What Is The Only Routing Protocol That Does Not Have A Separate Layer 3 Data Structure?

Interconnection Layer

Protocol Layers

Pierre Duhamel , Michel Kieffer , in Joint Source-Channel Decoding, 2010

vii.1.4 Wireless Networks Architecture

Plain, the tasks of transmitting, routing, segmenting the data according to some constraint, addressing the correct user, etc. are highly complex tasks. Moreover, they have to be uniform between very heterogeneous systems when connecting them. The classical solution in this case is ordinarily to separate the work to be done into separate tasks, each one having a modest number of interfaces so that its design is non besides complex, and can be adapted to a variety of situations. This is the reason that motivated the layered compages of communication systems.

The universal reference is the Open up Systems Interconnection (OSI) model, depicted in Figure vii.3. This model is fabricated of a stack of 7 layers, which define the rules that each task must follow. Within a receiver, each task receives information from the lower layers and forwards the issue of its own processing to the next one. Each processing is assumed perfect. Therefore, each layer in the transmission stack can be assumed being connected to its corresponding layer in the receiver through a protocol that, therefore, defines a virtual link betwixt corresponding layers.

The chore of each OSI layer is clearly defined and corresponds to a specific function. Ane may distinguish between the lower layers (i, 2, 3, and 4) that control the commitment of the data, and the upper layers (v, half dozen, and 7) that are doing some local processing involving only the server and the final. At all levels, the information is organized in blocks for which nosotros utilise the generic name packets, which have dissimilar names depending on the layer. Each layer is described below.

1.: The concrete layer ensures the last shaping of the binary data and then that they can correctly be received. This corresponds to the following tasks: (1) transformation of the binary bitstream into an analog waveform, adjusted to the channel (cable, cobweb, wireless aqueduct), (2) channel coding, for a improve protection of the data, (3) synchronization of the information between the transmitter and receiver.
2.: The link layer takes care of communications between two adjacent devices, connected through the physical medium. Its chief chore is to ensure the packetization of the information into slices, the size of which is adapted to the channel. Upon reception, it controls the integrity of the corresponding packets past incorporating error-detection mechanisms and may ask for the retransmission of erroneous packets. When the resource are shared amongst several users, it performs (jointly with PHY layer) the corresponding multiplex, also equally the resource allocation. In this level, a parcel is named frame.
3.: The network layer establishes the advice link betwixt the server and the terminal, and contains routing protocols that determine the routes the packets take. It is the just layer concerned with the network topology and is also the last layer supported by the central network equipments, whereas the upper layers are but supported past the terminal parts. At this level, the bundle is named datagram when the protocol is connectionless (e.one thousand., IP layer) or segment if information technology is connection-oriented (e.g., 10.25 network layer).
4.: The transport layer manages the transport of the awarding-layer messages between the client and the server sides of the application, by adapting the information transmission in the network and the service required by the user. It performs information multiplexing between the diverse processes, fragmentation of the packets coming from the upper layers into packets, the size of which is adapted to the network. There are two types of transport protocol, depending on the nature of the data to be transmitted. In the connection-oriented mode, the service includes guaranteed delivery of awarding-layer messages; there is no packet loss and the received packets are right. This may generate high transmission delays. In the connectionless style, packets are transmitted only in one case past the transmitter, and there is no acknowledgment procedure on the packets. This is a low delay, but risky manual. At this level, the packet can accept two names. It is named datagram when the protocol is connectionless (eastward.g., UDP) or segment if it is connection-oriented (eastward.one thousand., TCP).
v.: The session layer organizes and synchronizes the dialog between afar tasks. Information technology establishes a link between 2 programs that have to cooperate and control their connexion, e.thousand., by token management. If ever a connectedness has been broken, this layer allows to reconnect past using synchronization markers inserted in the data stream. At this level, the packet is named Bulletin.
6.: The presentation layer ensures compatibility of the data between communicating tasks. It is in accuse of the application-layer messages coding and ensures the format transition between user-related data format and the stream, which is transported past the network. Typical processing is data pinch, encryption, or conversion. At this level, the packet is named Message.
seven.: The application layer is where network applications and application-layer protocol reside. It is the interface betwixt the user and the network. At this level, the packet is named Message.

This model is fully generic, but when the Internet was developed, the selection was fabricated of a simpler protocol. The number of layers was reduced to iv, and is now named afterward the names of the first two layers: the IP (Postel, 1981a) of the network layer and the TCP (Postel, 1981b) of the ship layer. TCP/IP model, simpler, was preferred. Information technology is, thus, known under the acronym TCP/IP. It was first implemented, and then standardized. Both OSI and TCP/IP architectures are compared in Figure 7.four.

