Internet technology unit 2
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The document outlines various computer science courses, including B.Sc. in IT and CS, as well as details on protocols such as ARP and RARP, along with their operations and packet formats. It includes a discussion on the Internet Control Message Protocol (ICMP), its message types, and its role in error reporting and querying within networks. Additionally, the document touches on network address resolution techniques and highlights tools like ping and traceroute for network diagnostics.
Internet technology unit 2
- 1. COURCES WE OFFER: BSC(IT) FY,SY,TY BSC(CS) FY,SY,TY BSC(IT/CS) PROJECTS MCA (ENTRANCE) ENGG(IT/ELECTRONICS/EXTC) ADDRESS: 302 PARANJPE UDYOG BHAVAN, NEAR KHANDELWAL SWEETS, THANE STATION, THANE WEST. TEL: 8097071144/55 STAY CONNECTED FOR MORE UPDATES AND STUDY NOTES FACEBOOK : https://www.facebook.com/weittutorial EMAIL: [email protected] 1PHONE:8097071144/55
- 2. UNIT 2 1.Address Resolution Protocol (ARP) 2.Internet Control Message Protocol Version 4 (ICMPv4), 3.Mobile IP, 4.Unicast Routing Protocols (RIP, OSPF and BGP) 2PHONE:8097071144/55
- 4. CONTENTS • ARP • ARP PACKAGE • RARP 4PHONE:8097071144/55
- 5. Figure 7-1 ARP and RARP 5PHONE:8097071144/55
- 6. Figure 7-2 Position of ARP and RARP in TCP/IP protocol suite 6PHONE:8097071144/55
- 10. Figure 7-5 Encapsulation of ARP packet 10PHONE:8097071144/55
- 11. Figure 7-6:a Four cases using ARP 11PHONE:8097071144/55
- 12. Figure 7-6:b Four cases using ARP 12PHONE:8097071144/55
- 13. Figure 7-6:c Four cases using ARP 13PHONE:8097071144/55
- 14. Figure 7-6:d Four cases using ARP 14PHONE:8097071144/55
- 15. ATMARP An ATM network has its own definition for the physical address of a device. Binding between an IP address and a physical address is attained through a protocol called ATMARP An ATM network is not a broadcast network; another solution is needed to handle the task. PHONE:8097071144/55 15
- 16. Entering-point and exiting-point routers PHONE:8097071144/55 16
- 18. Hardware type (HTYPE). The 16-bit HTYPE field defines the type of the physical network. Its value is 0013base16 for an ATM network. Protocol type (PTYPE). The 16-bit PTYPE field defines the type of the protocol.For IPv4 protocol the value is 0800base16. Sender hardware length (SHLEN). The 8-bit SHLEN field defines the length of the sender’s physical address in bytes. For an ATM network the value is 20 if the binding is done across an ATM network and two levels of hardware addressing are necessary, the neighboring 8-bit reserved field is used to define the length of the second address. Operation (OPER). The 16-bit OPER field defines the type of the packet. Five packet types are defined as shown in Table. PHONE:8097071144/55 18
- 20. Sender protocol length (SPLEN). The 8-bit SPLEN field defines the length of the address in bytes. For IPv4 the value is 4 bytes. Target hardware length (TLEN). The 8-bit TLEN field defines the length of the receiver’s physical address in bytes. For an ATM network the value is 20. Target protocol length (TPLEN). The 8-bit TPLEN field defines the length of the address in bytes. For IPv4 the value is 4 bytes. Sender hardware address (SHA). The variable-length SHA field defines the physical address of the sender. For ATM networks defined by the ATM Forum, the length is 20 bytes. Sender protocol address (SPA). The variable-length SPA field defines the address of the sender. For IPv4 the length is 4 bytes. Target hardware address (THA). The variable-length THA field defines the physical address of the receiver. For ATM networks defined by the ATM Forum, the length is 20 bytes. This field is left empty for request messages and filled in for reply and NACK messages. Target protocol address (TPA). The variable-length TPA field defines the address of the receiver. For IPv4 the length is 4 bytes. PHONE:8097071144/55 20
- 21. ATMARP Operation There are two methods to connect two routers on an ATM network: 1. through a permanent virtual circuit (PVC) or If a permanent virtual circuit is established between two routers, there is no need for an ATMARP server. However, the routers must be able to bind a physical address to an IP address. The inverse request message and inverse reply message can be used for the binding. PHONE:8097071144/55 21
- 22. 2. through a switched virtual circuit (SVC). In a switched virtual circuit (SVC) connection, each time a router wants to make a connection with another router (or any computer), a new virtual circuit must be established. the virtual circuit can be created only if the entering-point router knows the physical address of the exiting-point router (ATM does not recognize IP addresses). To map the IP addresses to physical addresses, each router runs a client ATMARP program, but only one computer runs an ATMARP server program. The process of establishing a virtual connection requires three steps: 1. connecting to the server, 2. receiving the physical address, and 3. establishing the connection PHONE:8097071144/55 22
