What are two fundamental cryptography principles?

In this article we shall discuss about the two fundamental principles that govern a cryptographic system. 

1. Redundancy

- Some redundancy must be there in all the encrypted messages. 

- By redundancy here, we mean the information that is not required for understanding the message reducing the chances for a passive intruder to make attacks. 

- Passive intruder attacks involve putting the stolen information to misuse without understanding it. 

- This can be more easily understood by an example of a credit card. 

- The credit card number is not alone sent over the internet rather it is accompanied by other side info such as the DOB of the card holder, its validity date and so on. 

- Including such info with the card number cuts down on the changes for making up the number. 

- Adding a good amount of redundancy prevents the active intruders from sending garbage values and then getting it verified as some valid message. 

- The recipient must be capable of determining whether the message is valid or not by  doing some inspection and simple calculation. 

- Without redundancy the attackers would simply send junk message and the recipient will decode it as a valid message. 

- However, there is a little concern also with this. 

- N number of zeroes must not be put at the beginning or the end of the message for redundancy because such messages become easy to be predicted thus facilitating the crypt analysts work.

- Instead of zeroes, a CRC polynomial can be used because it proves to be more work. 

- Using cryptographic hash might be even better.

- Redundancy has also got a role to play in quantum cryptography. 

- Some redundancy is required in the messages for the bob to determine if the message has been tampered. 

- Repetition of the message twice is a crude form of redundancy.

- If the two copies are found to be identical, the bob states that somebody is interfering with the transmission or there is a lot of noise. 

- But such repetition process to be expensive. 

- Therefore, for error detection and correction the methods used are reed Solomon and hamming codes.

2. Update

- Measures must be compulsorily taken for the prevention of the attacks by active intruders who might play back the old messages. 

- The longer an encrypted message is held by an active intruder, the more is the possibility that he can break in to it. 

- One good example of this is the UNIX password file.

- For anybody who has an account on the host, the password is accessible. 

- A copy of this file can be obtained by the intruders and they can then easily de-crypt the password.

- Also, the addition of the redundancy allows the simplification of the messages’ decryption.

- It must be checked whether the message has been sent recently or is an old one. 

- One measure for doing so is including a time stamp of few seconds in the message. 

- This message then can be saved by the recipient for that many seconds and can be used for comparing with the incoming messages and filtering the duplicates.

- Messages which exceed this time period will be rejected as being too old.

Apart from the above two principles the following are some other principles of cryptography:

Ø Authentication: For ensuring that the message was generated by the sender itself and no one else so that no outsider can claim as being the owner of the message.

Ø Integrity: In cryptography, the integrity of the messages must be preserved while sending the message from one host to another. This involves ensuring that the message is not altered on the way. Using cryptographic hash is a way to achieve this.

Ø  Non-repudiation

What is meant by multiplexing?

- Multiplexing or muxing is a very important process in computer networks and the telecommunications. 

Using this process, a number of digital data streams or analog message signals are combined as one signal and then transported over the common medium. 

- Multiplexing is used wherever it is required to share a resource that is very expensive. 

- The most common example of multiplexing is of using one wire for several telephone calls. 

- The origin of the multiplexing dates back to 1870s when telegraphy was started.

- Now it is used to a great extent in the field of communications. 

- The telephone carrier multiplexing was developed by George Owen Squire in the field of telephony. 

- The communication channel over which the multiplexed signal might be transmitted might be a physical transmission medium. 

- The high level communication channel’s capacity is divided by multiplexing process in to a number of low level logical channels where for each message or data stream one channel is used. 

- Demultiplexing is the reverse process of multiplexing. 

- This is used for the extraction of the original signals on the reception side.

- A multiplexer or MUX is a device that is used for carrying out the multiplexing process and the demultiplexer or DEMUX is the device that performs demultiplexing. 

- IMUX or inverse multiplexing is another process whose aim is just the opposite of the multiplexing.

- It breaks down a single data stream in to various streams while transferring them at the same time over various communication channels.

- Later, the original stream is recreated.

Types of Multiplexing

Many different types of multiplexing technologies are available today. Each has its own significance:

Ø SDM or space-division multiplexing: 

This technique implies on using different point – to – point wires for individual communication channels. For example, an audio cable of analogue stereo, multi – pair telephone cable, switched star network, mesh network. However typically the wired SDM is not usually considered as multiplexing. In SDM a phased array antenna is formed by multiple antennas. For example MIMO (multiple – input and multiple – output), SIMO (simple – input and multiple – output), MISO (multiple – input and single – output) etc.

