saving; not understanding each other; due to too much work, women cannot complete housework; lack of experience in childcare; daily activities...
With a new member appearing, the relationship between mother-in-law and daughter-in-law also changes. Conflicts often occur more than before, but all conflicts after having grandchildren mainly revolve around the issue of children. Although there are certain changes, conflicts also appear more often. But since having grandchildren, in addition to the mother-in-law becoming: more difficult, more attentive; busier and more concerned, grandmothers when having grandchildren in the house become "happier" (42%/57 subjects); closer, more sympathetic and sharing with their children than before. Although in two generations, there are different perspectives on how to raise young children, according to research results of psychologists, young children living with grandparents are always left with invaluable educational and traditional moral lessons that others cannot do.
2. Factors affecting the emotions of first-time mothers .
Having a child is a big turning point for women, their psychology changes a lot. They experience emotions that are sometimes strong and clear, sometimes fleeting and vague. Those emotions are also influenced by different factors. There will be many factors that affect the mother's emotions: economy, regional culture, optimism, happiness... but within the limits of the topic, we only consider the following factors:
Maybe you are interested!
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Emotions of a first-time mother - 3 -
Emotions of a first-time mother - 1 -
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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Factors Affecting Business Performance of Meiko Trading and Construction Company Limited -
Research on factors affecting the decision to purchase gypsum board of Huy An private trading enterprise from institutional customers in Ho Chi Minh City - 13
2.1. Parents' psychological preparation for the birth of a child
Within the limits of the topic, we only conducted research on mothers in “wedding”. When they got married, according to our research, mothers had a clear plan for their pregnancy, only a few did not plan. Starting from pregnancy, they prepared for the best development for their children from

in the womb, diet, listening to music, working and sleeping properly. They are always ready to welcome their baby with love, expectation and everything is ready. In fact, most mothers, about 1 month before giving birth, prepare everything for their baby: clothes, diapers, milk, shoes, medicine... very carefully for their "angel" when the baby is born. This careful preparation, both mentally and physically, is clearly shown when the mother first welcomes her baby into her warm embrace, she feels "truly happy" (56.7%).
The birth of a child is psychologically prepared by the mother, not too surprising. Right from the time of pregnancy, they always try to keep a comfortable and happy mentality so that the child will not be affected later. According to the research results of scientists, they prove that if during pregnancy the mother is not comfortable, often irritable, sad, ... later the child will be greatly affected.
The first time welcoming a child is a process of psychological, health, economic, and other conditions preparation for parents. With good psychological and knowledge preparation when the child is born, they will easily overcome negative emotions and face it. Without prior preparation, the mother will easily fall into surprise and confusion in a specific situation. There are even young mothers who lead to postpartum depression - this case is not much, but it also says that without psychological preparation, it is easy to fall into unwanted things.
Even though they have prepared for a long time, when it comes time to give birth, they still cannot help but worry and wonder, will giving birth be as easy as everyone else? Will the baby be healthy? These feelings suddenly come because the mother is too nervous and anxious, unable to control and balance her emotions.
When asked about this psychological preparation, Ms. M said: “Since I was pregnant, I have read many books about child-rearing knowledge, and also anticipated what would happen to me. Asking grandparents and friends who had children before, they knew that raising children would be very difficult. A good child is better, but a fussy child, a lazy eater, or a sick child is out of the question. I understand that, but giving birth is still confusing and worrying. When I was pregnant, I was already very tired from morning sickness, and when I gave birth, I was in pain and struggled. There is nothing more tiring than that. However, in reality, raising children is much more difficult than being pregnant, compared to what I knew and thought before.”
Through the documents and websites we obtained, we found that: the majority of mothers who give birth and then raise their children share the same thoughts as Ms. M.
In short, psychological preparation greatly affects a mother's emotions when welcoming her child for the first time, in every situation that the mother will have to go through.
