Dynamic Host Configuration Protocol Using Fault Tolerant and Load Balancing

Transcription

1 Dynamic Host Configuration Protocol Using Fault Tolerant and Load Balancing Dr A.Chandrabose 1 T.Manivannan 2 Asst.Prof Dept Of Computer Science Research Scholar M.Jayakandan 3 S.Arunkumar 4 Research Scholar Research Scholar EdayathangudyG.S.Pillay Arts & Science College Nagapattinam. Abstract - To send and receive data on the Internet, a host needs an IP address and other information such as gateway address and DNS server address, which can be obtained through the Bootstrap Protocol (BOOTP).BOOTP is built on a client-server model. A diskless client contacts a BOOTP server to obtain such information as IP address, server IP address, boot image filename, and gateway IP address. BOOTP was designed for stable networks where each host gets a permanent network connection. The administrator configures a BOOTP configuration file that contains a set of parameters for each BOOTP client. Because the configuration is seldom changed, the configuration file remains unchanged accordingly for several weeks. As many people need to take their laptops across networks, the IP addresses need be changed accordingly. As a result, related configurations on hosts become more complex. BOOTP cannot solve these problems. Therefore, the Dynamic Host Configuration Protocol (DHCP) was introduced by IETF to provide a mechanism for assigning IP addresses dynamically. Keywords: DHCP,DHCPClient, DHCP server, DHCP relay agent,bootp client, Fault Tolerant and Load Balancing. I Introduction 1.1 DHCP is an enhanced version of BOOTP. It also adopts the client/server model. The DHCP server assigns network configuration parameters to DHCP clients.dhcp supports three mechanisms for IP address allocation:manual Allocation is the network administrator assigns an IP address to a client like a WWW server, and DHCP conveys theassignedaddress to the 216

2 IIDHCP Messaging: client.automatic Allocation is DHCP assigns a permanent IP address to a clientdynamic Allocation: DHCP assigns an IP address to a client for a limited period of time, which is called a lease. The client should apply for a new IP address upon lease expiration. The network administrator can select any of the three mechanisms as needed. 1.2 DHCP enhances BOOTP in the following two aspects.fast and dynamic IP address allocation. The network administrator needs to configure a DHCP server to provide agroup of IP addresses, called an address pool. Once a host is attached to the network, it communicates with the DHCPserver to apply for an IP address. Then, the DHCP server selects an IP address from the configured address pool and assigns the IP address to the host.more network configuration information for clients. 1.3 DHCP Related Terms DHCP Server:A DHCP server assigns IP addresses and other network configuration parameters to the DHCP clients.dhcp Client:A DHCP client obtains an IP address and other network configuration parameters from a DHCP server. It is the initiator of an IP address allocation.dhcp Relay Agent:A DHCP relay agent forwards DHCP messages between a DHCP server and DHCP clients. In this way, the clients need not be located on the same network as the DHCP server. 2.1 A DHCP snooping device can record the IP-to-MAC bindings from the received DHCP-ACK and CPLOCATE CPNODE HCPREQUEST CPDECLINE CPACK CPNAK CPRELEASE CPINFORM Table 2.1 Message Types 2.2 DynamicIP Address Allocation Process A DHCP client obtains a valid IP address from a DHCP server via four steps: Discovering: The client locates a DHCP server. Offering: A DHCP server offers configuration parameters such as an IP address to the client. Selecting: The client selects an IP address assigned by one of the DHCP servers. 217

3 2.3 Acknowledging: The DHCP server confirms the offered IP address. DHCP client DHCP server DHCP-LOCATE (Broadcast) DHCP-OFFER DHCP-REQUEST (Broadcast) Figure 2.3Dynamic IP address allocation process The dynamic IP address allocation steps which are described as follows: 3.1.Locate the DHCP Server The DHCP client broadcasts a DHCP-LOCATE message to locate a DHCP server. Since the DHCP server is unknown to the client, the client needs to broadcast a DHCP- LOCATE message. All the DHCP servers send replies to the client upon receiving the DHCP- LOCATE message Offering A DHCP server that receives the DHCP-LOCATE message offers an appropriate IP address with a lease and other configuration parameters (such as gateway IP address and DNS server address) to the client in a DHCP-NODE message. 3.3A DHCP server assigns an IP address to a client according to the following sequence: The IP address manually bound to the client s MAC address or ID The IP address that was ever assigned to the client. The IP address designated by the Option 50 field in the DHCP-LOCATE message from the client. The first assignable IP address found in a proper DHCP address pool. The IP address that was conflicting or passed its lease duration. 218

