CN1802567B - Method and system for performing compression on user datagram protocol packets - Google Patents

Abstract

Performing compression includes receiving, at a compressor, a flow including a plurality of packets, wherein each packet has a packet identifier. The packet identifier is associated with a predetermined increment, but any change to the predetermined increment is ignored. The packets are compressed and the stream is sent to a decompressor.

Description

Method and system for performing compression on user datagram protocol packets

technical field

The present invention relates generally to the field of communications, and more particularly, the present invention relates to performing compression on User Datagram Protocol packets. the

Background technique

Various known techniques can be used to compress User Datagram Protocol (UDP) packets. These known techniques can perform some packet loss procedures if a packet is lost. However, these procedures may exacerbate packet loss. Therefore, known techniques for compressing User Datagram Protocol packets do not satisfy certain situations. the

Contents of the invention

In accordance with the present invention, disadvantages and problems associated with prior techniques for compressing User Datagram Protocol (UDP) packets may be reduced or eliminated. the

According to one embodiment of the invention, performing the compression includes receiving at the compressor a stream comprising a plurality of packets, each packet having a packet identifier. A packet identifier is associated with a predetermined increment, such as ΔIP ID, but any change in this predetermined increment is ignored. These packets are compressed, and the stream is sent to a decompressor. the

Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment may be that the compressor can ignore any change in predetermined increments between packet identifiers of successive packets, and the decompressor can accept sequence number jumps without invalidating the context. These procedures can conserve available bandwidth and can reduce packet loss. Another technical advantage of an embodiment may be that the use of context identifiers between the compressor and decompressor may be synchronized, which may reduce or eliminate stream corruption. the

Certain embodiments of the present invention may include some, all, or none of the technical advantages described above. From the drawings, description and claims included herein, one skilled in the art

Description of drawings

For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a block diagram of one embodiment of a network that may be used according to the present invention;

The flowchart of Figure 2 shows an example of a method for sending a packet without relying on a packet identifier;

The flowcharts of FIGS. 3 to 5 illustrate embodiments of methods for synchronizing the use of context identifiers between a compressor and a decompressor. the

Detailed ways

Embodiments of the present invention and their advantages are best understood by referring to Figures 1 through 5 of the drawings, wherein like numerals are used to indicate like and corresponding parts in the various figures. the

The block diagram of Figure 1 illustrates one embodiment of a network 100 that can compress User Datagram Protocol (UDP) packets. In general, network 100 may ignore any change in predetermined increments between packet identifiers of successive packets. Ignoring these changes can save available bandwidth and can reduce packet loss. Network 100 can synchronize the use of context identifiers (CIDs) between compressors and decompressors, which can reduce or eliminate stream corruption. the

According to the illustrated embodiment, the network 100 comprises a first application node 10 , a first transport node 20 , a communication link 30 , a second transport node 40 and a second application node 50 coupled as shown in FIG. 1 . The first application node 10 receives and sends calls in the network 100 . The first application node 10 may comprise a Base Transmitter Station (BTS), a Base Station Controller (BSC), a router, a computer, a network, any other suitable telecommunications equipment for receiving and sending calls in the network 100, or any of the foregoing Some, all, or none of the aforementioned devices. According to the illustrated embodiment, the first application node 10 comprises a BTS operable to send and receive signals to and from the network 100 . These signals may include data communications, voice communications, signaling communications, or any other suitable type of communications. the

The first transport node 20 routes packets in the network 100 . A data packet consists of a packet of data organized in a particular way for transmission and can carry digital, audio, video, multimedia, or other types of information. The first transfer node 20 may transfer packets between the first application node 10 and the second transfer node 40 via the communication link 30 . The first transport node 20 may comprise one or more routers, or any other communication device suitable for receiving and sending data packets. the

According to one embodiment, the first transit node 20 may comprise a router having layer-3 and layer-2 entities. Layer 3 entities can be associated with routing functions such as sorting and queuing. For example, a classification function may include sorting data packets according to predetermined criteria, while a queuing function may include placing packets in an appropriate queue. Layer 2 entities may include compressors, multiplexers, load balancers, local call admission control, or other suitable components. the

