Illegal production is caused by the offender illegally storing, transporting, trading or appropriating drugs.
Because the unit of measurement is in milliliters, when determining substances
Liquid drugs require absolute accuracy, especially for
Drugs must not be packaged in tubes with symbols, content, and mass marked on them.
Maybe you are interested!
-
Rate of Vitamin D Deficiency and Frequency of Acute Respiratory Infections in Children Under 5 Years Old in An Lao District, Hai Phong City -
![Qos Assurance Methods for Multimedia Communications
zt2i3t4l5ee
zt2a3gs
zt2a3ge
zc2o3n4t5e6n7ts
low. The EF PHB requires a sufficiently large number of output ports to provide low delay, low loss, and low jitter.
EF PHBs can be implemented if the output ports bandwidth is sufficiently large, combined with small buffer sizes and other network resources dedicated to EF packets, to allow the routers service rate for EF packets on an output port to exceed the arrival rate λ of packets at that port.
This means that packets with PHB EF are considered with a pre-allocated amount of output bandwidth and a priority that ensures minimum loss, minimum delay and minimum jitter before being put into operation.
PHB EF is suitable for channel simulation, leased line simulation, and real-time services such as voice, video without compromising on high loss, delay and jitter values.
Figure 2.10 Example of EF installation
Figure 2.10 shows an example of an EF PHB implementation. This is a simple priority queue scheduling technique. At the edges of the DS domain, EF packet traffic is prioritized according to the values agreed upon by the SLA. The EF queue in the figure needs to output packets at a rate higher than the packet arrival rate λ. To provide an EF PHB over an end-to-end DS domain, bandwidth at the output ports of the core routers needs to be allocated in advance to ensure the requirement μ > λ. This can be done by a pre-configured provisioning process. In the figure, EF packets are placed in the priority queue (the upper queue). With such a length, the queue can operate with μ > λ.
Since EF was primarily used for real-time services such as voice and video, and since real-time services use UDP instead of TCP, RED is generally
not suitable for EF queues because applications using UDP will not respond to random packet drop and RED will strip unnecessary packets.
2.2.4.2 Assured Forwarding (AF) PHB
PHB AF is defined by RFC 2597. The purpose of PHB AF is to deliver packets reliably and therefore delay and jitter are considered less important than packet loss. PHB AF is suitable for non-real-time services such as applications using TCP. PHB AF first defines four classes: AF1, AF2, AF3, AF4. For each of these AF classes, packets are then classified into three subclasses with three distinct priority levels.
Table 2.8 shows the four AF classes and 12 AF subclasses and the DSCP values for the 12 AF subclasses defined by RFC 2597. RFC 2597 also allows for more than three separate priority levels to be added for internal use. However, these separate priority levels will only have internal significance.
PHB Class
PHB Subclass
Package type
DSCP
AF4
AF41
Short
100010
AF42
Medium
100100
AF43
High
100110
AF3
AF31
Short
011010
AF32
Medium
011100
AF33
High
011110
AF2
AF21
Short
010010
AF22
Medium
010100
AF23
High
010110
AF1
AF11
Short
001010
AF12
Medium
001100
AF13
High
001110
Table 2.8 AF DSCPs
The AF PHB ensures that packets are forwarded with a high probability of delivery to the destination within the bounds of the rate agreed upon in an SLA. If AF traffic at an ingress port exceeds the pre-priority rate, which is considered non-compliant or “out of profile”, the excess packets will not be delivered to the destination with the same probability as the packets belonging to the defined traffic or “in profile” packets. When there is network congestion, the out of profile packets are dropped before the in profile packets are dropped.
When service levels are defined using AF classes, different quantity and quality between AF classes can be realized by allocating different amounts of bandwidth and buffer space to the four AF classes. Unlike
EF, most AF traffic is non-real-time traffic using TCP, and the RED queue management strategy is an AQM (Adaptive Queue Management) strategy suitable for use in AF PHBs. The four AF PHB layers can be implemented as four separate queues. The output port bandwidth is divided into four AF queues. For each AF queue, packets are marked with three “colors” corresponding to three separate priority levels.
In addition to the 32 DSCP 1 groups defined in Table 2.8, 21 DSCPs have been standardized as follows: one for PHB EF, 12 for PHB AF, and 8 for CSCP. There are 11 DSCP 1 groups still available for other standards.
2.2.5.Example of Differentiated Services
We will look at an example of the Differentiated Service model and mechanism of operation. The architecture of Differentiated Service consists of two basic sets of functions:
Edge functions: include packet classification and traffic conditioning. At the inbound edge of the network, incoming packets are marked. In particular, the DS field in the packet header is set to a certain value. For example, in Figure 2.12, packets sent from H1 to H3 are marked at R1, while packets from H2 to H4 are marked at R2. The labels on the received packets identify the service class to which they belong. Different traffic classes receive different services in the core network. The RFC definition uses the term behavior aggregate rather than the term traffic class. After being marked, a packet can be forwarded immediately into the network, delayed for a period of time before being forwarded, or dropped. We will see that there are many factors that affect how a packet is marked, and whether it is forwarded immediately, delayed, or dropped.
Figure 2.12 DiffServ Example
Core functionality: When a DS-marked packet arrives at a Diffservcapable router, the packet is forwarded to the next router based on
Per-hop behavior is associated with packet classes. Per-hop behavior affects router buffers and the bandwidth shared between competing classes. An important principle of the Differentiated Service architecture is that a routers per-hop behavior is based only on the packets marking or the class to which it belongs. Therefore, if packets sent from H1 to H3 as shown in the figure receive the same marking as packets from H2 to H4, then the network routers treat the packets exactly the same, regardless of whether the packet originated from H1 or H2. For example, R3 does not distinguish between packets from h1 and H2 when forwarding packets to R4. Therefore, the Differentiated Service architecture avoids the need to maintain router state about separate source-destination pairs, which is important for network scalability.
