Mobile internet protocol

mobile computing

1. mobile internet protocol and transport layer S J Savitha Assistant Professor Computer Science and Engineering Sri Ramakrishna Institute of technology 1

2. TCP/IP protocol suite – top collection of protocols. Core protocols. IP is responsible for routing a packet to any host. Identified by IP addresses. In traditional IP addressing scheme, each LAN is assigned an address. When a host moves to a different location, it needs to change its IP address. Mobile IP – IETF(Internet Engineering Task Force). Mobile IP allows mobile computers to stay connected to the internet without changing their address. 2

3. Mobile IP Mobile IP stands for Mobile Internet Protocol A wireless connection to the Internet Designed to support host mobility Stay connected regardless of location without changing IP address. Mobile IP is a network layer solution for homogenous and heterogeneous mobility on  the global internet which is scalable, robust , secure and which allow nodes to maintain all ongoing communications while moving. 3

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5. Terminologies- mobile IP Mobile Node A node/device that changes its point of attachment to the Internet Home Agent A router in the home network that communicates with the mobile node Foreign Agent A router in a foreign network that delivers information between mobile node and its home agent Care-of-Address Mobile Node’s current IP address Correspondent Node Node/device that is communicating with the mobile node (i.e. web server) 5

6. Winter 2001 5 6. 6 Data transfer to the mobile system Internet sender FA HA MN home network foreign network receiver 1 2 3 1. Sender sends to the IP address of MN, HA intercepts packet (proxy ARP) 2. HA tunnels packet to COA, here FA, by encapsulation 3. FA forwards the packet to the MN CN

7. Winter 2001 6 6. 7 Data transfer from the mobile system Internet receiver FA HA MN home network foreign network sender 1 1. Sender sends to the IP address of the receiver as usual, FA works as default router CN

8. Discovering the care-of address Agent advertisement – Needed for mobile node to discover mobility agent. It is an advertisement message constructed by attaching a special extension to an ICMP router advertisement. If advertisement not received or needed sooner by mobile a solicitation may be generated. 8

9. Agent advertisement Allows for the detection of mobility agents Lists one or more available care-of addresses Informs mobile node about special feature provided by foreign agents, for example, alternative encapsulation techniques Allows mobile nodes to determine the network number and status of their link to the Internet Allows mobile node to determine whether the agent has the functionality to serve as a HA, a FA or both. Flag indicates whether it is home agent or a foreign agent. 9

10. Agent solicitation In case a MN(Mobile node) does not receive any COA, then the MN should send an agent solicitation message. These Solicitation message should not flood the network. A MN can send up to 3 solicitation messages(one per second) as soon as it enters a new network. The purpose of sending this message to search for a foreign agent. If an MN does not receive any address in response to its solicitation messages, then to avoid network flooding, the MN should reduce the rate of sending the solicitation messages. 10

11. Tunnelling process The packet is forwarded by the home agent to the foreign agent. When the packet comes to the foreign agent( COA) , it delivers the packet to the mobile node. Two primary functions : Encapsulation – data packet to reach the tunnel endpoint. Decapsulation – delivering packet at that endpoint. 11

12. Tunnelling and encapsulation Tunnelling establishes a virtual pipe for the packets available between a tunnel entry and an endpoint. Encapsulation refers to arranging a packet header and data in the part of a new packet. The operations of encapsulation and decapsulation takes place whenever a packet sent from a higher protocol to lower protocol. 12

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14. Packet Delivery STEP 1 : If the correspondant node wants to send an IP packet to a mobile node.CN sends the packet to the IP address of the mobile node. STEP 2 : In case MN is not present, then the packet is encapsulated by a new header and it is tunnelled to the COA and HA, acts as source address of a packet. 14

15. STEP 3 : The encapsulated packet is routed to foreign agent which performs decapsulation to remove the additional header and forwards the decapsulated packet to the MN . STEP 4 : The MN after receiving the packet from CN forward a reply packet to the CN by specifying its own IP address along with the address of the CN. 15

16. Overview Of Mobile IP Goal- Efficient packet transmission. A person working as a business development executive for a company needs to take care of many regional offices. How does he makes arrangements so that he would continue to receive postal mails regardless of his location? Two solutions: Address changing Decoupling mail routing from his address. 16

17. Features of mobile ip Transparency The IP address is to be managed transparently and there should not be any affect of mobility on any ongoing communication. Compatibility Mobile IP should be compatible. Security Mobile IP should, as for as possible, provide users with secure communications over the internet. Efficiency and Scalability Efficient when overhead occurs. Scalable to support billions of moving hosts worldwide . 17

18. Key Mechanisms in mobile IP Mobile IP is associated with three basic mechanisms. Discovering the care-of-address Registering the care-of-address Tunnelling to the care-of-address 18

19. Discovering the COA Mobile agents advertise their presence by periodically broadcasting the agent advertisement messages Mobile node receives the advertisement messages observes whether the message from HA or FA If a Mobile node does not wish to wait for a periodic advertisement , it can send out gent solicitation messages 19