2.2. The husband's care and sharing during pregnancy:
When pregnant, women's bodies change a lot, and their psychology also changes. During this period, women are very sensitive, easily hurt, and angry. At this time, they need special attention from their husbands. The husband's care and sharing gives pregnant women a comfortable and secure mentality for the best development of the child in the couple's womb. Many wives, when pregnant, are pampered by their husbands, who care for them, find out what to feed them, what music to let the "angel" in their womb listen to so that the child can develop comprehensively in all aspects of both body and mind. Normally, when pregnant, women's bodies are easily tired, uncomfortable, and their psychology is easily hurt. During pregnancy and child-rearing, women cannot do everything by themselves and need a lot of help and sharing from their husbands. Mothers should proactively discuss with their husbands about
knowledge about pregnancy and child rearing. To help her husband understand her hardships and difficulties, he is willing to share when she has difficulties.
The husband shares with his wife during pregnancy as well as prepares her mentally, giving her strength to welcome the couple's "beloved child". In fact, when a pregnant woman is shared a lot by her husband, after having a child, she is less likely to experience too much stress, excessive anxiety, and not fall into a state of fear, anger, etc. This caring and sharing is just the first step, but it is extremely important for the mother's psychology later on.
2.3. Psychological characteristics of the child
Each child is born with its own physical characteristics, and this factor also affects the mother's emotions. The mother is often worried, stressed, sad, tired... depending on whether the child is weak or strong, often sick, has a fever, sleeps easily, has trouble sleeping, or is restless... Reality shows that there are sick children who often cry, are lazy to eat, and have trouble sleeping. There are children who eat well but have trouble sleeping, and every time they sleep, their parents have to rock them to sleep for a long time. It is these characteristics of each child that make the mother often anxious, stressed, and tired. When the child's body is not healthy, the mother is always worried about the child, upset about this. Sometimes the child is sick, lazy to eat, and is always "snoring" and not feeling secure about the child. When the child's body is not good or is often restless, the mother can easily become irritable and depressed.
When talking about this issue, Ms. Ng shared: “My child is very fussy! After eating, I still feel uneasy. There are days when my child just finished eating and threw up everything, I am always worried, sometimes I even feel stressed about this. My child is extremely fussy, every day I see him throw up, I am both happy and strange. Before eating, cooking for him, my mind is always confused, wondering if he will be able to keep it after eating? In a month, I buy 7-8 boxes of milk, of which I deduct
I went through almost 4 boxes. I'm so sad, if only my child ate and drank less, I would be so happy.
On the contrary, if the child is healthy, has good resistance, rarely gets sick, eats and sleeps easily, the mother certainly does not have to be too sad, stressed or tired when the child is sick. The mother is always happy, comfortable and assured about the child. Whenever the child is sick, the mother is able to stay calm, alert and take good care of the child as usual.
In fact, there are couples who often quarrel and have conflicts just because their children are often sick. Normally, they are happy and cheerful, but when their children are sick, they argue and scold each other, blaming this and that, blaming the husband, blaming the wife, the grandparents blame the daughter-in-law, the daughter-in-law blames the grandparents. All the disagreements and conflicts also come from this situation of the child being sick. When the child is healthy and sleeps well, the family will also reduce a lot of arguments and scolding.
In short, the characteristics of the child's body also create emotions of joy, sadness, happiness, optimism, anxiety, stress, fatigue... in the mother.
In general, there are many factors that affect a mother’s emotions. These are the main factors, but we also think that an optimistic personality, economic status, and sense of happiness… also partly affect a first-time mother’s emotions.
2.4. Knowledge and experience in raising children of young mothers
This will be a factor that greatly affects the mother's emotions in the process of raising children. If women equip themselves with the best knowledge of raising children by reading information on mass media, reading books, sharing from previous generations, friends... certainly when they "get involved" they will be very confident with their own way. Of course, their emotions in specific situations: children are sick, have fever, are not eating well, are crying... are not too
stressed or scared when seeing their child like that. They worry about their child with motherly love, easily overcoming this without much difficulty.
