To strengthen the implementation of traffic laws, the following tasks must be carried out:
Firstly, promote propaganda, dissemination, education and guidance on traffic laws.
Along with the development and improvement of the Traffic Law, the regular and extensive dissemination and education of Traffic Law among all classes of people, so that everyone can understand and strictly comply with it, must be given utmost importance. The dissemination and education of the law is one of the top priorities to gradually improve people's legal knowledge, enhance their capacity to properly and strictly implement the law, establish discipline, promote democracy, stabilize socio-politics, and build a rule-of-law state.
In recent years, we have paid attention to maintaining the propaganda, dissemination and education of traffic laws. It can be said that the legal awareness of some traffic participants has been significantly improved, but in general, legal awareness is still limited, and there are still many violations of traffic laws. Some people violate due to lack of understanding of traffic laws, but many people have understanding but poor compliance, deliberately violating regulations on ensuring traffic safety and order. Through analysis of cases of traffic law violations that have been inspected, detected and the errors causing traffic accidents in recent years, the rate of traffic participants is up to 80%, often due to drivers violating speed, avoiding overtaking, and using alcohol. Among the causes of accidents caused by traffic participants, the fault of the vehicle driver accounts for the majority and is the direct cause.
Therefore, one of the most important measures is to regularly propagate, disseminate and educate about traffic laws. This plays a very important role, contributing to raising people's knowledge and awareness of complying with traffic laws in order to control the increase in the number of deaths due to traffic accidents. When people's knowledge level has been raised, traffic infrastructure has been completed, and traffic vehicles have decreased, the goal of reducing traffic accidents will be achieved. However, due to people's awareness, habits and lifestyles, making the implementation of traffic laws a part of the life of each person requires time, and sometimes results will be seen in later generations. This means that this is a measure that must be implemented persistently, regularly and long-term.
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Qos Assurance Methods for Multimedia Communications
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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
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Improving the Quality of Administrative Procedures and Strengthening the Direction and Management of the Heads of State Administrative Agencies at the Ministry Level -
Crimes in the field of land management and use in Vietnam Criminal Law Based on practical research in Hanoi city - 2 -
Concept of State Management by Law for Tourism Activities -
The Process of Formation and Development of Law and State Management by Law for Tourism Activities in the Democratic Republic of Vietnam
The purpose of propaganda, dissemination and education of traffic law will have different levels, which can be divided into:
The first level is :

- Improve understanding of traffic laws.
- Forming confidence in the need for traffic laws.
- Gaining sympathy with the law on traffic safety
Second level:
- Forming a sense of respect for traffic laws.
- Forming an uncompromising attitude towards violations of traffic laws at the level of administrative sanctions and criminal offenses.
- Forming legal behavior in the field of traffic, customs and habits of conduct according to the provisions of traffic law.
- Forming positive behavior in GTDB activities.
In theory, we can clearly analyze and set out requirements for the entire community. In reality, the above levels can be formed in each residential area and each person in a community at a different time.
Currently, "we only hope to improve understanding of traffic safety regulations. After 10 or 20 years, if we persist in legal education, we will have a generation that meets the requirements of the second level" [7, p.51].
The dissemination, popularization and education of traffic laws must be researched to suit each target group. It is necessary to focus on students, teenagers and young people; people using motorbikes and scooters; people driving rudimentary vehicles; car drivers; officials and employees in agencies and enterprises, and people living along the road. There must be diverse, rich and practical content and forms of propaganda.
The following propaganda contents and forms have been and are bringing about clear results and need to be focused on and promoted in the coming time:
- Oral propaganda : This is a form in which the speaker directly tells the listener about the contents and regulations of the Traffic Law. The ultimate goal is to make the listener understand and act according to the propagandist's purpose. This form can be carried out anywhere, in any situation for one person or many listeners. The effectiveness of oral propaganda is not only assessed on the spot when listening, receiving
The plan after listening is that the listener will maintain long-term faith in the law on traffic. Propagandists can go to agencies and schools to talk about the law on traffic, talk or answer interviews on television and radio; use cars and motorbikes with loudspeakers to travel to disseminate the law on traffic.
To achieve effective oral communication, it is necessary to prepare practical, concise content that is suitable for the audience and a way of speaking that attracts the listener.
- Launching contests to learn about traffic law : can organize writing contests, traffic law questions and answers, picking democratic flowers, through the form of dramatization, or learning about traffic law through traffic safety film contests, etc., for the masses to participate, need to focus on subjects such as students, teenagers, cadres, civil servants, armed forces
The content of the questions may include: general regulations of traffic laws, traffic signs, traffic patterns, situations in resolving a traffic accident, handling traffic congestion, or stating a violation case with many different errors to request analysis and handling.
- Propaganda through mass media : Newspapers, television, and radio are three mass media that effectively serve the work of propaganda and education of traffic law.
