Domain Name System and Dynamic Host Configuration Protocol.pptx
- 2. INTRODUCTION • A DNS is a computer server that contains a database of many IP addresses and their associated domain names. • It serves to translate a requested domain name into an IP address, so that the computer knows which DNS address to connect to for the requested contents. • The internet is a network of connected computers, and they communicate with each other through IP addresses. • See a DNS as a phone book, which matches a name to a telephone number. • Also a similar concept to smartphone’s contact list, which will match a contact name to a phone number.
- 3. WORKING • A DNS starts working immediately after a user enters a domain name in the address bar of a browser. • It will search through the internet to find the IP address that is associated with the entered domain name. • After successfully identifying the IP address, it then guides the user’s browser to connect to it, which will then serve the requested website contents. • The process happens very quickly with little delay and the user will be on his requested website almost immediately. • However, in the background, a DNS has executed many processes.
- 4. WORKING • The first step that a DNS does is to send a DNS query to several other DNS servers. • A DNS is not just a single server responding to over billions of domain name requests, but instead it is distributed globally across a network of DNS, which stores the IP address directory in a distributed manner.
- 5. WORKING • If a user is looking for a specific site and there is only one DNS server to process it, then it will take significantly longer to search through the millions of records in the directory. • What if at the same time there are also millions, if not billions of users who are also doing the same? That is going to take a long time, and the users’ browsing experience will definitely be affected negatively. • Therefore, DNS is set up to work collaboratively across several servers to provide the best browsing experience to users.
- 6. WORKING • When a website address is entered by a user in an internet browser, a DNS query is initiated and a DNS server sends the query to several other DNS servers, each tasked with translating a different part of the domain name the user entered. • There are mainly four servers which work together to translate the website address into a computer readable IP address, namely the DNS resolver server, the root server, the top- level domain (TLD) server and the authoritative name server.
- 7. WORKING • The DNS resolver is the server who does most of the process in translating a domain name to an IP address. • It receives the DNS query and in turn acts like a client to query the three other DNS servers mentioned above to translate the domain name. • It first queries the root server and the root server responds to the query by returning the IP address of a TLD server (like .Com, .Net, .Org etc.).
- 8. WORKING • A TLD server stores the information for its domains, and will return the IP address of the authoritative name server to the DNS resolver. • This is where the requested website is actually located. • It then returns the actual IP address of the requested website to the DNS resolver, which in turn response to the initial DNS query the actual IP address.
- 9. WORKING • Consider point 9 as shown in the illustration. The DNS resolver will perform a caching function to cache the data for a limited time, after it has retrieved the correct IP address for a given website. • The purpose of doing so is that in case the user requests for the same domain name again, it can immediately direct the user to the right web server without having to do the entire process of translating the domain name again. • It is also beneficial in a sense that if there are other users who request for the same domain name, their request can be processed instantly, and they can enjoy a great browsing experience.
- 10. WORKING • DNS Recursor • The recursor can be thought of as a librarian who is asked to go find a particular book somewhere in a library. The DNS recursor is a server designed to receive queries from client machines through applications such as web browsers. Typically the recursor is then responsible for making additional requests in order to satisfy the client’s DNS query. • Root Nameserver • The root server is the first step in translating (resolving) human readable host names into IP addresses. Typically it serves as a reference to other more specific locations.
- 11. WORKING • TLD Nameserver • This nameserver is the next step in the search for a specific IP address, and it hosts the last portion of a hostname (in example.com, the TLD server is “com”). • Authoritative Nameserver • The authoritative nameserver is the last stop in the nameserver query. If the authoritative name server has access to the requested record, it will return the IP address for the requested hostname back to the DNS recursor (the librarian) that made the initial request.
- 12. RECURSIVE DNS RESOLVER • The recursive resolver is the computer that responds to a recursive request from a client and takes the time to track down the DNS record. • It does this by making a series of requests until it reaches the authoritative DNS nameserver for the requested record (or times out or returns an error if no record is found). • Luckily, recursive DNS resolvers do not always need to make multiple requests in order to track down the records needed to respond to a client; caching is a data persistence process that helps short-circuit the necessary requests by serving the requested resource record earlier in the DNS lookup.
- 14. AUTHORITATIVE DNS SERVER • An authoritative DNS server is a server that actually holds, and is responsible for, DNS resource records. • This is the server at the bottom of the DNS lookup chain that will respond with the queried resource record, ultimately allowing the web browser making the request to reach the IP address needed to access a website or other web resources. • An authoritative nameserver can satisfy queries from its own data without needing to query another source, as it is the final source of truth for certain DNS records.
