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WO2000065782A1 - Technique de regulation de surcharge dans un reseau a commutation par paquets - Google Patents

Technique de regulation de surcharge dans un reseau a commutation par paquets Download PDF

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Publication number
WO2000065782A1
WO2000065782A1 PCT/EP1999/002856 EP9902856W WO0065782A1 WO 2000065782 A1 WO2000065782 A1 WO 2000065782A1 EP 9902856 W EP9902856 W EP 9902856W WO 0065782 A1 WO0065782 A1 WO 0065782A1
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WO
WIPO (PCT)
Prior art keywords
congestion
packet
data packet
congestion notification
tcp
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP1999/002856
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English (en)
Inventor
Jian Ma
Peng Fei
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Oyj
Nokia Inc
Original Assignee
Nokia Networks Oy
Nokia Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Networks Oy, Nokia Inc filed Critical Nokia Networks Oy
Priority to PCT/EP1999/002856 priority Critical patent/WO2000065782A1/fr
Priority to CA002372023A priority patent/CA2372023A1/fr
Priority to DE19983951T priority patent/DE19983951B4/de
Priority to GB0125202A priority patent/GB2364615B/en
Priority to AU40342/99A priority patent/AU4034299A/en
Publication of WO2000065782A1 publication Critical patent/WO2000065782A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/19—Flow control; Congestion control at layers above the network layer
    • H04L47/193—Flow control; Congestion control at layers above the network layer at the transport layer, e.g. TCP related
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/35—Flow control; Congestion control by embedding flow control information in regular packets, e.g. piggybacking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
    • H04L69/161—Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
    • H04L69/163—In-band adaptation of TCP data exchange; In-band control procedures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W80/00—Wireless network protocols or protocol adaptations to wireless operation
    • H04W80/06—Transport layer protocols, e.g. TCP [Transport Control Protocol] over wireless
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/16—Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]

Definitions

  • the present invention relates to a method for controlling overload in a packed-switched network, especially a wireless or mobile network in which the Transmission Control Protocol (TCP) is used as a transport layer protocol .
  • TCP Transmission Control Protocol
  • TCP is the most popular transport layer protocol for data transfer. It provides connection-oriented reliable transfer of data between two connecting hosts, wherein a host refers to a network-connected computer or to any system which can be connected to a network for offering services to another host connected to the same network. TCP uses several techniques to maximize the performance of the connection by monitoring different variables relating to the connection. For example, TCP includes an internal algorithm for avoiding congestion.
  • Congestion control relates to the general problem of traffic management for packet-switched networks.
  • Congestion means a situation in which the number of transmission requests at a specific time exceeds the transmission capacity at a certain network point (called a bottle-neck resource) .
  • Congestion usually results in overload conditions.
  • the buffers may overflow, for instance, so that packets are retransmitted either by the network or by the subscriber.
  • congestion arises, when the incoming traffic to a specific link is more than the outgoing link capacity.
  • the primary function of congestion control is to ensure good throughput and delay performance while maintaining a fair allocation of network resources to the users.
  • connection control poses a challenging problem. It is known that packet losses result in a significant degradation in TCP throughput. Thus, for the best possible throughput, a minimum number of packet losses should occur.
  • the Internet was intended to support best-effort service, and the TCP congestion control method that was actually implemented has been developed on the assumption that the network would be treated as a black box.
  • the end nodes do not exercise control by directly ascertaining the state of routers and transmission lines, but rather regulate the traffic by inferring the network load indirectly from packet loss and response time fluctuations.
  • this may not induce serious problems, as packet losses mainly occur due to congestion.
  • this reliance on packet drops as an indicator of congestion causes a significant degradation in TCP performance, since the TCP reacts to packet losses as it would in the wired environment.
  • Indirect-TCP protocol is described as one of the first protocols to distinguish different losses by splitting a TCP connection between a fixed and a mobile host into two separate connections at the base station, such that a more optimized wireless link-specific protocol tuned for better performance can be used over a one-hop wireless link.
  • drawbacks of this approach such as loss of semantics, application re-linking and software overhead.
  • an ELN (Explicit Loss Notification) protocol has been proposed, wherein an explicit loss notification option is added to TCP acknowledgments, when a packet is dropped on the wireless link.
  • future cumulative acknowledgments corresponding to each lost packet must always be marked to identify that a non- congestion-related loss has occurred.
