NT1210 Introduction to Networking. Unit 8:

Transcription

1 NT1210 Introduction to Networking Unit 8: Chapter 8, The Internet Protocol (IP) 1

2 Objectives Identify the major needs and stakeholders for computer networks and network applications. Identify the classifications of networks and how they are applied to various types of enterprises. Compare and contrast the OSI and TCP/IP models and their applications to actual networks. Explain the functionality and use of typical network protocols. 2

3 Objectives Differentiate t among major types of LAN and WAN technologies and specifications and determine how each is used in a data network. Explain basic security requirements for networks. Use network tools to monitor protocols and traffic characteristics. Plan and design an IP network by applying subnetting skills. Explain the functionality of typical network protocols. 3

4 Objectives Plan and design an IP network by applying subnetting skills. Categorize TCP/IP protocols according to network model layers. Describe how TCP/IP addressing moves data packets through networks. 4

5 Introducing the Internet Protocol (IP) TCP/IP Model review: Layers 1 and 2 Protocols Example LAN/WAN Standards and Types in the TCP/IP Model 5 Figure 8-1

6 Introducing the Internet Protocol (IP) TCP/IP Model review: Upper layers define non-physical (logical) networking functions Various Perspectives on the TCP/IP Model and Roles 6 Figure 8-2

7 Introducing the Internet Protocol (IP) Network Layer protocols IP: Most important protocol defined by Network layer Almost every computing device on planet communicates, and most use IP to do so Network layer also defines other protocols 7

8 Introducing the Internet Protocol (IP) Network Layer protocols: Part 1 Name Full Name Comments ICMP Messages that hosts and routers use to manage Internetwork Control and control packet forwarding process; used by Message Protocol ping command ARP Address Resolution Used by LAN hosts to dynamically learn Protocol another LAN host s MAC address DHCP DNS Dynamic Host Configuration Protocol Used by host to dynamically learn IP address (and other information) it can use Allows hosts to use names instead of IP address; needs DNS server to translate name into corresponding IP address (required by IP routing process) Domain Name System/Service p g ( q y Other TCP/IP Network Layer Protocols 8 Table 8-1

9 Introducing the Internet Protocol (IP) Network Layer protocols: Part 2 Name Full Name Comments Application that runs on routers so that routers RIP Routing Information dynamically learn IP routing tables (used to Protocol route IP packets correctly); open standard protocol defined d in RFC 2453 EIGRP Enhanced Interior Proprietary routing protocol owned by Cisco Gateway Routing Systems Protocol OSPF Open Shortest Path First Open source routing protocol defined in RFC 2328 Other TCP/IP Network Layer Protocols 9 Table 8-1

10 Introducing the Internet Protocol (IP) IPv6: Next generation of IP addressing. Needed because IPv4 addresses exhausted. 128-bit long addresses: or 3.4x1038 or over 340 undecillion IPs, that s 340 with 36 zero s after it. Customer usually gets /64 subnet, which h yields 4 billion times IPs available in all of IPv4. Comparison: Number of IPv4 addresses equal to weight of cat; number of IPv6 addresses equal to weight of Earth and provides enough IP addresses for every grain of sand on every beach on earth. 10

11 Introducing the Internet Protocol (IP) Migration to IPv6 has taken over decade d and still in process. IPv6 originally defined back in mid-1990s. June 6, 2012 Was the scheduled IPv6 Day, official worldwide switch over day, moved up to February IPv4 Vs. IPv6 Timeline 11 Figure 8-3

12 Introducing the Internet Protocol (IP) IP defines many functions that t work together th with one ultimate goal: To send data from one host to another host through any TCP/IP network. Most important functions include: Creating end-to-end physical paths through TCP/IP network by interconnecting physical networks (LANs and WANs) using routers Identifying individual hosts and groups of hosts using IP addressing Routing (forwarding) IP packets to correct destination host Example of a Post Office Sorting a Letter Sent to Hollywood, California 12 Figure 8-4

13 Introducing the Internet Protocol (IP) IP is like Post Office Example of a Post Office Sorting a Letter Sent to Hollywood, California 13 Figure 8-4

14 Introducing the Internet Protocol (IP) Routers in IP network: Interconnect t t LANs and WANs via physical connectors called interfaces Example: Cisco 1841 router with two built-in in Gigabit Ethernet LAN interfaces that use RJ-45 connectors Enterprise Class Router, LAN Interfaces, and WAN Interfaces 14 Figure 8-5

