The Performance Of Tcp Protocol And Security

Published Date: 02 Nov 2017

Wireless Mesh Network consists of mesh routers, mesh clients with Gateway. The function of Gateway is to serve as an access point between two different routers. It is not possible for each client to directly access the other router in the existing methods, which is possible in the case of Wireless Mesh Networks. The static Mesh router is the heart of WMNs and the mesh clients access the networks through mesh routers. The TCP protocol is the best protocol in case of wired networks very widely used in Internet Applications. The congestion loss in wired networks can be rectified by slow start threshold method. In case of wireless networks congestion loss creates damage to the system. The high packet loss causes TCP to respond slowly. A new method is proposed based on the integration of Virtual queue method with Network Coding. The goal of this paper is divided in to two modules 1.)Security is achieved based upon NC method 2.)Virtual queue based method is at the MAC layer in order to improve TCP performance. A new Architecture is proposed by the combination of these two modules which improves the TCP performance and security of the Network is also improved. Through some experiments the efficiency of the protocol is improved by comparing with the existing methods.

Introduction:

About the median filter:

Previously in TCP, retransmission time out (RTO) is implemented by using Jacobson algorithm. For estimation of RTT, Jacobson algorithm uses the EWMA (exponential weighted moving average) filter. For Gaussian distribution EWMA is very good. But in reality EWMA filter is not sufficient to estimate heavy-tailed distribution. But for eliminate positive and negative impulses median filter is good in image processing. For better results in heavy-tailed distribution we are using median filters.

In this paper, for transmission time out estimation we are applying the median filter on network simulations in heavy traffic.

About Optimal carrier sense multiple access:

Before going to know about the optimal carrier sense multiple access (OCSMA), we have to know about what is carrier sense multiple access (CSMA) and why we are using? For this question the best answer to all is that the CSMA is a basic protocol that used to transmits the data from sender to receiver. Because of this simple and distributed feature it becomes the most practical medium access control (MAC) in wireless networks. If we smartly changes the parameters like back-off time and holding time of a carrier sensing multiple access it becomes the most favourable in throughput and utility. That's why the name called Optimal Carrier Sensing Multiple Access.

About virtual queuing scheme:

A mechanism developed to ensure that the TCP flow link is scheduled less than others, the transmission intensity increased respectively. So the starvation loop is escaped by the transmission flow. Due to coupling of the MAC layer and TCP results poor TCP. Hence to decouple the MAC layer and the TCP the new counter is introduced named virtual queuing scheme. It is used to find the parameters of 0CSMA by using virtual length.

About Network Coding:

NC combines several packets and forms as a single packet. The main use of Network coding is it provides the network from being vulnerable. The incoming packets are encoded by using encryption technique. Public key and private key is assigned for each sender and receiver and the packets are encoded in X-or fashion. The destination node decodes these incoming packets by using decryption algorithm. The original packets are after received after decoding are placed in a Buffer.

Literature Survey:

Wireless Mesh Networks are the emerging technology in the Network environment. The main advantage of WMNs is, it gives better results than wired networks in cost efficient way. Though it gives better results, it suffers from lots of challenges such as interference of radio technologies, security of the Network, scalability, mobility etc… The main drawback of WMNs is the TCP protocol which is very useful for providing the Internet access doesn’t possess good results in wireless environment when compared to wired networks.

TCP protocol in wired network:

TCP protocol is connection oriented protocol. TCP has two process

Sliding window mechanism 2.congestion control mechanism

Sliding window mechanism:

This method has a sequential control between sender and receiver process i.e. control over data flow between sender and receiver. Sender sends data packets, it doesn’t wait for the ACK signal from the receiver. Receiver transfers the packets to the transmitter by acknowledging the packets from the sender. Number of packets delivered to the transmitter depends upon the window size. This method changes depending upon the quality of the Network.

Congestion Control Mechanism:

The main reason for packet loss in the network is due to congestion in the network. The main reason for congestion is network traffic. The congestion control depends upon the slow start threshold value.

TCP in wireless domain:

The Transmission Control Protocol (TCP) has several drawbacks such as networks resources suffers from proper allocation, inaccurate congestion control mechanism, novel based protocols.

The following are the advanced technologies that are undergoing currently on TCP protocol:

1. Advanced transport protocol design:

The TCP protocol used in a particular network, same is not useful for the integration of other networks. To implement different protocols for various networks is highly impossible task.

2. Cross layer Design:

Solving only Transport layer problems is not a good idea for TCP protocol because it depends upon the lower layers. So the improvement in lower layers optimize the drawbacks.

Some methods has already been proposed to improve the performance of TCP protocol in wireless networks such as Virtual queue based method, median filtering method, network coding method.

Existing system:

Three methods has taken in to consideration from several methods and their drawbacks have been proposed.

Virtual queue based method

Median Filtering method

Network coding method

Virtual queue based method:

A virtual queue is presented at the MAC layer such that it reduces middle link starvation problem in the Mesh Network. It integrates the actual MAC layer and TCP dynamics.

Advantages:

Middle link starvation problem is reduced.

It resolves the problem of TCP over OCSMA.

Fair allocation of network resources

Throughput is increased to a maximum level than normal OCSMA

Disadvantages:

There are more chances for attacks in the network. So security is the major factor.

Packets may loss in the transmission when sending from one node to another node.

Network coding method:

Several packets are encoded and forms as a single packet, the destination node decodes the encoded packets and place the original packets in a buffer. Encryption and Decryption algorithms are used for encoding and decoding of the transmission packets.