Regarding the form of propaganda and education on traffic law: reporting news, articles reflecting the situation of compliance with traffic law, mentioning traffic accidents to analyze the causes, proposing preventive measures, opening regular traffic safety and order columns, answering interviews, taking quizzes, developing programs: radio stories, art performances on the topic of traffic law; dramatizing propaganda on traffic law such as "SV", "Seven colors of the rainbow", "Kaleidoscope", "9th hour", "Meeting at the weekend"; the program "For national security"; "Security and life"; "Traffic safety", etc., developing reports and skits reflecting, propagating and educating traffic law. Every year or two, periodically organize a national video festival on traffic order, the films will be broadcast on central or local television for propaganda.
- Building and organizing photo exhibitions : Building billboards and photos about traffic order for mobile exhibitions at bus stations, train stations, schools, residential areas, and other venues.
organize conferences, seminars or exhibitions for a certain period of time..., to attract viewers, thereby promoting and educating traffic laws. At the exhibition, questions about traffic laws can be prepared for viewers to answer by drawing lots, if correct, they will be given a prize that implies the meaning of traffic safety.
The exhibition can display paintings, photos, diagrams, statistical tables analyzing traffic accidents, and images of serious traffic accidents that have occurred. If possible, display exhibits of motorbikes and cars damaged by traffic accidents.
- Propaganda by slogans : Write slogans in large letters to propagate and remind people to comply with traffic laws on main streets, along routes, in agencies, schools, conferences, etc., such as: "Traffic safety is happiness for everyone"; "strictly comply with traffic laws"; "pay attention to road sections where accidents often occur".
- Seminars : Organize seminars to research and discuss solutions to ensure traffic safety and order such as: seminars on passenger car safety, seminars on preventing illegal racing, seminars on safe driving, etc.
- Launch, build and maintain emulation movements to ensure traffic safety and order such as "Good driving, safe driving" among drivers, "Self-managed road" movement; "All people participate in maintaining traffic safety and order" movement launched by the Vietnam Fatherland Front. In addition, there are many other forms of propaganda such as organizing law clubs, information and propaganda teams on traffic law; disseminating and educating about traffic law through traditional festivals; cultural activities, printing and distributing leaflets, brochures, announcements on village, commune and ward bulletins, launching competitions to compose paintings, photos, short stories, reports, memoirs, plays, songs about traffic safety and order for propaganda on mass media; compiling brief documents on traffic law for the masses to learn through activities of self-managed People's Groups and signing commitments to comply.
A very important content in the dissemination of traffic law education is to include traffic law in the main curriculum at all levels from preschool to high school, college, university and vocational schools. First of all, it is necessary to focus on teaching and learning traffic law at preschool, primary and secondary schools. Schools are also places that can be used as training and meeting venues to disseminate knowledge.
Law for the masses. The team of teachers of ethics and civic education are also capable propagandists and need to be promoted.
On the other hand, the authorities need to coordinate with local authorities to regularly launch emulation movements, attract all sectors, all levels, and all people to participate in maintaining traffic order and safety, encourage, propagate, and set examples of good and safe drivers, and traffic participants with high awareness of traffic law compliance. Organize competitions and conferences to honor those with outstanding achievements in participating in ensuring traffic order and safety, and preventing traffic accidents. These are also highly effective measures to propagate and educate traffic law that need to be maintained regularly and expanded to all units, agencies, and enterprises.
The above forms of propaganda, dissemination and legal education, in order to achieve high efficiency, must combine community education with education by subject; combine family education with school and society education; combine education with enforcement; must be carried out regularly and continuously, with specific plans and programs, must build a team of propagandists with enough enthusiasm, sufficient knowledge of traffic laws, and be exemplary in complying with traffic laws.
Second, strengthen coordination between competent state management agencies in the field of road traffic.
Although Article 69 of the 2001 Road Traffic Law specifically stipulates the responsibility of State management in the field of road traffic of competent agencies in the field of road traffic, in the current management practice, there is still a lack of coordination and harmony between agencies. Therefore, the issue here is to strengthen the coordination between competent agencies in State management in the field of road traffic to avoid overlapping management or pushing and avoiding, reducing the effectiveness of State management by law in the field of road traffic. Currently and in the following years, it is necessary to strengthen the coordination between State management agencies in the field of road traffic in the following directions:
- Establish a mechanism for close and synchronous coordination between the Ministry of Transport and the Ministry of Public Security on issues such as construction of traffic works, traffic diversion, and handling of violations of traffic laws: clearly defining the authority of the Traffic Police and Traffic Inspectorate.
- The Ministry of Transport, the Ministry of Public Security, and the Provincial People's Committees shall develop a coordination mechanism in organizing traffic and decentralizing management.
- The Ministry of Trade, the Ministry of Transport, and the Ministry of Industry coordinate closely in managing the import of road vehicles. The types of vehicles imported are based on standards, techniques, and current road and bridge conditions.
- The Ministry of Education and Training, the Ministry of Culture and Information, the Ministry of Transport, the Ministry of Labor, War Invalids and Social Affairs, the Vietnam Fatherland Front and its member organizations coordinate in training, vocational training, propaganda, and dissemination of road traffic law education.