According to the illustrated embodiment, the first transmission node 20 may comprise a compressor 25 and a decompressor 26 . A compressor 25 compresses data packets received at the first transport node 20 and may include a processor 27 operable to manage the compression and a buffer 28 operable to store the packets. According to one embodiment, compressor 25 may include an algorithm operable to perform a compression operation, and may use any compression operation suitable for compressing IP packets such as RFC 2508. Decompressor 26 decompresses the data packets received from compressor 45 . According to one embodiment, decompressor 26 includes an algorithm operable to perform decompression, and may employ any decompression operation suitable for decompressing IP packets such as RFC 2508. According to the illustrated embodiment, decompressor 26 may be synchronized with compressor 45 . the

Communication links 30 carry communication signals to and from nodes of network 100 . Communication link 30 may include any suitable link associated with the public switched telephone network (PSTN), public or private data network, the Internet, wired or wireless network, local or regional or global communication network, intranet, other suitable Communication link, or any combination of the foregoing. the

According to one embodiment, the communication link 30 comprises a multi-directional link between the first transfer node 20 and the second transfer node 40 . According to the illustrated embodiment, communication link 30 may comprise part of a multi-link point-to-point (MLPPP) configuration. Any suitable number of links may be included in communication link 30 without departing from the scope of the present invention. the

According to the illustrated embodiment, the communication link 30 includes a first direction flow 32 and a second direction flow 34 . The first direction flow 32 may carry data packets from the first transport node 20 to the second transport node 40. However, the first directional flow 32 may operate in the opposite direction without departing from the scope of the present invention. The second direction flow 34 may carry data packets from the second transport node 40 to the first transport node 20 . The direction of the second directional flow 34 may also be reversed without departing from the scope of the present invention. the

Any suitable number of first directional flows 32 and second directional flows 34 may be used without departing from the scope of the present invention. For example, first direction flow 32 may represent the uplink direction of communication link 30 , while second direction flow 34 may represent the downlink direction of communication link 30 . Other communication links 30 in network 100 may utilize any other suitable uplink and downlink configurations to carry packets to and from transport nodes. the

The second transport node 40 routes packets in the network 100 . The second transfer node 40 may transfer packets between the first transfer node 20 and the second application node 50 . The second transfer node 40 may be substantially similar to the first transfer node 20, and may include a router. According to the illustrated embodiment, the second transmission node 40 comprises a compressor 45 and a decompressor 46 . Compressor 45 may be substantially similar to compressor 25 . According to the illustrated embodiment, the compressor 45 is operable to send the compressed packets to the decompressor 26 in the first transport node 20 via the second direction flow 34 . Decompressor 46 may be substantially similar to decompressor 26, and may include a processor 47 operable to manage decompression and a buffer 48 operable to store packets. The decompressor 46 is operable to receive the compressed data packets from the compressor 25 in the first transport node 20 via the first direction flow 32 . the

The second application node 50 may be substantially similar to the first application node 10 in operation. According to the illustrated embodiment, the second application node 50 comprises a base station controller (BSC) operable to receive and transmit signals in the network 100 . the

Various modifications, additions, or omissions may be made to the network 100 without departing from the scope of the present invention. For example, the first application node 10 and the second application node 50 may be omitted. As another example, first transfer node 20 and second transfer node 40 may be modified to include any suitable number of routers. Additionally, functions may be performed using any suitable logic including software, hardware, other logic, or any suitable combination thereof. "Each" as used in this document refers to each member of a set or each member of a subset of a set. the

Network 100 has certain advantages over known techniques. RFC2508 "Compressing IP/UDP/RTP Headers for Low-Speed Serial Links" published by the Internet Society describes a known technique for compressing Real-time Transport Protocol (RTP) streams according to the Compressed Real-time Transport Protocol (cRTP) header compression; and compressing User Datagram Protocol (UDP) streams according to Compressed User Datagram Protocol (cUDP). During a packet loss event, the RFC2508 technique of invalidating context may exacerbate packet loss and reduce bandwidth availability. The technique of RFC 2508 can also cause a stream to go bad if a complete header packet is lost in the stream. the