15 Introducing the Internet Protocol (IP) IP interconnects t LANs and WANs Interconnected LANs and WANs: Redundancy, but No LAN/WAN Detail 15 Figure 8-7

16 Introducing the Internet Protocol (IP) IPv4 Addresses 32 bits Expressed in binary and dotted decimal forms Source and destination IP addresses included in 20-byte IP header added to all IP packets IPv4 Header Format and Fields 16 Figure 8-8

17 Introducing the Internet Protocol (IP) Converting binary IP address to dotted d decimal 1. Separate 32 bits into 4 groups of 8 bits each 2. Do binary-to-decimal conversion of each 8-bit number (each decimal value between 0 and 255) 3. Put period (dot) between each decimal number Generic View of Converting from Binary IP Address to DDN Format 17 Figure 8-9

18 Introducing the Internet Protocol (IP) Example: Converting binary IP address to dotted d decimal Converting Binary IP Address to DDN Figure 8-10

19 Introducing the Internet Protocol (IP): Routing Routing IP Packets from Source to Destination IP addressing groups addresses into networks All addresses with same value in first parts of addresses considered to be in one network Example: All addresses that begin with 11, 12, 13, 14, or 15 in that particular network Example IP Address Groupings: All with the Same First Octet in the Same Group 19 Figure 8-11

20 Introducing the Internet Protocol (IP): Routing IP routing example with routing tables: PC11 in left LAN sends IP packet to address (LAN on upper right) Example IP Address Groupings: All with the Same First Octet in the Same Group 20 Figure 8-12

21 Introducing the Internet Protocol (IP): Routing Routers build routing tables in two ways Static configuration: Routes entered manually and do not change Dynamic routing protocol: Application router uses to automatically learn new routes from other routers Routing Protocols Advertising All Addresses that Begin with 12 as One Route 21 Figure 8-13

22 Introducing the Internet Protocol (IP): Other Protocols Domain Name System/Service (DNS): Mapping names to IP addresses Users use names; IP routing uses numbers DNS translates name into corresponding IP address DNS client sends DNS Request message DNS server returns DNS Reply DNS Name Resolution Request, Reply, and Packet to Server1 IP Address 22 Figure 8-14

23 Introducing the Internet Protocol (IP): Other Protocols Layer 3 - Network IP with its Support Protocols 23 Figure 8-15

24 IP Addressing on User LANs: Network Settings Locations Need IP addresses Each LAN and WAN interface on hosts and routers need IP address to communicate IP Addresses Used on Every LAN/WAN Interface 24 Figure 8-17

25 IP Addressing on User LANs: Network Settings IP Address grouping: Allows IP routing to work better Routers list one number to represent each network (address group) in routing tables IP Address Groupings: IP Networks 25 Figure 8-18

26 IP Addressing on User LANs: Network Settings Original IPv4 RFC defined way to group IPv4 addresses using IP address classes (classful IP addressing) Every possible IPv4 address falls into class First Octet Class Purpose 0 A Reserved A Unicast addresses, in class A networks 127 A Reserved for loopback testing B Unicast addresses, in class B networks C Unicast addresses, in class C networks D Multicast addresses; not used as unicast IP addresses E Experimental; not used as unicast IP addresses Summary of IPv4 Address Classes Based on First Octet Values 26 Table 8-2

27 IP Addressing on User LANs: Network Settings Class A includes lower half of IPv4 address space: All IPv4 address that begin with first octet between 0 and 127 Network ID Class A IP Network Concept Size (Number of Addresses) All addresses with a first octet equal to 1 > 16,000, All addresses with a first octet equal to 2 > 16,000, All addresses with a first octet equal to 3 > 16,000, All addresses with a first octet equal to 4 > 16,000,000 Etc. > 16,000, All addresses with a first octet equal to 126 > 16,000,000 Example Class A Networks 27 Table 8-3

28 IP Addressing on User LANs: Network Settings Class B includes ¼ of IPv4 address space with first octet value from Includes medium number (2 16 ) of medium sized IP networks for approximately 65,000 hosts per network Network ID Concept Size (Number of Addresses) All with a first two octets equal to > 65, All with a first two octets equal to > 65, All with a first two octets t equal to > 65, All with a first two octets equal to > 65, All with a first two octets equal to > 65, All with a first two octets equal to > 65,000 Example Class B Networks 28 Table 8-4