Chapter Conclusion
Chapter 2 has presented and clarified two main models of deploying and installing quality of service in IP networks. While the traditional best-effort model has many disadvantages, later models such as IntServ and DiffServ have partly solved the problems that best-effort could not solve. IntServ follows the direction of ensuring quality of service for each separate flow, it is built similar to the circuit switching model with the use of the RSVP resource reservation protocol. IntSer is suitable for services that require fixed bandwidth that is not shared such as VoIP services, multicast TV services. However, IntSer has disadvantages such as using a lot of network resources, low scalability and lack of flexibility. DiffServ was born with the idea of solving the disadvantages of the IntServ model.
DiffServ follows the direction of ensuring quality based on the principle of hop-by-hop behavior based on the priority of marked packets. The policy for different types of traffic is decided by the administrator and can be changed according to reality, so it is very flexible. DiffServ makes better use of network resources, avoiding idle bandwidth and processing capacity on routers. In addition, the DifServ model can be deployed on many independent domains, so the ability to expand the network becomes easy.
Chapter 3: METHODS TO ENSURE QoS FOR MULTIMEDIA COMMUNICATIONS
In packet-switched networks, different packet flows often have to share the transmission medium all the way to the destination station. To ensure the fair and efficient allocation of bandwidth to flows, appropriate serving mechanisms are required at network nodes, especially at gateways or routers, where many different data flows often pass through. The scheduler is responsible for serving packets of the selected flow and deciding which packet will be served next. Here, a flow is understood as a set of packets belonging to the same priority class, or originating from the same source, or having the same source and destination addresses, etc.
In normal state when there is no congestion, packets will be sent as soon as they are delivered. In case of congestion, if QoS assurance methods are not applied, prolonged congestion can cause packet drops, affecting service quality. In some cases, congestion is prolonged and widespread in the network, which can easily lead to the network being frozen, or many packets being dropped, seriously affecting service quality.
Therefore, in this chapter, in sections 3.2 and 3.3, we introduce some typical network traffic load monitoring techniques to predict and prevent congestion before it occurs through the measure of dropping (removing) packets early when there are signs of impending congestion.
3.1. DropTail method
DropTail is a simple, traditional queue management method based on FIFO mechanism. All incoming packets are placed in the queue, when the queue is full, the later packets are dropped.
Due to its simplicity and ease of implementation, DropTail has been used for many years on Internet router systems. However, this algorithm has the following disadvantages:
− Cannot avoid the phenomenon of “Lock out”: Occurs when 1 or several traffic streams monopolize the queue, making packets of other connections unable to pass through the router. This phenomenon greatly affects reliable transmission protocols such as TCP. According to the anti-congestion algorithm, when locked out, the TCP connection stream will reduce the window size and reduce the packet transmission speed exponentially.
− Can cause Global Synchronization: This is the result of a severe “Lock out” phenomenon. Some neighboring routers have their queues monopolized by a number of connections, causing a series of other TCP connections to be unable to pass through and simultaneously reducing the transmission speed. After those monopolized connections are temporarily suspended,
Once the queue is cleared, it takes a considerable amount of time for TCP connections to return to their original speed.
− Full Queue phenomenon: Data transmitted on the Internet often has an explosion, packets arriving at the router are often in clusters rather than in turn. Therefore, the operating mechanism of DropTail makes the queue easily full for a long period of time, leading to the average delay time of large packets. To avoid this phenomenon, with DropTail, the only way is to increase the routers buffer, this method is very expensive and ineffective.
− No QoS guarantee: With the DropTail mechanism, there is no way to prioritize important packets to be transmitted through the router earlier when all are in the queue. Meanwhile, with multimedia communication, ensuring connection and stable speed is extremely important and the DropTail algorithm cannot satisfy.
The problem of choosing the buffer size of the routers in the network is to “absorb” short bursts of traffic without causing too much queuing delay. This is necessary in bursty data transmission. The queue size determines the size of the packet bursts (traffic spikes) that we want to be able to transmit without being dropped at the routers.
In IP-based application networks, packet dropping is an important mechanism for indirectly reporting congestion to end stations. A solution that prevents router queues from filling up while reducing the packet drop rate is called dynamic queue management.
3.2. Random elimination method – RED
3.2.1 Overview
RED (Random Early Detection of congestion; Random Early Drop) is one of the first AQM algorithms proposed in 1993 by Sally Floyd and Van Jacobson, two scientists at the Lawrence Berkeley Laboratory of the University of California, USA. Due to its outstanding advantages compared to previous queue management algorithms, RED has been widely installed and deployed on the Internet.
The most fundamental point of their work is that the most effective place to detect congestion and react to it is at the gateway or router.
Source entities (senders) can also do this by estimating end-to-end delay, throughput variability, or the rate of packet retransmissions due to drop. However, the sender and receiver view of a particular connection cannot tell which gateways on the network are congested, and cannot distinguish between propagation delay and queuing delay. Only the gateway has a true view of the state of the queue, the link share of the connections passing through it at any given time, and the quality of service requirements of the
traffic flows. The RED gateway monitors the average queue length, which detects early signs of impending congestion (average queue length exceeding a predetermined threshold) and reacts appropriately in one of two ways:
− Drop incoming packets with a certain probability, to indirectly inform the source of congestion, the source needs to reduce the transmission rate to keep the queue from filling up, maintaining the ability to absorb incoming traffic spikes.
− Mark “congestion” with a certain probability in the ECN field in the header of TCP packets to notify the source (the receiving entity will copy this bit into the acknowledgement packet).
Figure 3. 1 RED algorithm
The main goal of RED is to avoid congestion by keeping the average queue size within a sufficiently small and stable region, which also means keeping the queuing delay sufficiently small and stable. Achieving this goal also helps: avoid global synchronization, not resist bursty traffic flows (i.e. flows with low average throughput but high volatility), and maintain an upper bound on the average queue size even in the absence of cooperation from transport layer protocols.