In contrast with the OSI model, the session and presentation layers are not contained anymore; their tasks are taken in charge by the application layer. Moreover, the concrete and link layers are grouped in the Host-to-Network layer (Tanenbaum, 2002) (note that other authors consider two dissever layers at this level). The implementation of this layer is not divers in the standard, just its role is defined: it must ensure access to the physical medium and to ship packets to the network. Practically, the required standard depends on the engineering science used in the local network (Ethernet, Wi-Fi).

Since our master involvement is in the existent-time manual (streaming) of video from a server to a mobile terminal, at present concentrate on the corresponding protocols. In this context, the transfer between the transmitter and receiver must be very fast, a fact that prevents any dialog between both terminals. The TCP, being connection-oriented, is not suited to this situation. Information technology is replaced by a set of ii protocols that constitute the RTP/UDP (Postel, 1980; Schulzrinne et al., 1996) layer. Moreover, even if the principles of JSCD do not depend on a precise situation, its actual implementation is strongly dependent on the detailed structure of the Host-to-Network layer, which corresponds to a given wireless communication standard. In this context, almost of our results will be illustrated on the Wi-Fi 802.11 (IEEE, 1999) standard that volition, thus, be described with some details. This standard provides the specifications of the physical (PHY) and link (MAC) layers. The complete transmission chain is shown in Figure 7.v.

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Cisco LocalDirector and DistributedDirector

Eric Knipp , ... Edgar Danielyan Technical Editor , in Managing Cisco Network Security (Second Edition), 2002

LocalDirector Technology Overview

Cisco's LocalDirector uses the Open up System Interconnection (OSI) Layers 3 and four (Network and Transport Layers respectively) every bit a load-balancing applied science that allows you to publish a single Uniform Resource Locator (URL) and a single IP address for an entire server farm. From a technical point of view, it acts as a transparent TCP/IP span within the network.

The LocalDirector determines which server is nearly appropriate past tracking network sessions and server load conditions in existent time.

Such technology helps decrease the response fourth dimension of your service while increasing service reliability. Service response fourth dimension is decreased because resource requests for a URL or IP address are directed to the most advisable server (the to the lowest degree busy server, for case) within the server farm. As well, service reliability is increased considering LocalDirector monitors individual servers in the server farm and forwards resource requests only to servers that are operating correctly.

Before the inception of this technology, y'all would have to know the name or IP address of every individual Web server in the server subcontract, or you lot would have to make utilize of multiple IP addresses associated with a single DNS proper noun (the so-called DNS circular-robin load balancing). Neither of these techniques were user friendly, nor did they event in appropriate load distribution. They were likewise unreliable, because no effort was made to verify the servers' availability in real fourth dimension.

Cisco's LocalDirector can be compared to an Automatic Call Distributor (ACD) in the telephony world. LocalDirector is similar to an ACD in that incoming telephone calls are routed to a pool of agents and answered as soon equally an agent is available. It works as a front-end for a Web server farm and redirects resource requests to the nearly appropriate server. Figure 7.1 depicts a typical LocalDirector implementation.

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Networks

Jeremy Faircloth , in Enterprise Applications Administration, 2014

Router

A router is a device intended to route communications based on their OSI Layer 3 addressing. As we discussed in the department on IP addressing, an address at this layer is comprised of both a network and a host address. The router uses the network address to determine which network it should route the bulletin to and and so sends the bulletin on its manner. Routers can likewise utilize some intelligence to their routing and, based on information available to the router, move communications to faster or less congested networks equally needed as long as there are multiple paths betwixt the router and the destination network.

Another function that is bachelor with most enterprise-quality routers is quality of service (QoS) routing. This feature is also available within some switches. Based on specific rules that are configured in the router, the router volition apply priority to the processing of specific types of traffic. For example, some home routers are calculation functionality which permit for the application of QoS rules to streaming media to ensure that communications for video and audio streams become priority. Enterprise networks may employ QoS rules to ensure that voice over IP (VOIP) communications take priority over other traffic. When a router uses QoS, information technology takes a look at all of the messages that it has been sent to process, moves the letters into a specific order based on the QoS rules, and and so processes them in priority order. If another message comes in that has a college priority, information technology will be moved to the front of the line.

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Packet-Switched Networks

Jean Walrand , Pravin Varaiya , in High-Operation Communication Networks (2d Edition), 2000

3.vi FRAME RELAY

Frame Relay is a connection-oriented data transport service for public switched networks. The Frame Relay protocols are a modification of the X.25 standards. Both X.25 and Frame Relay specify the everyman three OSI layers for virtual circuit networks. Frame Relay standards are specfied by the International Telecommunications Marriage (ITU) and ANSI, beginning in 1990.

