KR101396785B1 - Method for performing tcp functions in network equipmment - Google Patents

Abstract

The present invention provides a method for performing a TCP function in a network apparatus. The method comprises the steps of: setting a connection between a transmitting device and a receiving device; if receiving a packet from the transmitting device, storing the packet in a buffer and determining whether traffic exceeds packet processing capability; if the traffic exceeds the packet processing capability, reducing incoming packet rate; if there is no packet to be transmitted due to the reduction in the incoming packet rate, waiting until the received packet is completely filled in a congestion window; and transmitting the received packet to the receiving device.

Description

METHOD FOR PERFORMING TCP FUNCTIONS IN NETWORK EQUIPMMENT [0002]

The present invention relates to a method for performing a TCP function in a network device.

In order to use the Internet, the same communication protocol should be used between both terminals for exchanging information. Currently, T-CIP / IP comprising Transmission Control Protocol and Internet Protocol is most commonly used. This TPC / IP is now implemented in software and included in the operating system.

The TCP / IP protocol consists of an application layer, a transmission layer, an Internet layer, and a physical layer. Currently widely used transport layer protocols include protocols that control the transmission rate by considering the state of the network such as transmission control protocol (TCP) and unconditional data transmission such as User Datagram Protocol Protocol.

TCP is a protocol that uses a mechanism to control the transmission rate in consideration of network conditions. When a TCP session is established between end terminals (client or server), the amount of data to be transmitted is determined using the TCP window size do. After transmitting the data, the terminating terminal of the data information transmits a response (ACK) during a retransmission time out (RTO) calculated using a round trip time (RTT) If the message does not arrive, think that the network is congested and reduce the window size. As a result, packet loss due to network congestion causes RTO, which reduces the size of the window and the amount of data to be transmitted at one time.

On the other hand, recently, contents provider (CP) such as YouTube and Google have been making profits by providing services without any burden on the network, while they have been making large-scale It is necessary to expand the network. Accordingly, the International Telecommunication Union (ITU-T) can provide a value added service only if the smart network (ie, the network) is intelligent.

1 is a diagram illustrating a conventional network topology.

The conventional network topology transmits data according to an end-to-end network mechanism (ETEM). FIG. 1 shows a case where data is transferred between end terminals 2 and 4. If the terminating terminal 2 is the transmitting end terminal 2 and the terminating terminal 4 is the receiving terminating terminal 4 then the data is transferred from the transmitting terminating terminal 2 to the receiving terminating terminal 4 via n routers 11, 12, 15, 21, 22, 25, and the Internet network 20. In this case, the data in the router goes through the physical layer 11, the data link layer 12 and the network layer 13 according to an OSI (Open System Interface) model. The network layer 13 is responsible for routing data over the network. The data link layer 12 manages the interfaces and device drivers needed to interface with the physical elements of the network. The physical layer 11 is made up of physical parts of the network. Examples of physical layers include serial and parallel cables, Ethernet and Token Ring cabling, antennas and connectors. Thus, each of the routers 11, 12, 15, 21, 22, and 25 routes data according to the destination address of the data.

The TCP algorithm is implemented in an end-to-end connection in an end terminal, ie, a TCP sending terminal and a TCP receiving terminal, where the TCP sending terminal sequentially transmits data, controls the data rate, I have to retransmit. The TCP receiving terminal transmits an acknowledgment message to the TCP transmitting terminal to confirm the packet reception with respect to the received packet. This increases the total packet transmission time and wastes resources on the network.

International Publication No. WO 2004/051495

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for performing a TCP function in a network device.

A method for performing a TCP function in a network device according to an embodiment of the present invention for solving the above problems is a method for performing a TCP function in a network device, The method comprising the steps of: storing a packet in a buffer upon receipt of a packet from the transmitting apparatus, determining whether the traffic exceeds a packet processing capability, and decreasing an incoming packet rate if the traffic exceeds a packet processing capability And waiting until the received packet completely fills the congestion window if there is no packet to be transmitted according to the decrease of the packet reception rate, and transmitting the received packet to the receiving apparatus.

The step of decreasing the packet reception rate may be performed by delaying transmission of an arc message for confirming the reception of the packet to the transmission apparatus.

The step of decreasing the packet reception rate may be performed by transmitting a notify message to the transmission apparatus so as to decrease the packet transmission rate.

The method for performing a TCP function in the network device may further include transmitting an arc signal to the transmitting apparatus upon receipt of a packet from the transmitting apparatus.

