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Review of Layer 2 and Layer 3 Forwarding
Published in James Aweya, Designing Switch/Routers, 2023
The Spanning Tree Protocol (STP) in the IEEE 802.1D standard [IEEE802.1D04] (or its newer versions Rapid Spanning Tree Protocol (RSTP) in IEEE 802.1w and Multiple Spanning Tree Protocol (MSTP) in IEEE 802.1s) is used by Ethernet switches in a Layer 2 network to maintain a loop-free network, where frames will not be recursively forwarded. Without these protocols, if a loop were to form in the Layer 2 network, a flooded frame could follow the looped path, where it would be flooded again and again, in many cases resulting in a broadcast storm and congestion collapse.
Spanning Tree Protocol
Published in Iannone Eugenio, Telecommunication Networks, 2017
The spanning tree protocol (STP) is a link-management protocol that is part of the Institute of Electrical and Electronics Engineers (IEEE) 802.1 standard for bridges and switches. All the material of this appendix is a synthesis of IEEE Ethernet standards, so we will not repeat here the list of such standards, recommending the interested reader to use the list in the references of Chapter 3.
Next Generation Ethernet
Published in Goff Hill, The Cable and Telecommunications Professionals' Reference, 2012
Although the active topology is recalculated, it is evident that the alternative paths are only usable under failure conditions and hence no load sharing is possible. This has led to alternative solutions for resiliency being considered. A number of spanning tree solutions have been developed: 802.1d—Spanning Tree Protocol (STP) is the original version of a spanning tree. It has a significant limitation for larger networks in that it is slow to converge onto a new tree (sometimes 1 to 2 minutes). This results in a significant disruption to customer services. Although a common spanning tree for the entire network can be deployed regardless of the number of VLANs, this is not the most efficient use of topology and lowers overall network utilization. The reconfiguration time of STP is simply too slow for modern applications, and as a result 802.1w as subsequently described was developed.802.1s (now integrated into 802.1Q)—The standard describes the Multiple Spanning Tree (MST), which provides a means by which a number of paths can be used across an Ethernet network, thereby increasing network utilization and load sharing. This is achieved by running multiple instances of the spanning tree over the same network and configuring different bridges as the root for each instance. Network management configuration gives the provider control over the number of spanning tree instances and the assignment of ranges of VLANs to each instance, and in doing so allows creation of a number of logical topologies.802.1w (now integrated into 802.1D)—The Rapid Spanning Tree Protocol (RSTP) can be seen as a refinement of STP that uses many of the original capabilities but makes a number of changes that enhance performance. The limitation of STP where only the root bridge generates BPDUs and processes topology changes is overcome in RSTP by allowing all bridges to generate BPDUs and respond to topology changes. This and other changes mean that RSTP reduces the response time from a minute or so down to around a second (or less), resulting in an improved customer experience.
Smart grid mechanism for green energy management: A comprehensive review
Published in International Journal of Green Energy, 2023
Adila Fakhar, Ahmed M.A. Haidar, M.O. Abdullah, Narottam Das
The long-distance wireless communication from customers to the local utility has several drawbacks, such as limited bandwidth, considerable costs, and unstable quality of connection. Unlike wireless communication, the wired communication network enhances the security of the system and can provide reliable communication with accurate data transmission (Stefano, Scaglione, and Wang 2010). Although the uncertainty in the effectiveness of Ethernet for real-time substation automation has been investigated in many research studies, the application of Ethernet in distribution power systems considering the random characteristics of RER was not sufficiently reported. For substation communication networks, the Ethernet technology must comply with the IEC 61850 global standards. One of the specified requirements for time-critical applications is 10 msec in distribution substations while 3–4 msec in transmission substations. The coverage for communication in the distribution substation is (25–150) m whereas in the transmission substation is in the range of (50–300) m (Shuo et al. 2017). The spanning tree protocol (STP) as defined in the IEEE standard 802.1D was designed to solve the main problem of traffic and prevent accidental loops in the poorly structured and managed wiring closets. To pave the way for smart grid application, the mature technology of narrowband PLC standardization (IEEE P1901.2 with ITU-T G.hnem) which is still in service can be upgraded to the ITU-T G.hn and IEEE P1901 with the expanded Home Plug AV2 specification (Hadlach et al. 2017). Generally, the PLC comprises of two types, Narrowband PLC (NB-PLC) and Broadband PLC (BB-PLC). They are differentiated and classified based on the frequency range and transmission distance of signals as demonstrated in Table 10 (Haidar et al. 2011; Tonello et al. 2011). The NB-PLC is mainly suggested for the automation in smart grid application, this is due to its ability to communicate through transformers with bypass installment as it has a lower frequency range (Galli, Scaglione, and Wang 2011). Here, the automated systems do not require any additional communication network and can be used to control devices (lighting and heating systems), central control of home (doors and windows), and for security purposes. On the other hand, the major drawbacks of PLC are the noise and attenuation in the channel causing distortion and delay in transmitting the signal (Uribe-Pérez et al. 2017). Considering the characteristics of PLC, digital modulation techniques, that is, frequency shift keying, amplitude shift keying, and phase shift keying are more suitable than analog modulation techniques (Franek and Fiedler 2017). The major problem when using the amplitude shift keying in PLC is the noise susceptibility which may deteriorate the system performance (Haidar, Fakhar, and Muttaqi 2020).