50,926 research outputs found
Proactive TCP mechanism to improve Handover performance in Mobile Satellite and Terrestrial Networks
Emerging standardization of Geo Mobile Radio (GMR-1) for satellite system is
having strong resemblance to terrestrial GSM (Global System for Mobile
communications) at the upper protocol layers and TCP (Transmission Control
Protocol) is one of them. This space segment technology as well as terrestrial
technology, is characterized by periodic variations in communication properties
and coverage causing the termination of ongoing call as connections of Mobile
Nodes (MN) alter stochastically. Although provisions are made to provide
efficient communication infrastructure this hybrid space and terrestrial
networks must ensure the end-to-end network performance so that MN can move
seamlessly among these networks. However from connectivity point of view
current TCP performance has not been engineered for mobility events in
multi-radio MN. Traditionally, TCP has applied a set of congestion control
algorithms (slow-start, congestion avoidance, fast retransmit, fast recovery)
to probe the currently available bandwidth on the connection path. These
algorithms need several round-trip times to find the correct transmission rate
(i.e. congestion window), and adapt to sudden changes connectivity due to
handover. While there are protocols to maintain the connection continuity on
mobility events, such as Mobile IP (MIP) and Host Identity Protocol (HIP), TCP
performance engineering has had less attention. TCP is implemented as a
separate component in an operating system, and is therefore often unaware of
the mobility events or the nature of multi-radios' communication. This paper
aims to improve TCP communication performance in Mobile satellite and
terrestrial networks.Comment: 5 pages, 2 figure
Performance of TCP/UDP under Ad Hoc IEEE802.11
TCP is the De facto standard for connection oriented transport layer
protocol, while UDP is the De facto standard for transport layer protocol,
which is used with real time traffic for audio and video. Although there have
been many attempts to measure and analyze the performance of the TCP protocol
in wireless networks, very few research was done on the UDP or the interaction
between TCP and UDP traffic over the wireless link. In this paper, we tudy the
performance of TCP and UDP over IEEE802.11 ad hoc network. We used two
topologies, a string and a mesh topology. Our work indicates that IEEE802.11 as
a ad-hoc network is not very suitable for bulk transfer using TCP. It also
indicates that it is much better for real-time audio. Although one has to be
careful here since real-time audio does require much less bandwidth than the
wireless link bandwidth. Careful and detailed studies are needed to further
clarify that issue.Comment: 9 pages, 5 figures, ICT 2003 (10th International Conference on
Telecommunication
On the Trade-off Between Spectrum Efficiency with Dedicated Access and Short End-to-End Transmission Delays with Random Access in DVB-RCS2
This paper analyses the performance of TCP over random and dedicated access methods in the context of DVB-RCS2. Random access methods introduce a lower connection delay compared to dedicated methods. We investigate the potential to improve the performance of short flows in regards to transmission delay, over random access methods for DVB-RCS2 that is currently under development. Our simulation experiments show that the transmission of the first ten IP datagrams of each TCP flow can be 500 ms faster with random access than with dedicated access making the former of interest to carry Internet traffic. Such methods, however, are less efficient in regards to bandwidth usage than dedicated access mecanisms and less reliable in overloaded network conditions. Two aspects of channel usage optimization can be distinguished: reducing the duration of ressource utilization with random access methods, or increasing the spectrum efficiency with dedicated access methods. This article argues that service providers may let low-cost users exploit the DVB-RCS2 to browse the web by introducing different services, which choice is based on the channel access method
Off-Path TCP Exploits of the Mixed IPID Assignment
In this paper, we uncover a new off-path TCP hijacking attack that can be
used to terminate victim TCP connections or inject forged data into victim TCP
connections by manipulating the new mixed IPID assignment method, which is
widely used in Linux kernel version 4.18 and beyond to help defend against TCP
hijacking attacks. The attack has three steps. First, an off-path attacker can
downgrade the IPID assignment for TCP packets from the more secure
per-socket-based policy to the less secure hash-based policy, building a shared
IPID counter that forms a side channel on the victim. Second, the attacker
detects the presence of TCP connections by observing the shared IPID counter on
the victim. Third, the attacker infers the sequence number and the
acknowledgment number of the detected connection by observing the side channel
of the shared IPID counter. Consequently, the attacker can completely hijack
the connection, i.e., resetting the connection or poisoning the data stream.