- 24. Building the Table How does the ATM server build its mapping table? This is also done through the use of ATMARP and the two inverse messages (inverse request and inverse reply). PHONE:8097071144/55 24
- 25. Logical IP Subnet (LIS) AN can be divided into several subnets ATM network can be divided into logical (not physical) subnetworks routers B, C, and D belong to one logical subnet routers F, G, and H belong to another logical subnet Routers A and E belong to both logical subnets BCD belongs to AE and AE also belongs to FGH So BCD can connect to FGH using AE PHONE:8097071144/55 25
- 28. State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 900 180.3.6.1 ACAE32457342 P 2 2 129.34.4.8 P 14 5 201.11.56.7 R 8 450 114.5.7.89 457342ACAE32 P 12 1 220.55.5.7 F R 9 60 19.1.7.82 4573E3242ACA P 18 3 188.11.8.71 Original cache table 28PHONE:8097071144/55
- 29. Example 2 The ARP output module receives an IP datagram (from the IP layer) with the destination address 114.5.7.89. It checks the cache table and finds that an entry exists for this destination with the RESOLVED state (R in the table). It extracts the hardware address, which is 457342ACAE32, and sends the packet and the address to the data link layer for transmission. The cache table remains the same. 29PHONE:8097071144/55
- 30. Example 3 Twenty seconds later, the ARP output module receives an IP datagram (from the IP layer) with the destination address 116.1.7.22. It checks the cache table and does not find this destination in the table. The module adds an entry to the table with the state PENDING and the Attempt value 1. It creates a new queue for this destination and enqueues the packet. It then sends an ARP request to the data link layer for this destination. 30PHONE:8097071144/55
- 31. State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 900 180.3.6.1 ACAE32457342 P 2 2 129.34.4.8 P 14 5 201.11.56.7 R 8 450 114.5.7.89 457342ACAE32 P 12 1 220.55.5.7 P 23 1 116.1.7.22 R 9 60 19.1.7.82 4573E3242ACA P 18 3 188.11.8.71 Cache table for Example 3 31PHONE:8097071144/55
- 32. Example 4 Fifteen seconds later, the ARP input module receives an ARP packet with target protocol (IP) address 188.11.8.71. The module checks the table and finds this address. It changes the state of the entry to RESOLVED and sets the time-out value to 900. The module then adds the target hardware address (E34573242ACA) to the entry. Now it accesses queue 18 and sends all the packets in this queue, one by one, to the data link layer. 32PHONE:8097071144/55
- 33. State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 900 180.3.6.1 ACAE32457342 P 2 2 129.34.4.8 P 14 5 201.11.56.7 R 8 450 114.5.7.89 457342ACAE32 P 12 1 220.55.5.7 P 23 1 116.1.7.22 R 9 60 19.1.7.82 4573E3242ACA R 18 188.11.8.71 E34573242ACA Cache table for Example 4 33PHONE:8097071144/55
- 34. Example 5 Twenty-five seconds later, the cache-control module updates every entry. The time-out values for the first three resolved entries are decremented by 60. The time-out value for the last resolved entry is decremented by 25. The state of the next-to-the last entry is changed to FREE because the time-out is zero. For each of the three entries, the value of the attempts field is incremented by one. After incrementing, the attempts value for one entry (the one with IP protocol address 201.11.56.7) is more than the maximum; the state is changed to FREE, the queue is deleted. 34PHONE:8097071144/55
- 35. State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 840 180.3.6.1 ACAE32457342 P 2 3 129.34.4.8 F R 8 390 114.5.7.89 457342ACAE32 P 12 2 220.55.5.7 P 23 2 116.1.7.22 F R 18 874 188.11.8.71 E34573242ACA Cache table for Example 5 35PHONE:8097071144/55
- 38. The RARP request packets are broadcast; the RARP reply packets are unicast. 38PHONE:8097071144/55
- 40. Figure 7-12 Encapsulation of RARP packet 40PHONE:8097071144/55
- 41. Alternative Solutions to RARP When a diskless computer is booted, it needs more information in addition to its IP address. It needs to know its subnet mask, the IP address of a router, and the IP address of a name server. RARP cannot provide this extra information. New protocols have been developed to provide this information. In next Chapter we discuss two protocols, BOOTP and DHCP, that can be used instead of RARP. 41PHONE:8097071144/55