According to one embodiment, the network 100 can ignore any change in predetermined increments between packet identifiers of consecutive packets, and can ignore sequence number jumps, i.e., tolerate packet loss and continue decompression, which can save available bandwidth, and can Reduce packet loss. An embodiment of a method for sending a packet without a packet identifier will be described in more detail below with reference to FIG. 2 . According to another embodiment, the network 100 may also synchronize the use of context identifiers between the compressor 25 and the decompressor 46 . An embodiment of a method for synchronizing the use of context identifiers between the compressor 25 and the decompressor 46 will be described in more detail below with reference to FIG. 3 . the

The flowchart of Figure 2 illustrates one embodiment of a method for sending packets without storing packet identifiers, such as Internet Protocol identifiers. According to this embodiment, transmission can be optimized by ignoring predetermined incremental changes between packet identifiers of consecutive packets, ie not attempting to preserve packet identifiers. the

The method starts at step 200, where the compressor 25 of the first transport node 20 receives a packet with a packet identifier. A packet may include any suitable packet, and a packet identifier may include any label operable to identify a packet. For example, packets may include User Datagram Protocol packets, and packet identifiers may include Internet Protocol identifiers. The packet identifiers for consecutive packets may be incremented by predetermined increments. In step 204, the compressor 25 ignores any change in predetermined increments between packet identifiers of successive packets. Compressor 25 can ignore these changes by not notifying decompressor 46 of these changes, which can provide more available bandwidth. For example, even if there is a predetermined incremental change between the packet identifiers of successive packets, the compressor 25 does not send what can be considered a predetermined incremental ΔIP ID, which can save one to three bytes of bandwidth per packet. the

In step 208 the compressor 25 compresses the packet and in step 212 the first transport node 20 sends the packet to the second transport node 40 . In step 216, the decompressor 46 of the second transport node 40 receives these packets. In step 220, the sequence numbers of these packets are ignored. Sequence numbers may include any suitable identifier operable to place packets in packet order, such as a cRTP sequence identifier. Packets may be sequenced according to their order of departure. Regardless of whether the sequence number has been toggled or not, the method proceeds to step 224 where a packet identifier is generated for the packets. Since compressor 25 does not notify decompressor 46 of any changes in predetermined increments, the packet identifier generated by decompressor 46 for a packet may not necessarily match the packet identifier that the packet had at compressor 25 . Accordingly, the packet identifier of a packet entering compressor 25 may be different from the packet identifier of a packet leaving decompressor 46 . In step 228, decompressor 46 forwards the packet. After the packet has been forwarded, the method terminates. the

Sequence number jumps are acceptable since the unsaved IP ID field is the only field that may be affected. Accepting hops instead of invalidating the flow can save bandwidth, or reduce or eliminate packet loss. Invalidating the stream requires sending a context state packet from the decompressor 46 to the compressor 25, and then sending an uncompressed full header packet from the compressor 25 to the decompressor 46, rather than just accepting hops. Furthermore, this embodiment may allow only compressed packets lost between compressor 25 and decompressor 46 to be discarded, rather than discarding all packets according to the RFC 2508 technique, if the link is near or beyond maximum utilization. the

RFC 2508's sequence number checking process is generally problem-prone. For example, when packet loss occurs, each packet or consecutive packet loss in a flow may cause the next received packet to be dropped, which may double the packet loss for that flow. In addition, the decompressor sends a context status message to the compressor, which causes the compressor to send a full header packet the next time it receives a packet for that flow. Context state and full header packets each waste bandwidth. In addition, any packets in the stream's packets that pass between the time the decompressor invalidates the stream and the time the compressor processes the context state may also be lost. Additionally, if packet loss occurs due to link congestion, context state and full header packets may cause more packet loss, which leads to even more link overload and more loss. By canceling the sequence number checking process, and generating outgoing packet identifiers at the decompressor, only packets lost during transmission from the compressor to the decompressor are lost, and no additional link bandwidth is used for context state and complete head. the

Modifications, additions or omissions may be made to the method without departing from the scope of the present invention. Additionally, steps may be performed in any suitable order without departing from the scope of the invention. the