Advantages:

Session-key is shared successfully as on-demand fashion.

There is no leakage while sharing the session keys-efficient sharing of session keys.

Security is achieved-less vulnerable to attacks.

Disadvantages:

Security is achieved but network resources are not utilized properly.

Packets may loss when there is any link failure.

Median Filtering method:

Median filtering method is used to calculate the retransmission time and reduce impulse noise in burst traffic by using Jacobson algorithm

Advantages:

To reduce impulsive noise when the data is transmitted.

Which reduces the packet losing

Reducing the retransmission timeout estimation.

Disadvantage:

There is chance of invisible noise to occur

Proposed system:

A new method is proposed by integrating the existing methods and an efficient solution is proposed in which it reduces the drawbacks in the existing methods.

A

D

F

C

B

K

P1 p2 p3

(p1 x-or p2 x-or p3)

P1 p2 p3

E:

Fig: 1

A, B, C-Source nodes

D, E, F-Destination nodes

Actual Queue Virtual Queue

Sn[t] Sn[t]

To achieve high data throughput is a high concern in wireless networks. Network coding has a major security drawback. To overcome this drawback ANOC is implemented by using ONION routing protocol. In this, as the name suggests ONION having different layers and we can peel of the each layer separately. The same manner is using here, first we broadcast or encrypt the all the packets and destination takes the packets of upper layer and sends to the next destination. In fig: 1 shows, a node A need to sends a packet to D, and B need to sends a packet to node E and node C need to sends a packet to node F. Without network coding, the communication cost will high in total of six transmissions: (1)A sends P1 to k, (2) K forward to D, (3)B sends P2 to K, (4) K forward to E, (5)C sends P3 to k, (6) K forward to F. With the network coding the node K only needs to broadcast A Ex-or B Ex-or C the packets which are coming from nodes A,B and C. In this the transmission can be saved at K.

Not only transmission, in addition to that privacy preservation is also an important issue in wireless networks. In the previous papers, they used OCSMA to improve the TCP. The main disadvantage of TCP is that with TCP, even though lot of scheduling algorithms would not be able to increase its queue length, which is for starved links. This is because window based congestion control in TCP, which is using ACK clocking for generation of packets. A mechanism developed to ensure that the TCP flow link is scheduled less than others, the transmission intensity increased respectively. So the starvation loop is escaped by the transmission flow. Due to coupling of the MAC layer and TCP results poor TCP. Hence to decouple the MAC layer and the TCP the new counter is introduced named virtual queuing scheme. It is used to find the parameters of 0CSMA by using virtual length. This virtual queue method is used at MAC layer to improve TCP performance than the OCSMA.

Previously in TCP, retransmission time out (RTO) is implemented by using Jacobson algorithm. For estimation of RTT, Jacobson algorithm uses the EWMA (exponential weighted moving average) filter. For Gaussian distribution EWMA is very good. But in reality EWMA filter is not sufficient to estimate heavy-tailed distribution. But for eliminate positive and negative impulses median filter is good in image processing. For better results in heavy-tailed distribution we are using median filters.

In this paper, for transmission time out estimation we are applying the median filter on network simulations in heavy traffic.

Estimation of RTT problem:

Previous we have Jacobson algorithm to find the difference between the old estimated and the sample RTT.

X=Si-1-Oi-1

Where O is the old estimated RTT

S is the sample RTT

Next to find the new estimated RTT

Ni=Oi-1+K(X)

Where K is constant which is equal to 1/8

And G is the prediction error is some of the following errors

Noise measurement error, which is unpredictable. Which denote this part as En.

Poor choice of A and this part is denote as Ep.

Error rate is calculated by using Virtual Queue based method:

Vqn[t+1]=[vqn[t] + L/ vqn[t] –Sn[t]]

Where,

L-Positive control parameter

L/ vqn[t]-amount of incoming packets

Error rate=> pn[t+1]*mn[t+1]=exp(d* Vqn[t+1])

Throughput of the network is calculated by:

Throughput,α=(8*f*g/ Ni*(Error rate))

Results:

The below table shows the calculation of New estimated RTT:

Sample RTT

S i-1

Old Estimated

RTT(O i-1)

X= S i-1-O i-1

New Estimated

RTT (Ni= O i-1+K(X))

1.5

1

0.5

1.0625

1.3

0.7

0.6

1.0075

1.2

0.5

0.7

1.0875

Table: a

Calculation of Error rate:

Vqn[t]

L/vqn[t]

Sn[t]

Vqn[t+1]

Error Rate

1

500

400

101

0.707

2

250

100

152

1.064

3

166.66

50

119.66

0.837

Calculation of TThroughput by virtual queue based method and proposed method:

Sample RTT

New Estimated

RTT

Sqrt(Error rate)

Throughput1

Throughput2

1.5

1.0625

0.84

6507.93

9187.63

1.3

1.0075

1.03

6123.97

7901.90

1.2

1.0875

0.91

7509.15

8285.96

Conclusion:

The results shows that the proposed method shows increase in throughput by comparing with existing methods. Security of the network is achieved by using network coding. The number of resources are allocated in a sequential manner. By using the virtual queue based method the performance of TCP has improved. Our results shows that when compared to the virtual queue based method, the performance of TCP protocol has improved. Some invisible noise may occur when data transfer between source and destination. This shows some decrement in throughput, but this factor is negligible since security is achieved.