From 10 to under 50
6.73%
From 50 to under 200
1.38%
Over 500 billion
0.12%
From 200
under 5
0.42
From 5 to under 10 billion
7.19%
From 1 to under 5 billion
45.62%
under 0.5 billion
18.02%
from 0.5 to under 1
20.52%
Source: Current status of enterprises - General Statistics Office; NCS survey 2011
Table 2.2. Structure of wood processing enterprises divided by capital scale
The number of enterprises with capital from 50 billion to under 200 billion accounts for a very small number. Although in 2000 there were 12 enterprises, in 2005 it increased to 30 enterprises, meaning an increase of 2.5 times, but it still only accounts for 1.74% of the total number of enterprises. In 2010 there were 36 enterprises, an increase of 0.83 times compared to 2005. The number of enterprises with capital over 200 billion is even more modest.
Table 2.4. Scale of human resources in Vietnamese IT enterprises
Unit: person
Region
2005 | 2010 | 2011 | |||||||
Total number of employees | Female number | Number Labor Union | Total number of employees | Female number | Number Labor Union | Total number of employees | Female number | Number Labor Union | |
Nationwide | 113304 | 51192 | 64 | 253914 | 136553 | 99 | 259054 | 140640 | 99 |
North | 37095 | 16760 | 41 | 22503 | 12102 | 45 | 23509 | 12763 | 45 |
Red River Delta | 26500 | 11973 | 50 | 5282 | 2841 | 38 | 5738 | 3115 | 38 |
Winter North | 4125 | 1863 | 25 | 8029 | 4319 | 37 | 8103 | 4399 | 37 |
Northwest | 740 | 335 | 37 | 612 | 330 | 36 | 828 | 450 | 36 |
North Central set | 5730 | 2589 | 30 | 8580 | 4614 | 65 | 8840 | 4799 | 65 |
Southern | 76209 | 34432 | 89 | 231411 | 124451 | 113 | 235545 | 127877 | 113 |
South Central University | 15004 | 6779 | 124 | 38335 | 20616 | 205 | 40180 | 21814 | 205 |
West original | 7210 | 3256 | 70 | 20570 | 11062 | 110 | 21230 | 11526 | 110 |
Winter South | 49543 | 22382 | 103 | 16849 8 | 90618 | 111 | 17060 7 | 92623 | 111 |
Mekong Delta | 4452 | 2011 | 42 | 4008 | 2155 | 24 | 3528 | 1915 | 24 |
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Human Resources for IT and E-commerce of Enterprises -
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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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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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Results of Evaluating the Level of Dedication to Work of Human Resources at Tourism Enterprises in Da Nang City, 2017 -
Completing the analysis of business efficiency in wood processing enterprises for export in the South Central region - 27 -
Characteristics of Human Resources Management in Tourism Enterprises
Source: Viforest 2011 and Enterprise Status, General Statistics Office 2005-2011
Therefore, it can be said that the scale of the BOT enterprises in terms of capital and human resources is mostly small and medium-sized. The market is mostly dominated by medium-sized enterprises. The remaining enterprises with large scale in terms of both capital and human resources are very few and do not have the power to dominate the whole industry.
The number of employees working in the industry in 2005 increased 2.24 times compared to 2000. In the North, the number of employees decreased but gradually increased in the South. The number of employees in a Southern enterprise was 2.5 times higher than that in the Northern enterprise. The Southeast region had the highest concentration of employees in the CNCBG industry in the country. The highest number of employees in an enterprise was in the South Central Coast - an economic region with 6 provinces and the most concentrated CNCBG enterprises was Quy Nhon with Phu Tai industrial park. This is also the region with the second largest number of employees in CNCBG enterprises among the 8 economic regions of the country.
b
h
Red River Delta
2.21%
Northeast 3.13%
Northwest 0.32%
Mekong Delta
1.36%
North Central
3.41%
Fate
Central
Southeast
Central Highlands
Source: Viforest 2011
Table 2.3. Human resources in CNCBG divided by economic region
The participation and role of economic sectors in CNCBG have changed: Private sector participates and plays a leading role in processing and supplying wood products. In 2000, the proportion of state-owned enterprises accounted for 40.85% of the total number of enterprises nationwide, of which the North had a rate of 45.86%, the Northeast 52% and the Red River Delta more than 50%, the South had a rate of 35.6%. The rest were non-state enterprises and joint-stock enterprises (collectively called private enterprises).