  • routers drop packets rather than setting the ECN in the packet header .
  • a method for controlling overload in a packet-switched network comprising traffic sources, traffic destinations and network nodes, said method comprising the steps of: transmitting data packets from one of said traffic sources to one of said traffic destinations; transmitting an acknowledgment packet from said one traffic destination to said one traffic source, if a data packet has been received correctly at said one destination; and adding a congestion notification information to a data packet following a data packet lost due to a buffer overflow.
  • a packet- switched telecommunication network comprising: network nodes interconnected by transmission lines; user terminals connected to said network nodes, said user terminals acting as traffic sources which transmit data packets and as traffic destinations which receive data packets ; detecting means for detecting a loss of a data packet due to a buffer overflow in one of said network nodes; and control means for adding a congestion notification information to a data packet following a data packet lost due to said buffer overflow, in response to a detection result of said detection means.
  • a short-cut ECN mechanism (Wireless-ECN) which preferably can be used in wireless or mobile environments.
  • the mechanism is arranged to communicate the reason for a packet loss to the TCP source.
  • the source can be informed that a loss happened due to reasons related to a network congestion, such that congestion control can be decoupled from retransmissions.
  • the congestion window is only reduced in case the congestion notification information has been received, without considering packet losses.
  • congestion control and loss recovery mechanism can be separated. This mechanism is simple to implement and compatible with the existing TCP congestion control.
  • Wireless-ECN When Wireless-ECN is used in the traditional ECN environment, Wireless-ECN is interpreted by the TCP source as a new instance of congestion.
  • the integration of Wireless-ECN into the known ECN mechanism allows congestion control to be initiated by WECN or ECN messages . Since a WECN message should be added at least not later than the threshold number of following packets, it may invoke congestion control even sooner than with the fast retransmission mechanism.
  • the integration of the WECN into the ECN mechanism not only avoids unnecessary congestion- induced packet losses, but also prevents the unnecessary delayed initiation of congestion control which often occurs due to a loss of an ECN packet or an inefficient effect of the ECN mechanism or other exceptions in the ECN mechanism.
  • said following data packet directly follows said lost data packet.
  • the congestion notification may be added in the header of said following data packet.
  • bit No. 5 in the IPv 4 TOS octet can be used, for example.
  • each of the network nodes should be able to add the congestion notification information to thereby indicate a congestion-related data loss.
  • multiple WECN messages provide a robustness against the possibility of dropping a WECN packet in the bi-directional transmitting paths .
  • the congestion notification information is allowed to be added to those following data packets which belong to the same congestion window in the successively past routers. Moreover, each network node is allowed to add the congestion information only once. Thus each congestion notification information added in a transmission window belongs to another network node .
  • the traffic destination Having received a data packet with an added congestion notification information, the traffic destination preferably sets a congestion notification flag in the header of an acknowledgment packet.
  • the congestion notification flag may be bit No. 8 in the TCP header of the subsequent acknowledgment packet. Since the TCP uses the WECN message to invoke congestion control, only a retransmission mechanism is performed in case of a packet loss without a WECN message. Thus, the TCP data flow rate is not affected. This is very useful in wireless or mobile networks, since the network itself has the function of distinguishing different sources of packet losses. By notifying the source with a WECN acknowledgment packet whenever a congestion-related loss has occurred, packet losses due to transmission errors cannot reduce the TCP flow control window (congestion window) , which results in a significant performance improvement. The congestion window can only be reduced by the congestion notification flag set due to a congestion loss .
  • a congestion processing is repeated at the traffic source only after the outstanding data packets transmitted before the first receipt of a congestion notification flag have all been acknowledged. Thereby, reduction of the congestion window is not repeated, if the packet was dropped before the source reduced its window in response to the congestion notification flag.
  • the WECN mechanism enables complete decoupling of the congestion control function from packet losses.
  • the WECN notification may inevitably be added, since the dropped packets give the buffer time to vacate some space for holding and transmitting new data.
  • this loss will result in a failure of congestion control for that flow and an increased congestion of the network, since the assumed source of data loss was not a congestion.
  • other WECNs are added for subsequent dropped packets in the next congestion window.
  • the mechanism is very secure and robust compared to the ECN mechanism where the loss of an ECN will not cause another addition of an ECN packet.