Ø  FDM or frequency-division multiplexing: 

This is considered to be an analog process, here the signals are sent in to different frequency ranges over a shared medium. For example, TV and radio broadcasting from satellite stations through the earth’s atmosphere. One cable is given in each house but over this cable many signals can be sent to other subscribers also. For accessing the desired signal, the users require to tune to that particular frequency. WDM or wavelength division multiplexing is a variant of FDM.

Ø TDM or time-division multiplexing: 

Unlike FDM, TDM is a digital technology but very rarely it might be used as an analog technology also. The process involves putting bytes in a sequence for each input stream one by one. this sequencing is done in such a way that the receiver can appropriately  receive them. If this is done quickly, the fact that another logical communication path was served in that circuit time won’t be detected by the receiver.

Ø  CDM or code-division multiplexing: 

In this multiplexing technique, the same frequency spectrum is shared by the several channels at the same time. Also the bandwidth of the spectrum is quite high when compared to the symbol rate or the bit rate. It is implemented in either of the two forms namely direct sequence spread spectrum and frequency hopping.

Some other types of multiplexing techniques which are less prominent are:

Polarization-division multiplexing: Used in optical and radio communications.

Orbital angular momentum multiplexing

What is fragmentation?

- The fragmentation technique is implemented in the IP (internet protocol) for breaking down the datagrams into smaller pieces. 

- This is done so that it becomes easy for the data packets to be passed through the link with a datagram size smaller than that of the original MTU or the maximum transmission unit. 

- The procedure for the IP fragmentation along with the procedures for reassembling and transmitting the datagrams is given in the RFC 791. 

- For determining the optimal MTU path, the IPv6 hosts are needed so that the packets can be sent. 

- If in case the PDU i.e., the protocol data unit received by the router is larger than the MTU of the next hop, then there are two options are available if IPv4 transport is being used:

Ø Dropping the PDU and sending an ICMP (internet control message protocol) message indicating that the condition packet is quite big.

Ø  Fragmenting the IP packet and then transmitting it over the link whose MTU is smaller. Any IPv6 packet with a size less than or equal to 1280 bytes can be delivered without having the need for using the IPv6 fragmentation.

- If a fragmented IP packet is received by the recipient host, its job is to reassemble the datagram and then send it over to the protocols at the higher layers. 

- The purpose of reassembling is expected to take place at the recipient’s host side but for some practical reasons it might be done by some intermediate router. 

- For example, the fragments might be reassembled by the NAT (network address translation) for translating the data streams. 

- Excessive re-transmission can result as a consequence of the IP fragmentation whenever packet loss might be encountered by the fragments. 

- It is required for all the reliable protocols (example, TCP) for re-transmitting the fragments in their correct order for recovering from the single fragment loss. 

Thus, typically two approaches are used by the senders for determining datagrams of what size should be transmitted over the network:

1. First approach: The sender must transmit an IP datagram of size as same as that of the first hop’s MTU.
2. Second approach: Running the path MTU discovery algorithm.

- Fragmentation does leave an impact on the network forwarding. 

- When there are multiple parallel paths for the internet router the traffic is split by the technologies such as the CEF and LAG throughout the links via some hash algorithms. 

- The major goal of this algorithm is to make sure that all the packets with the same flow are transmitted out on the same path for the minimization of the not so required packet reordering. 

- If the TCP or UDP port numbers are used by the hash algorithm, the fragmented packets might be forwarded through different paths. 

- This is so because the layer 4 information is contained only in the first fragment of the packet. 

- As a result of this, usually the initial fragment arrives after the non-initial fragments. 

- This condition is often treated as an error by most of the security devices in the hosts.  

- Therefore, they drop these packets.

- The fragmentation mechanism differs in IPv4 and IPv6. 

- In the former, the fragmentation is performed by the router. 

- On the other hand, in IPv6 fragments that are larger than MTU are dropped by the routers.

- Also, in both the cases there is a variation in the header format. 

- Since fragmentation is carried out using analogous fields, therefore the algorithm can be used again and again for the purpose of fragmentation and reassembling. 

- A best effort should be made by the IPv4 hosts for reassembling the datagram fragments. 

