Message Access Protocol • Email client provides the functionality of both protocols within one application
  • 21. Presentation_ID 21© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols SMTP, POP, and IMAP
  • 22. Presentation_ID 22© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols SMTP, POP, and IMAP (Continued) Simple Mail Transfer Protocol (SMTP)  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
  • 23. Presentation_ID 23© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols SMTP, POP, and IMAP (Continued) Post Office Protocol (POP)  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  POP does not store messages  POP3 is desirable for an ISP, because it alleviates their responsibility for managing large amounts of storage for their email servers
  • 24. Presentation_ID 24© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Common Application Layer Protocols SMTP, POP, and IMAP (Continued) Simple Mail Transfer Protocol (SMTP) • Transfers mail reliably and efficiently Post Office Protocol (POP) • Enables a workstation to retrieve mail from a mail server • With POP, mail is downloaded from the server to the client and then deleted on the server Internet Message Access Protocol (IMAP) • Another protocol that to retrieves email messages • Unlike POP, when the user connects to an IMAP-capable server, copies of the messages are downloaded to the client application • Original messages are kept on the server until manually deleted
  • 25. Presentation_ID 25© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services Domain Name Service A human legible name is resolved to its numeric network device address by the DNS protocol
  • 26. Presentation_ID 26© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services Domain Name Service A human legible name is resolved to its numeric network device address by the DNS protocol
  • 27. Presentation_ID 27© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services DNS Message Format • DNS server stores different types of resource records used to resolve names • Contain the name, address, and type of record • Record types are: • A - an end device address • NS - an authoritative name server • 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 • MX - mail exchange record; maps a domain name to a list of mail exchange servers • 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 • Windows ipconfig /displaydns displays all cached DNS
  • 28. Presentation_ID 28© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services DNS Hierarchy Examples top- level domains: .au - Australia .co - Colombia .com - business or industry .jp - Japan .org - non-profit organization
  • 29. Presentation_ID 29© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services 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
  • 30. Presentation_ID 30© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services Dynamic Host Configuration Protocol  DHCP allows a host to obtain an IP address dynamically  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 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
  • 31. Presentation_ID 31© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing IP Addressing Services DHCP Operation
  • 32. Presentation_ID 32© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing File Sharing Services File Transfer Protocol • FTP allow data transfers between a client and a server • FTP client is an application that runs on a computer that 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
  • 33. Presentation_ID 33© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing File Sharing Services Server Message Block • Clients establish a long term connection to servers • After the connection is established, the user can access the resources on the server as if the resource is local to the client host
  • 34. Presentation_ID 34© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Providing File Sharing Services Server Message Block
  • 35. Presentation_ID 35© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! The Internet of Things
  • 36. Presentation_ID 36© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Message Travels Through a Network
  • 37. Presentation_ID 37© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Message Travels Through a Network
  • 38. Presentation_ID 38© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Message Travels Through a Network
  • 39. Presentation_ID 39© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Getting the Data to the End Device
  • 40. Presentation_ID 40© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Getting the Data through the Internetwork
  • 41. Presentation_ID 41© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Move It! Getting the Data to the Right Application
  • 42. Presentation_ID 42© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application Layer Summary  Applications are computer programs with which the user interacts and which initiate the data transfer process at the user’s request.  Services are background programs that provide the connection between the application layer and the lower layers of the networking model.  Protocols provide a structure of agreed-upon rules and processes that ensure services running on one particular device can send and receive data from a range of different network devices.
  • 43. Presentation_ID 43© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Application Layer Summary  HTTP supports the delivery of web pages to end devices  SMTP, POP, and IMAP support sending and receiving email  SMB and FTP enable users to share files  P2P applications make it easier for consumers to seamlessly share media  DNS resolves the human legible names used to refer to network resources into numeric addresses usable by the network  All of these elements work together, at the application layer.  The application layer enables users to work and play over the Internet.
  • 44. Presentation_ID 44© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential