1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

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

9

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.