4 4.1 Acknowledging If no IP address is assignable, the server will not respond. 4. Selecting The client broadcasts the DHCP- REQUEST message to notify all the DHCP servers that it will use the IP address offered by the DHCP server specified in Option 54. In this way, other DHCP servers can reclaim the IP addresses they offered to the client. Upon receiving the DHCP- REQUEST message from the DHCP client, the DHCP server checks the lease record corresponding to the MAC address in the message. After the client receives the DHCP-ACK message, it will probe whether the IP address assigned by the server is in use by broadcasting a gratuitous ARP packet. If the client receives no response within a specified time, it will use this IP address. Otherwise, the client sends a DHCP-DECLINE message to the server to request an IP address again. Windows\System32\ipconfigall> dows IP Configuration cription...:realtekpcie FE Family troller ical Address...: C1-C8-F7 CP Enabled...:Yes o Configuration Enabled...:Yes 4 Address...: (Preferred) net Mask...: e Obtained...: Sat.AM 11:00:00 e Expires...: Sat.AM 12:00:00 ault Gateway...: CP Server...: S Server...: Figure 4.1Windows IP Configuration 219

5 Figure 4.2 DHCPPrivate Servers to DHCP Relay Agent Figure 4.3 DHCP Mechanisms V. DHCP Failover Configuration 5.1 On DHCP2, open the DHCP console, right-click the Contoso-scope1 DHCP scope and then click Configure failover. 220

6 Figure 5.1 DHCP Failover Configurations 6. Maximum Client Lead Time (MCLT) The Maximum Client Lead Time (MCLT) is additional time provided to a DHCP client after expiration of a DHCP lease. The MCLT is transmitted from the primary to the secondary server in the CONNECT message, and is the maximum amount of time that one server can extend a lease for a client beyond the time known by the partner server. The 1 minute MCLT value used here for test lab purposes only, to prompt lease renewal by the client. In a production environment, you should use a longer MCLT, such as 1 hour. 221

7 Figure 6.0DHCP Configure Failover relationships Figure 6.1 DHCP Failover Configurations Progress 222

8 Figure 6.2 Fault Tolerant and Load Balancing VII. Implementations 7.0 The DHCP protocol allows the implementation of fault tolerance and loadbalancing very easily. If you connect two DHCP servers to the same IP subnet, and both servers are configured to serve IP addresses on this subnet, the protocol handles all conflicts between the two servers. A system is fault-tolerant if it can continue to perform despite parts failing. Load balancing specifies the maximum number of DHCP/BINL requests to an OS deployment server in one minute. 7.1Fault tolerance helps to make your remote-boot infrastructure more robust. A system is fault-tolerant if it can continue to perform despite parts failing. Fault tolerance at the product level is implemented with two configuration parameters: Backup and Boot Reply Delay. VIII. Conclusion and Future Enhancements DHCP failover provides high availability of DHCP services without the challenges of clustering or split scope DHCP. Benefits of DHCP failover include. A wizard is provided to create DHCP failover relationships between DHCP servers. The wizard automatically replicates scopes and settings from the primary server to the failover partner. DHCP failover can also be configured for load balancing, with client requests distributed between both DHCP servers in a failover relationship based on the values you choose. DHCP servers share lease information, allowing one server to assume responsibility for servicing of clients if the other server is unavailable. DHCP clients 223

9 can keep the same IP address when a lease is renewed, even if the lease is issued by a different DHCP server. The DHCP protocol allows the implementation of fault tolerance and load-balancing very easily. If you connect two DHCP servers to the same IP subnet, and both servers are configured to serve IP addresses on this subnet, the protocol handles all conflicts between the two servers. A system is fault-tolerant if it can continue to perform despite parts failing. Load balancing specifies the maximum number of DHCP/BINL requests to an OS deployment server in one minute. IX. Futures Enhancements Fault tolerance helps to make your remote-boot infrastructure more robust. A system is fault-tolerant if it can continue to perform despite parts failing. Fault tolerance at the product level is implemented with two configuration parameters: Backup and Boot Reply Delay. X. References 1. Fault Tolerance: Principles and Practice: Volume 3 (Dependable Computing and Fault-Tolerant Systems) by Peter A Lee and Thomas Anderson IEEE Std : IEEE Recommended practice for Software Specifications. Software Engineering Standards Committee. Fault Tolerance IEEE Std : IEEE Recommended practice for Software Design Software Engineering Standards CommitteeLoad balancing 2002 SSR). 4..IEEE Std : IEEE Standard for Software Test Documentation Software Engineering Standards Committee of the IEEE Society DHCP IEEEStd : IEEE Standard for Software Unit Testing Software Engineering Standards Committee of theieee SocietyLoad balancing IEEEStd : IEEE Standard for Software User Documentation Software Engineering Standards Committee of the IEEE SocietyLoad balancing Devyani Bajaj, Neelesh Gupta, GPS Based Automatic Vehicle Tracking Using RFID, International Journal of Engineering and Innovative Technology (IJEIT) Volume 1, Issue 1, January Soyoung Hwang and Donghui Yu, GPS Localization Improvement of Smartphones Using Built-in Sensors, International Journal of Smart Home Vol. 6, No. 3, July, PankajVerma, J.S Bhatia, Design and Development of GPS_GSM Based Tracking System with Google Map Based Monitoring, International JouRrnal of Computer Science, Engineering and Applications (IJCSEA) Vol.3, No.3, June Akin ode J. L1, Alamode A. J2 and Ojuawo O. O3. Nigeria, "Improving National Security using GPS Trackinsystem Technology. Proceedings of the 1st International Technology, Education and Environment Conference(c) African Society for Scientific Research (A 224