20. REGISTERING THE COA 20

21. If a mobile node is on new network , it registers with the foreign agent by sending a registration request Request includes permanent IP address of mobile host and HA When the HA receives the Registration request , it updates the mobility binding table HA sends an acknowledgement to FA The FA updates its visitors list by inserting the entry of the mobile node 21

22. Tunnelling to the COA Tunnelling – forward an IP datagram from HA to COA Steps : When a HA receives a packet addressed to a mobile host, it forwards the packet to the COA using IP- within –IP HA inserts a new IP header in front of the IP header of any datagram Destination- set to the COA Source- set to the HA address After stripping out the first header , IP processes the packet again 22

23. Route Optimization Mobile IP protocol-all the data packets to the mobile node go through the home agent Heavy traffic between HA and CN in the network To overcome this problem , route optimization needs Enable direct notification of the corresponding host Direct tunnelling from the corresponding host to the mobile host Binding cache maintained at the corresponding host Binding – The Association of the home address with a care-of-address. 23

24. Four Messages : Binding Request Binding Acknowledgement Binding Update Binding Warning Binding Request : Node sends a request to HA to know the current location of MN. Binding Acknowledgement Node will return an acknowledgement after getting binding message. 24

25. Binding update : Message sent by HA to CN mentioning the correct location of MN. Message-MN IP address and COA. Binding Warning : If a node decapsulates a packet for a MN, but it is not the current FN, then this node sends a binding warning to HA of the MN. 25

26. DHCP Dynamic Host Configuration Protocol Developed based on BOOTP (Bootstrap protocol) Information including IP address IETF an extension to BOOTP DHCP client and server- handle roaming status and to assign IP address Significance of DHCP Static configuration Temporary IP address 26

27. DHCP- Three mechanisms for IP address allocation : Automatic allocation Dynamic allocation Manual allocation 27

28. TCP –Transmission Control Protocol Most popular transport layer protocol TCP- de facto Connection-oriented protocol UDP – Connectionless protocol in the TCP/IP suite Traditional TCP- Highly inefficient and unsatisfactory manner Special adaptations-wireless networks Developed by DARPA in 1969 28

29. Overview of TCP/IP 29

30. Four layers of protocol : Application layer Transport layer Internet layer Network Interface layer Application layer Application programmers and end users Messages will be passes to transport layer Transport layer Converts messages into small parts and attaches certain information. It passes segments to the Internet layer protocol 30

31. Internet Layer Attaches certain information to segments to form packets TCP segment carried one or more IP packets The IP passes the packets to the network interface layer Network Interface layer It converts the packets to frames by adding certain additional information such as checksum and then transmits them on the network 31

32. The reverse operation takes place when a frame arrives at a host The network interface layer protocol removes the information added by the corresponding network interface layer protocol at the sender-end and passes on the packet to IP layer The IP layer protocol at the destination removes the information added by the IP layer The transport layer protocol at the receiver stripes the information added by the transport layer protocol at the sender Reconstructs the message and sends it to the application layer 32

33. Terminologies of TCP/IP TCP – Transmission Control Protocol IP –Internet Protocol HTTP-Hyper Text Transmission Protocol SMTP-Simple Mail Transfer Protocol MIME-Multipurpose Internet Mail Extension FTP – File Transport Protocol SNMP- Simple Network Management Protocol ICMP-Internet Control Message Protocol ARP- Address Resolution Protocol RARP-Reverse Address Resolution Protocol BOOTP- Boot Protocol DNS-Domain Name System IGMP-Internet Group Management Protocol 33

34. Architecture of TCP/IP Application Layer : The protocols at this layer used by applications to communicate with other applications which possibly running on separate hosts Examples : HTTP FTP TELNET 34 APPLICATION LAYER TRANSPORT LAYER INTERNET LAYER NETWORK ACCESS LAYER

35. Transport Layer End-End data transfer services Host -to- host protocols To identify the end point , the concept of port number is used An application or a process specifies a port number on which it would receive a message Message reaches a host – demultiplexed using the port number at the transport layer It provides services by making use of services of its lower layer protocols It includes TCP (Transmission Control Protocol) UDP(User Datagram Protocol) 35

36. Internet Layer Packs data into data packets – IP datagrams IP datagram contains source and destination address(IP address) Responsible for routing of IP datagrams In a nutshell , this layer manages the addressing of packets and delivery of packets between networks using IP address Protocols includes : IP ICMP ARP RARP IGMP 36

37. Network access layer Encoding data and transmitting Provides error detection and packet framing functionalities ISO/OSI protocol suite – data link and physical layers Data link layer help to deliver protocols by use of physical layers Data link layer protocols - Ethernet , Token Ring,FDDI,X.25 Physical layer – how data is physically sent through network 37

38. Operation of TCP Client-server application Data transmission between client and server may span multiple networks – Sub networks Identification of hosts is not enough for data delivery Every process is identified by port number Message in the form of block of data is passed to TCP by sending application TCP breaks into many small parts and attaches certain control information(TCP header) Data along with TCP header called segment 38

39. Structure of tcp segment TCP Header Portion of Data 39 Control information TCP header includes : 1. Destination host 2.Checksum 3.Sequence number