29 IP Addressing on User LANs: Network Settings Class C includes 1/8 th of IPv4 address space with first octet between 192 and 223 Large number of small IP networks: over 2,000,000 IP networks, each with 256 IP addresses each Network ID Concept Size (Number of Addresses) All with a first three octets equal to All with a first three octets equal to All with a first three octets equal to All with a first three octets equal to All with a first three octets equal to All with a first three octets equal to Example Class C Networks 29 Table 8-5

30 IP Addressing on User LANs: Network Settings LAN IP address classes summary Summary of How Class Rules Break Down the IPv4 Address Space 30 Figure 8-20

31 IP Addressing on User LANs: Network Settings Private addresses: Classful IP networks reserved for enterprises to use in their network designs Can only be used on local LAN; can t be routed through WAN (non-routable) Not regulated by agencies such as ARIN or ICANN Network ID Concept Size (Number of Addresses) 10.x.x.x x.x x.x x.x Class A Private IP addressing space Class B Private IP addressing space Class C Private IP addressing space 31 Over 16,000,000 networks of over 16,000,000, IPs each Over 65,000 networks of over >65,000 IPs each Over 65,000 networks of 256 IPs each

32 IP Addressing on User LANs: Network Settings Static ti IP address assignment: Manually configured Static IP Address Assignment on Mac OS X 32 Figure 8-21

33 IP Addressing on User LANs: Network Settings Most host OS s allow static ti configuration of several network settings Host IP Settings 33 Figure 8-22

34 IP Addressing on User LANs: Network Settings Dynamic Host Configuration Protocol (DHCP) defines way hosts can lease IP address from DHCP network server so does not have to be configured statically Operates on client-server concept DHCP protocol defined by set of RFCs Sample Network for DHCP Discussions 34 Figure 8-23

35 IP Addressing on User LANs: Network Settings Example: IP address assignment design using both DHCP and statically assigned addresses Location Type Range Atlanta LAN Static DHCP Boston LAN Static DHCP San Fran LAN Static DHCP Address Planning: Some Static, Some DHCP, for Every LAN 35 Table 8-6

36 IP Addressing on User LANs: Network Settings Once DHCP server exists in network and has been configured with set of IP addresses to lease, DHCP clients can request IP addresses DHCP Lease Process between a DHCP Client and Server 36 Figure 8-24

37 IP Addressing on User LANs: Network Settings User can see results of DHCP process from computer DHCP Client Configuration on Mac OS X 37 Figure 8-25

38 IP Addressing on User LANs: Network Settings DHCP example: Crossing networks to access DHCP server Remote DHCP Client in Boston 38 Figure 8-26

39 Short Break Take 10 39

40 IP Routing with Focus on Layer 3 IP defines how to route packets across TCP/IP network Some routing tasks must use logic from lower two layers because Network layer (3) cannot physically send bits Network layer relies on Layers 1 and 2 logic for this IP Routing Perspective, While Ignoring LAN/WAN Details 40 Figure 8-27

41 IP Routing with Focus on Layer 3 Router must have IP routing table with useful entries to route IP packets. Routing table may list multiple routes. Each IP route identifies network, as well as other information about how to send packets to that network. Routers look at incoming packet s destination IP address and compare it to list of network IDs in its routing table to determine where to send packet to destination. 41

42 IP Routing with Focus on Layer 3 Finding a classful l network ID based on IP address Five Classful Networks in a Small Corporate Network 42 Figure 8-28

43 IP Routing with Focus on Layer 3 Each route in routing table lists: Information about how to match IP packets Forwarding instructions that tell router where to forward packets to (e.g., next router) Example: R1 s IP routing table shows five network IDs so it knows routes to all five networks R1 Routing Table with Routes for Five Classful Networks 43 Figure 8-29

44 IP Routing with Focus on Layer 3 Router compares incoming i IP packet s destination address to information in its routing tables to find best route to destination How Router R1 Uses its IP Routing Table: Match and Forward 44 Figure 8-30

45 IP Routing with Focus on Layer 3 Routing from End-to-End: Multiple Cooperative Routing Decisions 45 Figure 8-31

46 IP Routing with Focus on Layer 3: Subnetting Classful l IP networks and wasted IP addresses Subnetting: Process of subdividing network to create smaller groups of consecutive IP addresses Subnets (subdivided networks): Smaller groups of addresses Numbers of Classful Networks, and Their Sizes 46 Figure 8-32