  • the WECN mechanism can be implemented in a simple manner and opens the way to a further deployment of the ECN mechanism. It is to be noted that the WECN mechanism is compatible with all TCP congestion control mechanisms, as long as they are invoked by packet losses, and it is easy to incorporate them into wireless and mobile networks. With the incremental deployment of the ECN mechanism, the integration of WECN into ECN may allow congestion control to be initiated by WECN or ECN messages and WECN packet functions only if a packet lost due to a congestion arrives earlier than an ECN within the corresponding data window.
  • WECN since WECN is required to be added not later than after a threshold number of duplicate acknowledgements , improved TCP performance in wired network environments can be expected, since the initiation of congestion control is accelerated by the WECN message. Moreover, if this message is used for triggering the transmission or retransmission data packets, it can hasten the speed of entering into the TCP recovery phase due to congestion, such that congestion-induced lost packets are quickly retransmitted.
  • Fig. 1 shows a general block diagram of a flow control loop in a TCP over ATM network, in which the preferred embodiment of the present invention is implemented;
  • Fig. 2 shows a general block diagram of an intermediate node arranged between a traffic source and a traffic destination, according to the preferred embodiment of the present invention
  • Fig. 3 shows a general block diagram of two subsequent intermediate nodes according to the preferred embodiment of the present invention
  • Fig. 4 shows a diagram of transmissions between a traffic source and a traffic destination, in case a wireless congestion notification (WECN) arrives at the traffic source before a usual congestion notification (ECN) within the same transmission window;
  • WECN wireless congestion notification
  • ECN usual congestion notification
  • Fig. 5 shows a diagram of transmissions between the traffic source and the traffic destination, in case a non- congestion packet loss is detected before a congestion notification within the same transmission window;
  • Fig. 6 shows a diagram of transmissions between the traffic source and the traffic destination, in case a WECN arrives at the traffic source after an ineffective ECN implementation in the preceding transmission window;
  • Fig. 7 shows a diagram of transmissions between the traffic source and the traffic destination, in case a WECN is received at the traffic source after a normal ECN within the same transmission window;
  • Fig. 8 shows a diagram of transmissions between the traffic source and the traffic destination, in case a WECN is set before three following packets in the same transmission window;
  • Fig. 9 shows a diagram of transmissions between the traffic source and the traffic destination, in case of a WECN and a non-congestion packet loss within the same transmission window
  • Fig. 10 shows a diagram of transmissions between the traffic source and the traffic destination, in case of a delayed set of WECN and multiple congestion losses within the same transmission window.
  • ATM Asynchronous Transfer Mode
  • ITU-T the international telecommunication standardization organization
  • B-ISDN broadband Integrated Services Digital Network
  • the problems of conventional packet networks have been eliminated in the ADM network by using short packets of a standard length (53 bytes), known as cells.
  • ATM networks are quickly being adopted as backbones for the various parts of TCP/IP networks such as the Internet. This also applies to wireless or mobile networks.
  • a connection between two user terminals A and B in the TCP over ATM network is shown, i.e. the user terminals using TCP as a transport layer protocol.
  • two access nodes ANl and AN2 of the user terminals, one intermediate node Nl and transmission lines TLl, TL2 connecting the nodes are shown.
  • TCP Transmission Control Protocol
  • segment refers to the unit of information passed by TCP to IP (Internet protocol) .
  • IP headers are attached to these TCP segments to form IP datagrams, i.e. TCP segments are transferred to the receiver within IP datagrams as the information units used by IP.
  • TCP segments are transferred to the receiver within IP datagrams as the information units used by IP.
  • Each uncorrupted TCP segment including the hand shaking segments is acknowledged.
  • the user terminal A transmits one TCP segment to the user terminal B.
  • the user terminal A adds an IP header to this TCP segment to form an IP datagram.
  • This datagram is converted into standard ATM cells in the access node ANl located at the edge of the ATM network ANW.
  • the cells of the datagram are then routed through the ATM network to the access node AN2 of the user terminal B.
  • This access node reconstructs the original IP datagram from the arriving cells and sends the IP datagram to the user terminal B.
  • the user terminal B removes the IP header to reveal the TCP segment. If the segment is received correctly, the user terminal B sends an acknowledging TCP segment ACK back to the user terminal A.
  • TCP is one of the few transport protocols that natively has a congestion control mechanism.
  • the preferred embodiment of the present invention relies on this known TCP control mechanism. Therefore, this mechanism is described briefly in the following.
  • TCP congestion control is based on two variables: the receiver's advertised window (Wrcvr) and the congestion window (CNWD) .
  • the receiver's advertised window is maintained at the receiver as a measure of the buffering capacity of the receiver, and the congestion window is maintained at the transmitter as a measure of the capacity of the network.
  • the TCP source can never transmit more segments than the minimum of the receiver's advertised window and the congestion window.
  • the TCP congestion control method comprises two phases : slow start and congestion avoidance.
  • a variable called SSTHRES Small Start Threshold
  • the source starts to transmit in the slow start phase by sending one TCP segment, i.e. the value of CWND is set to one at the beginning.
  • the source receives an acknowledgment, it increments CWND by one, and, as a consequence, transmits to more segments .
  • the value of CWND doubles every round trip time during the slow start phase, as each segment is acknowledged by the destination terminal.
  • the slow start phase ends and the congestion avoidance phase begins, when CWND reaches the value of SSTHRES.
  • the source does not receive an acknowledgment and performs a loss recovery operation.
  • the TCP source can be made to slow down its output rate. This is based on the fast retransmission and fast recovery algorithms which the source automatically performs after receiving a certain number of duplicate acknowledgments . These algorithms are widely implemented in different TCP versions. According to the algorithms, the source performs, after having received a predetermined threshold number of acknowledgments (e.g. three acknowledgements) , a retransmission of what appears to be the missing segment, without waiting for the expiry of a retransmission timer (fast retransmission algorithm) . After this, the source performs congestion avoidance, instead of slow start, in order not to reduce the data flow abruptly (fast recovery algorithm) .
  • a predetermined threshold number of acknowledgments e.g. three acknowledgements
  • a retransmission of what appears to be the missing segment without waiting for the expiry of a retransmission timer (fast retransmission algorithm) .
  • the source performs congestion avoidance, instead of slow start, in order not to reduce the data flow abruptly (fast recovery algorithm)
  • Fig. 2 shows a general diagram of an intermediate node connected to a TCP source A and a TCP destination B, which both may be workstations or the like.
  • a congestion is shown as a black star, a passing data packet as a solid square, and a data packet lost due to the congestion as a doted square.
  • a Wireless-ECN (WECN) control means C is provided in the intermediate node, which is arranged to mark a data packet with an explicit wireless congestion notification (WECN) immediately after a packet loss has occurred due to a buffer overflow which may be detected by a detecting means (not shown) .
  • the detecting means may be included in the control means C or may be a separate means in the intermediate node .
  • a WECN is added in the header of the immediately following passing packet.
  • the required time for this operation is available due to the dropped data packet which results in additional buffer time.
  • the WECN is added as quickly as possible after a packet loss, such that the network congestion can be alleviated as soon as possible.
  • an arrow at the bottom of Fig. 2 shows the transmitting path of the WECN, wherein the TCP destination B sets a WECN flag in the header of an acknowledgment packet in response to the receipt of a WECN data packet, to thereby notify the congestion in the intermediate node.
  • Each node in the network should be able to add the WECN to thereby indicate a congestion as soon as a packet loss occurs.
  • the WECN which may be a single WECN bit, may be added in the following packets belonging to the same transmission or congestion window by different ones of successive routers passed by the data packets.
  • the WECN may be a single WECN bit, may be added in the following packets belonging to the same transmission or congestion window by different ones of successive routers passed by the data packets.
  • the condition and buffer occupancy in each network node usually various greatly, not only one WECN is usually set in a transmission window during a round-trip time, because the first lost packet in each intermediate node may not occur at the same time.
  • each WECN added in a transmission window belongs to a different transmitting network node which is allowed to add the WECN only once.
  • Fig. 3 shows a general diagram of an intermediate node 1 and an intermediate node 2, successively connected in the direction of the forward path. In the present case, both intermediate nodes 1 and 2 are congested.
  • a WECN data packet having an added WECN is shown as a hatched square.
  • a control means Cl arranged in the intermediate node 1 adds a WECN to the second data packet, since the first data packet is lost due to the congestion. Furthermore, the third data packet is also lost due to the congestion. However, since the intermediate node 1 is only allowed to add the WECN once, the first data packet remains without a WECN addition.
  • the data packet sequence is then transmitted via the forward path to the intermediate node 2, where the fifth and sixth data packets are lost due to the congestion. Accordingly, a WECN is added to the seventh data packet by a control means C2 of the intermediate node 2.
