(The children took their bags and put all the books on the floor.)
(224) Es sitzt in einem Sessel.
(He plops down on the armchair.)
(225) Seine vorwurfsvollen Worte waren immer noch in meinen Ohren. (His reproachful words still ring in my ears.)
Type 4: The prepositions auf/in do not seem to be translated into Vietnamese. For example:
Maybe you are interested!
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Space/Time Art – A Picture of the World Through the Eyes of Women -
Contrast the spatial preposition auf - in in German with tren - trong in Vietnamese - 2 -
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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Orientation for Developing Hanoi Tourism Space -
Example Illustrating a Summary of an English Text
(226) Die Kinder saßen auf dem Boden. (The children sat on the floor.)
(227) Endlich stand er vorsichtig auf den Knien auf.

(Finally, he gently sat up on both knees.)
(228) Haus ist in Flammen. (The house is on fire.)
(229) Er wurde in die Enge getrieben. (He was cornered . )
3.3.2.2. Some comments
Regarding the common translations in types 1 and 2 , here the author would like to talk about types 3 and 4. These are two types that reflect different ways of expressing things between German and Vietnamese. facts as well as about idioms often related to action verbs. For example, in example (229) Er wurde in die Enge getrieben (He was cornered ) , here expresses the meaning that he was cornered, in a closed position. With this literal meaning, in Vietnamese there are many similar expressions, such as falling into a dead end/dead end,... with no way out, or even more serious, falling into death. Therefore, with the use of a locative structure with a metonymic meaning as in example (229), the translation into Vietnamese is satisfactory, because the locative structure here only has heavy descriptive value. rather than positioning.
For example (222) Der arme Mann kniete auf den Knien (The poor man knelt down ), it is also appropriate to use some locative construction with a verb like this ( kniete auf den Knien). a descriptive type. In German, the phrase kniete auf den Knien ( on both knees ) is implicitly understood or presupposed in the semantics of the verb "kneel" in Vietnamese. And here,
For Vietnamese, using the structures "kneel" (verb) and "down" (direction word) is enough to make sense. In most other cases, too, it reflects the different ways in which the situation is expressed in the two languages.
We examine some of the sentences above to see that people who have translated German documents into Vietnamese have had great success in translating from German to Vietnamese. However, considering the four types of translation of locative constructions above, not every locative construction of auf/ in in German can be translated by an equivalent locative construction in Vietnamese. Even the system of prepositions used does not have an equal correspondence in the two languages. For example, in , for example, when translated into Vietnamese, in has the equivalent meaning of in, here the ideal meaning is inclusive and is contained in the spatial relationship between the national team and the national team of in and in in the language. German and Vietnamese are basically no different. But many times it is translated into Vietnamese with meanings such as: in, beside, above, between, before, at ...
(230) Manchmal denke ich, ich bin in Deutschland. (Sometimes I think I'm in Germany.)
(231) Die Kinder zeichnen einen Kreis in den Sand. (The children drew a circle in the sand.)
(232) Es gibt sehr viele Fische in diesem Fluss. (There are many fish in this river.)
(233) Das Lied ist für immer in meinen Ohren. (The song keeps echoing in my ears.)
(234) Ein neuer Ort, in einem neuen Haus. (A new place, at a new home.)
Actually, the above examples are not enough to reflect what we have in the documents, but they are enough for us to have some necessary comparisons, contrasts and connections. It can be said that the spatial relationship between ĐĐĐĐ and ĐTQC is abstracted by Germans in the preposition in when the spatial positioning relationship is different. This also happens when we translate back from Vietnamese. into German with specific uses. This also reflects the quite diverse differences in the way of perceiving space for each specific DTĐV and TQC between German and Vietnamese.
In German, space is always positioned objectively, based on the spatial relationship between the national team and the national team. In Vietnamese, besides the subjective positioning method, there is also a popular subjective positioning method - based on the spatial relationship between the surveyor and the speaker or listener himself, the surveyor. And it is also this subjectivity that has determined the practices of using structures such as: in the sky, on the ground, in the house, in the yard, in the belly, on the surface, on the bank, in the river, on the tree, under the tree. , ....
However, the important thing is that the expression of Vietnamese's subjective way of positioning is expressed in many diverse ways, forming a habit, a permanent way of positioning behavior. This has caused many difficulties for Vietnamese people when learning and using spatial positioning prepositions in German. Considering the example (233) "The song keeps ringing in my ears" (Das Lied ist für immer in meinen Ohren ), it can be said that this is a quite strange positioning situation for Vietnamese people because for Vietnamese people when saying " inside " ear " is like something coming from outside, coming from afar. Because Vietnamese people still say " water in the ear " , " whirring sound in the ear " , " pain in the ear " ,...
Above is some brief analysis of the specific positioning situation of in . In theory as well as in practice, we cannot cover all cases of specific different situations. Therefore, a more appropriate way of comparing and contrasting would be to return to the locative format types of auf/ in and the corresponding means of use in Vietnamese with the ideal meaning content of auf /print in German.
3.3.3. The preposition “auf” viewed from a cognitive perspective compared to Vietnamese
Through the analysis of the usage patterns of auf in comparison with Vietnamese that was presented in chapter II, we see a number of issues emerging as follows:
A uf - above is the permanent distinction between subjective positioning and objective positioning. In German, if starting from a practical perspective, one can completely raise the question of whether there is a certain range in the locative types of auf where only one way of translation can exist.
Switch to Vietnamese (not two ways). In certain cases there may be such ranges. For example:
(235) Der Riss auf dem Boden. (Crack in the floor.)
Die Falten auf seiner Stirn (the wrinkles on his forehead); Die Bilder auf dem Fernsehbildschirm (images on the television screen); Es gibt einen Punkt auf Der Oberfläche (there is a point (on) a surface).
In the above cases, it is not possible to use " under " , this is the positioning scope of an entity or event associated with it or almost a part of the National Team within a specific scope ( that is the National Team). When translating into Vietnamese, Vietnamese people often add an element to more specifically express the meaning of positioning according to each specific situation in which usage habits have certain influences that make the word in space. also has inherent permanence. For example, with roads that have characteristics such as DTĐV (including geometric straight lines), Vietnamese people often use the word above and add words in front of it like: "potholes (in) the road" (Schlaglöcher auf der Straße), “there is a gas station (in) the road” (Es gibt eine Tankstelle auf der Straße ), “ripe rice (in) the field” (Reifer Reis auf dem Feld), “stains (in) on a shirt” (die Flecken auf dem Hemd), “(on) a straight line ( auf gerader Linie), “(on) bare ground ” ( auf freiem Feld), “(on) a bronze engraving”( auf einem alten Kupfertisch) ... while German only uses the word auf ... Thus, it can be understood more broadly that, in the Vietnamese way of perceiving space, most entities appear in a space. surface, a line, is perceived as being on the surface, on that line.
Through this, it can be said that the Vietnamese people's perception of objective spatial positioning is strongly influenced by the horizontal direction, in addition to being influenced by what is "visible" in the horizontal direction. horizontally into the semantic scope of above. Considering this relationship, the semantic content of below is often contrasted with above , and therefore has a more subjective positioning, for example " pothole under the road ". However, in many cases, under is also used with an objective positioning meaning, such as: "the book is under the bed". The two authors Ly Toan Thang [52, 53] and Tran Quang Hai [17] mentioned that this is what governs the ability to translate positioning types such as: " Er schlief auf dem Boden " translates into
“It sleeps on the floor ” (above is an objective positioning); “ It sleeps on the floor” (below is a subjective positioning).
In addition, as analyzed in chapter 2, in German, there are a number of on cases used to position situations where the national team is separated from the national team, for example Die dunklen Wolken auf der Insel (dark clouds). on the island). Second, German often uses auf for the positioning type of an “object above a part of itself ” ( see section d, section 2.2.1.1) . This type of positioning is quite strange to Vietnamese people, almost absent in Vietnamese. Rarely do Vietnamese people use constructions like "standing on your feet " corresponding to "steh auf deinen Füßen ", in German this sentence has both a literal and figurative meaning. In Vietnamese, we see that this usage often has a figurative meaning to refer to being independent, self-reliant, independent,
... . Meanwhile, structures such as: auf den Knien (on both knees), der Mann auf dem Rücken (man lying on his back), ... in German have no figurative meaning other than denoting "the object on part of itself ” . Constructions such as these examples can only be translated into Vietnamese by non-positional constructions such as “man lying on his back or resting on his back ” . Therefore, it is understandable that this type is quite strange to Vietnamese.
Above in Vietnamese, in addition to the positioning meaning of attachment, support, and contact , it also has a denotative meaning similar to über ( above ) in German. This is a topological vertical positioning of a mobile unit in a position above, separate (without strict distance limitations) from the national team.
Author Ly Toan Thang [52] has thoroughly analyzed the semantics, cognitive mechanism, and positioning strategy of the above word. Considering examples such as clouds in the sky and clouds flying overhead , the second example is a type of positioning that can be classified as both subjective and objective. However, considering the relationship between DTĐV and TQC, it is more reasonable to refer this case to the objective positioning type. As for example 1, it can be attributed to the subjective positioning type.
Thus, it can be said that, in Vietnamese, with the meaning of positioning that is spatially separated in the vertical direction, there is a specific scope corresponding to comparison with German, which is ĐĐĐĐV. considered above the national team, although the national team may not be in a position higher than the national team in a straight line.
standing, but both the National Team and the National Team are located higher than the speaker's vision. For example: lights on the ceiling.
In summary, in the comparison between German and Vietnamese, it can be seen that, if auf in German, in addition to the scope for the type of spatial positioning that is associated with ĐĐĐĐV and ĐTQC, there is a scope which has can cause a false "correspondence " between auf and above , for example: ein Apfel auf einem Ast (apple on a branch) , there are also some areas that need to be noted such as: eine Medaille auf einer Kette (a badge worn on a strap) - refers to one object attached to another. Or when talking about a physical object that is in contact with another object like: Lege deinen schmutzigen Finger nicht auf meinen sauberen Anzug (Don't touch your dirty fingers on my clean clothes). Or referring to an object that is part of itself, for example: der Mann auf dem Rücken (the man lying on his back) and other uses of TQC in character as geographical locations.