- 43. The IP protocol has no error-reporting or error-correcting mechanism. What happens if something goes wrong? What happens if a router must discard a datagram because it cannot find a router to the final destination, or because the time-to-live field has a zero value? What happens if the final destination host must discard all fragments of a datagram because it has not received all fragments within a predetermined time limit? Deficiencies The IP protocol also lacks a mechanism for host and management queries. 1. A host sometimes needs to determine if a router or another host is alive. 2. And sometimes a network manager needs information from another host or router. Internet Control Message Protocol (ICMP) has been designed to compensate for the above two deficiencies. It is a companion to the IP protocol PHONE:8097071144/55 43
- 44. ICMP encapsulation The value of the protocol field in the IP datagram is 1 to indicate that the IP data is an ICMP message. PHONE:8097071144/55 44
- 45. MESSAGES ICMP messages are divided into two broad categories: 1. error-reporting messages and 2. query messages. PHONE:8097071144/55 45
- 46. Message Format General format of ICMP messages PHONE:8097071144/55 46
- 47. Error-reporting messages The following are important points about ICMP error messages 1. No ICMP error message will be generated in response to a datagram carrying an ICMP error message. 2. No ICMP error message will be generated for a fragmented datagram that is not the first fragment. 3. No ICMP error message will be generated for a datagram having a multicast address. 4. No ICMP error message will be generated for a datagram having a special address such as 127.0.0.0 or 0.0.0.0. PHONE:8097071144/55 47
- 48. Destination Unreachable When a router cannot route a datagram or a host cannot deliver a datagram, the datagram is discarded and the router or the host sends a destination-unreachable message back to the source host that initiated the datagram. PHONE:8097071144/55 48
- 50. Source Quench The source-quench message in ICMP was designed to add a kind of flow control and congestion control to the IP. When a router or host discards a datagram due to congestion, it sends a source-quench message to the sender of the datagram. PHONE:8097071144/55 50
- 51. Time Exceeded time-exceeded message is generated in two cases 1. Whenever a router decrements a datagram with a time-to-live value to zero, it discards the datagram and sends a time-exceeded message to the original source. 2. When the final destination does not receive all of the fragments in a set time, it discards the received fragments and sends a time-exceeded message to the original source. PHONE:8097071144/55 51
- 52. Parameter Problem If a router or the destination host discovers an ambiguous or missing value in any field of the datagram, it discards the datagram and sends a parameter-problem message back to the source. 1. Code 0. There is an error or ambiguity in one of the header fields. 2. Code 1. The required part of an option is missing PHONE:8097071144/55 52
- 53. Redirection A host usually starts with a small routing table that is gradually augmented and updated. One of the tools to accomplish this is the redirection message. PHONE:8097071144/55 53
- 54. Code 0. Redirection for a network-specific route. Code 1. Redirection for a host-specific route. Code 2. Redirection for a network-specific route based on a specified type of service. Code 3. Redirection for a host-specific route based on a specified type of service. PHONE:8097071144/55 54
- 55. Query Messages ICMP can also diagnose some network problems. This is accomplished through the query messages. Echo Request and Reply The echo-request and echo-reply messages are designed for diagnostic purposes. Network managers and users utilize this pair of messages to identify network problems. Timestamp Request and Reply Two machines (hosts or routers) can use the timestamp-request And timestamp-reply messages to determine the round-trip time needed for an IP datagram to travel between them. PHONE:8097071144/55 55
- 56. DEBUGGING TOOLS There are several tools that can be used in the Internet for debugging. We can find if a host or router is alive and running. We can trace the route of a packet. We introduce two tools that use ICMP for debugging: ping and traceroute. Ping We can use the ping program to find if a host is alive and responding. Traceroute The traceroute program in UNIX or tracert in Windows can be used to trace the route of a packet from the source to the destination. PHONE:8097071144/55 56
- 59. Stationary Hosts The original IP addressing was based on the assumption that a host is stationary, attached to one specific network. the IP address 10.3.4.24/8 defines a host attached to the network 10.0.0.0/8. This implies that a host in the Internet does not have an address that it can carry with itself from one place to another. The address is valid only when the host is attached to the network. If the network changes, the address is no longer valid. This scheme works perfectly with stationary hosts. PHONE:8097071144/55 59
