1. 1 OSI Reference Model Benefits Standardizes interfaces Facilitates modular engineering Ensures interoperable technology Accelerates evolution Simplifies teaching and learning Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1

2. 2 Why a Layered Network Model? Reduces complexity Standardizes interfaces Facilitates modular engineering Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1

3. 3 Peer-to-Peer Communications Application Presentation Session Transport Network Data Link Physical HOST AHOST B segments packets frames bits Application Presentation Session Transport Network Data Link Physical

4. 4 MAC Address MAC address is burned into ROM on a network interface card 24 bits 0000.0c12. 3456 Vendor Code Serial Number ROM RAM Vendor assigned IEEE assigned IEEE -- Institute of Electrical and Electronics Engineers

5. 5 Ethernet/ IEEE 802.3 (CSMA/CD) ABCD Collision ABCD JAMJAMJAMJAMJAMJAMJAMJAMJAMJAMJAMJAM Back-off

6. 6 Ethernet 5-4 rule

7. 7

8. 8 TCP/IP Protocol Stack Map DOD model to the OSI Reference Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 Application Transport Internet Network Interface OSI Reference Model Ethernet, 802.3, 802.5, FDDI, and so on. TCP/IP Conceptual Layers US Department Of Defence (DOD)

9. 9 IP Datagram # Bits13481648 VERSHLEN Type of Service Total Length Identi- fication Flags Frag Offset TTL 3 # Bits8320~3216 32 Protocol Header Checksum Source IP Address Destination IP Address IP Options Data… Network Header Frame Trailer Frame Header Data

10. 10 IP Address Bit Patterns 1724 Class A: # Bits 1416 Class B: # Bits 3218 Class C: # Bits 0network #host # 1network #host #0 1network #host #10 2

11. 11 IP Address Bit Patterns Class D: # Bits Class E: # Bits 1 1 1 1 Multicast For Research 1 1 1 0

12. 12 Recognizing Classes in IP Addresses (First Octet Rule) High Order Bits (binary ) Octet in Decimal Address Class 0 10 110 1110 1111 1 – 126 128 – 191 192 – 223 224 – 239 240 – 255 ABCDEABCDE Network 127.0.0.0 Reserved for loopback. The address 127.0.0.1 often is used to refer to the local host

13. 13 Network And Host Number Address Class Network Number Host Number ABCABC 126 16,384 2,097,152 16,777,214 65,534 254 Network 126= 2 7 -2 (127.0.0.0 Reserved) 16384 = 2 14 2,097,152 = 2 21 Host 16,777,214 = 2 24 - 2 65,534 = 2 16 - 2 254 = 2 8 - 2

14. 14 Decimal Equivalents of Bit Patterns 10000000=128 11000000=192 11100000=224 11110000=240 11111000=248 11111100=252 11111110=254 11111111=255 128 6432168421

15. 15 Subnet Planning Other subnets 20 subnets 5 hosts per subnet Class C address: 201.222.5.0 20 subnets 5 hosts per subnet Class C address: 201.222.5.0 201.222.5.16 201.222.5.32201.222.5.48 20 subnets 5 Bits of Subnet 2 5 =32 Subnets 5 hosts per subnet 3 Bits of Host 2 3 -2= 6 Hosts 20 subnets 5 Bits of Subnet 2 5 =32 Subnets 5 hosts per subnet 3 Bits of Host 2 3 -2= 6 Hosts

16. 16 IP Host Address:201.222.5.121 Subnet Mask: 255.255.255.248 NetworkSubnetHost 2012225120 201.222.5.121:11001001 11111111 Subnet:1100100111011110 11111111 00000101 11111111 01111 001 11111 000 01111 000 255.255.255.248: Class C Subnet Planning Example Subnet Address = 201.222.5.120 Host Addresses = 0.0.0.1 Rang = 201.222.5.121–201.222.5.126 Broadcast Address = 201.222.5.127 Five Bits of Subnetting