To achieve the above goals, RED gateways must do the following:
− The first is to detect congestion early and react appropriately to keep the average queue size small enough to keep the network operating in the low latency, high throughput region, while still allowing the queue size to fluctuate within a certain range to absorb short-term fluctuations. As discussed above, the gateway is the most appropriate place to detect congestion and is also the most appropriate place to decide which specific connection to report congestion to.
− The second thing is to notify the source of congestion. This is done by marking and notifying the source to reduce traffic. Normally the RED gateway will randomly drop packets. However, if congestion
If congestion is detected before the queue is full, it should be combined with packet marking to signal congestion. The RED gateway has two options: drop or mark; where marking is done by marking the ECN field of the packet with a certain probability, to signal the source to reduce the traffic entering the network.
− An important goal that RED gateways need to achieve is to avoid global synchronization and not to resist traffic flows that have a sudden characteristic. Global synchronization occurs when all connections simultaneously reduce their transmission window size, leading to a severe drop in throughput at the same time. On the other hand, Drop Tail or Random Drop strategies are very sensitive to sudden flows; that is, the gateway queue will often overflow when packets from these flows arrive. To avoid these two phenomena, gateways can use special algorithms to detect congestion and decide which connections will be notified of congestion at the gateway. The RED gateway randomly selects incoming packets to mark; with this method, the probability of marking a packet from a particular connection is proportional to the connections shared bandwidth at the gateway.
− Another goal is to control the average queue size even without cooperation from the source entities. This can be done by dropping packets when the average size exceeds an upper threshold (instead of marking it). This approach is necessary in cases where most connections have transmission times that are less than the round-trip time, or where the source entities are not able to reduce traffic in response to marking or dropping packets (such as UDP flows).
3.2.2 Algorithm
This section describes the algorithm for RED gateways. RED gateways calculate the average queue size using a low-pass filter. This average queue size is compared with two thresholds: minth and maxth. When the average queue size is less than the lower threshold, no incoming packets are marked or dropped; when the average queue size is greater than the upper threshold, all incoming packets are dropped. When the average queue size is between minth and maxth, each incoming packet is marked or dropped with a probability pa, where pa is a function of the average queue size avg; the probability of marking or dropping a packet for a particular connection is proportional to the bandwidth share of that connection at the gateway. The general algorithm for a RED gateway is described as follows: [5]
For each packet arrival
Caculate the average queue size avg If minth ≤ avg < maxth
div.maincontent .s1 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 15pt; }
div.maincontent .s2 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 15pt; }
div.maincontent .p { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; margin:0pt; }
div.maincontent p { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; margin:0pt; }
div.maincontent .s3 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s4 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s5 { color: black; font-family:Times New Roman, serif; font-style: italic; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s6 { color: black; font-family:Times New Roman, serif; font-style: italic; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s7 { color: black; font-family:Wingdings; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s8 { color: black; font-family:Arial, sans-serif; font-style: italic; font-weight: bold; text-decoration: none; font-size: 15pt; }
div.maincontent .s9 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s10 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 9pt; vertical-align: 6pt; }
div.maincontent .s11 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 13pt; }
div.maincontent .s12 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 10pt; }
div.maincontent .s13 { color: black; font-family:Times New Roman, serif; font-style: normal; font-weight: normal; text-d](https://tailieuthamkhao.com/uploads/2022/05/15/danh-gia-hieu-qua-dam-bao-qos-cho-truyen-thong-da-phuong-tien-cua-chien-6-1-120x90.jpg)
Qos Assurance Methods for Multimedia Communications
zt2i3t4l5ee
zt2a3gs
zt2a3ge
zc2o3n4t5e6n7ts
low. The EF PHB requires a sufficiently large number of output ports to provide low delay, low loss, and low jitter.
EF PHBs can be implemented if the output port's bandwidth is sufficiently large, combined with small buffer sizes and other network resources dedicated to EF packets, to allow the router's service rate for EF packets on an output port to exceed the arrival rate λ of packets at that port.
This means that packets with PHB EF are considered with a pre-allocated amount of output bandwidth and a priority that ensures minimum loss, minimum delay and minimum jitter before being put into operation.
PHB EF is suitable for channel simulation, leased line simulation, and real-time services such as voice, video without compromising on high loss, delay and jitter values.
Figure 2.10 Example of EF installation
Figure 2.10 shows an example of an EF PHB implementation. This is a simple priority queue scheduling technique. At the edges of the DS domain, EF packet traffic is prioritized according to the values agreed upon by the SLA. The EF queue in the figure needs to output packets at a rate higher than the packet arrival rate λ. To provide an EF PHB over an end-to-end DS domain, bandwidth at the output ports of the core routers needs to be allocated in advance to ensure the requirement μ > λ. This can be done by a pre-configured provisioning process. In the figure, EF packets are placed in the priority queue (the upper queue). With such a length, the queue can operate with μ > λ.
Since EF was primarily used for real-time services such as voice and video, and since real-time services use UDP instead of TCP, RED is generally
not suitable for EF queues because applications using UDP will not respond to random packet drop and RED will strip unnecessary packets.
2.2.4.2 Assured Forwarding (AF) PHB
PHB AF is defined by RFC 2597. The purpose of PHB AF is to deliver packets reliably and therefore delay and jitter are considered less important than packet loss. PHB AF is suitable for non-real-time services such as applications using TCP. PHB AF first defines four classes: AF1, AF2, AF3, AF4. For each of these AF classes, packets are then classified into three subclasses with three distinct priority levels.
Table 2.8 shows the four AF classes and 12 AF subclasses and the DSCP values for the 12 AF subclasses defined by RFC 2597. RFC 2597 also allows for more than three separate priority levels to be added for internal use. However, these separate priority levels will only have internal significance.
