Critical Networking Switch

The concept of a Critical Networking Switch (inspired by time-space switching) is to re-organise network traffic with the minimum payload distance. From the transmitter packet arrival rate and the expected packet receiver arrival rate, as long as the total payload per packet to the receiver is also known, the Critical Networking switch can handle any discrepancy between the mismanagement of payload distance from the source to the switch, and from the switch to the destination. The Critical Networking switch can route traffic effectively by deciding the minimum payload distance from the source to the destination either by requesting more or less payload per packet (service rate) given the constraint of the link capacity in payload per second. Although, the NTO deterministic packet transmission rate is ideal for Critical Networking, as any continuous congestion delay can be compensated by a single phase shift from packet per second to payload per packet (alternating between buffering and flowing). Critical Networking traffic can also handle each networking incident as a discrete event (NTO continuous model is easier), but rapid processing power is required to respond to any unexpected change. A Critical Networking Switch would just maintain the NTO requirement, as it has already been re-organising traffic suitable for application, link

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capacity and receiver transmission specification. A NTO payload distance would be the same (Same number of packet per second from the source as it is to the destination (Figure 5.5).

Figure 5.5 this is an example of a Critical Networking Minimum distance calculation. The minimum distance is always the same distance from the source (A) to the switch (origin) as it is from the switch to the destination (B). Similarly the best time response can also be measured by considering the reduction of payload per second rate to their respective distance

Other non-NTO application traffic could possibly send packets at a random packet arrival rate to the switch (labelled as PA) and with a random payload per packet rate. The total payload per packet and packet per second expected from the receiver is the area of the two parameters (D) (labelled as PB). The function of a Critical Networking Switch is to organise a traffic routing plan to reduce the delay between the receiver and the transmitter, even when there is a reduced payload per second service rate (link capacity) from the transmitter to the switch and from the switch to the receiver.

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The reduced service rate is the difference between application payload per second requirement (application service rate) and the maximum link capacity (maximum service rate). The extra congestion delay can be worked out by the designated application payload per second (DA) and the link reduce payload per second rate (d1). The result is the increase of response time estimate between the distances. This deterministic congestion delay can also be used to decide whether to wait for more payloads per packet from the transmitter (increasing payload distance from PA to the switch) or to convert more payloads per packet to maximise the change in link capacity payload per second rate (d1) to the receiver (increasing payload distance from the switch to PB).

An NTO based network requires strict network resource management. Each network link must update its link capacity and reflect its information before assigning transmission. Dynamic network link capacity updating is crucial to maintain the Quality of Service amongst other real time critical applications (based on input measurement rather than another network management feedback protocol). Rather than using overhead (packet network information) to direct network traffic, flow can be directed using application frequency analysis. Frame overhead not only increases buffering delay by encumbering each frame with a larger payload, but it also restricts the level of freedom for network switching to manage traffic. Buffering delay is caused by large payload frames and congests the network by uncertain frame rates.

Using the NTO, the transmission of payloads with a fixed payload per second, D(t), by application protocols guarantees the oscillatory periodic transmission rates of both frames P(t) and frame sizes R(t). The two quantities P(t) and R(t) are ninety degrees out of phase using the NTO because of their sinusoidal nature and the relationship between them. The NTO parameters combine to deliver a deterministic payload per

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second (33). Thus a switching arrangement is achieved to remove network delay completely (the delay is the measurement between two payload transmissions). The transmission rate, D(t), is maintained consistently in a network to ensure the lowest minimum distance between the source and the destination.

When a continuous transmission uses a large payload per packet resource, it should also use less of the packet per second resource. These two parameters, R(t) and P(t), create the payload distance of the link. To illustrate the fundamental concept, transmission between nodes NA and NB via an intermediate node NC is considered as shown in Figure 5.5. NA has the (packet, payload) coordinates (PA, RA) and NB the

coordinates (PB, RB). That is the number of packets generated in one second by A is PA with a payload per packet RA. It is thus possible to define a payload distance for link AC by the square root of the sum of the squares of PA and RA. This may be converted to a time TAC by dividing by the payload per second value for the link NA- NC, which is denoted by d1: 𝑇𝐴𝐶 = √𝑃_𝐴2_{+ 𝑅} 𝐴2 𝑑1 Equation 5-12

Considering the transmission from NC-NB, a similar argument may be made to give a time over the link BC, with payload per second d2, of:

𝑇𝐶𝐵=

√𝑃_𝐵2 _{+ (𝑅}

𝐵− 𝑅𝐴)2 𝑑2

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The two source rates PA and PB are fixed as is the total payload per packet at NB. Therefore, the time is minimized by finding the optimum value of RA by differentiating the total time TAC+TCB with respect to RA. .

