IT220 Network Standards & Protocols. Unit 8: Chapter 8 The Internet Protocol (IP)

Transcription

1 IT220 Network Standards & Protocols Unit 8: Chapter 8 The Internet Protocol (IP)

2 IT220 Network Standards & Protocols REMINDER Student Evaluations

3 4 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.

4 5 Objectives Explain the functionality and use of typical network protocols. Differentiate 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.

5 6 Objectives Plan and design an IP network by applying subnetting skills. Explain the functionality of typical network protocols. 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.

6 TCP/IP Model Review Various Perspectives on the TCP/IP Model and Roles 7 Figure 8-2

7 8 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

8 Network Layer Protocols Name Full Name ICMP ARP DHCP DNS Internetwork Control Message Protocol Address Resolution Protocol Dynamic Host Configuration Protocol Domain Name System/Service Comments Messages that hosts and routers use to manage and control packet forwarding process; used by ping command Used by LAN hosts to dynamically learn another LAN host s MAC address 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) Other TCP/IP Network Layer Protocols 9 Table 8-1

9 Network Layer Protocols Name Full Name RIP EIGRP OSPF Routing Information Protocol Enhanced Interior Gateway Routing Protocol Open Shortest Path First Comments Application that runs on routers so that routers dynamically learn IP routing tables (used to route IP packets correctly); open standard protocol defined in RFC 2453 Proprietary routing protocol owned by Cisco Systems Open source routing protocol defined in RFC 2328 Other TCP/IP Network Layer Protocols 10 Table 8-1

10 IP Functions IP defines many functions that work together 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 11 Figure 8-4

11 IP Example: Post Office Example of a Post Office Sorting a Letter Sent to Hollywood, California 12 Figure 8-4

12 Routers in the IP Network Interconnect LANs and WANs via physical connectors called interfaces Example: Cisco 1841 router with two built-in Gigabit Ethernet LAN interfaces that use RJ-45 connectors Enterprise Class Router, LAN Interfaces, and WAN Interfaces 13 Figure 8-5

13 Routers in the IP Network Interconnected LANs and WANs: Redundancy, but No LAN/WAN Detail 14 Figure 8-7

14 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 15 Figure 8-8

15 IPv4 Addresses Converting binary IP address to dotted 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 16 Figure 8-9

16 17 IPv6 Addressing IPv6: Next generation of IP addressing. Needed because IPv4 addresses exhausted. 128-bit long addresses: 2128 or 3.4x1038 or over 340 undecillion IP s, that s 340 with 36 zero s after it. Customer usually gets /64 subnet, which 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.

17 Migration to IPv6 Migration to IPv6 has taken over decade 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 18 Figure 8-3

18 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

19 IP Routing Example 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

20 Routing Tables Routers build routing tables in two ways 1. Static configuration: Routes entered manually and do not change 2. Dynamic routing protocol: Application router automatically learn new routes from other routers Routing Protocols Advertising All Addresses that Begin with 12 as One Route 21 Figure 8-13

21 Other Network Protocols Used for Packet Transfer 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

22 Other Network Protocols Used for Packet Transfer Layer 3: Network IP with its Support Protocols 23 Figure 8-15

23 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

24 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

25 Classful IP Addressing Original IPv4 RFC defined a way to group IPv4 addresses using IP address classes (classful IP addressing) Every possible IPv4 address falls into a 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 26 Table 8-2

26 Classful IP Addressing: Class A 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

27 Classful IP Addressing: Class B Class B includes ¼ of IPv4 address space with first octet value from Includes medium number (216) of medium sized IP networks for approx. 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 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

28 Classful IP Addressing: Class C Class C includes 1/8th of IPv4 address space with first octet between 192 and 223 Large number of small IP networks: over 2,000,000 IP networks, 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

29 Classful IP Addressing Summary of How Class Rules Break Down the IPv4 Address Space 30 Figure 8-20

30 Private IP 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 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 31

31 Static Assignment of IP Addresses Most host OS s allow static configuration of several network settings Host IP Settings 32 Figure 8-22

32 Dynamic Assignment of IP Addresses 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 33 Figure 8-23

33 Assignment of IP Addresses Example 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 34 Table 8-6

34 DHCP 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 35 Figure 8-24

35 DHCP Example Remote DHCP Client in Boston 36 Figure 8-26

36 37 Short Break Take 10

37 IP Routing IP defines how to route packets across a 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 38 Figure 8-27

38 39 IP Routing 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.