Explain Border Gateway Protocol (BGP)?

- BGP or Border gateway protocol is the set of rules that is implemented for making the routing decisions at the core of the internet. 

- It involves the use of the IP networks table or we can say prefixes which are used for designating the reach-ability of the network to the autonomous systems. 

- This protocol falls under the category of the path vector protocol or sometimes classified as a variant of the distance vector routing protocols. 

- The metrics of the IGP or the interior gateway protocol are not used by the border gateway protocol rather paths, rule sets or polices are used for making decisions for routing. 

- This is why the border gateway protocol is often called a reach-ability protocol rather than being termed as a routing protocol. 

- The BGP has ultimately replaced the EGP or the exterior gateway protocol. 

- This is so because it allows the full decentralization of the routing process for making transition between the ARPANET model’s core and the decentralized system that consists of a NSFNET backbone and the regional networks associated with it. 

- The present version of the BGP that is being used is the version 4. 

- The earlier versions were discarded for being obsolete. 

- The major advantage is of the classless inter-domain routing and availability of a technique called the route aggregation for making reductions in the routing size. 

- The use of the BGP has made the whole routing system a decentralized system.

- BGP is used by most of the internet service providers for establishing a route between them. 

- This is done especially when the ISPs are multi-homed. 

- That’s why even though it is not used directly by the users; it is still one of the most important protocols in networking. 

- The BGP is used internally by a number of large private IP networks. 

- For example, it is used to combine many large open shortest path first or OSPF networks where these networks do not have the capability to scale to the size by themselves. 

- BGP is also used for multi-homing a network so as to provide a better redundancy. 

- This can be either to many ISPs or to a single ISP’s multi access points. 

- Neighbors of the border gateway protocol are known as the peers. 

- They are created by manually configuring the two routers so as to establish a TCP session on the port. 

- Messages called the 19 byte keep alive messages are sent to the port periodically by the BGP speaker for maintaining the connection. 

- Among the various routing protocols, the most unique is BGP since it relies up on TCP for transporting. 

- When the protocol is implemented in the autonomous system among two peers, it is called IBGP or the internal border gateway protocol. 

- The protocol is termed as the EBGP or the external border gateway protocol when it runs between many autonomous systems.

- Border edge routers are the routers that are implemented on the boundary for exchanging information between various autonomous systems.

- BGP speakers have the capability for negotiating with the session’s option capabilities such as the multi-protocol extensions and a number of recovery modes. 

- The NLRI (network layer reach-ability information) can be prefixed by the BGP speaker if at the time of the creation itself, the multi-protocol extensions are negotiated. 

- The NLRI is advertised along with some address family prefix. 

The family consists of the following:

Ø  IPv4

Ø  IPv6

Ø  Multicast BGP

Ø  IPv4/ IPv6 virtual private networks

- These days the border gateway protocol is being commonly employed as the generalized signaling protocol whose purpose is to carry information via the routes that might not form the global internet’s part. 

Explain multicast routing?

- Multicast routing is also known as the IP multicast. 

- For sending the IP (internet protocol) data-grams to a group of receivers who are interested in receiving the data-grams, multicast routing is used.

- The data-grams are sent to all the receivers in just one transmission. 

- Multicast routing has got a special use in the applications that require media streaming on private networks as well as internet. 

- Multicast routing is IP specific version. 

- A more general version is the multicast networking.

- Here, the multicast address blocks are especially reserved in IPv6 and IPv4. 

- Broadcast addressing has been replaced by multicast addressing in IPv6. 

- Broadcast addressing was used in IPv4. 

- RFC 1112 describes the multicast routing and in 1986 it was standardized. 

This technique is used for the following types of real – time communication over the IP infrastructure of the network:

Ø  Many – to – many

Ø  One – to – many

- It scales up to receiving population that is large enough and it does not require either knowledge regarding the receivers and the identity of the receivers. 

- Network infrastructure is used efficiently by the multicast efficiently and requires source sending packet to a large number of receivers only once. 

- The responsibility of the replication of the packet is of the nodes which are nothing but the routers and the network switches.

- The packet has to be replicated till it reaches the multiple receivers. 

- Also, it is important that the message is sent only once over the link.   

- UDP or the user data gram protocol is the mostly used protocol of low level. 