The method for performing a TCP function in the network device may further include transmitting a packet stored in the buffer to the receiving device, and waiting for an arc signal from the receiving device.

The method for performing a TCP function in the network device may further include resetting the size of the congestion window.

According to the present invention, by installing the TCP function in the network equipment, network resources can be prevented from being wasted during retransmission or flow control.

1 is a diagram illustrating a conventional network topology.
2 is a diagram illustrating a network topology including a pseudo TCP agent according to the present invention.
3 is a diagram illustrating a location of a pseudo TCP agent according to the present invention on a network.
4 is a diagram illustrating a connection establishment procedure between pseudo TCP agents according to the present invention.
5 is a diagram showing a data transfer procedure of a pseudo TCP agent between a previous agent connected to the pseudo TCP agent and the next agent.
6 illustrates TCP flow control according to a preferred embodiment of the present invention.
FIGS. 7 and 8 are graphs comparing performance between the SBSM scheme and the ETEM (End-To-End MEchanism) scheme according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention. In addition, the size of each component in the drawings may be exaggerated for the sake of explanation and does not mean a size actually applied.

2 is a diagram illustrating a network topology including a pseudo TCP agent according to the present invention.

Referring to FIG. 2, a network topology including a pseudo TCP agent according to the present invention transmits data according to a Segment-by-Segment Network Mechanism (SBSM). More specifically, data transmission / reception is performed between the end terminals 2 and 4. It is assumed that data is transmitted from the terminal transmitting terminal 2 to the receiving terminal 4. Data travels through n routers.

The pseudo TCP agent 100 according to the present invention divides the data path into at least two individual segments, in Fig. 2, a first segment and a second segment. If the packet is lost in the second segment, the lost panic is retransmitted from the pseudo TCP agent 100, not the terminating transmitting terminal 2. [

The pseudo TCP agent 100 is preferably implemented in a network equipment, such as an edge router. The pseudo TCP agent 100 performs a packet retransmission performed by a transmitting terminal when a packet loss occurs and transmits an arc message that was performed by the receiving terminal when a packet is received. That is, the lost packet is retransmitted by the pseudo TCP agent 100 instead of being retransmitted from the transmitting terminal.

Pseudo TCP agent 100 may reside at some point between end terminals 2 and 4 on the network.

3 is a diagram illustrating a location of a pseudo TCP agent according to the present invention on a network.

Referring to FIG. 3, the pseudo TCP agent 100 is preferably implemented in an edge router. The pseudo TCP agent 100 may be implemented in an edge router on the LAN 70 and may be implemented in an edge router on a Transit ISP (Internet Service Provider) 80 or a peer ISP 82. Or the edge router 100 may be implemented in an edge router on the ISP edge domain. No modifications are required to the operation of the terminating terminal, that is, the TCP transmitter or the TCP receiver.

The pseudo TCP agent 100 according to the present invention intercepts and processes TCP packets, and then transmits the pseudo TCP agents to a pseudo TCP agent. Hereinafter, connection setup, data transmission, and connection termination procedures in the pseudo TCP agent 100 will be described.

If the pseudo TCP agent 100 is implemented on the network path, the connection establishment process is handled separately in each independent segment. Each segment establishes independent communication between its endpoints. The order of the connection establishment steps is shown in Fig.

4 is a diagram illustrating a connection establishment procedure between pseudo TCP agents according to the present invention.

Referring to FIG. 4, first, a Synchronized message (Syn) transmitted from a previous node 99 is intercepted by the pseudo TCP agent 100 (step 202). The pseudo TCP agent 100 then immediately sends an acknowledged message (Ack) to the previous agent 99 (step 204). Simultaneously or almost simultaneously, the pseudo TCP agent 100 transmits the synchronization message Syn to the next agent 101 (step 212). The next agent 101 then sends an acknowledged message (Ack) to the pseudo TCP agent 100 (step 214).

Through this process, the pseudo TCP agent 100 and the transfer agent 99 are connected (step 206), and the pseudo TCP agent 100 and the next agent 101 are connected (step 216).

The data transfer process in each segment is started after the connection setup is completely completed. In other words, if there is a problem sending or receiving a packet, the communication needs to react immediately to the problem. For example, if the receiver has not received the message, the pseudo TCP agent 100 sends a non-acknowledged message (Nack) to the transmitter to indicate that the packet was not received correctly and that a retransmission is needed. After multiple retransmissions, if the connection is still not set, then a notification message to terminate the connection needs to be sent to all pseudo TCPs on the data path.