39 IP Routing Example Five Classful Networks in a Small Corporate Network 40 Figure 8-28

40 IP Routing Table 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 41 Figure 8-29

41 IP Routing Example Routing from End-to-End: Multiple Cooperative Routing Decisions 42 Figure 8-31

42 Subnetting Classful 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 43 Figure 8-32

43 Subnetting Example Example: Several subnets created by subnetting network Each subnet has subnet/network ID Subdividing (Subnetting) Class A Network Figure 8-33

44 IP Routing Example: Using Subnetting IP addresses and networks replaced with five subnets of network Sample Corporate Network Using Subnets of Network Figure 8-34

45 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 46 Figure 8-35

46 Default Subnet Mask Classful networks have default subnet mask based on each class Class A: (8 bits) 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 47 Figure 8-35

47 48 Calculating Subnets How to calculate 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)

48 49 Calculating Subnets Example Example: Calculating subnets for network Class: C 2. Number of subnets needed: Number of bits needed to supply 14 subnets: 3 4. Number of bits left to determine number of IPs per subnet: 5 (results in 32 IPs per subnet) 5. Subnet mask: (default 16 bits + 3 more bits for subnetting = 19 bits)

49 50 Calculating Subnets Example Subnet No. Network ID Host Range IPs Broadcast IP

50 Routing Example: No 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 determines destination is in same subnet 3. PC11 sends packet directly to PC12 without going through router R1 not quite!!! IP Host Routing Logic: Local Destination 51 Figure 8-36

51 Routing Example: Subnetting What happens when PC11 sends IP packet to PC12: Different subnets 1. Host 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 packet IP Host Routing Logic: Remote Destination 52 Figure 8-37

52 Encapsulation 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) (Note Steps 1, 2, & 3) Encapsulation Review: Application, Transport, and Network Layers 53 Figure 8-38

53 Layer 1, 2, and 3 Encapsulation PC encapsulating IP packet into Ethernet frame (step 4) Sending bits over LAN cable into network (step 5) Encapsulation Review: Data Link Layer 54 Figure 8-39

54 De-Encapsulation De-encapsulation: On the destination side De-encapsulation on a Receiving Host (S1) 55 Figure 8-40

55 Address Resolution Protocol (ARP) 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 ARP Destination IP 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 56 Table 8-9

56 ARP Request and Reply Used to discover MAC addresses ARP Request (ARP Broadcast): Sending device queries for MAC address of destination device; sends Request as broadcast to all other devices on subnet ARP Request (Broadcast) 57 Figure 8-43

57 ARP Request and Reply 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) 58 Figure 8-43

58 ARP Request and Reply 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) 59 Figure 8-44

59 IP Routing 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 60 Figure 8-46

60 IP Routing and Data Link Headers Removing/adding Data Link headers: Router removes IP packet from incoming Data Link frame (de-encapsulation) and then adds new Data Link header and trailer before sending packet (encapsulation) Steps router goes through: 1. De-encapsulates IP packet from inside 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

61 IP Routing and Data Link Headers Example R1 receives packet destined to subnet on R2 Routers Discard Old and Add New Data Link Framing 62 Figure 8-48

62 ARP on 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 63 Figure 8-49

63 64 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.

64 65 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 layer 3 logic when routing IP packets.

65 66 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.

66 Questions? Comments? 67