- 16. TYPES OF DNS QUERIES • In a typical DNS lookup three types of queries occur. By using a combination of these queries, an optimized process for DNS resolution can result in a reduction of distance traveled. • In an ideal situation cached record data will be available, allowing a DNS name server to return a non-recursive query.
- 17. TYPES OF DNS QUERIES • Recursive Query • In a recursive query, a DNS client requires that a DNS server (typically a DNS recursive resolver) will respond to the client with either the requested resource record or an error message if the resolver can't find the record.
- 18. TYPES OF DNS QUERIES • Iterative Query • In this situation the DNS client will allow a DNS server to return the best answer it can. • If the queried DNS server does not have a match for the query name, it will return a referral to a DNS server authoritative for a lower level of the domain namespace. • The DNS client will then make a query to the referral address. • This process continues with additional DNS servers down the query chain until either an error or timeout occurs.
- 19. TYPES OF DNS QUERIES • Non-recursive Query • Normally this will occur when a DNS resolver client queries a DNS server for a record that it has access to either because it's authoritative for the record or the record exists inside of its cache. • Typically, a DNS server will cache DNS records to prevent additional bandwidth consumption and load on upstream servers.
- 20. DNS LOOKUP • DNS translates human-readable domain names (google.com) to machine-readable IP addresses (142.251.46.238). • To achieve better scalability, the DNS servers are organized in a hierarchical tree structure.
- 21. DNS LOOKUP 1. google.com is typed into the browser, and the browser sends the domain name to the DNS resolver. 2. The resolver queries a DNS root name server. 3. The root server responds to the resolver with the address of a TLD DNS server. In this case, it is .Com. 4. The resolver then makes a request to the .Com TLD. 5. The TLD server responds with the IP address of the domain’s name server, google.com (authoritative name server). 6. The DNS resolver sends a query to the domain’s nameserver. 7. The IP address for google.com is then returned to the resolver from the nameserver. 8. The DNS resolver responds to the web browser with the IP address (142.251.46.238) of the domain requested initially. • DNS lookups on average take between 20-120 milliseconds to complete.
- 22. STATIC & DYNAMIC IP ADDRESS • IP address may be a unique numerical symbol allotted to every device on a network to spot each affiliation clearly. • The distinction between static and dynamic IP address lies inside the length of allotted scientific discipline address. • The static scientific discipline address is fastened scientific discipline address that is manually allotted to a tool for a protracted amount of your time. • On the opposite hand, the dynamic scientific discipline address often changes whenever user boots his/her machine, and it’s mechanically allotted.
- 23. STATIC & DYNAMIC IP ADDRESS
- 24. S.NO Static IP Address Dynamic IP address 1. It is provided by ISP (Internet Service Provider). While it is provided by DHCP (Dynamic Host Configuration Protocol). 2. Static IP address does not change any time, it means if a static IP address is provided then it can’t be changed or modified. While dynamic IP address change any time. 3. Static IP address is less secure. While in dynamic IP address, there is low amount of risk than static IP address’s risk. 4. Static IP address is difficult to designate. While dynamic IP address is easy to designate. 5. The device designed by static IP address can be traced. But the device designed by dynamic IP address can’t be traced. 6. Static IP address is more stable than dynamic IP address. While dynamic IP address is less stable than static IP address. 7. The cost to maintain the static IP address is higher than dynamic IP address. While the maintaining cost of dynamic IP address is less than static IP address. 8. It is used where computational data is less confidential. While it is used where data is more confidential and needs more security. 9. Simplifies the troubleshooting as the IP is always the same. While dynamic IP increases the complexity of diagnosing the network issues.
- 25. DHCP • DHCP stands for Dynamic Host Configuration Protocol. • It is the critical feature on which the users of an enterprise network communicate. • DHCP helps enterprises to smoothly manage the allocation of IP addresses to the end-user clients’ devices such as desktops, laptops, cellphones, etc.
- 26. COMPONENTS OF DHCP • DHCP Server: DHCP server is basically a server that holds IP addresses and other information related to configuration. • DHCP Client: it is basically a device that receives configuration information from the server. It can be a mobile, laptop, computer, or any other electronic device that requires a connection. • DHCP Relay: DHCP relays basically work as a communication channel between DHCP client and server. • IP Address Pool: it is the pool or container of IP addresses possessed by the DHCP server. It has a range of addresses that can be allocated to devices.
- 27. COMPONENTS OF DHCP • Subnets: subnets are smaller portions of the IP network partitioned to keep networks under control. • Lease: it is simply the time that how long the information received from the server is valid, in case of expiration of the lease, the tenant must have to re-assign the lease. • DNS Servers: DHCP servers can also provide DNS (domain name system) server information to DHCP clients, allowing them to resolve domain names to IP addresses. • Default Gateway: dhcp servers can also provide information about the default gateway, which is the device that packets are sent to when the destination is outside the local network.