- Even though if this protocol does not guarantees reliability i.e., the packets might get delivered or get lost. 

- There are other multicast protocols available that are reliable such as the PGM or the pragmatic general multicast. 

It has been developed for adding the following two things a top the IP multicast:

Ø  Retransmission and

Ø  Loss detection

The following 3 things are key elements of an IP multicast:

1. Receiver driven tree creation
2. Multicast distribution tree
3. IP multicast group address

- The receivers and the sources use the last for sending as well as receiving the multicast messages. 

- The group address serves as the destination address of the data packets for the sources whereas it is used for informing the network whether or not the receivers want those packets.

- Receivers need a protocol for joining a group. 

- One most commonly used protocol for this purpose is the IGMP i.e., the internet group management protocol. 

- The multicast distribution trees are set up using this protocol. 

- Once a group has been joined by the receiver, the PIM (protocol independent multicast) protocol is used for constructing a multicast distribution tree for this group. 

- The multicast distribution trees set up with the help of this protocol are used for sending the multicast packets to the members of the multicast group. 

PIM can be implemented in any of the following variations:

1. SM or sparse mode
2. DM or dense mode
3. SSM or source specified mode
4. SDM or sparse – dense mode or bidirectional mode (bidir)

- Since 2006, the sparse mode is the most commonly used mode. 

- The last two variations are more scalable and simpler variations of PIM and are also popular. 

- An active source is not required for carrying out an IP multicast operation and knowing about the group’s receivers. 

- The receiver drives the construction of the IP multicast tree. 

- The network nodes which lie closer to receiver are responsible for initiating this construction.

- This multicast then scales to a receiver population that is large enough. 

- It is important for a multicast router to know which all multicast trees can be reached in the network. 

- Rather, it only requires knowledge of its downstream receivers. 

- This is how the multicast – addressed services can be scaled up. 

What is meant by multi-destination routing?

- So many routing algorithms have been devised to aid in routing under different conditions.
- Effective routing algorithms have been developed that are capable of routing the messages from one source node to a number of receiving nodes i.e., the multiple destination nodes.
- These algorithms are termed as the multi – destination routing algorithms and the process is therefore called as the multi – destination routing.
- This type of routing has been developed for the minimization of the cost of the network i.e., NC (network cost).
- Network cost can be defined as the sum of all the links’ weights that consist of the routing path.
- There are many heuristic algorithms available for determining the NC min path.
- This problem falls under the category of the NP – complete problems.
- Heuristics are available for the traveling salesman problem and MST (minimum spanning tree) variations.
- Global information is used by both of them.
- Another set of such heuristics is available that uses only shortest paths for reaching the destinations.
- The best worst case performance is exhibited by the MST algorithm.
- However, one study revealed that effectiveness of the simpler heuristics is higher.
- The network cost (NC) is often compared with the destination cost (DC).
- Destination cost is the sum of the cost of all the shortest paths that lead to the destination.
- A scheme of algorithms has been developed for trading off between these two costs i.e., the NC and DC.  
- The sender of the transmitted data cannot be taken as a single node in a network where the cooperative communication is supported.
- This asks for the re-investigation of the traditional link concept.
- Any routing scheme thus depending up on this link concept needs to be reconsidered.
- Also, the potential performance gain resulting because of the cooperative communication needs to be exploited.

- Routing often gets complicated for some networks where the selection of the paths is no longer the job of a single entity.
- Rather, a number of entities are involved in the selection of the paths.
- Multiple entities can even select specific parts of a path.
- If these selected paths are chosen by the entities for their own objectives optimization then it can lead to inefficiency or serious complications in the network since they may or may not conflict with the other entities’ objectives.
- This would become clear from the following example, consider traffic moving in a system of roads.
- Now here each driver selects a path that would minimize only his/her traveling time.
- In this kind of routing, there are longer equilibrium routes (i.e., longer than the optimal.) for almost all other drivers.
- This is often termed as the Braess paradox.
- Another example is of the routing the AGVs (automated guided vehicles) by a model on some terminal.
- For prevention of the simultaneous usage of the infrastructure’s same part reservations are made. - This is called as the context – aware routing.
- The internet is divided in to a number of divisions which are nothing but Ass i.e., the autonomous system like ISPs.
- All these systems have control over the routes that lie in their own network at various different levels.