40. IP datagram Ip packet- datagram Datagram- variable length up to 65,536 bytes Two fields – header and data 40

41. Version - IP version number Eg :IPV4 or IPV6 Hlen – Header length as multiples of 4 bytes Service – priority of datagram Total length – allotted 16 bits to define length of IP datagram Identification – To identify fragmentation that belongs to networks Flags – Deals with fragmentation Fragment Offset – Pointer to the offset of data in original datagram Time to live – total number of hops and operation time 41

42. Protocol – 16 bits , Example : UDP , TCP , ICMP Header checksum – 16 bit field to check the integrity of the packets Source address – define the original source Destination address – defines the destination of datagram Port address – Data encapsulation Facilities requests Destination sub-network address 42 PROTOCOL PORT TELNET 23 SMTP 25 RPC 111 DNS 53

43. Adaptation of TCP window Flow control techniques to control congestion in a network Traffic occurs when the rate at which data injected to a host exceeds the rate at delivered to a host Flow control technique Prevents congestion in the network Prevents buffer overrun at the slow receivers If data transmissions occur at faster rate than network infrastructure support , then packets get built up. Faster rate at sender > faster rate at receiver Receiver uses flow control mechanism to restrict the faster rate at sender 43

44. Receiver indicates an advertise window , when sender starts to send data packets Advertised window- set equal to the size of the receiver buffer Congestion window – max number of segments without acknowledgements A sender sets size to 1 and keeps on increasing until it receives duplicate acknowledgements TCP detects packet loss - RTO – Retransmission timeout and duplicate ack In wireless – packet loss due to mobility and channel errors Wireless are vulnerable to noise 44

45. Improvement in tcp performance TCP designed for traditional wired networks Overview Traditional networks TCP in mobile networks TCP in Single-hop wireless networks TCP in multi-hop wireless networks 45

46. Traditional networks In wired networks - packet losses are primarily Congestion control mechanisms – reduces congestions Important mechanisms used by TCP Slow start Congestion Avoidance Fast retransmit / fast recovery RTT – Round Trip Time RTO calculated based on RTT 46

47. Slow s tart Slow start mechanism used when TCP session is started Lowest window size and then doubled after each successful transmission Rate of doubling- rate of ack come back Doubling size occurs at every RTT RTT – Time that elapses between a segment is transmitted by a sender and ack is received Congestion detected – window size is reduced to half of its current size 47

48. Congestion avoidance The CA algorithm starts when slow start stops When Congestion window reaches the congestion threshold level – window size doubling is avoided TCP reduces its transmission rate to half the previous value when congestion occurs Less aggressive than the slow start phase 48

49. Fast retransmit /fast recovery Sender initiates a timer after transmitting a packet and sets timeout value(RTO) RTO is calculated based on RTT When the timer expires , it retransmits the packet R etransmission is not triggered by timer, triggered by receipt of three duplicate copies of ack When retransmission occurs , the congestion window size is reduced by half 49

50. TCP in mobile networks TCP – de facto standard protocol The main differences between wired and wireless networks : Lower bandwidth Bandwidth fluctuations Higher delay Intermittent disconnections High bit error rate Poor link reliability 50

51. TCP in single-hop wireless networks The modifications proposed to TCP to make it effective in single-hop wireless networks Indirect TCP(I- TCP) Fast Retransmission Snooping TCP(S-TCP) Mobile TCP (M-TCP) Freeze TCP 51

52. Indirect TCP Proposes by Bakre and Badrinath Wired part and wireless part Wired part – Connection between Fixed host and base station Wireless part – Connection between base station and Mobile host Two separate connections : fixed network and wireless link Advantage - split connection of I-TCP is that it does not need any changes to be made to standard protocol Disadvantage – Does not maintain end-end semantics of TCP 52

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54. Fast Retransmission Proposed by Caceres et al Overcomes the delay in transmissions caused due to intermittent disconnections Advantage Reduces the time for MH to get reconnected Disadvantage Does not propose a general approach for TCP communications in mobile wireless networks Example : Does not address the specific error characteristics of the wireless medium 54

55. Snooping Tcp Proposed by Balkrishnan et al – protocol that improves the performance of TCP by modifying the Software Modified software – Snoop Monitors every packet passes through Tcp Connection If Congestion occurs , it retransmits locally and hides the duplicate ack Advantage : Maintains TCP semantics by hiding the duplicate ack 55

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57. Mobile TCP Proposed by Kevin Brown et al It tries to avoid the sender window As I-TCP , mobile host is segmented into wired and wireless parts Wired part – Connection between FH and SH (Supervisor Host) Wireless part – Connection between SH and MH SH supervises all packets transmitted to MH Sets full window size - MH is connected State transfer takes place when MH moves New SH can maintain TCP connection between FH and MH 57

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59. Freeze TCP The idea is to “freeze” the TCP senders before a disconnection occurs “Zero Windows Advertisement” – informs the sender that the receiver cannot receive data at that moment When sender resumes its connectivity ,the receiver can unfreeze the sender by sending the value Advantage – Avoidance of slow start period Does not require the involvement of intermediate nodes 59