However, each child has different physical characteristics, sometimes rigidly applying what is taught in the book is not an effective solution. At this point, the experience of a real child-raiser is needed. In terms of knowledge, according to our research, today women are always proactive in all tasks, even in caring for and raising children, so they have enough knowledge and understanding about child care. But besides that, the lack of experience makes mothers feel confused, worried, and stressed when their children encounter problems that are not mentioned in books or shared by relatives. When we asked the question "After having a child, what worries you the most?", the thing that worries mothers the most is "the couple has no experience in raising children" (66.7%). This number shows that the experience of raising children for first-time mothers is the top priority. Mothers always wonder how to raise their children well? How to eat properly...? Countless questions are asked by inexperienced mothers in raising children. Some are even clumsy when it comes to feeding, changing diapers, bathing their children... knowledge has been read, but in reality, not all mothers are proficient and confident in doing these things.
In this research, we have not had the opportunity to study mothers who have given birth for the second time. However, in reality, in situations such as when the child is sick, has a fever, is teething, has intestinal problems, has anorexia... due to previous experience in raising children, these mothers are less likely to fall into a state of stress, fatigue or worry. As for mothers who have given birth for the first time, due to not having enough knowledge and not having experienced such things, when they encounter feelings of sadness, anxiety, and stress, they easily "overwhelm" the mother, even causing psychological imbalance.
2.5. The unity of husband and wife in the issue of child rearing
Conflicts occur when everyone thinks their way is right, the other is wrong, and they insist on doing things their way. According to psychologist Tran Hong Ha, Deputy Director of the Love - Marriage - Family Counseling Center under the Vietnam Youth Union, conflicts in child-rearing methods are one of the most common reasons for conflicts between couples. Ms. Ha said that, right from the time they get married and have children, couples should talk to each other about how to raise children to have a unified opinion on this matter. However, in reality, very few people do this, only when there are disagreements about how to care for and educate children, couples begin to pay attention to this matter. Conflicts appear when everyone thinks their way is right, criticizing the other. Psychologist Hong Ha said that when couples disagree about children, the suffering will double because not only will both people be sad and tired, but it will also affect the psychological development and personality of the child.
When a couple disagrees on how to raise their children, arguing about this issue will create tension in the family and make the mother sad.
When stressed, sad, easily irritable, scolding children, the family atmosphere is heavy. When this conflict becomes a big problem, "disagreement between you and your husband" (8.3%) becomes the biggest sadness today. Or creating the most stress for mothers, when we asked "I think the thing that stresses me the most is...", 13% were due to disagreement between husband and wife in raising children. Moreover, mothers cannot help but worry, fear family matters, parents' conflicts children have to bear (13.3%). When there is a conflict between husband and wife about how to raise children, many women also try to find a way to resolve it so that the family is not heavy. Ms. H - Thanh Tri District said
know: “My husband and I rarely have conflicts about this issue, but sometimes we disagree about raising children, but when my husband is happy about other things such as: success in work, I whisper to my husband to analyze right and wrong, so that we can both come to an agreement.” Besides, there are wives who are always comfortable in this matter because their husbands let them decide how to raise their children or completely support their wives' way of raising their children. When encountering problems of disagreement, finding a common voice in raising children, mothers have many ways to solve this. Some are resolute, some follow their husbands, and discuss with their husbands. According to the test results we obtained: 3 subjects avoided mentioning this issue, the remaining 57 subjects shared “when my husband does not agree on how to raise children, I often……” they argued with their husbands; got angry (10.5%); ignored but then thought to themselves, am I wrong?; discuss to find common views to reach agreement (14%); do it my way (15.8%); analyze for husband to understand and support (15.8%); listen to husband's opinion; find more books and newspapers to read before deciding; sit and listen and draw experience to improve; tell mother to find a solution.
No matter how it is resolved, when a couple does not share the same views on raising children, it creates feelings of stress, fatigue, and boredom for the mother. It affects the relationship between the couple for better or worse. In fact, couples who disagree on raising children are not many, only a small number. Therefore, most mothers are supported by their husbands, which makes them feel comfortable and secure in raising their children.
In the case where the man does not share with his wife in raising the children, the wife raises them however she wants, without caring, only worrying about the economy, food, clothing, and shopping for the family, making the mothers feel upset and frustrated. There are even some women who "do not get their husbands to share in raising the children".



![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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