- 60. Mobile Hosts When a host moves from one network to another, the IP addressing structure needs to be modified. Changing the Address One simple solution is to let the mobile host change its address as it goes to the new network. The host can use DHCP to obtain a new address to associate it with the new network. This approach has several drawbacks First, the configuration files would need to be changed. Second, each time the computer moves from one network to another, it must be rebooted. Third, the DNS tables (see Chapter 19) need to be revised so that every other host in the Internet is aware of the change. Fourth, if the host roams from one network to another during a transmission, the data exchange will be interrupted. This is because the ports and IP addresses of the client and the server must remain constant for the duration of the connection. PHONE:8097071144/55 60
- 61. Two Addresses The approach that is more feasible is the use of two addresses. The host has its original address, called the home address, and a temporary address, called the care-of address. Mobile IP has two addresses for a mobile host: one home address and one care-of address. The home address is permanent; the care-of address changes as the mobile host moves from one network to another. PHONE:8097071144/55 61
- 62. AGENTS To make the change of address transparent to the rest of the Internet requires a home agent and a foreign agent. Home Agent The home agent is usually a router attached to the home network of the mobile host. The home agent acts on behalf of the mobile host when a remote host sends a packet to the mobile host. The home agent receives the packet and sends it to the foreign agent. Foreign Agent The foreign agent is usually a router attached to the foreign network. The foreign agent receives and delivers packets sent by the home agent to the mobile host. PHONE:8097071144/55 62
- 63. When the mobile host and the foreign agent are the same, the care-of address is called a colocated care-of address. The advantage of using a colocated care-of address is that the mobile host can move to any network without worrying about the availability of a foreign agent. PHONE:8097071144/55 63
- 64. THREE PHASES To communicate with a remote host, a mobile host goes through three phases: 1. Agent discovery 2. registration 3. data transfer PHONE:8097071144/55 64
- 65. Agent Discovery first phase in mobile communication agent discovery, consists of two subphases. A mobile host must discover (learn the address of) a home agent before it leaves its home network. A mobile host must also discover a foreign agent after it has moved to a foreign network. This discovery consists of learning the care-of address as well as the foreign agent’s address PHONE:8097071144/55 65
- 66. The discovery involves two types of messages: Advertisement When a router advertises its presence on a network using an ICMP router advertisement, it can append an agent advertisement to the packet if it acts as an agent. solicitation. When a mobile host has moved to a new network and has not received agent advertisements, it can initiate an agent solicitation. It can use the ICMP solicitation message to inform an agent that it needs assistance. PHONE:8097071144/55 66
- 67. Registration The second phase in mobile communication is registration. After a mobile host has moved to a foreign network and discovered the foreign agent, it must register. Registration Request A registration request is sent from the mobile host to the foreign agent to register its care-of address and also to announce its home address and home agent address. Registration Reply A registration reply is sent from the home agent to the foreign agent and then relayed to the mobile host. The reply confirms or denies the registration request. PHONE:8097071144/55 67
- 69. Data Transfer From Remote Host to Home Agent From Home Agent to Foreign Agent From Foreign Agent to Mobile Host From Mobile Host to Remote Host Transparency In this data transfer process, the remote host is unaware of any movement by the mobile host. PHONE:8097071144/55 69
- 71. INEFFICIENCY IN MOBILE IP Double Crossing Double crossing occurs when a remote host communicates with a mobile host that has moved to the same network (or site) as the remote host PHONE:8097071144/55 71
- 72. Triangle Routing Triangle routing, the less severe case, occurs when the remote host communicates with a mobile host that is not attached to the same network (or site) as the mobile host. PHONE:8097071144/55 72
- 74. CONTENTS • INTERIOR AND EXTERIOR ROUTING • RIP • OSPF • BGP 74PHONE:8097071144/55
- 76. Figure 13-1 Popular routing protocols 76PHONE:8097071144/55