X.25, introduced in 1974, was designed to operate with noisy transmission lines. Appropriately, the link level protocol of 10.25 (called LAPB for Link Access Procedure B) performs error detection and recovery using the Go Back N protocol with a window size of 8 to 128. LAPB also provides for some link level flow control by enabling a receiver to stop the sender temporarily by sending it a command frame. The network layer of 10.25 specifies that upward to 4,096 virtual circuits can be prepare on any given physical link. An stop-to-end window menses control can be implemented along each virtual circuit independently of the link level flow control.

Frame Relay is simpler than X.25. It is designed to have advantage of links with a higher transmission rate and small bit error rate. (X.25 is intended to piece of work with 64-Kbps links; Frame Relay works with 56-Kbps, 1.5-Mbps, and higher-speed links.) The main departure with X.25 is that Frame Relay does not control errors at the link level. Instead, error control and recovery are washed by college layers. Consequently, the package or frame processing fourth dimension at each node is smaller than for 10.25. Moreover, the transmissions on a link are not slowed down as they would be by the Go Back N protocol of X.25 when its window has been transmitted and the sender waits for the acknowledgments to come up back before resuming the transmissions. Thus, Frame Relay is a virtual circuit service which does non provide reliability.

We will explicate why information technology is advantageous to supervene upon link level mistake control by end-to-terminate control when the flake fault rate is minor. We will then show why Go Back N slows downwards transmissions when the bandwidth-filibuster product of the link exceeds the window size. These two observations justify the superiority of Frame Relay over X.25 for college-speed, depression-error links. Since Frame Relay is simpler than X.25, nearly vendors of 10.25 equipment provide software to run Frame Relay on their switches. Frame Relay is a pop means to interconnect networks.

For the first ascertainment, consider the virtual circuit connection model of Effigy 3.28. The connection goes through k nodes. Each node takes a fixed time σ₁ to process and transmit each frame. Assume that each transmission from one node to the adjacent corrupts the frame with probability 1 − p. If errors are controlled by the link and each frame is retransmitted until it is successfully received, then each frame must be transmitted 1/p times on average earlier being successfully received. Consequently, the average transmission time of the frame past the yard nodes is equal to kσ₁/p. If no link level error command is performed, and then the node processing and transmission time is assumed to be σ₂ < σ₁. (The difference in practise is large: σ_ane ∼ 50 ms compared with σ_two ∼ three ms.) The full transmission time by the k nodes is at present kσ₂. All the same, this finish-to-stop transmission fourth dimension must take place one/q times on average, where q is the probability that no transmission corrupts the package, that is, q = p ^k. Since mσ₁/p > kσ₂/p ^m whenever p is sufficiently close to 1 (i.east., the chip error rate is sufficiently small), the end-to-end error control becomes faster than the link level error control.

In section 2.vi.3 we defined the efficiency of a manual protocol as the fraction of time the transmitter is sending new packets. We showed that the efficiency of the Go Back N protocol is

$Efficiency = min {\frac{N TRANS}{TRANS + ACK+2PROP}, 1},$

where TRANS is the packet transmission time, ACK is the time to transmit the acknowledgment, and PROP is the propagation time between sender and receiver. Thus to achieve Efficiency = 1 nosotros must have N TRANS ≥ TRANS + ACK + 2PROP. Neglecting ACK, this implies N should be at to the lowest degree 2PROP/TRANS, that is, the window should be large enough to "fill up up the piping." For instance, suppose the finish-to-stop distance is 5,000 km, then PROP equals 5 × 5,000 = 25 μs. For a one,000-byte packet and a transmission speed of 50 Mbps, TRANS =160 μs. This gives a window size of well-nigh 300 packets.

The frame format is shown in Figure 3.29. The 2-byte header contains address information (DLCI and EA, explained beneath) for routing, congestion-control information (F/BECN and DE, also explained beneath) for notification and enforcement, and the C/R bit whose usage is application-specific. The frame check sequence FCS is a 16-bit CRC for mistake detection: erroneous frames are discarded and are non retransmitted by the network. The standard specifies the employ of Permanent Virtual Circuits (PVCs) for connections.

A PVC is a fixed route assigned between two users when they subscribe to a Frame Relay service. A PVC is identified at the network interface by a 12-chip data link connection identifier (DLCI). DLCIs specify and distinguish separate connections across an access link and therefore can exist used to multiplex several connections. The DLCI field allows for 1,024 PVCs per access link. Of these, nearly one,000 tin can be assigned to users, and the residual are reserved for control purposes. The header may exist extended to 4bytes to conform more DLCIs. The EA (extended address) bit is used for that purpose: EA = 0 indicates that the next byte is also an address byte; EA = one indicates the last accost byte.