17. 17 192.1.1.64/26 192.1.1.208/28 192.1.1.248/30192.1.1.244/30 Subnet Planning 192.1.1.192/28 R1 R3 R2 R4 192.1.1.128/26 ? An additional subnet required for a Ethernet link between R1 and R2 as shown in the diagram. Which subnet address can be configured in this network to provide a maximum of 14 useable addresses for this link while wasting the fewest addresses? 192.1.1.16/26 192.1.1.196/27 192.1.1.96/28 192.1.1.160/28 192.1.1.224/28 192.1.1.240/28

18. 18 192.1.1.64/26 192.1.1.208/28 192.1.1.248/30192.1.1.244/30 Subnet Planning 192.1.1.192/28 R1 R3 R2 R4 192.1.1.128/26 ? 01000000 11110100 10000000 11000000 11111000 11010000 192.1.1.96/28 192.1.1.160/28 192.1.1.224/28 192.1.1.240/28 96 －－ 01100000 160 －－ 10100000 224 －－ 11100000 240 －－ 11110000

19. 19 Broadcast Addresses 172.16.1.0/24 172.16.2.0/24 172.16.3.0/24 172.16.4.0/24 172.16.3.255 (Directed broadcast) 255.255.255.255 (Local network broadcast) X

20. 20 AddressClassSubnetBroadcast 201.222.10.60255.255.255.248C201.222.10.63201.222.10.56 Subnet Mask 15.16.193.6255.255.248.0A15.16.199.25515.16.192.0 128.16.32.13255.255.255.252B128.16.32.15128.16.32.12 Exercise: Broadcast Addresses 15 --- 0000111112 --- 0000110013 --- 00001101

21. 21 All Subnets Broadcast 172.16.1.0/24 172.16.2.0/24 172.16.3.0/24 172.16.4.0/24 172.16.255.255 (All Subnets Broadcast)

22. 22 Address Resolution Protocol 172.16.3.2 172.16.3.5 IP: 172.16.3.5 = ??? I need the Ethernet address of 176.16.3.2.

23. 23 Address Resolution Protocol 172.16.3.2 IP: 172.16.3.5 Ethernet: 0800.0020.1111 172.16.3.5 I need the Ethernet address of 176.16.3.2. I heard that broadcast. The message is for me. Here is my Ethernet address. IP: 172.16.3.5 = ???

24. 24 Address Resolution Protocol Map IP Ethernet Local ARP 172.16.3.2 IP: 172.16.3.5 Ethernet: 0800.0020.1111 172.16.3.5 I need the Ethernet address of 176.16.3.2. I heard that broadcast. The message is for me. Here is my Ethernet address. Destination local IP: 172.16.3.5 = ???

25. 25 Finding the MAC Address Router A Destination not local Host Z Host Y Response Routing Table: Net for Host Z Routing Table: Net for Host Z Map IP Ethernet Not Local ARP Broadcast Host Y MAC Host Y MAC 172.16.3.1 IP: 172.16.3.1 MAC? Host Y MAC Host Y MAC Router A MAC Router A MAC IP: 172.16.3.1 Ethernet: 0000.0c12.3456 I want access the Host Z. 172.16.3.2 10.1.0.5 Request Response

26. 26 Proxy ARP Router A Host Z Host Y Request Routing Table: Net for Host Z Routing Table: Net for Host Z Broadcast Host Y MAC Host Y MAC 172.16.3.1 IP: 172.16.1.5 MAC? I want access the Host Z. 172.16.3.2 172.16.1.5/24 The router response its own MAC Address Response Host Y MAC Host Y MAC Router A MAC Router A MAC IP: 172.16.1.5 Ethernet: 0000.0c12.3456 Response

27. 27 Transport Layer Overview Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Application Transport Internet Network Interface Hardware TCP : Connection-oriented services UDP : Connectionless services

28. 28 Determines destination upper-layer protocol IP Datagram Protocol Field Transport Layer Internet Layer TCP UDP Protocol Numbers IP 176