Currently, the division of state-owned enterprises by economic sector has changed significantly. The proportion of state-owned enterprises accounts for 4% and private enterprises 96%. The region with the most state-owned enterprises is still mainly in the Southeast, South Central Coast, and Red River Delta. The region with the fewest state-owned enterprises in the country is the Northwest with 3 northern mountainous provinces: Lai Chau, Son La, and Hoa Binh.
Table 2.5. Classification of wood processing enterprises by economic sector
Unit: enterprise
Region
Year 2000 | 2010 | |||||||
Total number | DN NN | DN NNN | DN LD | Total | DN NN | DN NNN | DN LD | |
Nationwide | 896 | 355 | 514 | 27 | 2564 | 108 | 2043 | 413 |
North | 351 | 161 | 184 | 6 | 505 | 40 | 423 | 42 |
Red River Delta | 118 | 60 | 56 | 2 | 139 | 6 | 118 | 15 |
Northeast | 72 | 38 | 32 | 2 | 217 | 16 | 184 | 17 |
Northwest | 10 | 10 | 0 | 0 | 17 | 2 | 15 | 0 |
North Central | 151 | 53 | 96 | 2 | 132 | 16 | 106 | 10 |
Southern | 545 | 194 | 330 | 21 | 2059 | 68 | 1620 | 371 |
South Central University | 124 | 60 | 62 | 2 | 187 | 16 | 159 | 12 |
Central Highlands | 125 | 57 | 68 | 0 | 187 | 45 | 141 | 1 |
Southeast | 254 | 70 | 165 | 19 | 1518 | 4 | 1159 | 355 |
Mekong Delta | 42 | 7 | 35 | 0 | 167 | 3 | 161 | 3 |
(Source: Viforest, 2011 and General Statistics Office 2010
With the fluctuations of the socio-economic situation in general and the economic sector in particular, after 10 years, the state-owned enterprises decreased from 40% in 2000 to 4% in 2010. This proves the strength of the people in participating in economic activities.
Non-state enterprise
57%
Joint venture enterprise
3%
State-owned enterprise
40%
Enterprise ownership structure in CNCBGVN in 2016
Joint venture enterprise
16%
State-owned enterprise
4%
Non-state enterprise
80%
Enterprise ownership structure in CNCBGVN
(Source: Viforest 2011)
Table 2.4. Structure of business types in Vietnam's CNCBG industry
Currently, Vietnamese wooden products are present in the markets of 120 countries around the world. The price and quality of products are relatively suitable to the requirements and tastes of consumers. From 2005 to now, the US has always been the country that imports the most Vietnamese wooden products with 25.8% of the total output of exported wooden products of Vietnam, followed by Japan with 16%; UK with 11%; Taiwan with 6.1%; France with 4.6%; Germany with 4.3%; Australia with 3.5%; Netherlands with 3.2%; Korea with 3%;
China 2.8%; Belgium 2%; Spain 1.7%; Denmark 1.6%; Malaysia 1.4%; Other countries 17.8%.
Denmark
1.60%
Belgium
2%
Spain
1.70%
Malaysia
1.40%
Other countries
17.80%
America
25.80
China
2.80%
Korea
3%
Older brother
11%
Netherlands
3.20% Australia
3.50%
Virtue
4.30%
France
Taiwan
6.10%
(Source: Viforest 2011)
Table 2.5. Export market structure of Vietnamese wooden products
Characteristics of human resource classification in Vietnamese wood processing industry enterprises
Indirect human resources in enterprises often fluctuate little, but direct human resources have a high level of fluctuation each year. Indirect human resources usually account for about 5%-7% of the human resources of each enterprise, which are cadres with college, university and intermediate degrees, very few cadres with post-university degrees. Every year, enterprises recruit new human resources, accounting for about 7%/year. Level 5 workers and above are technical workers who can do most of the work and technical operations of the CNCBG industry, this number accounts for about 15%. The rest are seasonal or short-term contract workers [122] .