Frames are discarded at a node or switch when erroneous or when buffers overflow. To reduce buffer overflow, the switch can exercise flow control equally follows. When a switch experiences some congestion, it notifies the sources and destinations of all the active PVCs passing through the node. This is done past setting the FECN (forrard explicit congestion notification) scrap in user frames going in the forward direction to inform the destination or the BECN (backward explicit congestion notification) fleck in user frames going in the opposite direction to inform the source. FECN may exist used by destination-controlled menstruation-command protocols, whereas BECN may be used past source-controlled flow-control protocols. The Frame Relay standard, yet, does non define congestion, nor does information technology specify how users should respond to information technology.

The DE (discard eligibility) bit may be gear up by users to indicate depression-priority frames such every bit some sound or imaging frames with less significant data. Note, however, that compressed video is more sensitive to losses and then that such packets might not have the DE fleck set. The DE bit may too be fix by a network node. The network would preferentially discard frames with DE = 1 when necessary to convalesce congestion. (ATM packets besides incorporate a 1-bit priority; see Chapter vi.) DLCI = 1,023 is a PVC reserved for communication between the user and the network. The user and the network periodically exchange "keep alive" messages on that PVC. A user could also poll the network on that PVC, at which indicate the network would report all active DLCIs on that access link and their traffic parameters such as CIR (explained below). That PVC can also be used for period control, especially when in that location is likewise trivial traffic through a congested node in the reverse management for a timely notification of congestion past the BECN.

At subscription time, each DLCI is assigned iii parameters (T _c, B _c, B _e) for traffic shaping. These parameters are used as follows. Time is slotted into intervals of duration T _c. The network guarantees transport of B _c bytes of information in each interval. This guarantees a "committed information rate" CIR = B _c/T _c. If the user injects more than B _c bytes beyond the user-network interface in an interval, the network may acknowledge the first B _{due east} bytes of excess data with their DE bits ready. Farther frames in that interval may be discarded. The DLCI is guaranteed a long-term bandwidth of CIR and a maximum burst size of B _eastward. This traffic-shaping scheme regulates the input load to the Frame Relay network, thus reducing the likelihood of congestion. The scheme may exist implemented by using a leaky bucket for each PVC at the network archway. (The leaky-saucepan scheme is described in department 3.7.) Traffic-shaping schemes are discussed in Chapters 8 and 9.

In summary, Frame Relay is an improvement over X.25 networks, taking reward of better transmission links past streamlining the X.25 protocol. Yet, its switches lack the adequacy to reserve resources for private connections, and and then Frame Relay is unsuitable for applications that require guaranteed filibuster. It is interesting to notation, nevertheless, that many of the developments used to differentiate service quality occur almost simultaneously in Frame Relay, SMDS, and ATM. Of these three designs, ATM will be the most successful in offering differentiated services. The Frame Relay and ATM Forums are developing interworking standards and specifications.

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Configuring PPP and CHAP

Dale Liu , ... Luigi DiGrande , in Cisco CCNA/CCENT Exam 640-802, 640-822, 640-816 Training Kit, 2009

Publisher Summary

Point-to-Point Protocol (PPP) is a Layer two broad area network (WAN) protocol used for basic data encapsulation and transmission across a network. PPP is configured to piece of work at the information link Open Systems Interconnection (OSI) layer and helps data transmission by utilizing a multiprotocol setup via the concrete, data link, and network layers of the OSI model. PPP is ordinarily used to encapsulate a connection on a Transmission Control Protocol/Internet Protocol (TCP/IP) based network through a modem and a telephone line, a router connected to another router, and via other connection methods and media. Challenge Handshake Authentication Protocol (CHAP) is the preferred protocol, considering CHAP uses a iii-way handshake, whereas Countersign Hallmark Protocol uses only a 2-way handshake. When CHAP is used over a WAN connection the router receiving the connection sends a challenge, which includes a random number. This random number is input into a Message Digest authentication algorithm to provide an encryption central. This key is and so used to ship hallmark information between Routers 1 and 2. CHAP uses encryption and has a verification mechanism in place and then it is an inherently secured protocol.

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Mobile Network and Transport Layer

Vijay K. Garg , in Wireless Communications & Networking, 2007

14.iv TCP/IP Suite

The TCP/IP suite (Figure fourteen.8) occupies the heart five layers of the 7-layer open system interconnection (OSI) model (come across Figure 14.9) [30]. The TCP/IP layering scheme combines several of the OSI layers. From an implementation standpoint, the TCP/IP stack encapsulates the network layer (OSI layer 3) and transport layer (OSI layer 4). The concrete layer, the information-link layer (OSI layer 1 and 2, respectively) and application layer (OSI layer vii) at the top can be considered not-TCP/IP-specific. TCP/IP can be adapted to many different physical media types.