PHB Class
PHB Subclass
Package type
DSCP
AF4
AF41
Short
100010
AF42
Medium
100100
AF43
High
100110
AF3
AF31
Short
011010
AF32
Medium
011100
AF33
High
011110
AF2
AF21
Short
010010
AF22
Medium
010100
AF23
High
010110
AF1
AF11
Short
001010
AF12
Medium
001100
AF13
High
001110
Table 2.8 AF DSCPs
The AF PHB ensures that packets are forwarded with a high probability of delivery to the destination within the bounds of the rate agreed upon in an SLA. If AF traffic at an ingress port exceeds the pre-priority rate, which is considered non-compliant or “out of profile”, the excess packets will not be delivered to the destination with the same probability as the packets belonging to the defined traffic or “in profile” packets. When there is network congestion, the out of profile packets are dropped before the in profile packets are dropped.
When service levels are defined using AF classes, different quantity and quality between AF classes can be realized by allocating different amounts of bandwidth and buffer space to the four AF classes. Unlike
EF, most AF traffic is non-real-time traffic using TCP, and the RED queue management strategy is an AQM (Adaptive Queue Management) strategy suitable for use in AF PHBs. The four AF PHB layers can be implemented as four separate queues. The output port bandwidth is divided into four AF queues. For each AF queue, packets are marked with three “colors” corresponding to three separate priority levels.
In addition to the 32 DSCP 1 groups defined in Table 2.8, 21 DSCPs have been standardized as follows: one for PHB EF, 12 for PHB AF, and 8 for CSCP. There are 11 DSCP 1 groups still available for other standards.
2.2.5.Example of Differentiated Services
We will look at an example of the Differentiated Service model and mechanism of operation. The architecture of Differentiated Service consists of two basic sets of functions:
Edge functions: include packet classification and traffic conditioning. At the inbound edge of the network, incoming packets are marked. In particular, the DS field in the packet header is set to a certain value. For example, in Figure 2.12, packets sent from H1 to H3 are marked at R1, while packets from H2 to H4 are marked at R2. The labels on the received packets identify the service class to which they belong. Different traffic classes receive different services in the core network. The RFC definition uses the term behavior aggregate rather than the term traffic class. After being marked, a packet can be forwarded immediately into the network, delayed for a period of time before being forwarded, or dropped. We will see that there are many factors that affect how a packet is marked, and whether it is forwarded immediately, delayed, or dropped.
Figure 2.12 DiffServ Example
Core functionality: When a DS-marked packet arrives at a Diffservcapable router, the packet is forwarded to the next router based on
Per-hop behavior is associated with packet classes. Per-hop behavior affects router buffers and the bandwidth shared between competing classes. An important principle of the Differentiated Service architecture is that a router's per-hop behavior is based only on the packet's marking or the class to which it belongs. Therefore, if packets sent from H1 to H3 as shown in the figure receive the same marking as packets from H2 to H4, then the network routers treat the packets exactly the same, regardless of whether the packet originated from H1 or H2. For example, R3 does not distinguish between packets from h1 and H2 when forwarding packets to R4. Therefore, the Differentiated Service architecture avoids the need to maintain router state about separate source-destination pairs, which is important for network scalability.
Chapter Conclusion
Chapter 2 has presented and clarified two main models of deploying and installing quality of service in IP networks. While the traditional best-effort model has many disadvantages, later models such as IntServ and DiffServ have partly solved the problems that best-effort could not solve. IntServ follows the direction of ensuring quality of service for each separate flow, it is built similar to the circuit switching model with the use of the RSVP resource reservation protocol. IntSer is suitable for services that require fixed bandwidth that is not shared such as VoIP services, multicast TV services. However, IntSer has disadvantages such as using a lot of network resources, low scalability and lack of flexibility. DiffServ was born with the idea of solving the disadvantages of the IntServ model.
DiffServ follows the direction of ensuring quality based on the principle of hop-by-hop behavior based on the priority of marked packets. The policy for different types of traffic is decided by the administrator and can be changed according to reality, so it is very flexible. DiffServ makes better use of network resources, avoiding idle bandwidth and processing capacity on routers. In addition, the DifServ model can be deployed on many independent domains, so the ability to expand the network becomes easy.
Chapter 3: METHODS TO ENSURE QoS FOR MULTIMEDIA COMMUNICATIONS
In packet-switched networks, different packet flows often have to share the transmission medium all the way to the destination station. To ensure the fair and efficient allocation of bandwidth to flows, appropriate serving mechanisms are required at network nodes, especially at gateways or routers, where many different data flows often pass through. The scheduler is responsible for serving packets of the selected flow and deciding which packet will be served next. Here, a flow is understood as a set of packets belonging to the same priority class, or originating from the same source, or having the same source and destination addresses, etc.
In normal state when there is no congestion, packets will be sent as soon as they are delivered. In case of congestion, if QoS assurance methods are not applied, prolonged congestion can cause packet drops, affecting service quality. In some cases, congestion is prolonged and widespread in the network, which can easily lead to the network being "frozen", or many packets being dropped, seriously affecting service quality.
Therefore, in this chapter, in sections 3.2 and 3.3, we introduce some typical network traffic load monitoring techniques to predict and prevent congestion before it occurs through the measure of dropping (removing) packets early when there are signs of impending congestion.
3.1. DropTail method
DropTail is a simple, traditional queue management method based on FIFO mechanism. All incoming packets are placed in the queue, when the queue is full, the later packets are dropped.
Due to its simplicity and ease of implementation, DropTail has been used for many years on Internet router systems. However, this algorithm has the following disadvantages:
− Cannot avoid the phenomenon of “Lock out”: Occurs when 1 or several traffic streams monopolize the queue, making packets of other connections unable to pass through the router. This phenomenon greatly affects reliable transmission protocols such as TCP. According to the anti-congestion algorithm, when locked out, the TCP connection stream will reduce the window size and reduce the packet transmission speed exponentially.