47 IP Routing with Focus on Layer 3: Subnetting Example: Several subnets created by subnetting network Each subnet has subnet/network ID Subdividing (Subnetting) Class A Network Figure 8-33

48 IP Routing with Focus on Layer 3: Subnetting Example continued: IP addresses and networks replaced with five subnets of network Sample Corporate Network Using Subnets of Network Figure 8-34

49 IP Routing with Focus on Layer 3: Subnetting Subnet mask: Shows how much of IP address for each device is in common to all IPs in subnet Example (/24): First three octets (first 24 bits) must be equal for all subnets in network PC11 sends packet to PC21 (destination IP address ) R1 will have route for PC21 s subnet (network ID ) Routing Logic with Subnets and Masks 49 Figure 8-35

50 IP Routing with Focus on Layer 3: Subnetting Classful l networks have default subnet mask based on each class ClassA:255000(8bits) Class B: (16 bits) Class C: (24 bits) If subnet mask anything other than default, then subnetting being used Routing Logic with Subnets and Masks 50 Figure 8-35

51 IP Routing with Focus on Layer 3: Subnetting How to calculate l subnets 1. Determine network class (A, B, or C) 2. Determine EITHER number of hosts needed for each subnet OR how many subnets needed 3. Determine how many bits needed to provide correct number of hosts/subnets; last subnet is NOT usable 4. Calculate IPs for each subnet; first IP identifies subnet (Network ID) and last IP identifies broadcast address 5. Determine subnet mask (total number of bits for network/subnet ID) 51

52 IP Routing with Focus on Layer 3: Subnetting Example: Calculating l subnets for network Class: C Number of subnets needed: 14 Number of bits needed to supply 14 subnets: 3 Number of bits left to determine number of IPs per subnet: 5 (results in 32 IPs per subnet) Subnet mask: (default 16 bits + 3 more bits for subnetting = 19 bits) 52

53 IP Routing with Focus on Layer 3: Subnetting Subnet No. Network ID Host Range IPs Broadcast IP

54 IP Routing with Focus on Layer 3: Subnetting What happens when PC11 sends IP packet to PC12: Same subnet 1. PC11 determines its own IP address and subnet mask ( and ) 2. PC11 decides determines destination is in same subnet 3. PC11 sends packet directly to PC12 without going through router R1 IP Host Routing Logic: Local Destination 54 Figure 8-36

55 IP Routing with Focus on Layer 3: Subnetting What happens when PC11 sends IP packet to PC12: Different subnets 1. Host s s default gateway (default router) setting tells it where to send packets when they have destination address in different subnet 2. Default gateway tells host IP address of router attached to its LAN 3. Router then consults its routing table and determines how to deliver er packet IP Host Routing Logic: Remote Destination 55 Figure 8-37

56 IP Routing with Layer 1, 2, and 3 Interactions Encapsulation: Action taken by lower layer when it takes data from higher layer and adds header (and sometimes trailer) to higher layer s data Example: PC11 opened web browser and tried to connect to URL at web server: PC11 creating bits it uses to send to server S1 (web server) Encapsulation Review: Application, Transport, and Network Layers 56 Figure 8-38

57 IP Routing with Layer 1, 2, and 3 Interactions PC encapsulating IP packet into Ethernet t frame (step 4) Sending bits over LAN cable into network (step 5) Encapsulation Review: Data Link Layer 57 Figure 8-39

58 IP Routing with Layer 1, 2, and 3 Interactions De-encapsulation: On the destination side De-encapsulation on a Receiving Host (S1) 58 Figure 8-40

59 IP Routing with Layer 1, 2, and 3 Interactions Addressing frames and packets when crossing SAME subnet: Both MAC and IP addresses in Ethernet frame and encapsulated IP packet IP and Ethernet Addresses, PC11 to server S1, Same Subnet 59 Figure 8-42

60 IP Routing with Layer 1, 2, and 3 Interactions To learn destination MAC address, sending device uses Address Resolution Protocol (ARP) and info in ARP table Address Short Answer Long Answer Source MAC On NIC Given to Ethernet NIC by manufacturer; sending host can find MAC on NIC hardware. Source IP Configuration Either through static configuration or DHCP Destination MAC Destination IP ARP User From its ARP table, or if not found, by using ARP protocol and sending ARP Request and waiting for ARP Reply from destination Either typed or clicked by user How a Sending IP Host Knows What Addresses to Use 60 Table 8-9