We evaluate the impacts of this off-path TCP attack in the real world. Our
case studies of SSH DoS, manipulating web traffic, and poisoning BGP routing
tables show its threat on a wide range of applications. Our experimental
results show that our off-path TCP attack can be constructed within 215 seconds
and the success rate is over 88%. Finally, we analyze the root cause of the
exploit and develop a new IPID assignment method to defeat this attack. We
prototype our defense in Linux 4.18 and confirm its effectiveness through
extensive evaluation over real applications on the Internet
Tools and Techniques for Simplifying the Analysis of Captured Packet Data
Students acquire an understanding of the differences between TCP and UDP (connection-oriented vs. connection-less) data transfers as they analyze network packet data collected during one of a series of labs designed for an introductory network essentials course taught at Boise State University. The learning emphasis of the lab is not on the capture of the data, but instead on the analysis that follows. By assisting students in developing techniques to filter large batches of data using open-source tools, they gain considerable insight into the differences between aforementioned protocols
An Enhanced TCP Corruption Control Mechanism For Wireless Network
Mobile Ad Hoc networks are collections of mobile nodes, dynamically forming a temporary network without pre-existing network infrastructure or centralized administration. Transmission control protocol (TCP) provides connection oriented, reliable and end to end mechanism. Comparing to wire networks, there are many different characteristics in wireless environments. In this paper an improved mechanism for TCP corruption control is presented. It considers the influences sending rate to TCP sender's packet not only by the congestion but also by the corruption. The sending window size calculated after each transmission, based on number of corrupted packet. So, there is less packet drop in transmission. The comparative study of Enhanced TCP (ETCP) with other TCP variants is also presented on various parameters like mobility, size of network and the speed. The improved mechanism is implemented with fewer overheads and is effectively improve reliability with small variances of throughput and delay. Implementation and Simulation is performed in QualNet 4.0 simulator
Design and evaluation of protocols for wireless networks taking into account the interaction between transport and network layers.
We recognized two important shortcomings of the current TCP protocol: misinterpretation of delayed acknowledgments and competition among different TCP flows. In this dissertation, we propose to address these two issues by a use of novel protocol that uses immediate and delayed acknowledgment schemes and provides a coordination mechanism among independent TCP flows. We also address certain important issues that are related to the implementation of our proposed protocol: can we maintain the end-to-end semantics of TCP? Are there additional benefits that can be harvested if intermediate nodes with TCP protocol can be used? (Abstract shortened by UMI.)The Transmission Control Protocol (TCP) provides end-to-end data reliability and is the primary transport layer protocol for many applications such as email, web access, and file transfer. There has been a plethora of research activity that aims to improve the performance of TCP both in wired and wireless networks. Protocols for the computer networks have been very structured and layered to allow for easier upgrades and maintenance. The network layer protocol (e.g. IP) is independent and below the transport layer protocol (e.g. TCP). Our main goal in this dissertation is to examine the interaction and dynamics between the network layer protocols and TCP in the wireless environment.Towards this goal, we examined the network layer protocols in one-hop wireless (e.g. cellular networks) and multi-hop wireless, e.g. distributed Wi-Fi (Wireless Fidelity) networks. For each of these networks we, for the first time, propose transport layer protocols that take into account the interaction between the network layer and transport layer. For the one-hop wireless networks we have investigated analytical methods to determine the buffer requirements at base stations and estimate disruption time which is the time between two packet arrivals at the mobile host. We will show that the estimation of buffer requirements and disruption time is not only dependent on the wireless TCP scheme used, but also its interaction with the underlying network protocol. We also propose a comprehensive study of the effectiveness of wireless TCP and network protocols taking into account different networking environments that is decided on many factors such as mobility of senders and receivers, simplex and duplex communication among communicating peers, connection oriented and connection less communication at the network layer, rerouting schemes used after movement, and with and without hint handoff schemes
- …