The pseudo TCP agent 100 acts as a destination host for the previous agent by sending an arc message for all packets received from the old agent 99 or the previous node. In addition, pseudo TCP agent 100 operates similarly to the source host for the next segment by performing TCP flow control, error detection, and congestion control algorithms.

5 is a diagram showing a data transfer procedure of a pseudo TCP agent between a previous agent connected to the pseudo TCP agent and the next agent.

Referring to FIG. 5, the pseudo TCP agent 100 first receives a TCP packet, classifies the received TCP packet based on a protocol field of an IP (Internet Protocol) header, and stores the received TCP packet in the buffer 120 (Step 240). The pseudo TCP agent 100 then sends an Ack message to the previous node 99 informing that the packets have been correctly received in order (step 242).

The pseudo TCP agent 100 then updates the last acknowledgment message number based on the received Ack message and resets the congestion window size. Finally, the pseudo TCP agent 100 sends the packet stored in the buffer 120 to the next node 101 (step 248). Steps 242 and 244 in the data transfer procedure of this pseudo TCP agent can be performed simultaneously.

Conventionally, a packet is routed through a physical layer 111, a data link layer 112 and a network layer 113 in a network equipment, for example, a router. In the present invention, the packet is routed through the physical layer 111, the data link layer 112, the network layer 113, and the pseudo TCP layer 114. The pseudo TCP layer 114 is implemented in the pseudo TCP agent 100 in accordance with the present invention.

Specifically, the pseudo TCP agent 100 allocates resources for a new TCP connection based on the current resources, such as the availability of the buffer 120 and the current congestion state. If the packet transmission rate is larger than the packet reception rate, there is no packet to be transmitted in the pseudo PCT agent. The pseudo PCT agent must wait until the received packet completely fills the congestion window size to continue sending data. Pseudo TCP agent 100 reduces the congestion window size as soon as it recognizes that there is no packet to send due to congestion in the previous segment. If a serious problem occurs during data transmission, it is necessary to send a notification message to all TCP aware devices on the network path to terminate the connection. The notification message may be sent from the source or destination nodes or from any pseudo TCP agent for which an error has been detected. The pseudo TCP agent allocates a fixed resource for new connections and the pseudo TCP agent must control the congestion state based on the allocated resources. If the packet reception rate is greater than the packet transmission rate, the buffer exponentially increases to a threshold.

Therefore, the pseudo TCP agent delays the transmission of the ARC message confirming the reception of the packet to the previous node or reduces the transmission rate to the previous pseudo TCP agent so that the reception packet rate does not exceed the packet processing capability according to the allocated resource Should be transmitted.

Finally, the TCP connection may be terminated by the source user, the destination user, or by sending a termination message to these users. The termination message needs to be detected by all pseudo TCP aware devices on the data path to release the allocated resources.

6 illustrates TCP flow control according to a preferred embodiment of the present invention.

In FIG. 6, it is assumed that N packets are transmitted between two end terminals. Also, the latency in the TCP flow is referred to as the term "round ". The round starts with the transmission of the packet window and ends when it receives one arc message for these packets. In rounds, packets are lost independently of losses in other rounds. However, losses in one round correlate with each other, and not all packets after the first packet in the round or previous packets in that round are lost.

Referring to FIG. 6, when N packets are to be transmitted between two end terminals in one round, the pseudo TCP agent 100 determines whether the current received packet (i-th packet) is the N-th packet (Step 302). As described above, N packets are transmitted in one round. Since the 0th packet is transmitted and the current packet is the Nth packet, N packets have already been transmitted, and the corresponding round should be ended.

If the current received packet is included in the round, the pseudo TCP agent 100 reduces the incoming packet rate if the traffic exceeds the packet processing capability (step 304). Specifically, when the packet reception rate is higher than the packet transmission rate, the pseudo TCP agent 100 notifies the previous agent 99 to delay transmission of an arc message for confirming reception of the packet or decrease the packet transmission rate Send a message (notify). The pseudo TCP agent 100 then determines whether there are any packets to be stored in its buffer 120 and to be forwarded to the next agent 101 (step 306). Since the packet reception rate is reduced, when the packet transmission rate becomes larger than the packet reception rate, the pseudo TCP agent 100 does not have a packet to be transmitted. The pseudo TCP agent 100 waits until the received packet completely fills the congestion window if there is no packet to be transmitted to the next agent 101. [

As is well known, TCP uses a congestion window to control when network congestion occurs. When packet loss occurs due to network congestion, the size of congestion window is adjusted to be small and the congestion state is controlled by sending packet slowly at the transmitting side and increasing the size of congestion window if not.