- 79. Figure 13-3 Example of updating a routing table 79PHONE:8097071144/55
- 80. Figure 13-4 Initial routing tables in a small autonomous system 80PHONE:8097071144/55
- 81. Figure 13-5 Final routing tables for the previous figure 81PHONE:8097071144/55
- 82. Figure 13-6 RIP message format 82PHONE:8097071144/55
- 84. Example 1 What is the periodic response sent by router R1 in Figure 13.8 (next slide)? Assume R1 knows about the whole autonomous system. 84PHONE:8097071144/55
- 86. Solution R1 can advertise three networks 144.2.7.0, 144.2.9.0, and 144.2.12.0. The periodic response (update packet) is shown in Figure 13.9 (next slide). 86PHONE:8097071144/55
- 87. Figure 13-9 Solution to Example 1 87PHONE:8097071144/55
- 89. Example 2 A routing table has 20 entries. It does not receive information about five routes for 200 seconds. How many timers are running at this time? 89PHONE:8097071144/55
- 90. Solution The timers are listed below: Periodic timer: 1 Expiration timer: 20 - 5 = 15 Garbage collection timer: 5 90PHONE:8097071144/55
- 97. RIP version 2 supports CIDR. 97PHONE:8097071144/55
- 99. RIP uses the services of UDP on well-known port 520. 99PHONE:8097071144/55
- 101. Figure 13-18 Areas in an autonomous system 101PHONE:8097071144/55
- 102. Figure 13-19 Types of links 102PHONE:8097071144/55
- 106. Figure 13-23 Example of an internet 106PHONE:8097071144/55
- 107. Figure 13-24 Graphical representation of an internet 107PHONE:8097071144/55
- 108. Figure 13-25 Types of LSAs 108PHONE:8097071144/55
- 111. Figure 13-28 Summary link to network 111PHONE:8097071144/55
- 112. Figure 13-29 Summary link to AS boundary router 112PHONE:8097071144/55
- 114. Example 3 In Figure 13.31 (next slide), which router(s) sends out router link LSAs? 114PHONE:8097071144/55
- 115. Figure 13-31 Example 3 and Example 4 115PHONE:8097071144/55
- 116. Solution All routers advertise router link LSAs. R1 has two links, Net1 and Net2. R2 has one link, Net1 in this AS. R3 has two links, Net2 and Net3. 116PHONE:8097071144/55
- 117. Example 4 In Figure 13.31, which router(s) sends out the network link LSAs? 117PHONE:8097071144/55
- 118. Solution All three network must advertise network links: Advertisement for Net1 is done by R1 because it is the only router and therefore the designated router. Advertisement for Net2 can be done by either R1, R2, or R3, depending on which one is chosen as the designated router. Advertisement for Net3 is done by R3 because it is the only router and therefore the designated router. 118PHONE:8097071144/55
- 119. In OSPF, all routers have the same link state database. 119PHONE:8097071144/55
- 120. Figure 13-32-Part 1 Shortest path calculation 120PHONE:8097071144/55
- 121. Figure 13-32-Part 2 Shortest path calculation 121PHONE:8097071144/55
- 122. Figure 13-32 Part 3 Shortest path calculation 122PHONE:8097071144/55
- 123. Figure 13-33 Types of OSPF packets 123PHONE:8097071144/55
- 126. Figure 13-36 Database description packet 126PHONE:8097071144/55
- 127. Figure 13-37 Link state request packet 127PHONE:8097071144/55
- 128. Figure 13-38 Link state update packet 128PHONE:8097071144/55
- 130. Figure 13-40 Router link LSA 130PHONE:8097071144/55
- 131. Example 5 Give the router link LSA sent by router 10.24.7.9 in Figure 13.41. 131PHONE:8097071144/55
- 133. Solution This router has three links: two of type 1 (point-to- point) and one of type 3 (stub network). Figure 13.42 shows the router link LSA. 133PHONE:8097071144/55
- 134. Figure 13-42 Solution to Example 5 134PHONE:8097071144/55
- 135. Figure 13-43 Network link advertisement format 135PHONE:8097071144/55
- 136. Example 6 Give the network link LSA in Figure 13.44. 136PHONE:8097071144/55
- 138. Solution The network, for which the network link advertises, has three routers attached. The LSA shows the mask and the router addresses. See Figure 13.45. Note that only one of the routers, the designated router, advertises the network link. 138PHONE:8097071144/55
- 139. Figure 13-45 Solution to Example 6 139PHONE:8097071144/55
- 140. Figure 13-46 Summary link to network LSA 140PHONE:8097071144/55
- 141. Figure 13-47 Summary link to AS boundary LSA 141PHONE:8097071144/55
- 142. Figure 13-48 External link LSA 142PHONE:8097071144/55
- 143. Figure 13-49 Link state acknowledgment packet 143PHONE:8097071144/55
- 144. OSPF packets are encapsulated in IP datagrams. 144PHONE:8097071144/55
- 146. Figure 13-50 Path vector packets 146PHONE:8097071144/55
- 147. Figure 13-51 Types of BGP messages 147PHONE:8097071144/55
- 148. BGP supports classless addressing and CIDR. 148PHONE:8097071144/55
- 149. Figure 13-52 BGP packet header 149PHONE:8097071144/55
- 154. BGP uses the services of TCP on port 179. 154PHONE:8097071144/55
- 155. Refer printed notes for theory. 155PHONE:8097071144/55