Although IPv4 is still working, IPv6 is considered as the backbone and characteristic of the NGI. With the
development of Internet, new protocols and network equipments are required to develop. It is necessary to test the new
protocols and network equipments extensively before deployment. This paper proposes the design and implementation of
RENEW, a useable and accurate network emulator which supports both IPv4 and IPv6 protocols. Besides, it also works
on Windows platform. In our IPv6 testbed, we use RENEW to emulate various network characteristics and conditions
including bandwidth, delay packet loss and jitter. Compared with the expected values, results are acceptable. Through
implementation and experimentation study, we have shown that RENEW does provide the real-time control and change
on the parameters of IPv6 network conditions effectively and expediently on Windows. It also gives enough accuracy
and more satisfactory convenience to the development and test work for the new protocols.
Load distribution across multiple parallel paths is an important consideration. In many practical contexts, the aggregate traffic from source to sink may be such that no single link can carry the load. In an MPLS domain, this problem can be addressed by instantiating multiple paths. The main objective of this paper balances traffic at the flow level among the parallel Label Switched Paths (LSPs) in MPLS networks. Different from other proposals, our new framework is based on the distributable traffic (DT), where cross-traffic in real networks is considered, and each LSP is modeled as an M/G/1 processor-sharing queue. We define a flow to be a sequence of packet having the same identifier, and dispatch packet belonging to one flow to the same path, so the packet disorder problem is avoided effectively. This mechanism only needs to be implemented in the ingress LSRs and the egress LSRs. A new defined cost function is being used to distribute traffic to path. We computer the cost function based on the delay and packet loss of each LSPs, and minimize the cost function. The minimized cost function is inverse ratio to DT. If the cost function of a certain LSP is smaller, it means that more traffic can be distributed on this LSP. Extensive simulations using NS2 are performed with MPLS modules. Simulation results show that our approach so effective that the throughput is increased significantly and reduces the end-to-end delay and the packet drop rate, and it can distribute the traffic onto parallel LSPs more evenly and fairly.
As the use of streaming media applications increased dramatically in recent years, streaming media security
becomes an important presumption, protecting the privacy. This paper proposes a new encryption scheme in view of
characteristics of streaming media and the disadvantage of the living method: encrypt the control message in the
streaming media with the high security lever and permute and confuse the data which is non control message according
to the corresponding control message. Here the so-called control message refers to the key data of the streaming media,
including the streaming media header and the header of the video frame, and the seed key. We encrypt the control
message using the public key encryption algorithm which can provide high security lever, such as RSA. At the same time
we make use of the seed key to generate key stream, from which the permutation list P responding to GOP (group of
picture) is derived. The plain text of the non-control message XORs the key stream and gets the middle cipher text. And
then obtained one is permutated according to P. In contrast the decryption process is the inverse process of the above.
We have set up a testbed for the above scheme and found our scheme is six to eight times faster than the conventional
method. It can be applied not only between PCs but also between handheld devices.
With the fast development of ad hoc networks, SIP has attracted more and more attention in multimedia service. This paper proposes a new architecture to provide SIP service for ad hoc users, although there is no centralized SIP server deployed. In this solution, we provide the SIP service by the introduction of two nodes: Designated SIP Server (DS) and its Backup Server (BDS). The nodes of ad hoc network designate DS and BDS when they join the session nodes set and when some pre-defined events occur. A new sip message type called REGISTRAR is presented so nodes can send others REGISTRAR message to declare they want to be DS. According to the IP information taken in the message, an algorithm works like the election of DR and BDR in OSPF protocol is used to vote DS and BDS SIP servers. Naturally, the DS will be replaced by BDS when the DS is down for predicable or unpredictable reasons. To facilitate this, the DS should register to the BDS and transfer a backup of the SIP users' database. Considering the possibility DS or BDS may abruptly go down, a special policy is given. When there is no DS and BDS, a new election procedure is triggered just like the startup phase. The paper also describes how SIP works normally in the decentralized model as well as the evaluation of its performance. All sessions based on SIP in ad hoc such as DS voting have been tested in the real experiments within a 500m*500m square area where about 30 random nodes are placed.
Real-time video transmission over ad hoc networks faces many challenges including low bandwidth, long end-to-end
delay, high packet loss rate, frequently changing topology and limited-powered mobile nodes. This paper presents an
effective real-time video transmission scheme and improves implementation of DSR (Dynamic Source Routing)
protocol. We set up a test-bed by using DSR routing in the IP layer, and an application transmitting video stream over
UDP protocol. We get a continuous JPEG image stream from a ZC0301p web camera and split each image into small
blocks according to the MCU (Minimum Coding Unit) borderline. The strong point of splitting JPEG image is that IP
layer fragmentation can be avoided so we can determine which part of data in the frame gets lost to do loss recovery at
the receiver. By using JPEG image stream, the video encoding complexity is reduced, which can save computing power
of mobile nodes compared with MPEG and other Multiple Description Coding (MDC) methods. We also improve
implementation of DSR to make it suitable to transfer real-time multimedia data. First different priorities are given to
different traffic classes in DSR routing. Second the route maintenance scheme is modified to decrease overhead and link
failure misjudgments. We carry out two experiments both indoors and outdoors using six mobile nodes. The first is to
transmit continuous JPEG images using our former DSR implementation according to DSR draft. The second is that we
split JPEG images into blocks and then transmit them using improved DSR implementation. Results show the latter
gives better video stream fluency and higher image quality.
The dynamic load meter with MCS-51 used as micro processor, with pressure sensor as measurement
element has many features such as low cost, multifunction, movability, etc. Being a new powerful
tool for modernization of both the traffic supervision and control, it can measure the loads of
moving vehicles and record the traffic statistical figures,
The theory of the dynamic traffic supervision and software progranning method is described in
this paper in detail,
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