Following steps are involved in multi – destination routing:
1. The BGP protocol is used for selecting the AS – level paths.
2. A sequence of autonomous systems is produced by the BGP protocol via which the packet flow will take place.
3. The neighboring Ass offer multiple paths for each of the AS from which it can choose. Paths are selected based up on the relationships between the neighboring systems.
4. Each selected path refers to multiple corresponding router level paths.

What are applications of flooding algorithm?

- Flooding algorithm and its many other variants are used as material distributing algorithm.

- This algorithm distributes the messages to all the hosts in the entire graph. 

- This algorithm since it acts like a flood and therefore has been named so. 

- In this simple yet useful distribution or routing algorithm, every packet that a node receives is transmitted to every other outgoing link. 

This algorithm is available in many variants but in every variant the following two things are common:

1. Each node acting as receiver and transmitter.

2. Each node responsible for forwarding received message to all its neighboring nodes except the one from which the message came. 

- Thus, the messages are eventually delivered to the hosts spread across the network. 

- Flooding algorithm might have been more useful if it would have been more complex. 

- Also, then it would have been possible to avoid the duplicate messages and infinite loops that occur because of them. 

Applications of Flooding Algorithm

In this article we list some of the application of the flooding algorithm.

1. Used in computer networking

2. Used in graphics

3. These algorithms are quite useful for solving numerous mathematical problems such as the maze problems.

4. Used for solving problems in the graph theory. 

5. Used in systems which make use of bridging. 

6. Used in systems like usenet.

7. Implemented in peer – to – peer file sharing

8. Flooding algorithms are often implemented as a part of some of the routing protocols as in OSPF, DVMRP and so on. 

9. It is also used in the protocols used in the ad hoc wireless networks.

10.There is a variant of flooding algorithm called the selective flooding which is capable on addressing various issues of flooding algorithm partially by allowing the packets to be sent only in the appropriate right direction. The packets are not sent on each and every line. 

11. Another variant of the flooding algorithm called the similarity algorithm is used graph matching algorithm. 

- This variant of the flooding algorithm is quite versatile and has got an application in the schema matching. 

- Matching the contents of the two data schemas has got an important role to play in many biochemical applications, e – business and other data warehousing applications etc. 

- The similarity flooding algorithm is based on a computation that is fixed and can be used across a number of scenarios. 

- Two graphs are passed to the algorithm as the input parameters. 

- These graphs might be of catalogs, schemas or even data structures etc. 

- The algorithm then produces a mapping between the corresponding nodes of the two graphs as output. 

- It depends on the goal of the matching what subset of the mapping has to be chosen using filters. 

- After the algorithm has been executed, a human tester is expected is expected to check and verify the results. 

- The results might be adjusted by the tester if required. 

- In this method, the accuracy of the algorithm is evaluated by number of the adjustments that are necessary.

- In some cases, an accuracy metric might be used for the estimation of the labor savings that could be obtained by the users by means of this similarity flooding algorithm for obtaining a first matching pair.

- Finally, this algorithm can be deployed as an operator of very high level in a test bed that has been implemented for the management of the output mappings and the information models. 

- There are different types of matching problems and thus each type requires following a different approach. 

- For example, the relational schemas can only be matched using SQL data types.

Flooding - a kind of static algorithm

An algorithm designed for the distribution of the material to each and every part of the graph is referred to as the flooding algorithm. 

- The algorithm has got its name from the concept that involves inundation caused by a flood. 

- The main application of these algorithms is in graphics and computer networking. 

- These algorithms also come very handy in solving a number of mathematical problems. 

- Examples of such problems that are graph theory problems, maze problems and so on. 

- Flooding algorithm though it sounds complicated is quite a simple one. 

- Here, every incoming packet is sent via every outgoing link. 

- Only the link through which the packet arrived is saved. 

This algorithm has many applications in the following:

1. Systems that require bridging, systems like use net.
2. Peer to peer file sharing.
3. Used as a part of the routing protocols such as the DVMRP, OSPF etc.
4. Used in protocols used for the adhoc wireless networks.

Nowadays the flooding algorithm is available with its many variants. The following are two main steps that each variant follows while working:

1. Each node in the network might act as both receiver and the transmitter.
2. The incoming message is forwarded by the receiving node to each of its neighboring nodes except the one which is the source code.

- This causes the message to be delivered to each and every part of the network that is reachable. 

