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Quality of Service in Switch/Routers
Published in James Aweya, Designing Switch/Routers, 2023
The 8-bit Type-of-Service (ToS) field was originally defined as part of the IP packet header [RFC791]. Figure 8.2 shows the location of the ToS field in the IP header. Similar to the IEEE 802.1Q tag in Ethernet frames, the IP header was defined to contain a field that specifies a priority value for an IP packet. The ToS is now an obsoleted IP header mechanism for providing packet prioritization and is replaced with a 6-bit DSCP field [RFC2474] and a 2-bit Explicit Congestion Notification (ECN) field [RFC3168]; the original 8-bit ToS field has been replaced by these two fields. ECN provides an optional end-to-end mechanism for signaling network congestion to network devices without dropping packets. The optional ECN feature (the two least significant bits) may be used between two ECN-enabled nodes when the underlying network infrastructure supports this feature.
Measuring Network Congestion
Published in Christos N. Houmkozlis, George A. Rovithakis, End-to-End Adaptive Congestion Control in TCP/IP Networks, 2017
Christos N. Houmkozlis, George A. Rovithakis
TCP supports ECN using two flags in the TCP header. Those two bits are used to echo back the congestion indication and to acknowledge that the congestion-indication echoing was received. These are the ECN-Echo (ECE) and congestion window reduced (CWR) bits.
Ad Hoc Networks
Published in Jerry C. Whitaker, Microelectronics, 2018
Michel D. Yacoub, Paulo Cardieri, Élvio João Leonardo, Álvaro Augusto Machado Medeiros
A key feature of this approach is that the standard TCP is not modified, but an intermediate layer, called ad hoc TCP (ATCP), is inserted between IP and TCP (transport) layers. Therefore, ATCP is invisible to TCP and terminals with and without ATCP installed can interoperate. ATCP operates based on the network status information provided by the internet control message protocol (ICMP) and the explicit congestion notification mechanism (ECN) (Floyd, 1994). The ECN mechanism is used to inform the TCP destination of the congestion situation in the network. An ECN bit is included in the TCP header and is set to zero by the TCP sender. Whenever an intermediate router detects congestion, it sets the ECN bit to one. When the TCP destination receives a packet with ECN bit set to one, it informs the TCP sender about the congestion situation, which in turn reduces its transmission rate. ATCP has four possible states: normal, congested, loss, and disconnected. In the normal state ATCP does nothing and is invisible to TCP. In the congested, loss, and disconnected states, ATCP deals with congested network, lossy channel, and partitioned network, respectively. When ATCP sees three duplicate ACKs (likely caused by channel induced errors), ATCP transitions to the loss state and puts TCP into persist mode, ensuring that TCP does not invoke its congestion control mechanisms. In the loss state, ATCP retransmits the unacknowledged segments. When a new ACK arrives, ATCP returns to the normal state and removes TCP from the persist mode, restoring the TCP normal operation. When network congestion occurs, ATCP sees the ECN bit set to one and transitions to congested state. In this state, ATCP does not interfere with TCP congestion control mechanisms. Finally, when a route failure occurs, a destination unreachable message is issued by ICMP. Upon receiving this message, ATCP puts TCP into persist mode and transitions to the disconnected state. While in the persist mode, TCP periodically sends probe packets. When the route is eventually reestablished, TCP is removed from persist mode and ATCP transitions back to the normal state.
Fractional-order PID control of tipping in network congestion
Published in International Journal of Systems Science, 2023
Jiajin He, Min Xiao, Yunxiang Lu, Zhen Wang, Wei Xing Zheng
A proliferation of progress have been made in the communication network, whether wired or wireless, but communication network always encounters performance bottlenecks due to the limited network load. Then, network congestion occurs when resource demands exceed the capacity (Welzl, 2005), which results in the decline of network performance, and even the collapse of the communication network. Therefore, novel network congestion control algorithms were developed to efficiently use all available capacity, and acquire higher bandwidth, higher reliability, and lower latency, e.g. dynamic explicit congestion notification (ECN) marking threshold algorithm (Lu et al., 2018) and active queue management (AQM) methods (Shen et al., 2022). Dual congestion algorithm models are commonly and widely used in congestion control (Srikant & Başar, 2004), which principally considers the dynamic nature of the link and the static nature of the source. Representative dual congestion models possessing one link and one delay were obtained, and the effect of delay on the model was investigated (Raina, 2005). However, many aspects of the simplified model are still worthy of further study to improve its efficiency and applicability, and so it is with the research of other network congestion models as well.
Dynamic Deep Genomics Sequence Encoder for Managed File Transfer
Published in IETE Journal of Research, 2022
Amandeep Kaur, Ajay Pal Singh Chauhan, Ashwani Kumar Aggarwal
The available network solutions for efficient transfer of genomics data control network congestion and channelize traffic flow. The congestion in the network is managed by packet-based protocols that regulate the rate of incoming traffic and hence save the network resources [27]. Data Center Transmission Control Protocol (DCTCP) handles the transmission rate according to congestion in the network [28], and Deadline-Aware Datacenter Transmission Control Protocol (D2TCP) is a protocol that uses an explicit congestion notification mechanism as a feedback system for traffic regulation [29,30]. The bit rate of data transmission controls the traffic flow [31]. The bandwidth can also be increased by hardware resources that provide high internet speed like internet2project [32]. Reducing the size of the dataset by compression and encoding are also suggested as a solution to efficient data transfer [33]. Multi Fasta Compress [34] and Bzip2-libbzip2 [35] are genomics data compression algorithms used over HTTP before data transmission. The performance of these techniques for data transfer is based on a trade-off between transfer time and security. The compression algorithm is unsuitable for time-bound applications because it requires more time to compress the data. There is also a compromise in security while applying the compression technique as one key encoding scheme is used for whole dataset [36]. Also, not all the browsers support compression algorithms. Therefore, an efficient data encoding technique is preferred over compression. A bit torrent-based genomics data transfer protocol (gene torrent) was previously used for peer-to-peer transfer of genomics data files [37,38]. Gene torrent uses several machines present at different locations to distribute files and at the time of file access request. With parallel transmission, each device transfers some part of the file to the requesting server. But it is an obsolete method now, and genomics data is transmitted by general transfer protocols only.