- 28. COMPONENTS OF DHCP • Options: DHCP servers can provide additional configuration options to clients, such as the subnet mask, domain name, and time server information. • Renewal: DHCP clients can request to renew their lease before it expires to ensure that they continue to have a valid IP address and configuration information. • Failover: DHCP servers can be configured for failover, where two servers work together to provide redundancy and ensure that clients can always obtain an IP address and configuration information, even if one server goes down. • Dynamic Updates: DHCP servers can also be configured to dynamically update DNS records with the IP address of DHCP clients, allowing for easier management of network resources.
- 29. COMPONENTS OF DHCP • Audit Logging: DHCP servers can keep audit logs of all DHCP transactions, providing administrators with visibility into which devices are using which IP addresses and when leases are being assigned or renewed.
- 30. DHCP SCOPE • A DHCP scope is a range of IP addresses that a DHCP server can distribute to clients on a specific network segment. • Whenever a DHCP server has to assign an IP Address to a client device, it will randomly choose any available address to the device. • A DHCP server can have multiple scopes for different subnets or VLANS, and each scope must have a unique name and ID.
- 31. WHY USE DHCP SCOPE • It simplifies the management of IP addresses, as you don't have to configure them manually on each device. • It also reduces the risk of IP conflicts, as the DHCP server ensures that each device gets a unique address. • It also allows you to change the network settings centrally, by modifying the scope parameters. For example, you can change the DNS servers or the gateway without affecting the devices.
- 32. DHCP RESERVATION • The DHCP reservation functionality empowers the DHCP server to allocate a dedicated IP address for a specific device within the network. • A reservation is based on the MAC address of the device, which is a unique identifier for its network interface. • A reserved address is not part of the pool of available addresses, and it is always assigned to the same device, regardless of the lease duration. • A DHCP server can have multiple reservations for different devices within a scope.
- 33. WHY USE DHCP RESERVATION • It allows you to ensure that a device always has the same IP address, which can be useful for security, monitoring, or access control purposes. • For example, you can use reservation for a printer, a server, a camera, or a firewall, so that you can always reach them by the same address. • It also allows you to override the scope parameters for a specific device, by configuring them individually. • For example, you can assign a different gateway or DNS server to a device with a reservation.
- 34. DHCP LEASE • A lease is defined as the time period for which a DHCP server allocates an IP address to a client. The lease can be extended upon subsequent requests. • If the client no longer needs the IP address, it can release the address back to the server before the lease expires. The server is then free to assign this address to a different client if no other idle IP address is available. • The lease period configured for a DHCP server applies to all of the IP addresses that a DHCP server dynamically assigns to its clients. • A different DHCP server may have a different lease term for its clients. A statically allocated IP address is not subject to the lease terms.
- 35. DHCP LEASE • A DHCP client does not wait for its lease to expire, because it may be assigned a different IP address. Instead, when a DHCP client reaches the halfway point of its lease period, it attempts to extend its lease so that it retains the same IP address.
- 36. ADDRESS POOLS • An address pool is a set of all the IP addresses that a DHCP server has reserved for dynamic client allocation. • Along with each IP address, the server stores certain network parameters, such as a default lease length for the IP address and other configuration parameters (for example, a subnet mask and the address of the default gateway) to be sent to the client when it is assigned that IP address. • Address pools are classified into Interface Address Pools and Global Address Pools.
- 37. ADDRESS POOLS • Interface Address Pool • After an IP address is configured for an interface on a DHCP server, you can create an address pool on the same network segment as this interface. • Addresses in the address pool can be allocated only to clients connected to the interface. • The interface address pool can allocate IP addresses to clients on the same network segment as the DHCP server.
- 38. ADDRESS POOLS • Global Address Pool • On a DHCP server, you can create an address pool on the specified network segment in the system view. • Addresses in the address pool can be allocated to all clients connected to the DHCP server, even if the server and clients are on different network segments.
- 39. DYNAMIC DNS • Dynamic DNS (DDNS) is a method of automatically updating a name server in the domain name system (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information. • The term is used to describe two different concepts. • The first is "dynamic DNS updating" which refers to systems that are used to update traditional DNS records without manual editing. these mechanisms use TSIG to provide security. • The second kind of dynamic DNS permits lightweight and immediate updates often using an update client, which do not use the RFC2136 standard for updating DNS records
- 40. DHCP OPTIONS • Supplying DHCP options is a smart way to configure network clients during the early phase of network access deployment. In addition to providing the IP address, the DHCP protocol is able to set a large bunch of options that are very useful for device configuration. • Each option has a name and a numerical identifier to be transported in the protocol frames. • https://www.incognito.com/tutorials/dhcp-options-in-plain-english/