− Can cause Global Synchronization: This is the result of a severe “Lock out” phenomenon. Some neighboring routers have their queues monopolized by a number of connections, causing a series of other TCP connections to be unable to pass through and simultaneously reducing the transmission speed. After those monopolized connections are temporarily suspended,
Once the queue is cleared, it takes a considerable amount of time for TCP connections to return to their original speed.
− Full Queue phenomenon: Data transmitted on the Internet often has an explosion, packets arriving at the router are often in clusters rather than in turn. Therefore, the operating mechanism of DropTail makes the queue easily full for a long period of time, leading to the average delay time of large packets. To avoid this phenomenon, with DropTail, the only way is to increase the router's buffer, this method is very expensive and ineffective.
− No QoS guarantee: With the DropTail mechanism, there is no way to prioritize important packets to be transmitted through the router earlier when all are in the queue. Meanwhile, with multimedia communication, ensuring connection and stable speed is extremely important and the DropTail algorithm cannot satisfy.
The problem of choosing the buffer size of the routers in the network is to “absorb” short bursts of traffic without causing too much queuing delay. This is necessary in bursty data transmission. The queue size determines the size of the packet bursts (traffic spikes) that we want to be able to transmit without being dropped at the routers.
In IP-based application networks, packet dropping is an important mechanism for indirectly reporting congestion to end stations. A solution that prevents router queues from filling up while reducing the packet drop rate is called dynamic queue management.
3.2. Random elimination method – RED
3.2.1 Overview
RED (Random Early Detection of congestion; Random Early Drop) is one of the first AQM algorithms proposed in 1993 by Sally Floyd and Van Jacobson, two scientists at the Lawrence Berkeley Laboratory of the University of California, USA. Due to its outstanding advantages compared to previous queue management algorithms, RED has been widely installed and deployed on the Internet.
The most fundamental point of their work is that the most effective place to detect congestion and react to it is at the gateway or router.
Source entities (senders) can also do this by estimating end-to-end delay, throughput variability, or the rate of packet retransmissions due to drop. However, the sender and receiver view of a particular connection cannot tell which gateways on the network are congested, and cannot distinguish between propagation delay and queuing delay. Only the gateway has a true view of the state of the queue, the link share of the connections passing through it at any given time, and the quality of service requirements of the
traffic flows. The RED gateway monitors the average queue length, which detects early signs of impending congestion (average queue length exceeding a predetermined threshold) and reacts appropriately in one of two ways:
− Drop incoming packets with a certain probability, to indirectly inform the source of congestion, the source needs to reduce the transmission rate to keep the queue from filling up, maintaining the ability to absorb incoming traffic spikes.
− Mark “congestion” with a certain probability in the ECN field in the header of TCP packets to notify the source (the receiving entity will copy this bit into the acknowledgement packet).
Figure 3. 1 RED algorithm
The main goal of RED is to avoid congestion by keeping the average queue size within a sufficiently small and stable region, which also means keeping the queuing delay sufficiently small and stable. Achieving this goal also helps: avoid global synchronization, not resist bursty traffic flows (i.e. flows with low average throughput but high volatility), and maintain an upper bound on the average queue size even in the absence of cooperation from transport layer protocols.
To achieve the above goals, RED gateways must do the following:
− The first is to detect congestion early and react appropriately to keep the average queue size small enough to keep the network operating in the low latency, high throughput region, while still allowing the queue size to fluctuate within a certain range to absorb short-term fluctuations. As discussed above, the gateway is the most appropriate place to detect congestion and is also the most appropriate place to decide which specific connection to report congestion to.
− The second thing is to notify the source of congestion. This is done by marking and notifying the source to reduce traffic. Normally the RED gateway will randomly drop packets. However, if congestion
If congestion is detected before the queue is full, it should be combined with packet marking to signal congestion. The RED gateway has two options: drop or mark; where marking is done by marking the ECN field of the packet with a certain probability, to signal the source to reduce the traffic entering the network.
− An important goal that RED gateways need to achieve is to avoid global synchronization and not to resist traffic flows that have a sudden characteristic. Global synchronization occurs when all connections simultaneously reduce their transmission window size, leading to a severe drop in throughput at the same time. On the other hand, Drop Tail or Random Drop strategies are very sensitive to sudden flows; that is, the gateway queue will often overflow when packets from these flows arrive. To avoid these two phenomena, gateways can use special algorithms to detect congestion and decide which connections will be notified of congestion at the gateway. The RED gateway randomly selects incoming packets to mark; with this method, the probability of marking a packet from a particular connection is proportional to the connection's shared bandwidth at the gateway.
− Another goal is to control the average queue size even without cooperation from the source entities. This can be done by dropping packets when the average size exceeds an upper threshold (instead of marking it). This approach is necessary in cases where most connections have transmission times that are less than the round-trip time, or where the source entities are not able to reduce traffic in response to marking or dropping packets (such as UDP flows).