  • the TCP destination B receives the data packet sequence comprising the WECN packets number 2 and 7 and sets the WECN flags of the corresponding acknowledgment packets to be returned to the TCP source A.
  • the successive routers may not erase a WECN bit in arriving packets, to thereby maintain the WECN compliance in the network.
  • the TCP destination B sets a WECN flag in the TCP header of an acknowledgment packet in response to each IP packet with an added WECN bit
  • the TCP source A may receive a plurality of WECN packets coming from different intermediate nodes within a congestion window. Since the main function of WECN is to initiate a congestion control, i.e. to reduce the congestion window, only once in a transmission window in the event of a network congestion, these multiple WECN messages also provide a robustness against the possibility of dropping a WECN packet in the bi-directional transmitting path.
  • bit No. 6 and bit No. 7 of the IPv4 TOS octet are designated as the ECT bit and the CE bit, respectively.
  • bit No. 5 in the IPv4 TOS octet can be chosen as the WECN- Echo flag used to indicate congestion packet losses by intermediate routers or other network elements. Thereby, a different window reduction can be initiated by the WECN congestion control.
  • the TCP destination B when it receives a CE data packet, it sets the ECN-Echo flag in the TCP header of the subsequent ACK packet.
  • two different flags of the TCP header are requirted. Since bit No. 9 is designated as the ECN-Echo flag of the TCP header, bit No. 8 can be used as the WECN-Echo flag.
  • bit No. 9 is designated as the ECN-Echo flag of the TCP header
  • bit No. 8 can be used as the WECN-Echo flag.
  • the number of WECN packets will not exceed the number of total network nodes to be passed by the data packet. Thereby, the burden of providing an interphase facility between IP and TCP at the destination side can be relieved.
  • end nodes detect dropped data packets by receiving a WECN message set by the intermediate network nodes just in times of buffer overflow, wherein the congestion response of the end nodes to a received CE packet is at least as strong as the congestion response to a dropped data packet which is independent of congestion control.
  • TCP related to the ECN mechanism proposed by ITEF, wherein TCP requires a less conservative response as compared to the case of a dropped packet, especially over small time scales, since a buffer overflow has not yet occurred.
  • the additional requirement for the TCP source A to react to multiple WECN acknowledgment packets is that it should not repeat the reduction of the congestion window since the packet was probably dropped before the TCP source A has reduced its congestion window in response to an earlier WECN acknowledgment packet .
  • the TCP source A should react to a WECN acknowledgment packet at most once per round-trip time. This can be achieved by adapting the TCP source A in such a manner that it reacts to a subsequent WECN acknowledgment packet only after the outstanding data packets, transmitted before the TCP source A entered into a loss recovery phase upon receiving the first WECN acknowledgment packet, have all been acknowledged.
  • the TCP could be changed so as to provide a negotiation phase during setup to determine if both end nodes are WECN capable .
  • the WECN mechanism leads to an independence of the TCP from the packet loss as an indicator of congestion. Since the TCP uses the WECN message to invoke congestion control whenever a packet loss occurs, only a retransmission mechanism is started as a response to a packet loss without a WECN message, such that the TCP data flow rate is not affected in such a case. This is very useful in wireless or mobile networks, since the network itself has the function of distinguishing different sources of packet losses. Thus, the TCP congestion window can only be reduced by the WECN message which is set due to congestion losses.
  • the TCP source A may only react once during a round-trip time and generally to the earliest one of received WECN and ECN ACKs . If an ECN ACK is received at first, the conventional congestion control is invoked at the TCP source A. However, when some packet losses due to congestion arrive before the ECN messages within a round- trip time, the WECN messages added just upon the first packet loss caused by the congestion will arrive in time to initiate a general congestion control e.g. with half reduction of window size instead of waiting for the later arrival of the ECN packets. Thus, WECN leads to a congestion control which is completely free from non- congestion lost packets and high performance is assured without having to resort to islands of different sources of packet losses in wireless and mobile networks.
  • the WECN mechanism not only leads to a decoupling of congestion control from loss recovery but also contributes to the loss recovery phase. Since it is required that the WECN is set immediately after the packet loss occurs, it is very likely that the WECN acknowledgement packet arrives before the threshold number of duplicate acknowledgement packets. If this WECN message is used to trigger the transmission or retransmission of any data packets, it can increase the speed of entering the TCP recovery phase so as to quickly retransmit congestion-related lost packets. However, the ECN cannot always be added immediately after a lost packet in case there are several successive packet losses or disordered packets before the arrival of the ECN message.