IP is the basic protocol. This protocol operates at the network layer (layer 3) in the OSI model, and is responsible for encapsulating all upper layer transport and awarding protocols. The IP network layer incorporates the necessary elements for addressing and subnetting (dividing the network into subnets), which enables TCP/IP packets to exist routed across the network to their destinations. At a parallel level, the ARP serves as a helper protocol, mapping concrete layer addresses typically referred to every bit MAC-layer addresses to network layer (IP) addresses.

There are two ship layer protocols above IP: the UDP and TCP. These transport protocols provide commitment services. UDP is a connectionless delivery transport protocol and used for bulletin-based traffic where sessions are unnecessary. TCP is a connection-oriented protocol that employs sessions for ongoing information commutation. File transfer protocol (FTP) and Telnet are examples of applications that utilise TCP sessions for their send. TCP also provides the reliability of having all packets best-selling and sequenced. If data is dropped or arrives out-of-sequence, the stack'south TCP layer will retransmit and resequence. UDP is an unreliable service, and has no such provisions. Applications such every bit the simple postal service send protocol (SMTP) and hyper text transfer protocol (HTTP) apply transport protocols to encapsulate their information and/or connections. To enable like applications to talk to 1 another, TCP/IP has what are chosen "well-known port numbers." These ports are used as sub-addresses inside packets to place exactly which service or protocol a bundle is destined for on a particular host.

TCP/IP serves as a conduit to and from devices, enabling the sharing, monitoring, or controlling those devices. A TCP/IP stack can have a tremendous result on a device's memory resources and CPU utilization. Interactions with other parts of the system may be highly undesirable and unpredictable. Bug in TCP/IP stacks can render a system inoperable.

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Finalizing the Installation

Thomas Norman CPP, PSP, CSC , in Integrated Security Systems Design (Second Edition), 2014

Architectural Security

The OSI reference model (OSI seven-layer network model) has many opportunities to both secure and exploit weaknesses in data communications. The OSI levels accept been discussed previously; here, I discuss how those layers affect the security of the organisation and the organization.

OSI layer 1 is the physical layer. Information technology is imperative to prevent physical access to network switches, routers, firewalls, and servers if the security organisation is to be secure. All these devices should be backside locked doors and in alarmed rooms.

OSI layer 2 is defined as the data link layer. This is the layer on which switches operate. Each TCP/IP device has a physical address called a media access control (MAC) address. This accost is unique for every device that is difficult coded into the network interface bill of fare of every TCP/IP device. The MAC addresses of the devices within the organisation should exist stored in a tabular array, and those addresses should exist reserved such that they are the only authorized devices on the network, assuasive no other devices on the network. Additionally, network switches should exist programmed to detect whether a device reporting a given approved MAC address is in fact the real device, or if the MAC accost is being "spoofed" by a rogue device.

OSI layer three is the network layer. This is the layer on which routers operate. This is often chosen the protocol layer. Layer iii manages the IP protocol. Subnets, supernets, VLANs, and VPNs are all managed using OSI layer 3.

OSI layer 4 is the transport layer. Layer 4 manages TCP, UDP, RTP, and other protocols. Better network switches provide for prioritizing of sure packet types (e.grand., intercom traffic over video traffic). Layer 4 devices include firewalls and layer 4 session switches.

OSI layer 5 is the session layer. Layer 5 opens and closes network sessions, controls the institution and termination of links between network devices and users, and reports whatsoever upper layer errors. Secure Socket Layer security operates on layers 5–vii. Layer 5 information management can also optimize network data traffic past establishing a TCP proxy that reduces the amount of exterior network traffic immune to see the host.

OSI layer vi is the presentation layer. Layer half-dozen performs network encryption and compresses and decompresses data.

OSI layer 7 is the application layer. Layer 7 manages application usernames and passwords.

A good network designer secures his or her system at all seven layers of the OSI network model. Any layer that is not secured is vulnerable to an internal or external system hacker.

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Introduction

In Networks-On-Chip, 2015

1.two Advice-axial cross-layer optimizations

Although there have already been neat breakthroughs in the design of many-core processors in the theoretical and practical fields, there are however many disquisitional problems to solve. Unlike in single-core processors, the big number of cores increases the pattern and deployment difficulties for many-core processors; the design of efficient many-core architecture faces several challenges ranging from loftier-level parallel programming paradigms to depression-level logic implementations [2, seven]. These challenges are too opportunities. Whether they can exist successfully and efficiently solved may largely decide the time to come development for the entire calculator architecture customs. Figure ane.i shows the three central challenges for the pattern of a many-core processor.