Critical Networking encourages application payload per second to be the same as the

link capacity payload per second transmission rate. This method allows the network switching process the freedom to delegate other link resources for other real time critical applications and transmit non-critical applications when the network becomes available.

The router setup can mirror that agreed by the NTO to produce a fixed time interval in a network, rather than variable uncertain congestion and buffer delay. This also removes the need for packet retransmission and packet timeout due to the fixed flow rate, eliminating packet loss from exceeding the critical time window. The timeless parameter payload per packet (R) is the main concept for network traffic oscillation and network workload management, and it is only increased in size when multiple packets arrive simultaneously (within the hold time control). The buffer regulates payload to packet; when packets are merged, an effective application payload is released as payload per second (D). The buffer size dictates the pace of each individual application’s payload per packet and its payload per packet operates with the flow controller. The function of the latter is to evenly distribute the available physical medium bandwidth into packets (time slots) but depending on the payload, it should also increase the packet distribution based on payload. The two aspects of payload per packet and packets per second form the basis of the NTO time vector metric when one time slot of transmission is considered that will be sent over a link with payload capacity dL

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By careful choice of the P and R values for each transmission in the network (packets are separated into different queues based on their traffic load), it is possible to minimise this metric and match application payload per second to the link capacity

payload per second. Correct matching removes random queuing delays and enables deterministic performance to be achieved. Random P and R may appear in the router. Traditionally EIGRP has been utilised to manage packets on an individual basis). The NTO promotes a separate queue for each type of packet, with the payload per packet R used to achieve the separation. The expected delay is calculated by measuring the magnitude of the payload per second of the packet/payload. The expression (Equation 5-16) is compared to the lower expected service rate (d1) also in payload per second per server queue. When the router is placed in a mesh network, the total delay expected of the packet depends on its P and R values as well as the arrival rates of P and R at the sender. In Figure 5.6, a mesh network of two nodes with a router in the middle is considered. The sender (node A) can transmit a random number of packets per second (P) to the router with a random payload per packet sizes (R). The router has the ability to reduce or increase the payload size of the packet to improve the response time to node B. The total payload distance can be worked out by calculating the payload distance from node A to the router and from the router to node B. The time delay of this transmission depends on the service rates of the two links (A to router, router to B), this is labelled D1 and D2. The service time (buffering delay) is determined via the inverse of the service rate (Figure 5.5).

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Figure 5.6 Real time critical Ethernet network simulation designed to mimic the air traffic SWIM infrastructure in an airport

The lowest service time is the minimum service time of the payload size (Equation 5-14). The true time distance is worked out by the similar relationship of a sine function (Equation 5-15). The minimum delay is when the link transmission delays match; this yields a “Snell’s law” using payload per second (service rate) (Equation 5-16).

𝑇𝑁𝑇𝑂=𝑇′(𝑡)= 𝑅𝐴(𝑡)

𝐷1(𝑡)√𝑃𝐴(𝑡)2+ 𝑅𝐴(𝑡)2

− 𝑅𝐵(𝑡) − 𝑅𝐴(𝑡)

𝐷2(𝑡)√𝑃𝐵(𝑡)2+ (𝑅𝐵(𝑡) − 𝑅𝐴(𝑡))2

151 𝑠𝑖𝑛(𝜔1𝑡) = 𝑅_𝐴(𝑡) √𝑃𝐴(𝑡)2+ 𝑅𝐴(𝑡)2 and 𝑠𝑖𝑛(𝜔2𝑡)= 𝑅_𝐵(𝑡) − 𝑅_𝐴(𝑡) √𝑃𝐵(𝑡)2+ (𝑅𝐵(𝑡) − 𝑅𝐴(𝑡))2 Equation 5-15 At 𝑇′(t)=0 𝑠𝑖𝑛(𝜔1𝑡) 𝐷₁(𝑡) = 𝑠𝑖𝑛(𝜔2𝑡) 𝐷₂(𝑡) Equation 5-16

An oscillating traffic model would have an angular payload velocity, and using this property, the NTO traffic only requires angular phase shift by rearranging the sine function on the left hand side with the different of the link payload per second ratio (Figure 5.7).

Figure 5.7 Oscillating Traffic can easily compensates the different in transmission rate (payload per second service rate) of the two link capacity

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