3.2.2 Algorithm
This section describes the algorithm for RED gateways. RED gateways calculate the average queue size using a low-pass filter. This average queue size is compared with two thresholds: minth and maxth. When the average queue size is less than the lower threshold, no incoming packets are marked or dropped; when the average queue size is greater than the upper threshold, all incoming packets are dropped. When the average queue size is between minth and maxth, each incoming packet is marked or dropped with a probability pa, where pa is a function of the average queue size avg; the probability of marking or dropping a packet for a particular connection is proportional to the bandwidth share of that connection at the gateway. The general algorithm for a RED gateway is described as follows: [5]
For each packet arrival
Caculate the average queue size avg If minth ≤ avg < maxth
div.maincontent .s1 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 15pt; }
div.maincontent .s2 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 15pt; }
div.maincontent .p { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; margin:0pt; }
div.maincontent p { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; margin:0pt; }
div.maincontent .s3 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s4 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s5 { color: black; font-family:"Times New Roman", serif; font-style: italic; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s6 { color: black; font-family:"Times New Roman", serif; font-style: italic; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s7 { color: black; font-family:Wingdings; font-style: normal; font-weight: normal; text-decoration: none; font-size: 14pt; }
div.maincontent .s8 { color: black; font-family:Arial, sans-serif; font-style: italic; font-weight: bold; text-decoration: none; font-size: 15pt; }
div.maincontent .s9 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: bold; text-decoration: none; font-size: 14pt; }
div.maincontent .s10 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 9pt; vertical-align: 6pt; }
div.maincontent .s11 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 13pt; }
div.maincontent .s12 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-decoration: none; font-size: 10pt; }
div.maincontent .s13 { color: black; font-family:"Times New Roman", serif; font-style: normal; font-weight: normal; text-d -
Measure 4: Make Tools and Toys to Use in Children's Play Activities -
Internal control of revenue and expenditure activities at the National Children's Hospital - 2 -
Some characteristics and risk factors of hearing loss in children from 2 to 5 years old in inner-city kindergartens in Hanoi - 1
quantity... the unit of measurement of which is approximately equal to or (above, below) one hundred milliliters but less than two hundred and fifty milliliters.
o) Possessing two or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in one of the points from point g to point n, clause 2 of this article;
This crime is similar to the case specified in Point i, Clause 2, Point e, Clause 3, Point d, Clause 4, Article 193 of the Penal Code. The determination of the total quantity of narcotic substances has been guided in
Joint Circular No. 01/1998/TTLT/TANDTC-VKSNDTC-BNV dated January 2,
1998 of the Supreme People's Court, the Supreme People's Procuracy and the Ministry of Home Affairs guiding the application of a number of provisions of the Law amending and supplementing a number of articles of the Penal Code.30
p) Dangerous recidivism.
This crime is similar to the case prescribed in
Point k, Clause 2, Article 193 of the Penal Code stipulates the crime of illegal production.
narcotics31, only
other
in place
dangerous recidivist
in this case the person has been convicted of a very serious crime, a special crime
especially serious due to intention, not yet cleared of criminal record but still storing, transporting
Illegally transferring, trading or appropriating narcotics in the cases specified in Clause 2, Clause 3, or Clause 4 of Article 194, or having re-offended, not having had his criminal record expunged, but committing the crime of illegally storing, transporting, trading or appropriating narcotics.
Committing a crime under the circumstances specified in Clause 2, Article 194 of the Penal Code shall result in imprisonment from seven to fifteen years, which is a very serious crime.
Compared with Clause 2 of Articles 185c and 185d of the 1985 Penal Code, if based only on the level of punishment, Clause 2 of Article 194 of the Penal Code
1999 is neither lighter nor heavier. However, clause 2
Article 194 of the 1999 Penal Code stipulates a number of additional circumstances as factors in determining the penalty framework that are not stipulated in Clause 2 of Articles 185c and 185d of the 1985 Penal Code, so Clause 2 of Article 194 must be considered an invalid provision.
30 See the analysis of points i, clause 2, point e, clause 3, point d, clause 4, Article 193 of the Penal Code.
31 See the analysis of point k, clause 2, Article 193 of the Penal Code.
beneficial to the offender. Therefore, the crime of illegally storing and transporting narcotics falls under the cases specified in Clause 2, Article 185c and Clause
2 Article 185d does not provide as follows: “Using children to commit crimes” occurs
If the crime was committed before 0:00 on July 1, 2000 but is only processed after 0:00 on July 1, 2000, Clause 2, Article 194 of the 1999 Penal Code cannot be applied, but only Clause 1, Article 185c, Article 185d or Article 185e of the 1985 Penal Code can be applied to the offender, because according to the provisions of Clause 2, Article 7 of the Penal Code, "a provision providing for a new aggravating circumstance cannot be applied to a crime committed before that provision comes into effect."
Compared to Clause 2 of Articles 185d and 185e of the 1985 Penal Code, Clause 2 of Article 194 of the 1999 Penal Code is lighter, because the lowest penalty in the penalty range is only seven years compared to ten years prescribed in Clause 2 of Articles 185d and 185e of the 1985 Penal Code, and Article 194 is also lighter than Articles 185d and 185e. Therefore, the crime of illegal trading or appropriation of narcotics occurring before 0:00 on July 1, 2000 but not handled until after 0:00 on July 1, 2000 shall be subject to Clause 2 of Article 194 of the 1999 Penal Code.
As with other criminal cases, in addition to basing on the provisions of the Penal Code on deciding on punishment, if the offender only falls into one case specified in Clause 2 of the article, has many mitigating circumstances specified in Clause 1, Article 46 of the Penal Code, and has no aggravating circumstances, the Court may impose a sentence of less than seven years in prison but not less than two years in prison because according to the provisions of Article 47 of the Penal Code, when there are at least two mitigating circumstances specified in Clause 1, Article 46 of the Penal Code, the Court may impose a sentence of less than seven years in prison.
may decide on a penalty below the lowest level of the penalty range,
but must be within the adjacent penalty frame
light
more than the law. If
The offender falls into many cases specified in Clause 2 of the law, has many aggravating circumstances and no mitigating circumstances, then the penalty is at the high end of the penalty range (fifteen years in prison).
3. Committing a crime in one of the cases specified in Clause 3, Article 194 of the Penal Code
a) Opium resin, cannabis resin or coca extract weighing from one kilogram to less than five kilograms
This crime case is similar
like
case specified in
Point g, Clause 2 of the article, only
other
in place
plastic weight
opium, cannabis resin or coca extract is from one kilogram to less than five
kilogram. The determination of opium resin. cannabis resin or coca extract also
similar to the case prescribed in other laws on these drugs.
b) Heroin or cocaine weighing from thirty grams to less than one hundred grams.