The flowcharts of FIGS. 3 to 5 illustrate embodiments of methods for synchronizing the use of context identifiers between the compressor 25 and the decompressor 46 . A context identifier may be used to identify a packet flow, and a full header packet may be used to indicate the use of a context identifier for a new packet flow. According to an embodiment, a context identifier is reserved for a flow as long as the flow is active (ie, currently sending packets). Compressor 25 and decompressor 46 monitor the period of inactivity of the stream to determine the inactivity time of the stream. Once a flow has been inactive for a predetermined maximum allowed inactivity period, its context identifier expires and the flow must restart compression by sending a full header packet. Expired context identifiers can be reused for compression of new streams. the

In the absence of synchronization between compressor 25 and decompressor 46, if a complete header packet for a new stream is lost, the compressed packets of the new stream may be incorrectly interpreted by decompressor 46 as belonging to the old stream. flow, causing the flow to go bad. According to this embodiment, flow deterioration may be reduced or eliminated. The method may be used with any suitable compression technique, such as that of RFC 2508, or the embodiment of the method for sending packets described with reference to FIG. 2 . the

Referring to FIG. 3, the method of FIG. 3 starts at step 300, in which step the compressor 25 of the first transport node 20 receives a stream of packets. In step 302 , if the flow is not associated with an existing context, the method proceeds to step 304 . In step 304, the compressor 25 checks whether there is a context identifier available. Available context identifiers may refer to context identifiers that are reusable despite having been used in the past. If there is no context identifier available, the method proceeds to step 308 where the packet is sent to the second transport node 40 uncompressed. After sending the uncompressed packet, the method terminates. the

If there are available context identifiers, the method proceeds to step 312 where available context identifiers are assigned to packet flows. In step 314, the context inactivity timer of the compressor 25 is started. The context inactivity timer measures the inactivity time of the context. In step 316, the full header packet is sent. A full header packet may be sent before the compressed packet to indicate that the context identifier is being used for the new flow. After sending the complete header packet, the method terminates. the

In step 302 , if the flow is associated with an existing context, the method proceeds to step 320 . If in step 320 the context inactivity timer has expired, the method proceeds to step 314 where the context inactivity timer is started. If in step 320 the context inactivity timer has not expired, the method proceeds to step 322 where compressor 25 compresses the packet. In step 324, the context inactivity timer is restarted. In step 330, the first transmission node 20 sends the compressed packet to the second transmission node 40. After sending the compressed packets, the method terminates. the

Referring to FIG. 4, the method of FIG. 4 begins at step 400 in which decompressor 46 receives a compressed stream of packets having a context identifier associated with a context. A context inactivity timer at the decompressor 46 measures the inactivity time of the context. If the context inactivity timer has expired, the decompressor 46 expects the full header packet of the expired context identifier, not the compressed packet. Since decompressor 46 received the compressed packet, decompressor 46 determines that the full header packet is missing. Therefore, if in step 410 the context inactivity timer has expired, the method proceeds to step 412 . In step 412, decompressor 46 discards the compressed packet and invalidates the context. After invalidating the context, the method terminates. the

If in step 410 the context inactivity timer has not expired, the method proceeds to step 416 where the packet is decompressed. In step 420, the context inactivity timer is restarted. In step 424 the decompressed packets are forwarded. After forwarding the packet, the method terminates. the

Referring to FIG. 5, the method of FIG. 5 begins at step 500 in which decompressor 46 receives a complete header packet for a stream having a context identifier associated with a context. In step 504, the state data of the flow is saved according to the context identifier. In step 506, a context inactivity timer of the decompressor 46 is started. In step 510, decompressor 46 forwards the packet. After forwarding the packet, the method terminates. the

In summary, the compressor 25 and the decompressor 46 synchronize the reuse of their context identifiers by using synchronized expiration times. The context identifier is only reused if the decompressor 46 expects a new stream with a context identifier, and the compressor 25 and decompressor 46 know that the context identifier can be reused for the new stream. Compressor 25 and decompressor 46 use synchronized expiration times. When a context identifier expires and becomes available at the compressor 25, the decompressor 46 knows that the context identifier has expired and expects a full header packet indicating that the context identifier is being used for a new stream. According to one embodiment, a stream may be required to restart compaction at the end of the maximum allowed period of inactivity prior to expiration of the context identifier at the end of the expiry period. This requirement may reduce the probability of a situation where a flow's context identifier expires while packets are in transit between compressor 25 and decompressor 46. the