61 IP Routing with Layer 1, 2, and 3 Interactions Discovering MAC addresses using ARP: ARP Request and ARP Reply ARP Request (ARP Broadcast): Sending device queries for MAC address of destination device; sends Request as broadcast to all other devices on subnet Example: PC11 wants to send packet to server S1 (in same subnet) but does not know S1 s MAC address; PC11 sends ARP Request to all devices on subnet ARP Request (Broadcast) 61 Figure 8-43

62 IP Routing with Layer 1, 2, and 3 Interactions ARP Reply: Lists IP address ARP Request asked about with corresponding MAC address of that host Example: ARP Reply that server S1 makes in response to PC11 s ARP Request ARP Reply is unicast since ARP Request generated from one particular device ARP Reply (Unicast) 62 Figure 8-44

63 IP Routing with Layer 1, 2, and 3 Interactions Routing data between different subnets IP packets in network act like person traveling to destination, using all forms of transportation; packet goes from end-to-end Data Link frames act like individual vehicles used for only part of trip (e.g., just train); frames never leave their own LAN/WAN Example, IP Packet End-to-End, Data Link Heads Stay on LAN or WAN 63 Figure 8-45

64 IP Routing with Layer 1, 2, and 3 Interactions Addressing frames and packets when crossing subnets example: PC11 ( ) sends IP packet to PC21 ( ) Hosts sit on different LANs (may also be in different subnets) IP Addresses Stay the Same Through End-to-End Path 64 Figure 8-46

65 IP Routing with Layer 1, 2, and 3 Interactions Example: PC11 sends IP packet to PC21 PC11 s logic tells it to send packet to default router because destination is in different network or subnet PC11 encapsulates packet inside Ethernet frame with destination MAC address R1 Ethernet Frames Use MAC on that LAN (Only) 65 Figure 8-47

66 IP Routing with Layer 1, 2, and 3 Interactions Removing/adding Data Link headers: Router removes IP packet from incoming Data Link frame (deencapsulation) and then adds new Data Link header and trailer before sending packet (encapsulation) Steps router goes through: 1. De-encapsulates IP packet from inside id Data Link frame 2. Makes routing decision using packet s destination IP address and its own IP routing table, identifying correct outgoing interface 3. Encapsulates packet into new Data Link frame that works on outgoing interface 4. Sends packet through outgoing interface to destination Routers Discard Old and Add New Data Link Framing 66 Figure 8-48

67 IP Routing with Layer 1, 2, and 3 Interactions Example: When R1 receives packet destined d to subnet on R2 Routers Discard Old and Add New Data Link Framing 67 Figure 8-48

68 IP Routing with Layer 1, 2, and 3 Interactions Using ARP with routers: R2 needs to deliver IP packet to host PC21 1. R2 builds Ethernet header with PC21 s MAC address as destination 2. If R2 does not know PC21 s MAC address (i.e., it is not in its ARP table), R2 uses ARP to learn MAC address 3. When R2 receives ARP Reply with PC21 s MAC address, sends frame Example of Router R2 Using ARP to Learn a Local Host s MAC Address 68 Figure 8-49

69 Summary, This Chapter Described the main functions of the TCP/IP network layer in regards to its focus on either physical or logical functions, and the focus on the network or endpoint hosts. Listed three major functions defined by IP. Listed common TCP/IP network layer functions in addition to IP. Examined a figure of an Enterprise TCP/IP network and determine where IP address groups (IP networks or subnets) would be needed. 69

70 Summary, This Chapter Looked at any IP version 4 address and determined its class, and if a unicast IP address, determined the class A, B, or C network ID of the network in which it resides. Listed the four IP settings typically set on IP hosts during static configuration. Described the layer 3 logic used by routers when routing IP packets. Described an IP host s s layer 3 logic when routing IP packets. 70

71 Summary, This Chapter Explained the basic ideas of how the IP subnetting process subdivides a classful network into smaller groups. Predicted the MAC and IP addresses used by two hosts on the same LAN subnet when they send IP packets to each other. Predicted the MAC and IP addresses used throughout an IP packet s journey from a host in one subnet to a host in another subnet. 71

72 Questions? Comments? 72