This crime is similar to the case specified in Point h, Clause 2 of the Article, except that the weight of Heroin or Cocaine is from thirty grams to less than one hundred grams.
The laws governing heroin or cocaine are similar to those governing other drugs.
like
cases specified in the
c) Cannabis leaves, flowers, fruits or coca leaves weighing from twenty-five kilograms to less than seventy-five kilograms
This crime is similar to the case prescribed.
at point i clause 2 of the law, the only difference is the weight of leaves, flowers, and fruits.
Cannabis plants or coca leaves weighing from twenty-five kilograms to less than seventy-five kilograms. The determination of cannabis leaves, flowers, fruits or coca leaves is similar to the case prescribed in other laws on these drugs.
d) Dried opium fruit weighing from two hundred kilograms to less than six hundred kilograms.
This crime is similar to the case prescribed.
at point k clause 2 of the article, only different
in weight
medicine
Dried opium weighs from two hundred kilograms to less than six hundred kilograms. The determination of dried opium is similar to the provisions of other laws on this drug.
d) Fresh opium poppy weighing from fifty kilograms to less than one hundred and fifty kilograms
This crime is similar to the case prescribed.
at point l clause 2 of the law, the only difference is the weight of the drug.
Fresh opium weighing from fifty kilograms to less than one hundred years
ten kilograms. The determination of the fruit
Fresh opium is similar.
like
cases specified in other laws on this drug.
e) Other solid narcotics weighing from three hundred grams to less than three hundred grams
one hundred grams
This crime is similar to the case specified in Point m, Clause 2 of the article, except that the weight of the narcotic substances is different.
Other drugs in solid form with a weight of from The determination of other drugs
one hundred grams to under three hundred grams.
in solid state is similar to field
consistent with the provisions of other laws on these drugs.
g) Other liquid narcotics from two hundred and fifty milliliters to less than seven hundred and fifty milliliters
This crime is similar to the case prescribed.
at point n clause 2 of the law, the only difference is the weight of the narcotic substances.
Other drugs in liquid form from two hundred and fifty milliliters to less than seven hundred and fifty milliliters. The determination of other drugs in liquid form is similar to the provisions of other laws on these drugs.
h) Possessing two or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in one of the points from point a to point g, clause 3 of this article.
This crime is similar to the case specified in Point n, Clause 2 of this Article, except that there are two or more narcotics whose total quantity is equivalent to the quantity of narcotics specified in one of the points from Point a to Point g, Clause 3 of this Article. Determining that there are two or more narcotics whose total quantity is equivalent to the quantity of narcotics specified in one of the points from Point a to Point g, Clause 3 of this Article is similar to the case specified in other articles on these narcotics.
4. Committing a crime in one of the cases specified in Clause 4, Article 194 of the Penal Code
a) Opium resin, cannabis resin or coca extract weighing five kilograms or more
This crime case is similar
like
case specified in
Point g, Clause 2, Point a, Clause 3 of the law, the only difference is that the weight of opium resin, cannabis resin or coca extract is from five kilograms or more. The determination of opium resin, cannabis resin or coca extract is similar to the case prescribed in other laws on these narcotic substances.
b) Heroin or cocaine weighing one hundred grams or more
This crime case is similar
like
case specified in
Point h, Clause 2, Point b, Clause 3 of the article, the only difference is that the weight of Heroin or Cocaine is one hundred grams or more. The determination
Heroin or cocaine are subject to similar laws regarding these drugs.
as provided in the articles
c) Cannabis leaves, flowers, fruits or coca leaves weighing seventy-five kilograms or more
This crime case is similar
like
case specified in
Point i, Clause 2, Point c, Clause 3 of the law, the only difference is that the weight of the leaves, flowers, fruits of the cannabis plant or coca leaves is seventy-five kilograms or more. The determination of the leaves, flowers, fruits of the cannabis plant or coca leaves is also
similar to the case prescribed in other laws on these drugs.
d) Dried opium fruit weighing six hundred kilograms or more
This crime case is similar
like
case specified in
Point k, Clause 2, Point d, Clause 3 of the law, the only difference is that the weight of the dried opium fruit is from six hundred kilograms or more. The determination of dried opium fruit is similar to the case prescribed in other laws on this drug.
d) Fruit
Fresh opium weighing from
one hundred and fifty
kilograms or more
This crime case is similar
like
case specified in
Point l, Clause 2, Point d, Clause 3 of the article, the only difference is the weight.
Fresh opium poppy weighing one hundred and fifty kilograms or more
The determination of fresh opium poppy fruit is similar to the provisions of other laws on this drug.
e) Other solid narcotics weighing from or more
three hundred grams
This crime case is similar
like
case specified in
Point m, Clause 2, Point e, Clause 3 of the article, the only difference is in weight.
other solid narcotics weighing three hundred grams or more.
The determination of other drugs in solid form is similar to the case prescribed in other laws on these drugs.
g) Other drugs in liquid form from seven hundred and fifty milliliters or more
go up;
This crime case is similar
like
case specified in
Point n, Clause 2, Point g, Clause 3 of the article, the only difference is that the weight of other drugs in liquid form is from seven hundred and fifty milliliters or more.
Determination of other drugs in liquid form is similar to the case
prescribed in other laws on these drugs.
h) Possessing two or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in one of the points from point a to point g, clause 4 of this article.
This crime case is similar
like
case specified in
Point o, Clause 2, Point h, Clause 3 of the article, the only difference is that there are two or more
or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in one of the points from point a to point g, clause 4 of this article. Determining the presence of two or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in
One of the points from point a to point g, clause 3 of this article is similar to the case prescribed in other laws on these drugs.
