Chapter 2 Layer Architecture of Network Protocols. School of Info. Sci. & Eng. Shandong Univ.

Transcription

1 Chapter 2 Architecture of Network Protocols School of Info. Sci. & Eng. Shandong Univ.

2 Outline 2.1 Examples of ing 2.2 OSI Reference Model (Continued from last time) 2.3. TCP/IP Architecture 2.4 Berkeley API (Skip) 2.5 Application Protocols and TCP/IP Utilities

3 Problems for Chapter Find, install, test an Internet tool. Write a paragraph on who, what, when, where -- on it.

4 Overall ISO Model 7-layer cake model discussed last time At end of class, I have some terms for you to define, including what each of these layers do, so think about it Specific network architectures don t fit this model exactly; they are divided into modules that may perform part of the functions of two or more ISO layers

5 Application A Application B Application Presentation Session Transport Communication Network Application Presentation Session Transport Network Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Electrical and/or Optical Signals Figure 2.6

6 The big picture for accessing Web page The Internet is a true distributed (democratic) system in that every host is equal However, in discussing dialog between two hosts, it is usually helpful to think of one as client, the other as server. In accessing a Web page, actually two servers are often used. (What are they?)

7 HTTP client Request Response HTTP server Figure 2.1

8 1. The user clicks on a link to indicate which document is to be retrieved. 2. The browser must determine the address that contains the document. It does this by sending a query to its local name server. 3. Once the address is known the browser establishes a connection to the specified machine, usually a TCP connection. In order for the connection to be successful, the specified machine must be readyto accept TCP connections. 4. The browser runs a client version of HTTP, which issues a request specifying both the name of the document and the possible document formats it can handle. 5. The machine that contains the requested document runs a server version of HTTP. It reacts to the HTTP request by sending an HTTP response which contains the desired document in the appropriate format. 6. The TCP connection is then closed and the user may view the document. Figure 1.4 -Introduces topic

9 HTTP client HTTP server Ephemeral Port # Port 80 GET 80, # TCP TCP #, 80 STATUS Figure 2.2

10 n-pdus n entity n entity Figure 2.3

11 n+1 entity n+1 entity n-sap n-sdu n-sdu n-sap n-sdu H n entity n entity H n-sdu n-pdu Figure 2.4

12 (a) Segmentation n-sdu Reassembly n-sdu n-pdu n-pdu n-pdu n-pdu n-pdu n-pdu (b) Blocking Unblocking n-sdu n-sdu n-sdu n-sdu n-sdu n-sdu n-pdu n-pdu Figure 2.5

13 C PS = packet switch C PS PS PS C = computer PS C C C Figure 2.7

14 net 1 G net 3 G G G net 5 net 2 G net 4 G G = gateway/router Figure 2.8

15 ISO Model, including PDUs at Each Level All computer systems consist of hardware, programs, and data. The information data structures used in network protocols consist of PDU exchanged at each layer A PDU generally consists of the information bits from the next higher layer (the SDU) plus a header that contains the necessary additional info for that layer (+ trailer sometimes) What are the PDUs called at each layer on the next slide?

16 Application A data Application B Application data ah Application Presentation data ph Presentation Session data sh Session Transport data th Transport Network data nh Network Data Link dt data dh Data Link Physical bits Physical Figure 2.9

17 TCP/IP Architecure (5 layers counting physical layer) Application Transport Internet Transport Internet Application Network Interface Network Interface (a) (b) Figure 2.10

18 TCP/IP in Use Machine A Application Transport Internet Network Interface Router/Gateway Internet Network Interface Machine B Application Transport Internet Network Interface Network 1 Network 2 Figure 2.11

19 TCP/IP Protocol Graph (There s More, too) HTTP SMTP DNS RTP TCP UDP IP Network Interface 1 Network Interface 2 Network Interface 3 Figure 2.12

20 (a) (1,1) (2,1) s router (1,3) r PPP (2,2) Ethernet w (b) (1,2) Server HTTP HTTP PC TCP Router TCP IP IP IP Net Interface Net Interface Net Interface Ethernet PPP Figure 2.13

21 IP Header Header contains source and destination physical addresses; network protocol type Ethernet Header Frame Check Sequence Figure 2.14

22 HTTP Request Header contains source and destination port numbers TCP Header Header contains source and destination IP addresses; transport protocol type IP Header Header contains source and destination physical addresses; network protocol type Ethernet Header Frame Check Sequence Figure 2.15

23 socket interface Application 1 Application 2 socket interface user kernel user kernel Socket Socket Underlying communication Protocols Underlying communication Protocols Communications network Figure 2.16

24 User Interface Server PI Control Connection User PI Server DTP Data Connection User DTP Server FTP User FTP PI = Protocol interpreter DTP = Data transfer process Figure 2.19

25 C:\WINDOWS>ping nal.toronto.edu Pinging nal.toronto.edu [ ] with 32 bytes of data: Reply from : bytes=32 time=118ms TTL=243 Reply from : bytes=32 time=118ms TTL=243 Reply from : bytes=32 time=118ms TTL=243 Reply from : bytes=32 time=118ms TTL=243 C:\WINDOWS> Figure 2.20

26 Can you define? Application layer Connectionless service Physical Frame PDU ISO Internetworking Socket Network Architecture Telnet Client/server Daemon Encapulatio n Port HTTP SDU SMTP TCP/IP Architecture UDP FTP Confirmed service Data Link layer PPP Header Segment Internet layer Transport Traceroute The Meaning of Life