Meanwhile, above in Vietnamese creates different ranges such as: subjective positioning range - in the sky ( im Himmel) , positioning range with spatial separation - "The white clouds over the mountains ” (Weiße Wolken in den Bergen ). In addition, the presence of visible semantic features, as mentioned above, also creates other specific cases of difference such as:
Bombenkrater auf dem Feld (bomb crater in the field ), das Loch in der Wand
(a hole in the wall) . Or some specific uses such as: in the world ( in der Welt), on the road ( auf der Straße)... also create very noticeable differences.
Above are some basic differences that the author has presented in detail along with illustrated examples. Although not comprehensive, they still partly represent a necessary basic visualization. about the relationship between auf and above from two different cognitive perspectives of Germans and Vietnamese.
3.3.4. The preposition “in” is viewed from a cognitive perspective compared to Vietnamese
Talking about the two prepositions auf and in in German, perhaps in is the preposition that contains the most cognitive content in the comparison between German and Vietnamese. Although, at first glance, it seems that printing does not depend much on the way of visualizing the space between ĐĐĐV and ĐTQC as auf . But in reality, through survey and analysis of documents, it shows that the difference between printed and printed is quite good
large, and it has a lot to do with how people perceive containment and which object can be the container (DTTQC) of another object (DTĐV).
Most of the differences between in German and in Vietnamese mainly focus on the extent to which TQCs have a spatial or one-dimensional model. The differences with the TQCs with three-dimensional space models are not much. We would like to give some examples below:
(236) Es gibt Punkte in der Linie.
(There are points on the line.)
(237) Das Loch in der Wand. (A hole in the wall.)
(238) Er hob sein Glas in die Luft.
(He raised his glass high/in the air.)
(239) Ein Mann in einem schwarzen roten Hut. (A man in a red and black hat.)
(240) Sie saßen in dem Schatten eines Baumes. (They sat under the shade of the tree.)
(241) Es gibt keine Apotheke in der Nachbarschaft. (There is no pharmacy in the vicinity.)
With the above cases, it is possible to set out contents related to the way of perceiving space for each specific national team. For example, in example (237) the use of the preposition in evokes the three-dimensional model of the wall ( der Wand ). In the case of example (238) “ in die Luft” refers to the German perception of “air” or “sky” or “air” as a three-dimensional space, which in Vietnamese is also There is a way to locate " in the air/ in the air/ in the sky ". But in Vietnamese, there are many subjective positioning methods, and this method has created highly "customary" positioning structures, such as: in the sky, on the ground, under water, etc. .birds fly in the sky, fish swim in the water). In specific cases like example (238), the positioning structure " in die Luft" can only be translated into Vietnamese as up (like: raise a glass or raise a glass ) . But if it is “Vögel fliegen in den Himmel” , it means “bird flying in the sky” or, more appropriately, “bird flying in the air ”.
As for example (241) the concept “ in der Nachbarschaft” , this is often visualized as a two-dimensional spatial model, as for example (236) “ in der Linie” , the use of the preposition in Here it is considered a one-dimensional spatial model. However, the permanent and popular ideal meaning of in is mainly related to TQCs with a three-dimensional spatial model, often associated with the concept of " containment " of the semantic content of the preposition in . This is mentioned by author Le Van Thanh [48, p.152] as a system of:
A- DĐĐV has any spatial model + in + DĐTQC has a three-dimensional space model
B - DĐĐV has a two-dimensional or one-dimensional space model or most simply "one point" + in + DTQC has a two-dimensional space model
C - DĐĐV has a one-dimensional or "one-point" space model + in + DTQC has a one-dimensional space model.
Here printing is also applied to both two-way or one-way TQCs (usually the cases of using printing with one-way TQCs are considered special cases and are not common). Therefore, the spatial model of the TQC focuses mainly on the "containment" to better fit the semantic content of " containment ". In general, the concept of "container" does not seem to be really suitable for situations where the DVT has a more multidimensional spatial model than the spatial model of the DTQC. And this concept is visualized through the fact that the national team is within the surface scope of the national team.
In example (236), der Linie is a geometric line, but DDT here is Punkte (points). Indeed, we have not seen any views discussing the issue of whether a point is a dimensional or non-dimensional entity. But according to logic, if a line is a one-dimensional entity, then a point is non-dimensional. However, there are also some cases where an object that is inherently two-dimensional can be perceived as three-dimensional, as in example (240), Schatten (tree shadow). Here we see, the shadow of a tree is basically recognized through its projection onto a certain, seemingly invisible part, a shade of a tree that when we go out in the sun and sit under the tree, we will be shaded. by the shadow of this invisible tree. And so, in our opinion, we have reinforced the perception of " tree shadow" as a three-dimensional object.
We discuss some of the above contents about spatial perception for the TQC of print in relation to the TQC. Just like the preposition auf



![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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