Committing crimes in the cases specified in Clause 4, Article 194 of the Criminal Code.
criminal law
then the offender is
imprisonment
twenty years, life imprisonment
or death penalty is a particularly serious crime. Compared to Clause 4 of Articles 185c, 185d, 185e and 185e of the 1985 Penal Code, Clause 4 of Article 194 of the 1999 Penal Code is lighter, because the lowest level of the penalty is twenty years in prison compared to life imprisonment as prescribed in Clause 4 of Articles 185c, 185d, 185e and 185e of the 1985 Penal Code. At the same time, Article 194 of the 1999 Penal Code is also lighter than Articles 185c, 185d, 185e and 185e of the 1985 Penal Code. Therefore, the crime of illegally storing, transporting, trading or appropriating narcotics occurred before 0:00 on July 1, 2000 but was only handled after 0:00 on July 1, 2000. Article 194, Clause 4 of the 1999 Penal Code is applied.
As with other crimes, in addition to basing on the provisions of the Penal Code on deciding on penalties, if the offender only falls into one case specified in Clause 4 of the article, has many mitigating circumstances specified in Clause 1, Article 46 of the Penal Code, and has no aggravating circumstances, the Court may impose a sentence of less than twenty years in prison but not less than fifteen years in prison, because according to the provisions of Article 47 of the Penal Code, when there are at least two mitigating circumstances specified in Clause 1, Article 46 of the Penal Code, the Court may decide on a penalty below the lowest level of the penalty range, but must be within the adjacent lighter penalty range of the article. If the offender falls into many cases specified in Clause 4 of the article, has many aggravating circumstances and has no mitigating circumstances, is a person subject to severe punishment as specified in paragraph 2, Clause 2, Article 3 of the Penal Code, he or she may be sentenced to death.
As with Clause 4, Article 193 of the Penal Code, to specify the application of Clause 4, Article 194 of the Penal Code, the Council of Judges of the Supreme People's Court issued Resolution No. 01/2001/NQ-HDTP dated 15-
3-2001. According to this Resolution, when applying Clause 4, Article 194 of the Civil Code,
criminal offenses of illegal possession, transportation, trading or appropriation
Drugs to watch out for:
In case there are no aggravating circumstances and no mitigating circumstances or there are both aggravating and mitigating circumstances, but the aggravating and mitigating natures are assessed as equivalent, then
punish the offender with a sentence corresponding to the weight of the drug
as follows:
Punishable by twenty years imprisonment if:
- Opium resin, cannabis resin or coca extract weighing from 5 kilograms to less than ten kilograms;
- Heroin or cocaine weighing from one hundred grams to less than three hundred grams
grams;
- Cannabis leaves, flowers, fruits or coca leaves weighing seven or more
fifty-five kilograms to under two hundred kilograms;
- Dried opium fruit weighing from six hundred kilograms to less than one thousand five hundred kilograms;
- Fruit
Fresh opium weighing from
one hundred and fifty
kilograms to under four hundred and fifty kilograms;
- Other solid narcotics weighing from three hundred grams to less than nine hundred grams;
- Other drugs in liquid form from seven hundred and fifty milliliters to less than two thousand milliliters;
- There are two or more drugs, the total quantity of which is
equivalent to the amount of one of the above drugs.
Life imprisonment if:
- Opium resin, cannabis resin or coca extract weighing from kilograms to less than twenty kilograms;
ten
grams;
- Heroin or cocaine weighing from three hundred grams to less than six hundred grams
- Cannabis leaves, flowers, fruits or coca leaves weighing two hundred grams or more
kilogram to
- Fruit
Dry opium weighs from
one thousand five hundred
kilograms to under four thousand five hundred kilograms;
- Fruit
Fresh opium weighing from
four hundred and fifty
kilograms to under one thousand two hundred kilograms;
- Other solid narcotics weighing from nine hundred grams
under two thousand five hundred grams;
- Other drugs in liquid form from two thousand milliliters to less than five thousand milliliters;
- There are two or more drugs, the total quantity of which is
equivalent to the amount of one of the above drugs.
Death penalty if:
- Opium resin, cannabis resin or coca extract weighing ten kilograms or more;
- Heroin or cocaine weighing six hundred grams or more;
two
- Leaves, flowers, fruits weighing hundreds of kilograms or more;
cannabis plants or coca leaves weighing six
- Fruit
Dry opium weighs from
four thousand five hundred
kilograms or more;
- Fruit
Fresh opium weighing from
one thousand two hundred
kilograms or more;
- Other narcotics 100 grams or more;
in solid form weighing two thousand years
- Other drugs in liquid form from five thousand milliliters or more;
- There are two or more drugs, the total quantity of which is
equivalent to the amount of one of the above drugs.
Regarding the circumstance of "having two or more narcotic substances, the total quantity of which is equivalent to the quantity of narcotic substances specified in one of the points from..." specified in Point h, Clause 4, Article 194 of the Penal Code, it is calculated as follows:
Case 1:
If those drugs are all specified in the same point of Clause 4, Article 194, then add the weight of those drugs together and compare it with the weight guided above to consider what level of punishment the offender should be punished with.
For example: A person buys and sells 115 grams of Heroin and 125 grams of Cocaine. Since Heroin and Cocaine are both regulated in the same point b, clause 4, Article 194, the total weight of Heroin and Cocaine is 240 grams (115 grams + 125 grams = 240 grams). Compare with the weight given
As mentioned above, point b, clause 4, Article 194 must be applied to commit the crime with a sentence of 20 years in prison.
Second case:
punish people
If such narcotic substances are specified in different points of Clause 2, Clause 3, Clause 4, Article 194, the calculation of the total quantity of these narcotic substances equivalent to the quantity of one of the narcotic substances specified in Clause 4, Article 193 or in Clause 4, Article 194 shall be carried out in the following order:
Take each drug substance among the drugs that the offender has produced, stored, transported, illegally traded or appropriated as the standard. Calculate the weight of the remaining drugs among the drugs that the offender has stored, transported, illegally traded or appropriated corresponding to how many grams, kilograms or milliliters of the drug substance taken according to the minimum weight ratio of the drugs.