The first challenge lies in the parallel programming prototype layer [vii, 31]. For many years, only a small number of researchers used parallel programming to conduct large-scale scientific computations. Present, the widely available multicore and many-core processors make parallel programming essential even for desktop users [103]. The programming paradigm acts every bit a bridge to connect the parallel applications with the parallel hardware; it is one of the nigh significant challenges for the development of many-core processors [7, 31]. Application developers want an opaque paradigm which hides the underlying architecture to ease programming efforts and ameliorate application portability. Architecture designers hope for a visible paradigm to utilize the hardware features for loftier performance. An efficient parallel programming epitome should be an first-class tradeoff between these ii requirements.

The 2d challenge is the interconnection layer. The traditional bus and crossbar structures have several shortcomings, including poor scalability, low bandwidth, large latency, and loftier power consumption. To address these limitations, the network-on-chip (NoC) introduces a packet-switched cloth for the on-chip communication [ 25], and information technology becomes the de facto many-core interconnection mechanism. Although significant progress has been made in NoC enquiry [102, 115], most works have focused on the optimizations of pure network-layer operation, such every bit the zilch-load latency and saturation throughput. These works practise non consider sufficiently the upper programming paradigms and the lower logic implementations. Indeed, the cross-layer optimization is regarded every bit an efficient fashion to extend Moore's police force for the whole information manufacture [2]. The future NoC design should run across the requirements of both upper programming paradigms and lower logic implementations.

The third challenge appears in the logic implementation layer. Although multicore and many-core processors temporarily mitigate the problem of the sharply rising power consumption, the reckoner architecture volition again face up the power consumption claiming with the steadily increasing transistor count driven past Moore'southward law. The evaluation results from Esmaeilzadeh et al. [38] show that the power limitation volition strength approximately 50% of the transistors to exist off for processors based on 8nm technology in 2018, and thus the emergence of "dark silicon." The "dark silicon" miracle strongly calls for innovative low-power logic designs and implementations for many-core processors.

The same three key challenges direct determine whether many-core processors can be successfully developed and widely used. Amongst them, the design of an efficient interconnection layer is one of the most disquisitional challenges, considering of the following issues. Start, the many-cadre processor design has already evolved from the "computation-centric" method into the "communication-centric" method [12, 53]. With the arable computation resources, the efficiency of the interconnection layers largely and heavily determines the operation of the many-cadre processor. Second, and more importantly, mitigating the challenges for the programming image layer and the logic implementation layer requires optimizing the design of the interconnection layer. The opaque programming prototype requires the interconnection layer to intelligently manage the application traffic and hide the advice details. The visible programming paradigm requires the interconnection layer to leverage the hardware features for depression communication latencies and high network throughput. In addition, the interconnection layers induce significant power consumption. In the Intel SCC [59], Sunday Niagara [81], Intel Teraflops [57] and MIT Raw [137] processors, the interconnection layer'south ability consumption accounts for 10%, 17%, 28%, and 36% of the processor's overall power consumption respectively. The design of low-ability processors must optimize the power consumption for the interconnection layer.

On the basis of the "advice-centric cross-layer optimization" method, this book explores the NoC pattern infinite in a coherent and uniform fashion, from the depression-level logic implementations of the router, buffer, and topology, to network-level routing and period command schemes, to the co-optimizations of the NoC and high-level programming paradigms. In Section 1.3, we first behave a baseline pattern infinite exploration for NoCs, then in Section one.iv we review the electric current NoC research status. Section 1.5 summarizes NoC design trends for several existent processors, including academia prototypes and commercial products. Section 1.6 briefly introduces the main content of each affiliate and gives an overview of this book.

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Internet of Things: from hype to reality

Arun Kumar Singh , ... Prem Chand Vashist , in An Industrial IoT Arroyo for Pharmaceutical Manufacture Growth, 2020

7.three.two The open systems interconnection model

The OSI model is important in IoT model functioning. There are seven layers to the OSI model and these are discussed briefly hither [18]. Information technology consists of seven layers, namely:

one.: Physical layer
ii.: Data link layer
three.: Network layer
iv.: Ship layer
5.: Session layer
half dozen.: Presentation layer
seven.: Application layer

Each stratum or layer is accountable for providing some kind of distinct and structured services to the associated terminate-to-end layer either upwards or downward in the stack. While the division differentiates each layer with its separate role, they create the flow of information without disconnecting from each other past working independently and simultaneously (Fig. vii.5).