When the received packet completely fills the congestion window, the pseudo TCP agent 100 determines in step 312 whether the current mode is the normal mode. The normal mode corresponds to a case where a packet is normally transmitted without loss. The replication mode corresponds to a case where packet loss occurs and a packet is retransmitted to the transmitting terminal or the next agent 101. [

If the pseudo TCP agent 100 is in the normal mode, the pseudo TCP agent 100 proceeds to step 314 to update the congestion window size and transmit a new packet to the next agent 101. Upon receipt of the ARC message from the next agent 101, the pseudo TCP agent 100 determines that there is no packet loss, increases the packet number, i increases (step 318), and proceeds to the next round (step 350) .

Also, the pseudo TCP agent 100 determines whether the number of transmitted packets is three or more if the packet is lost. If the number of transmitted packets is 3 or more, the flow advances to step 324 to switch to the duplication mode. If the number of transmitted packets is less than 3, the corresponding round is terminated and the round proceeds again.

If the received packet completely fills the congestion window, the pseudo TCP agent 100 determines whether the current mode is a normal mode (step 312). If the received packet is not a normal mode, the pseudo TCP agent 100 determines whether the current mode is a duplicated mode (Step 332). If the current mode is the duplicate mode, the pseudo TCP agent 100 determines in step 336 whether a packet loss has occurred. If packet loss has not occurred, the packet number is updated, the lost packet is retransmitted, and a transition is made to the normal mode (step 344). If packet loss has occurred, it is determined whether the number of packets transmitted in step 338 is 3 or more (step 338). If the number of transmitted packets is 3 or more, the flow advances to step 344 to update the packet number, retransmit the lost packet, and switch to the normal mode. If the number of transmitted packets is less than 3, the pseudo TCP agent 100 switches to the timeout mode in step 340 and proceeds to step 342. [

If it is determined in step 332 that the current mode is the timeout mode, the pseudo TCP agent 100 proceeds to step 342 and waits until the timeout, then switches to the normal mode and proceeds to the next round.

FIGS. 7 and 8 are graphs comparing performance between the SBSM scheme and the ETEM (End-To-End MEchanism) scheme according to the present invention.

As shown in FIG. 7, the result of simulating the number of retransmissions shows that the SBSM is much reduced as shown in the following table. Also, as shown in FIG. 8, it can be seen that the SBSM is also improved in the case of the network resource related to the retransmission

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical spirit of the present invention should not be limited to the above-described embodiments of the present invention, but should be determined by the claims and equivalents thereof.

99: old agent 100: pseudo TCP agent
101: Next agent 120: Buffer

Claims (6)

A method for performing a TCP function in a network device,
Performing connection setting between the transmitting apparatus and the receiving apparatus;
Receiving a packet from the transmitting device, storing the packet in a buffer and determining whether the traffic exceeds a packet processing capability;
Reducing an incoming packet rate if the traffic exceeds a packet processing capability,
Waiting until the received packet completely fills the congestion window if there is no packet to be transmitted according to the decrease of the packet reception rate;
And transmitting the received packet to the receiving device,
Wherein at least one network device disposed between two separate segments adjacent to each other when dividing the transmission device and the receiving device into two or more separate segments transmits an arc (ACK) to the transmitting device with respect to a packet stored in the buffer, Transmitting a message to the receiving device, and retransmitting the packet stored in the buffer to the receiving device when the packet transmitted to the receiving device is lost. The method according to claim 1,
The step of decreasing the packet reception rate
And delays transmission of an arc message for confirming the reception of the packet to the transmitting apparatus. The method according to claim 1,
The step of decreasing the packet reception rate
And transmitting a notification message (notify) to reduce the packet transmission rate to the transmitting apparatus. The method according to claim 1,
And transmitting an arc signal to the transmitting device upon receiving a packet from the transmitting device. The method according to claim 1,
Transmitting a packet stored in the buffer to the receiving apparatus;
And waiting for an arc signal from the receiving device. The method according to claim 1,
And resetting the size of the congestion window.

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