To understand the characteristics of direct NNL classification in modern Vietnamese enterprises, we must first understand the production process in enterprises. Normally, the process is often divided into the following stages:
- The process of making blanks (pre-processing) from round wood includes sawing, drying, gluing, and bending to get rough blanks. The blanks must be produced according to the correct specifications and ensure accurate machining allowance. To be able to cut,
To mill, carve, and join accurately and according to technical design, the wood needs to be drawn before processing.
- The machine stage (refining) has the following stages: planing, milling, cutting fine details, mortising, drilling holes, rough sanding, fine sanding. This is the stage that determines product quality, requiring workers in the production line to understand and correctly implement the production process as well as have a sense of responsibility and comply with labor discipline. The processed details must be in accordance with the technical design drawings and samples issued by the technician. Workers at each production stage must be responsible for the products they operate, checking the quality of sawn wood brought in from previous stages before carrying out their work operations. All wood surfaces processed at this stage must be carefully sanded before being transferred to the assembly stage.
- The assembly and finishing stages include: planing, milling, cutting fine details, mortising, drilling holes, rough sanding, fine sanding. This is the stage that determines product quality, requiring workers in the production line to understand and correctly implement the production process as well as have a sense of responsibility and comply with labor discipline. The processed details must comply with the technical design drawings and samples issued by the technician. Workers at each production stage must be responsible for the products they operate and are also responsible for checking the quality of sawn timber brought in from previous stages, before carrying out their work operations.
From this production process, enterprises arrange direct production workers in each stage depending on production requirements.
Assembly and completion
36% good
Preliminary processing
24%
Refined
40%
Source: NCS 2011 survey
Table 2.6. Percentage of human resources working at wood processing stages in the production process at modern wood processing enterprises in Vietnam
When comparing the theoretical stages and the actual survey at enterprises, the researcher found no difference between the production stages. The three basic stages above include many
Many stages can be classified into preliminary processing or refining sections. The preliminary processing section usually includes stages in the blanking and machine stages. The refining section also includes stages in the machine stage, assembly and finishing stages. These are technical production stages, some of which are performed on machines and some of which are performed manually (scraping, scraping, caulking, wiping glue at joints, etc.). Each stage requires different implementation capabilities, techniques and skills, and requires human resources to have certain skills for each production stage.
2.1.4. Production and consumption situation of wooden products
Along with the development of the Vietnamese CNCBG industry in recent times, the actual demand for raw wood has grown strongly. The total volume of wood used in 2000 was over 8.8 million m3 , of which 51.61% was used for CNCBG. In 2005, the total volume of raw wood used was 10 million m3 and 53.4% was used for CNCBG. In 2010, the total volume of raw wood used was about 11 million m3, of which raw wood for CNCBG accounted for 57.34%. Vietnam's source of raw wood is domestic plantation wood and imported wood. In the 2000s, the amount of raw wood from
Domestic forests meet about 60%-70% of the demand. However, the output of exploited wood is gradually decreasing and becoming increasingly scarce, leading to the amount of imported wood for production currently being about 80%.
Southeast
4.47%
Mekong Delta
3.69%
Northwest
2.20%
Northeast
23.18%
Central Highlands
34.20%
Red River Delta
0.23%
Central University
North Central Coast
Source: Vietnam Timber and Forest Products Association - Viforest 2011
Table 2.7. Distribution of forests - raw material sources for Vietnamese wood processing enterprises
By 2010, imported raw wood used for industrial enterprises accounted for up to 80%. The reason for the large import is that Vietnam's exploited forest area is low and the quality of exploited wood is not high, small wood and young wood account for the majority of exploited wood, so the processing of raw wood pushes up production and business costs.
