OSI Data Link & Network Layer

Transcription

1 OSI Data Link & Network Layer Erkki Kukk 1

2 Layers with TCP/IP and OSI Model Compare OSI and TCP/IP model 2

3 Layers with TCP/IP and OSI Model Explain protocol data units (PDU) and encapsulation 3

4 Addressing and Naming Schemes Explain how labels in encapsulation headers are used to manage communication in data networks 4

5 Layer 2 addressing and its Impact on Network Operation and Performance Ethernet Unicast, Multicast and Broadcast 5

6 Explain the Address Resolution Protocol (ARP) process Mapping IP to MAC Addresses 6

7 Explain the Address Resolution Protocol (ARP) process ARP Destinations Outside the Local Network 7

8 Explain the Address Resolution Protocol (ARP) process ARP Removing Address Mappings 8

9 Explain the Address Resolution Protocol (ARP) process ARP Broadcasts - Issues 9

10 Compare and Contrast the Use of Ethernet Switches versus Hubs in a LAN Describe how a switch can eliminate collisions, backoffs and re- transmissions, the leading factors in reduced throughput on a hub-based Ethernet network 10

11 Network Layer Protocols and Internet Protocol (IP) Define the basic role of the Network Layer in data networks 11

12 Network Layer Protocols and Internet Protocol (IP) Identify the basic characteristics and the role of the IPv4 protocol 12

13 Network Layer Protocols and Internet Protocol (IP) Describe the implications for the use of the IP protocol as it is connectionless 13

14 Network Layer Protocols and Internet Protocol (IP) Describe the implications for the use of the IP protocol as it is considered an unreliable protocol 14

15 Network Layer Protocols and Internet Protocol (IP) Describe the implications for the use of the IP as it is media independent 15

16 Network Layer Protocols and Internet Protocol (IP) Describe the role of framing in the Transport Layer and explain that segments are encapsulated as packets 16

17 Network Layer Protocols and Internet Protocol (IP) 17

18 Addressing the Network IPv4 18

19 IP Addressing Structure Describe the dotted decimal structure of a binary IP address and label its parts 19

20 IP Addressing Structure Practice converting 8-bit binary to decimal 20

21 Convert decimal to 8-bit binary Alternatiiv on kahega jagamine ja pärast jääkide järjestamine tagantpoolt: 172/2=86(0), 86/2=43(0), 43/2=21(1), 21/2=10(1), 10/2=5(0), 5/2=2(1), 2/2=1(0), 1/2=0(1) Järjestades tulemuse tagantpoolt saame

22 IP Addressing Structure Practice converting decimal to 8-bit binary 22

23 IPv4 address An IP address has two parts: network number host number

24 IPv4 Address Newer technology - Classless IP Addressing The subnet mask determines the network portion and the host portion. Value of first octet does NOT matter (older classful IP addressing) Hosts and Classless Inter-Domain Routing (CIDR). Classless IP Addressing is what is used within the Internet and in most internal networks. Older technology - Classful IP Addressing (later) Value of first octet determines the network portion and the host portion. Used with classful routing protocols like RIPv1. The Cisco IP Routing Table is structured in a classful manner 24

25 Types of Addresses Network address - The address by which we refer to the network Broadcast address - A special address used to send data to all hosts in the network Host addresses - The addresses assigned to the end devices in the network 25

26 Dividing the Network and Host Portions Subnet Mask Used to define the: Network portion Host portion 32 bits Contiguous set of 1 s followed by a contiguous set of 0 s 1 s: Network portion 0 s: Host portion 26

27 Dividing the Network and Host Portions Dotted decimal: Slash notation: /16 Expressed as: Dotted decimal Ex: Slash notation or prefix length /16 (the number of one bits) 27

28 Determine the network portion of the host address and the role of the subnet mask Use the subnet mask and ANDing process to extract the network address from the IP address. 28

29 Determine the network portion of the host address and the role of the subnet mask Observe the steps in the ANDing of an IPv4 host address and subnet mask 29

30 Calculating Addresses Given a subnet address and subnet mask, calculate the network address, host addresses and broadcast address 30