  • Fig. 4 shows a diagram of transmissions between the TCP source A and the TCP destination B, wherein the transmission of a first message X and a second message Y is depicted as a plurality of forward and backward arrows each indicating the transmission of a data packet and an acknowledgement packet (ACK) , respectively.
  • the transmission proceeds from the top to the bottom and corresponding ACK messages are indicated by the backward arrows from the destination B to the source A.
  • a transmission window is indicated by the time period (vertical direction) from the starting point of a forward arrow to the end point of the corresponding backward arrow.
  • the second data packet is lost due to a congestion loss 1 notified to the TCP destination B by the subsequent third data packet.
  • an acknowledgement packet with a set WECN-Echo flag is returned to the TCP source A before any ECN message has arrived.
  • the TCP source A Based on the received acknowledgment and duplicate acknowledgement with the set WECN-Echo flag, the TCP source A performs a congestion control by reducing SSTHRES to half of the current CWND value. Then, CWND is set equal to the new SSTHRES.
  • an ECN is set delayed in the fifth data packet, such that an ECN-Echo flag is set in the corresponding ACK packet.
  • the ACK with ECN-Echo flag is ignored, since the WECN ACK has already been received in the same transmission window (i.e. forward and backward arrow relating to the transmission of the message Y) .
  • the conventional TCP fast retransmission algorithm is started for the lost packet 1, since the threshold number of duplicate ACKs, i.e. 3 ACKs, has been received.
  • an additional congestion loss 2 occurs at the sixth data packet, such that a WECN is set in the seventh data packet so as to initiate an ACK with a WECN-Echo flag.
  • the WECN message is also ignored at the TCP source A, since the ACK with WECN-Echo flag is also received within the above same transmission window.
  • the conventional TCP fast retransmission algorithm is performed for the lost packet 2 after the receipt of 3 duplicate ACKs.
  • Fig. 5 shows a diagram similar to the diagram according to Fig. 4, wherein a non-congestion loss 1 occurs during the transmission of the first data packet of the message X.
  • the treshold number of duplicate acknowledgements arrive at the TCP source A before the receipt of the ECN acknowledgment.
  • a congestion loss 2 occurs during the transmission of the sixth data packet of the message X.
  • the conventional fast retransmission algorithm is performed, i.e. the lost data packet is retransmitted after three duplicate acknowledgments have been received.
  • the conventional congestion control e.g. reduction of SSTHRES to 0.625CWND and setting of a new CWND equal to the new SSTHRES, is performed in response to the receipt of the ECN acknowledgment.
  • a WECN is set in response to the non-congestion loss 2.
  • the corresponding WECN ACK is ignored, since it is received within the same transmission window. Nevertheless, due to the conventional retransmission algorithm, the lost packet 2 is retransmitted after the receipt of three duplicate acknowledgements .
  • Fig. 6 shows another transmission example, wherein an ECN is set in a previous transmission window (message X) due to a detected congestion and, despite of the conventional congestion performed in response to the receipt of the ECN ACK, a subsequent packet loss occurs in the following transmission window (message Y) .
  • the conventional fast retransmission is performed after the receipt of three duplicate acknowledgements, to thereby retransmit the lost data packet.
  • the subsequent ECN message is ignored due to its receipt within the same transmission window.
  • Fig. 7 shows a transmission example in which an ECN message is received before a subsequent non-congestion packet loss 1 and congestion packet loss 2 within the same transmission window.
  • a conventional congestion control is performed in response to the receipt of the ECN ACK.
  • the non-congestion loss 1 does not initiate a WECN message.
  • the conventional retransmission of the non-congestion loss 1 is performed.
  • the subsequent WECN ACK set in response to the congestion loss 2 is ignored at the TCP source A, since it has occurred in the same transmission window. Nevertheless, again, the conventional retransmission is performed after the receipt of three duplicate acknowlegments .
  • Fig. 8 shows a case in which the second and sixth data packets of a message X are lost due to congestion, and the seventh data packet is a disordered packet.
  • WECN messages are set in the third and eighth data packet, since the seventh data packet is a disordered one.