Nosotros now talk over each of the layers and their private capacities:

i.: OSI layer 7: This layer is known every bit the "awarding layer," and starts at the top. Information technology provides abstraction to the user level of the intrinsic details of all the layers below it. It also specifies protocols for sharing and the interface methods in use by the hosts within a network. This is a place where a user interacts with the network utilizing advanced level protocols [19]. The DNS, HTTP, Telnet, SSH, FTP, SMTP, RDP (remote desktop protocol), etc. are used at this layer.
2.: OSI layer 6: This layer is known as the presentation layer, and it lies beneath the application layer. In this layer are OS services like Linux, Unix, Mac, Windows, etc. The presentation layer is committed to delivering and formatting of information in ii steps toward the awarding layer, which may or may non perform additional processing. It takes care of any issues that may arise equally a outcome of sending data from one node to some other. The presentation layer removes the business organisation of the application layer in dealing with syntactical differences to stand for data residing in cease-user systems [twenty]. Examples include the translation of an EBCDIC (extended binary coded decimal interchange code)-coded file in the form of text to an ASCII (American Standard Lawmaking for Information Interchange)-coded file, while also adding some encryption for security, such as secure sockets layer (SSL) protocol.
3.: OSI layer v: Session layer is beneath the presentation layer in the OSI model. Information technology has the job of dealing with the communications in order to institute a session amid the two network nodes [21]. Examples include the establishment of a session between a reckoner and the server.
4.: OSI layer 4: This layer is the transport layer. Information technology helps to establish an endways communication through the endpoints. This utilizes the notion of windowing, in which i is responsible for the conclusion of the amount of information flow or the data to be sent at ane point in time connecting the two nodes in a network [22].
5.: OSI layer 3: The layer three is the network layer. The routers operate at this level. This layer helps to put the data into packets which nosotros may phone call IP datagrams. They have IP address data of the source and destination address which is transmitted to the hosts and over the network. They also assist in routing of IP datagrams that are marked with IP addresses. At that place is a specific routing protocol which enables routers to communicate with each other. The transfer of data among 2 nodes is enabled by this, and the routing algorithms help to specify the routes. Every router contains the prior information of the networks to which they are attached. So at that place is a routing protocol, which helps to share the coming information to the immediate neighbors and then to the other ends within the network. The routers learn this mode around the existing topology of the network they are working in. Though layers 3 and 4, that is, the network and transport layers, are unlike, they are closely knit together in practice. The name of the Internet protocol TCP/IP comes from the transport layer protocol (TCP) and network layer protocol (IP) [2–four]. Hither the host enables the message transfer in the network by placing over information technology the data to be sent, marked with a destination address in the hope that it will be sent to the specified location. The packets containing messages could arrive in an altered club, and non as specified during the transfer. The next task of the higher layers that exist at the destination point is to rearrange the society of the packets and so supply them to the applications stratum that features applications functioning.
six.: OSI layer 2: This stratum is known as the information link layer. It helps switches to work on the data link layer. This layer decides when to deal with the delivery of frames amid devices that are placed on the aforementioned LAN and uses media access control addresses. The frames are not allowed or they practise not accept the office to cross the borders of a local network. The internetwork routing is controlled by layer 3. This helps to permit the data link protocols to emphasize their attending on local railroad vehicle, giving the accost scheme and media intercession. Therefore the data link layer is comparable to a local neighborhood traffic cop, which does the mediation among parties struggling for entry through the medium, without the input of the final destination. For instance, the data link protocols include the Ethernet used in multinode course in LAN and the betoken-to-bespeak protocol [23].
7.: OSI layer ane: This is the basic stratum of the OSI model and is called the physical layer. This concrete layer describes the physical world interface with the virtual globe using an electrical or mechanical interface for establishing the physical medium. This contains the idea of bones networking hardware transmission technologies. The wiring and cabling are function of this layer. This layer is committed to outlining the patterns of diffusing raw bits over a concrete link that binds together network nodes, copper wires, fiberoptic cables, radio links, etc. The physical layer governs stream of bits and their placement from the data link layer on to the pins for a USB printer interface, an optical fiber transmitter, or a radio carrier, etc. [24].

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Cisco IOS Switch Basics

Dale Liu , in Cisco Router and Switch Forensics, 2009

Switch Concepts

The lesser line is that switches have many major advantages over hubs in terms of efficiency and security in communications. Much has been learned of using network switching engineering science and both Information technology administrators and purchasers have a deeper understanding of the costs and benefits of using switches in an enterprise. Earlier we swoop into the technicalities, permit's start with some terms that volition assist u.s. along:

▪: Collision Occurs when two hosts endeavor to access (or transmit) on a shared medium at the aforementioned time, resulting in a collision of their frames.
▪: Broadcasts Refers to both Open Systems Interconnection (OSI) Layer 2 (data link) broadcasts where frames are destined to all hosts on a subnetwork, and OSI Layer 3 (Internet) broadcasts where packets are destined to all hosts on a network. Layer two broadcast frames accept a destination Media Access Control (MAC) accost of FF:FF:FF:FF:FF:FF and Layer 3 broadcast addresses have a destination Cyberspace Protocol (IP) address that is prepare for the circulate of that particular network (the address varies, and so don't always assume that an IP address catastrophe with 255 is the broadcast address).
▪: MAC address Refers to the hardware, Ethernet, or burned-in address of an Ethernet network interface. It is composed of a 48-bit address in a hexadecimal string of characters that designate the manufacturer ID and a unique serial number for the device.
▪: Host For the purposes of this discussion, a calculator with a network card capable of communicating on an Ethernet network.
▪: Bridges The predecessors to switches and switching technology. Bridges accept limitations that switches better on.
▪: Frame A unit that is practical to the OSI model that defines the size and composition of a stream of network communication. In terms of the Ethernet specification, information technology is basically composed of a source MAC address, a destination MAC address, protocol information, and a data payload consisting of data from the upper layers of the OSI model.

Advantages over Hubs

Non long ago, switches were considered an extravagance, and the mainstream network product to deploy onto a campus network was a hub. In fact, like shooting fish in a barrel-to-call up formulas allowed anyone to make up one's mind in what circumstance hubs should be deployed in a network.

The good news is that we've passed a major milestone where the price of switches has come up downward and they are easy to notice on most whatsoever retail shelf. This helps attract penny-focused firms and motivates them to take the plunge and purchase more switching hardware. In fact, when comparing dollars to performance comeback switches cost an infrastructure less coin and offer more operation if properly used. Not every system is pushing 100 million or 1 billion bits per 2d in and out of the switch, all of the time. Recall of the bandwidth in terms of slices. For example, say that at one moment yous are nearly saturating the network with a database query asking that goes out of the switch's upstream port to somewhere out of the function. The side by side moment your system is tranquility; this is where your coworker is using the bandwidth to download an Adam Sandler video from YouTube. Because switches are using switched compages to go along these 2 communications separate from each other, the finite amount of bandwidth is accordingly used. If this occurred on a cheaper set of hubs, both you and your coworker would take been saturating the network, preventing each other from transmitting any packets and possibly causing frame collisions.

The other reason switches are a better investment in terms of efficiency compared to cost is at the heart of the switching engineering congenital within switches. Without getting into electric and computer engineering concepts, switches are effective at keeping conversations that occur between ii ports separated from whatever other ports or pairs of ports, without sacrificing the speed of transmission/reception or bandwidth. So, suppose y'all desire to download that Adam Sandler video from your coworker. Both of you volition make maximum utilise of the bandwidth between you lot as long as you are on the same switch. But at present say that two other coworkers are busy downloading PC games from a game-sharing Web site using Hypertext Transfer Protocol (HTTP). If they happened to be on the same switch as you and your cubical neighbor, both sets of network traffic communications would not interfere with each other, and this raises the efficiency of the workplace, at least on a theoretical facilitation attribute.

Now, it'southward pretty tough to notice a hub these days, let alone one that has more a scattering of ports, and that helps when it comes to computer security. A hub is really a multiport repeater. Given that you are now on a basic network hub, now the network traffic that hits the wire when you send your database query request actually goes to every port and every workstation that is connected to the hub, perhaps causing frame collisions. (Retrieve back in the erstwhile days, Ethernet transmission collisions occurred when two workstations transmitted their bits onto the network at near the aforementioned fourth dimension over a shared medium unbeknownst to each other. This serial of bits overlapped each other, resulting in a standoff. Then every workstation had to cease "talking" for a brusque but random menses of time until everything settled back down on the network.) Switches manage to keep the medium shared in such a way that circulate frames are transmitted to each port of the switch, just unicast frames are non, in virtually cases. A switch has to broadcast a unicast frame when it does non know which port a destination MAC address is connected to, so it has to broadcast information technology to every port, and when its port-to-MAC address tabular array (known equally the content-addressable memory, or CAM) is filled and cannot accept more entries, it is forced to revert to the behavior of a hub. Otherwise, it keeps switched conversations autonomously from each host that is communicating on the switch.

Since the conversations are separated from each other, it also means that our workstation cannot eavesdrop on or "sniff" the unicast traffic using a network analyzer considering of the separation in nigh cases. Even so, sometimes you lot can configure a calculator network card to accept traffic destined to anyone else (chosen promiscuous manner) equally well as being physically located on either 1 of the switch's truck ports or traffic spanning port that was left unsecured.

Every advance in progress, and peculiarly in technology, has a caveat or vulnerability. So, when you lot experience the urge to avowal about how secure your new rack full of switches is, ensure that the IOS (or CatOS, if that is the example) is the latest supported version, logins and passwords are managed, data logging is going to a syslog facility of some sort, unwanted or unneeded services are turned off, and configurations are routinely checked. You should practise all of this and more to reduce the chance of commercial or open source tools turning your fancy switch farm into a hub by flooding its port-to-MAC clan table.

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