- The Ministry of Finance, the Ministry of Public Security, and the Ministry of Transport coordinate synchronously in collecting fines for administrative violations in the field of road traffic, and unify the issuance and management of receipts and documents for collecting fines for administrative violations in road traffic.
Third, promote the building of a mass movement to enforce the law.
GTDB
The masses are a large, numerous force, present everywhere, at all times, in all situations.
routes, public transport areas, the participation of the masses in organizing the implementation of traffic laws will help competent authorities in the field of traffic to solve traffic problems in the fastest and most effective way, such as when the masses discover a traffic accident or traffic jam, they immediately report it to the traffic police so that this force can promptly be present to resolve the issue.
On May 19, 2000, the Standing Committee of the Central Committee of the Vietnam Fatherland Front signed Joint Resolution No. 02/NQLT with the National Traffic Safety Committee to mobilize "All people to participate in ensuring traffic order and safety". Next, the National Traffic Safety Committee and the Central Committee of the Ho Chi Minh Communist Youth Union signed Joint Resolution No. 124/2001/NQLT on mobilizing young people to participate in ensuring traffic order and safety with the aim of raising awareness and compliance with traffic safety laws for young people, thereby affecting other classes in society. At the same time, the Ministry of Public Security and the Central Committee of the Ho Chi Minh Communist Youth Union also coordinated to implement Program No. 174 on maintaining traffic order and safety and preventing illegal racing in Ho Chi Minh City, Hanoi, Hai Phong, and Da Nang. It can be said that these campaigns have initially brought about many positive results. However, in the coming time, it is necessary to promote the following tasks:
- Establish a "Self-management Traffic Safety Committee" in communes, wards and towns. In residential areas, establish a self-management traffic safety team with the Head of the Front Committee as the head of the self-management team; the head of the village, hamlet, and neighborhood as the deputy head, plus a number of team members including police officers, the Secretary of the Ho Chi Minh Communist Youth Union and a number of prestigious people, village elders and village chiefs.
- Conduct investigations into the situation of traffic participants; existing means of transport; traffic accident situation... in each residential area, neighborhood, hamlet, village, commune, ward, and town.
- Develop an action program to mobilize "All people to participate in ensuring traffic safety and order" in residential areas, taking the motto "Traffic safety is happiness for every family" with the goal of building "Residential areas ensuring traffic safety and order" and need to add the following contents to the conventions and village regulations of agencies, schools, and residential areas:
Propaganda and education in agencies, schools, clinics, organizations and people in residential areas about the law in general and traffic law in particular.
Raise public awareness of responsibility to work with the State to protect transport infrastructure.
Report and detect acts of groups and individuals violating traffic safety regulations.
- Each residential area, agency, and school establishes a "Legal Learning Club" so that everyone can participate in activities and learn about the law, including traffic law.
- In key traffic residential areas of large cities, it is necessary to coordinate with the Ho Chi Minh Communist Youth Union to establish a "Youth Volunteer Team" to participate in ensuring traffic order and safety at intersections that often cause traffic jams. This team includes youth union members in residential areas, schools, and agencies. In each school, a "Youth Team to protect traffic order and safety at the school gate and the road to school" should be established.
- Expanding self-management forms in residential areas such as "Self-managed safe roads", "Self-managed safe bus stations", "Self-managed safe ferry terminals".
- Village chiefs, hamlet chiefs, neighborhood chiefs, and heads of self-governing residential groups organize households to sign commitments. The commitment includes: implementing conventions and village covenants, participating in learning to understand the law in general, and the law on road traffic in particular, not violating the law in general, and the law on road traffic in particular, not violating traffic safety corridors... with the goal of building "Traffic-safe residential areas", "Cultural households", "Advanced residential areas and excellent residential areas" in the campaign "All people unite to build a cultural life in residential areas".
- The Front Working Committee in residential areas, based on the September peak traffic safety action program and the Tet peak traffic safety month, coordinate with forces in residential areas to organize and launch a response to the implementation of the peak traffic safety month (note intersections where accidents often occur, markets, bus stations, school gates, level crossings, etc.).
- Build a "Traffic safety violation complaint box" in residential areas.
- Summarize three months, six months, September peak traffic safety month, Tet peak traffic safety month and summarize one year of ensuring traffic safety, thereby evaluating the advantages, disadvantages, causes of advantages and disadvantages, proposing effective solutions to successfully implement the movement "People participate in ensuring traffic safety and order".
Fourth, improve the effectiveness of implementing legal regulations on road traffic infrastructure.
The implementation of legal regulations on road traffic infrastructure to develop and upgrade road traffic infrastructure is an important and inevitable need that the State is interested in and focuses on directing. The road traffic infrastructure in our country has changed a lot, however, compared to other countries in the region and the world, the road traffic infrastructure in our country still has many limitations. Because our country's road system is still narrow, it is not possible to separate motorized traffic flows and rudimentary traffic flows on national highways and main roads. The intersections are still mainly at-grade intersections, even with railways. People living along the roads, including newly built roads, are developing as houses spread out. The use of roads and road safety corridors according to regulations is still a difficult problem...

![Qos Assurance Methods for Multimedia Communications
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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
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