  • the congestion control according to the preferred embodiment of the present invention is then performed in response to the receipt of the first WECN ACK. Thereafter, a conventional retransmission is performed in response to the receipt of three duplicate ACKs.
  • the second WECN ACK which is accompanied by one duplicate WECN ACK (due to the disordered packet) is ignored, since it is received within the same transmission window. Nevertheless, the conventional retransmission is again performed for the lost packet 2 after the receipt of three duplicate ACKs. Since the disordered packet cannot be identified, a retransmission thereof is not possible.
  • a further transmission example is shown, wherein a non-congestion loss 1 (first data packet) and a later congestion loss 2 (fifth data packet) followed by a non- congestion loss 3 (sixth data packet) occur during the transmission of a message X.
  • the first non-congestion loss 1 does not initiate any congestion control procedure and leads to a conventional retransmission after the receipt of three duplicate ACKs. Due to the immediately following non-congestion loss, the WECN set in the sixth data packet in response to the congestion loss 2 is not received at the TCP destination B. Since the sixth data packet is lost due to the non- congestion loss 3 , no WECN is set in the seventh data packet. Thus, the WECN ACK is transmitted in response to the receipt of the eighth data packet, to thereby initiate the congestion control procedure according to the preferred embodiment of the present invention. Due to the lost sixth and non-WECN seventh data packet, the WECN ACK is accompanied by two duplicate WECN ACKs. Thereafter, the losses 2 and 3 are retransmitted according to the conventional retransmission algorithm. Finally, Fig. 10 shows a case in which three congestion losses 1 to 3 occur during the transmission of the message X, wherein the corresponding WECN are set delayed.
  • each of the three lost data packets 1 to 3 is retransmitted by the TCP source A in response to the receipt of the respective three duplicate ACKs (retransmission of lost packet 3 not shown) .
  • the congestion control procedure according the preferred embodiment of the present invention is delayed until the first WECN ACK has been received. However, the subsequent WECN ACK within the same transmission window is ignored.
  • the above described ECN-based overload control method may be utilized in any packet network. According to the above description, the overload control can be performed without substantially changing the conventional overload control processing of the TCP.
  • the invention relates to a method for controlling overload in a packet-switched network, especially a mobile or wireless network where the transmission control protocol (TCP) is used as the transport layer protocol.
  • TCP transmission control protocol
  • a congestion notification information is added to a data packet following a data packet lost due to a buffer overflow.
  • This is an effective way to improve TCP performance in wireless and mobile networks, since congestion control can be performed completely independent from retransmissions.
  • the proposed mechanism provides a simple way of introducing TCP congestion avoidance control strategies into wireless and mobile networks.
  • the congestion notification information should be added at least not later than a threshold number of following packets to thereby fasten the rate of congestion control initiation and loss recovery due to congestion.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé permettant de réguler une surcharge dans un réseau à commutation par paquets, en particulier, un réseau mobile ou sans fil dans lequel on utilise le protocole de commande de transmission (TCP) comme protocole de couche de transport. On ajoute des informations de notification d'encombrement à un paquet de données qui suit un paquet de données perdu à cause d'un débordement de tampon. Cela constitue une manière efficace d'améliorer le fonctionnement du protocole TCP dans des réseaux mobiles ou sans fil, du fait qu'il est possible d'agir sur l'encombrement de façon totalement indépendante des retransmissions. Le mécanisme proposé constitue une manière simple de mise en place de stratégies de régulation permettant d'éviter l'encombrement du protocole TCP dans des réseaux mobiles ou sans fil. En outre, les informations de notification de congestion doivent être ajoutées au moins avant d'excéder un nombre seuil de paquets suivants de façon à fixer la cadence du déclenchement de la régulation de l'encombrement et de la récupération des pertes dues à l'encombrement.