29. 29 TCP Segment Format # Bits616324166 32 Source Port Dest. Port Sequence Number Acknowledgement Number HLENReserved Code Bits 16 Window 16 Check- sum 16 Urgent 0 or 32 OptionData... Transport Header Network Header Data Frame Trailer Frame Header

30. 30 Port Numbers TCP Port Numbers FTPFTP Transport Layer TELNETTELNET DNSDNS SNMPSNMP TFTPTFTP SMTPSMTP UDP Application Layer 2123255369161 80 HTTPHTTP

31. 31 Port Numbers assigned range Port numbers have the following assigned ranges: Port number are 16 bits long (0~65535) Numbers from 1 to 1023 are well-known port number (controlled by the IANA) Numbers above 1023 are dynamically assigned port numbers

32. 32 TCP Sequence and Acknowledgment Numbers # Bits616324166 32 Source Port Dest. Port Sequence Number Acknowledgement Number HLENReserved Code Bits 16 Window 16 Check- sum 16 Urgent 0 or 32 OptionData...

33. 33 TCP Window size # Bits616324166 32 Source Port Dest. Port Sequence Number Acknowledgement Number HLENReserved Code Bits 16 Window 16 Check- sum 16 Urgent 0 or 32 OptionData...

34. 34 Window size = 3 Send 4 Window size = 3 Send 2 TCP Windowing Sender Receiver Window size = 3 Send 1 Window size = 3 Send 3 Window size = 3 Send 3 ACK 5 Window size = 2 ACK 3 Window size = 2 Packet 3 is Dropped

35. 35 UDP no sequence or acknowledgment fields Application-layer protocols can provide for reliability UDP Segment Format 16 Source Port 16 Destination Port 16 Length 16 ChecksumData… # Bits

36. 36 Application Layer Overview *Used by the router Application Transport Internet Network Interface Hardware File Transfer - TFTP * - FTP - NFS E-Mail - SMTP Remote Login - Telnet * - rlogin Network Management - SNMP * Name Management - DNS* File Transfer - TFTP * - FTP - NFS E-Mail - SMTP Remote Login - Telnet * - rlogin Network Management - SNMP * Name Management - DNS*

37. 37 Classless Routing Protocols Classless Routing Protocols: RIPv2 EIGRP OSPF IS-IS BGPv4 Classful Routing Protocols: RIPv1 IGRP 注意 : 有类和无类路由协议在构建路由表时采用不同的方法；而有类和 无类的路由行为是关于如何查找路由表的方法 ( 这时路由表已经 建立 ) 。 有类和无类路由协议与有类和无类路由行为 ( 通过 ip classless 和 no ip classless 控制 ) 是相互独立的。

38. 38 Use discontiguous major network number ABC 20.1.1.0/30 E0S0 S1S0E0 Routing Table 20.1.1.0 30.1.1.0 0 0 0 0 S0 1 1 S1 1 1 S0 S1 Routing Table 30.1.1.0 S0 0 0 10.2.2.0 E0 0 0 Routing Table 10.2.1.0 20.1.1.0 E0 S0 0 0 Network Interface Hops 30.1.1.0/30 10.0.0.0 Same major network and separate by other major network RIP 10.0.0.0 /8/8 10.2.1.0/24 10.2.2.0/24

39. 39 With no ip classless Drop R2(config)#no ip classless ip classless Command S0 Default Route 10.5.0.0/16 E0 10.1.0.0 10.2.0.0 To get to 10.5.0.3 : R2 R3 R1 Network Protocol Destination Network 10.1.0.0 10.2.0.0 202.112.10.0 0.0.0.0 Exit Interface E0 S0 C C R S* 10.5.0.3 202.112.10.0

40. 40 With ip classless Default R2(config)#ip classless ip classless Command S0 Default Route E0 10.1.0.0 10.2.0.0 R2 R3 R1 Network Protocol Destination Network Exit Interface E0 S0 C C R S* 202.112.10.0 10.1.0.0 10.2.0.0 202.112.10.0 0.0.0.0 To get to 10.5.0.3 : 10.5.0.0/16 10.5.0.3