31 Classify and Define IPv4 Addresses Determine the network, broadcast and host addresses for a given address and prefix combination 31

32 Classify and Define IPv4 Addresses Name the three types of communication in the Network Layer and describe the characteristics of each type 32

33 Address classes Identify the historic method for assigning addresses and the issues associated with the method 33

34 Special Unicast IPv4 Addresses /8 - Loopback Address /16, /16, /24, /24 reserved by IANA for future usage /16 - Link-Local Addresses Can be automatically assigned to the local host by the operating system in environments where no IP configuration is available /24 - TEST-NET Addresses These addresses can be used in documentation and network examples /24 6to4 relay router 34

35 Private IP Addresses RFC to ( /8) to ( /12) to ( /16) The addresses will not be routed in the Internet Need NAT/PAT (next) Should be blocked by your ISP 35

36 Assigning Addresses Explain the importance of using a structured process to assign IP addresses to hosts and the implications for choosing private vs. public addresses 36

37 Assigning Addresses Explain how end user devices can obtain addresses either statically through an administrator or dynamically through DHCP 37

38 Assigning Addresses Explain which types of addresses should be assigned to devices other than end user devices 38

39 Who assigns IP Network Addresses? Internet Assigned Numbers Authority (IANA) ( is the master holder of the IP addresses. Today, the remaining IPv4 address space has been allocated to various other registries to manage for particular purposes or for regional areas. Regional Internet Registries (RIRs) 39

40 Regional Internet Registries (RIR) The 5 RIR s are: AfriNIC - APNIC - ARIN - LACNIC - RIPE NCC

41 OSI Layer3 devices 41

42 Grouping Devices into Networks and Hierarchical Addressing List several ways in which dividing a large network can increase network security 42

43 Grouping Devices into Networks and Hierarchical Addressing Explain the communication problems that emerge when very large numbers of devices are included in one large network 43

44 Grouping Devices into Networks and Hierarchical Addressing Describe how hierarchical addressing solves the problem of devices communicating across networks of networks 44

45 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Describe the role of an intermediary gateway device in allowing devices to communicate across sub-divided networks 45

46 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Describe the role of a gateway and the use of a simple route table in directing packets toward their ultimate destinations 46

47 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Describe the purpose and use of the destination network in a route 47

48 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Trace the steps of several IP packets as they are routed through several gateways from devices on one sub network to devices on other sub networks 48

49 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Describe the purpose of routing protocols and the need for both static and dynamic routes 49

50 Fundamentals of Routes, Next Hop Addresses and Packet Forwarding Explain how routes are manually configured to build routing table 50

51 Testing the Network Layer Describe the general purpose of the ping command, trace the steps of its operation in a network, and use the ping command to determine if the IP protocol is operational on a local host 51

52 Testing the Network Layer Use ping to verify that a local host can communicate with a gateway across a local area network 52

53 Testing the Network Layer Use ping to verify that a local host can communicate via a gateway to a device in remote network 53

54 Testing the Network Layer Use tracert/traceroute to observe the path between two devices as they communicate and trace the steps of tracert/traceroute's operation 54

55 Lab Exercises 55

56 Remind the address classes 56

57 1. Use the IP address chart and your knowledge of IP address classes to answer the following questions: 1. What is the decimal and binary range of the first octet of all possible Class B IP addresses? Decimal: From: To: Binary: From: To: 2. Which octet(s) represent the network portion of a Class C IP address? 3. Which octet(s) represent the host portion of a Class A IP address? 4. What is the maximum number of useable hosts with a Class C network address? 5. How many Class B networks are there? 6. How many hosts can each Class B network have? 7. How many octets are there in an IP address? How many bits per octet? 57

58 2. Fill in the table: Host IP Address Class Network Address Host Address Broadcast Address Default Subnet Mask

59 3. Given an IP address of and a subnet mask of , answer the following questions: What is the binary equivalent of the second octet? What is the class of the address? What is the network address of this IP address? Is this a valid IP host address (Y/N)? Why or why not? 59

60 4. Fill in the table: IP address Valid address? Why or why not? 60

61 61