- Algorithms are required as a precaution for avoiding the wastage of the infinite loops and the duplicate deliveries and for allowing the messages for expiring. 

- All these issues are addressed partially by a variant of the flooding algorithm called the selective flooding.

- The usual flooding algorithm sends the packets to all the routers that lie in the same direction. 

- But the selective flooding algorithm does not send the packet to each router rather it selects only few of them which lie in the right direction approximately. 

Advantages and Disadvantages of Flooding Algorithm

Advantages:

1. If it is possible for delivering the packet, it will be delivered but a number of times.
2. In flooding algorithm every path in the network is naturally utilized and so the shortest path is also used.
3. The implementation of the flooding algorithm is quite simple.

Disadvantages:

1. The cost of the flooding algorithm can be very high because a lot of bandwidth is wasted. Even if there is one destination of the message, it will be sent to all the hosts on the network unnecessarily. If in case there occurs a denial of service attack or a ping flood, the reliability of the whole network will be affected badly.
2. In the computer network, the message might get duplicated. This in turn can increase the load on the bandwidth of the network. This will call for increasing the complexity of the processing for rejecting the duplicates of the messages.
3. The packets that are duplicate might keep on circulating forever, if the following precautions are not taken:

Ø  Using a time to live count or a hop count to be included with every packet. The value of the count has to include the number of the nodes through which the packets have to be passed while on the way to destination.

Ø  Each and every node should be used for keeping track of every packet that passes through it and a packet should be forwarded only once.

Ø  The network topology must be enforced without any loops. 

What is a routing algorithm in network layer?

About Routing

- The process of path selection in the network along which the data and the network traffic could be send is termed as routing. 

- Routing is a common process carried out in a number of networks such as the transportation networks, telephone networks (in circuit switching), electronic data networks (for example, internet). 

- The main purpose of routing is to direct the packet forwarding from source to its destination via the intermediate nodes. 

- These nodes are nothing but hardware devices namely gateways, bridges, switches, firewalls, routers and so on. 

- A general purpose system which does not have any of these specialized routing components can also participate in routing but only to a limited extent.

But how to know where the packets have to be routed? 

- This information about the source and the destination address is found in a table called the routing table which is stored in the memory of the routers. 

- These tables store the records of routers to a number of destinations over the network. 

- Therefore, construction of the routing tables is also an important part of efficient routing process. 

- Routing algorithms are used to construct this table and for selecting the optimal path or route to a particular destination. 

- A majority of the routing algorithms are based on single path routing techniques while few others use multi-path routing techniques. 

- This allows for the use of other alternative paths if one is not available. 

- In some, the algorithm may discover equal or overlapping routes. 

- In such cases the following 3 basis are considered for deciding up on which route is to be used:

1. Administrative distance: This basis is valid when different routing protocols are being used. It prefers a lower distance.
2. Metric: This basis is valid when only one routing protocol is being used throughout the networks. It prefers a low cost route.
3. Prefix-length: This basis does not depends on whether the same protocol is being used or there are many different protocols involved. It prefers the longer subnet masks.

Types of Routing Algorithms

Distance Vector Algorithms: 

- In these algorithms, the basic algorithm used is the “Bellman – Ford algorithm”. 

- In this approach, a cost number is assigned to all the links that exist between the nodes of a network.

- The information is send by the links from point A to point B through the route that results in the lowest total cost.

- The total cost is the sum of the costs of all the individual links in the route. 

- The manner of operation of this algorithm is quite simple.

- It checks from its immediate neighboring nodes that can be reached with the minimum cost and proceeds.

Link-state Algorithms: 

- This algorithm works based up on the graphical map of the network which is supplied as input to it. 

- For producing this map, each of the nodes assembles the information regarding to which all nodes it can connect to in the network. 

- Then the router can itself determine which path has the lowest cost and proceed accordingly. 

- The path is selected using standard path selection algorithms such as the Dijkstra’s algorithm. 

- This algorithm results in a tree graph whose root is the current node. 

- This tree is then used for the construction of the routing tables.

Optimized link state Routing Algorithm: 

- This is the algorithm that has been optimized to be used in the mobile ad-hoc networks. 

- This algorithm is often abbreviated to OLSR (optimized link state routing). 

- This algorithm is proactive and makes used of topology control messages for discovering and disseminating the information of the link’s state via mobile ad-hoc network.