Table 2.6. Structure of wood material usage of Vietnamese wood processing enterprises
Content
2000 | 2005 | 2010 | |
1. Total volume of raw wood used (million m 3 ) | 8.8 | 10 | 11 |
2. Usage structure (%) | |||
- Wood used for CBG industry | 51.6 | 53.4 | 57.34 |
- Wood used as raw material for particle board, MDF | 20.19 | 20.19 | 24.2 |
- Wood for pulp and paper processing industry | 25.52 | 25.52 | 17.6 |
- Wood used for mine pillars | 0.68 | 0.89 | 0.86 |
Source: Viforest 2011 The countries exporting the most wood to Vietnam are Malaysia, in descending order are Laos, the US, China, Myanmar, Cambodia, Thailand, Brazil, New Zealand, Taiwan and about 20 other countries. The volume of imported wood is large but in Vietnam, there is currently no centralized raw wood market, making the transaction and purchase of raw materials for production inconvenient. Therefore, the import of raw wood materials by enterprises of wood processing and exporting enterprises depends entirely on direct transactions through foreign partners, lacking
uniformity and synchronization in importing wood materials among Vietnamese wood processing enterprises.
The main export products currently include: outdoor furniture 32%; furniture, living room, dining room 31.4%; bedroom furniture 4.1%; kitchen furniture 3.25%. Other types of wooden furniture 17.8% and wooden furniture combined with other materials 5.1%. The export market is 120 countries but the 3 main export markets of the BCG enterprises are the US, EU and Japan.
Table 2.7. Export turnover of wood products in 3 main markets
Unit: million USD
Market Year
2000 | 2005 | 2010 | |
America | 115.46 | 566,968 | 930 |
EU | 160.74 | 457.63 | 630 |
Japan | 137.91 | 240.80 | 300 |
Source: Viforest 2011
The period from 2003 to 2007 was a period of strong development in the export of wood and wood products in Vietnam. In 2003, the export turnover of wood and wood products nationwide reached 567 million USD, in 2004 it was 1.1 billion USD. In the following years, the export turnover of wood and wood products of
Vietnam continues to maintain a high growth rate, increasing by 35% in 2005, increasing by 23.5% in 2006. In 2007, it reached 2.4 billion USD, an increase of 24.5% compared to 2006 and in 2010, it reached 3 billion USD. This proves that Vietnam has found a foothold, gradually asserting its position in the world wooden furniture market. With domestic production and consumption, finding data for analysis is extremely difficult. Objective reasons: due to socio-economic development leading to a very rapid growth in demand for wooden products, the development of wooden production facilities to serve domestic needs is almost spontaneous without complete statistics. Subjective reasons: in the past ten years, there have been only a few small studies on production and domestic consumption of wooden products, the statistics are not specific and inaccurate. Therefore, the NCS focuses on researching export-oriented enterprises, using documents from typical enterprises in the industry for research and analysis.
2.2. Current status of human resource quality in Vietnamese wood processing industry enterprises
2.2.1. Quality of human resources through intelligence
2.2.1.1. Education level
With 8 economic regions in the country, the South Central Coast is the region with the largest number of laborers in an enterprise, including 6 provinces: Da Nang, Quang Nam, Quang Ngai, Binh Dinh, Phu Yen and Khanh Hoa, of which Binh Dinh is the province with the largest number of enterprises. Binh Dinh has Phu Tai Industrial Park, Long My Industrial Park and Nhon Hoi Economic Zone. All three of these industrial parks have enterprises with many different industries, but mainly forestry enterprises and are mostly concentrated in Phu Tai Industrial Park. This is the largest industrial park in Binh Dinh province with laborers participating in labor and creating a large volume of products as well as export value of Binh Dinh province.
According to the data of Binh Dinh Economic Zone Management Board, the number of human resources in enterprises of all sectors in 2010 in the province was 21,789 people, of which the CNCBG industry alone accounted for 17,657 people (81.03% of the total number of human resources in all enterprises of all economic sectors). This shows that the CNCBG industry in Binh Dinh has developed very well and attracted human resources to work in recent years.