PCT/EP1999/002856 1999-04-27 1999-04-27 Technique de regulation de surcharge dans un reseau a commutation par paquets Ceased WO2000065782A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
PCT/EP1999/002856 WO2000065782A1 (fr) 1999-04-27 1999-04-27 Technique de regulation de surcharge dans un reseau a commutation par paquets
CA002372023A CA2372023A1 (fr) 1999-04-27 1999-04-27 Technique de regulation de surcharge dans un reseau a commutation par paquets
DE19983951T DE19983951B4 (de) 1999-04-27 1999-04-27 Überlast-Steuerungsverfahren für ein paketvermitteltes Netzwerk
GB0125202A GB2364615B (en) 1999-04-27 1999-04-27 Overload control method for a packet-switched network
AU40342/99A AU4034299A (en) 1999-04-27 1999-04-27 Overload control method for a packet-switched network

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PCT/EP1999/002856 WO2000065782A1 (fr) 1999-04-27 1999-04-27 Technique de regulation de surcharge dans un reseau a commutation par paquets

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WO2000065782A1 true WO2000065782A1 (fr) 2000-11-02

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DE (1) DE19983951B4 (fr)
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EP1249972A1 (fr) * 2001-04-09 2002-10-16 Telefonaktiebolaget L M Ericsson (Publ) Procédé de régulation de mémoire tampon pour file d'attente
WO2004068800A1 (fr) * 2003-01-28 2004-08-12 Telefonaktiebolaget Lm Ericsson (Publ) Procede et dispositif avisant d'un encombrement survenu dans ses reseaux a commutation par paquets et en indiquant les differentes raisons
WO2006085184A1 (fr) * 2005-02-09 2006-08-17 Nokia Corporation Notification d'encombrement dans un acces radio 3g
RU2313915C2 (ru) * 2003-01-28 2007-12-27 Телефонактиеболагет Лм Эрикссон (Пабл) Способ и устройство уведомления о перегруженности в сетях пакетной передачи с указанием нескольких различных причин перегруженности
DE102008013349A1 (de) 2008-03-10 2009-09-17 Rohde & Schwarz Professional Mobile Radio Gmbh Kommunikationsverfahren und Kommunikationssystem mit Paketabstands- und Paketlängen-Regelung
US20140334296A1 (en) * 2013-05-13 2014-11-13 Futurewei Technologies, Inc. Aggressive Transmission Control Protocol (TCP) Retransmission
CN110495139A (zh) * 2017-04-24 2019-11-22 泰拉丁公司 测试通信协议
CN114747169A (zh) * 2019-11-29 2022-07-12 意大利电信股份公司 分组交换通信网络中的往返分组丢失测量

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1249972A1 (fr) * 2001-04-09 2002-10-16 Telefonaktiebolaget L M Ericsson (Publ) Procédé de régulation de mémoire tampon pour file d'attente
WO2002082747A3 (fr) * 2001-04-09 2003-02-20 Ericsson Telefon Ab L M Procede de controle d'une memoire tampon de file d'attente
WO2004068800A1 (fr) * 2003-01-28 2004-08-12 Telefonaktiebolaget Lm Ericsson (Publ) Procede et dispositif avisant d'un encombrement survenu dans ses reseaux a commutation par paquets et en indiquant les differentes raisons
RU2313915C2 (ru) * 2003-01-28 2007-12-27 Телефонактиеболагет Лм Эрикссон (Пабл) Способ и устройство уведомления о перегруженности в сетях пакетной передачи с указанием нескольких различных причин перегруженности
WO2006085184A1 (fr) * 2005-02-09 2006-08-17 Nokia Corporation Notification d'encombrement dans un acces radio 3g
US7760646B2 (en) 2005-02-09 2010-07-20 Nokia Corporation Congestion notification in 3G radio access
DE102008013349A1 (de) 2008-03-10 2009-09-17 Rohde & Schwarz Professional Mobile Radio Gmbh Kommunikationsverfahren und Kommunikationssystem mit Paketabstands- und Paketlängen-Regelung
US20140334296A1 (en) * 2013-05-13 2014-11-13 Futurewei Technologies, Inc. Aggressive Transmission Control Protocol (TCP) Retransmission
CN110495139A (zh) * 2017-04-24 2019-11-22 泰拉丁公司 测试通信协议
CN110495139B (zh) * 2017-04-24 2023-06-16 泰拉丁公司 测试通信协议
CN114747169A (zh) * 2019-11-29 2022-07-12 意大利电信股份公司 分组交换通信网络中的往返分组丢失测量
CN114747169B (zh) * 2019-11-29 2024-03-12 意大利电信股份公司 分组交换通信网络中的往返分组丢失测量

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Publication number Publication date
AU4034299A (en) 2000-11-10
CA2372023A1 (fr) 2000-11-02
DE19983951T1 (de) 2002-10-10
DE19983951B4 (de) 2009-06-25
GB2364615A (en) 2002-01-30
GB0125202D0 (en) 2001-12-12
GB2364615B (en) 2004-03-31

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