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Figure 3-2: TCP/IP Standards (Study Figure)
Origins Defense Advanced Research Projects Agency
(DARPA) created the ARPANET
An internet connects multiple individual networks
Global Internet is capitalized
Internet Engineering Task Force (IETF)
Most IETF documents are requests for comments (RFCs)
Internet Official Protocol Standards: List of RFCs that are official standards
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Figure 3-2: TCP/IP Standards (Study Figure)
Hybrid TCP/IP-OSI Architecture (Figure 3-3) Combines TCP/IP standards at layers 3-5 with OSI standards at layers 1-2
TCP/IP
Application
Transport
Internet
OSI
Subnet Access: UseOSI Standards Here
Hybrid TCP/IP-OSI
Application
Presentation
Session
Application
Transport Transport
Network Internet
Data Link Data Link
Physical Physical
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Figure 3-2: TCP/IP Standards (Study Figure)
OSI Layers Physical (Layer 1): defines electrical signaling
and media between adjacent devices
Data link (Layer 2): control of a frame through a single network, across multiple switches
SwitchedNetwork 1
Data Link
Physical Link Frame
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Figure 3-2: TCP/IP Standards
Internet Layer Governs the transmission of a packet across an
entire internet. Path of the packet is its route
SwitchedNetwork 1
SwitchedNetwork 2
Switched Network 3 RouterRoute
Packet
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Figure 3-2: TCP/IP Standards (Study Figure)
Frames and Packets Frames are messages at the data link layer
Packets are messages at the internet layer
Packets are carried (encapsulated) in frames
There is only a single packet that is delivered from source to destination host
This packet is carried in a separate frame in each network
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Figure 3-2: TCP/IP Standards (Study Figure)
Internet and Transport Layers Purposes
Internet layer governs hop-by-hop transmission between routers to achieve end-to-end delivery
Transport layer is end-to-end (host-to-host) protocol involving only the two hosts
Internet Protocol (IP)
IP at the internet layer is unreliable—does not correct errors in each hop between routers
This is good: reduces the work each router along the route must do
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Figure 3-2: TCP/IP Standards (Study Figure)
Transport Layer Standards Transmission Control Protocol (TCP)
Reliable and connection-oriented service at the transport layer
Corrects errors
User Datagram Protocol (UDP) Unreliable and connectionless service at the
transport layer Lightweight protocol good when catching
errors is not important
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Figure 3-7: Internet and Transport Layers
Transport LayerEnd-to-End (Host-to-Host)
TCP is Connection-Oriented, ReliableUDP is Connectionless Unreliable
Client PC ServerInternet Layer(Usually IP)
Hop-by-Hop (Host-Router or Router-Router)Connectionless, Unreliable
Router 1 Router 2 Router 3
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Figure 3-2: TCP/IP Standards (Study Figure)
Application Layer To govern communication between application
programs, which may be written by different vendors
Document transfer versus document format standards HTTP / HTML for WWW service SMTP / RFC 822 (or RFC 2822) in e-mail
Many application standards exist because there are many applications
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Figure 3-8: HTML and HTTP at the Application Layer
Webserver
60.168.47.47
Hypertext Markup Language (HTML) Document or Other File (jpeg, etc.)
Client PC with Browser 123.34.150.37
Hypertext Transfer Protocol (HTTP) Requests and Responses
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Figure 3-3: TCP/IP and OSI Architectures: Recap
TCP/IP
Application
Transport
Internet
OSI
Subnet Access: UseOSI Standards Here
Hybrid TCP/IP-OSI
Application
Presentation
Session
Application
Transport Transport
Network Internet
Data Link Data Link
Physical Physical
Note: The Hybrid TCP/IP-OSI Architecture is used on the Internet anddominates internal corporate networks.
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