According to one embodiment, the decompressor 46 may use an expiration period ET and the compressor 25 may use an expiration period adjusted by the delta time dT. According to one embodiment, the expiration time period ET may be based on F_MAX_TIME of RFC 2509, and the delta time dT may be based on the average time it takes a packet to travel from the compressor 25 to the decompressor 46. At the compressor 25, the maximum allowed inactivity period may be defined as ET-dT, and the context identifier expiration period may be defined as ET+dT. If a stream has been inactive at the compressor 25 for a duration greater than the maximum allowed inactivity period ET-dT, the stream must restart compression. The context identifier expires after ET+dT at the compressor 25 . Optimization can be achieved by allowing a flow that has been inactive for longer than ET-dT but shorter than ET to continue using its own context identifier while sending full header packets. If a full header packet is lost, but the next packet still arrives at the decompressor 46 before the context identifier at the decompressor 46 expires, the context is still valid and compression of the stream can continue. the

Modifications, additions or omissions may be made to the method without departing from the scope of the present invention. Additionally, steps may be performed in any suitable order without departing from the scope of the invention. the

Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment is that any change in predetermined increments between packet identifiers of successive packets can be ignored, which can save available bandwidth and can reduce packet loss. Another technical advantage of an embodiment is that the use of context identifiers between the compressor and decompressor can be synchronized, which can reduce or eliminate stream corruption. the

Although the embodiments of the present invention and its advantages have been described in detail, various substitutions, additions and omissions can be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. the

Claims (15)

1. method that is used to carry out compression comprises:

Receive the stream that comprises a plurality of groupings at the compressor reducer place, each grouping has a packet identifier, and this packet identifier is associated with predetermined increment;

Ignore the change of the predetermined increment that is associated with said packet identifier;

Compress said a plurality of grouping;

Said stream is sent to decompressor;

The inertia time of confirming to be associated with said stream, said stream had context identifier above the maximum permission inertia time period; And

, confirmed the inertia time of confirming to be associated with said stream that the context identifier of said stream can use in response to having surpassed the maximum permission inertia time period.

2. the method for claim 1 also comprises:

The place receives said stream at said decompressor, and each grouping of said stream has sequence number;

Ignore the saltus step of said sequence number of a plurality of groupings of said stream; And

Acceptance has the said stream of said sequence number saltus step.

3. the method for claim 1 also comprises:

Grouping after said decompressor place confirms to comprise compression in the position of said stream in full header packet; And

Confirm that said full header packet loses.

4. the method for claim 1 also comprises:

The context inactivity timer is set after compressed packet.

5. the method for claim 1 also comprises:

Confirm that said context identifier can use;

Said context identifier is distributed to a new stream;

With adding said stream to corresponding to the full header packet of said context identifier; And

Said stream is retransmitted to said decompressor.

6. system that is used to carry out compression comprises:

Compressor reducer, can operate:

Reception comprises the stream of a plurality of groupings, and each grouping has a packet identifier, and this packet identifier is associated with predetermined increment;

Ignore the change of the predetermined increment that is associated with said packet identifier;

Compress said a plurality of grouping;

Send said stream;

The inertia time of confirming to be associated with said stream that is associated, said stream had context identifier above the maximum permission inertia time period; And

, confirmed the inertia time of confirming to be associated with said stream that the context identifier of said stream can use in response to having surpassed the maximum permission inertia time period; With

Decompressor, it is coupled to said compressor reducer, and can operate the said stream that decompresses.

7. system as claimed in claim 6, said decompressor also can be operated:

Receive said stream, each grouping of said stream has sequence number;

Ignore the saltus step of said sequence number of a plurality of groupings of said stream; And

Acceptance has the said stream of said sequence number saltus step.

8. system as claimed in claim 6, said decompressor also can be operated:

Confirm the grouping said stream comprises compression in the position of full header packet after; And

Confirm that said full header packet loses.

9. system as claimed in claim 6, said compressor reducer also can be operated:

The context inactivity timer is set after compressed packet.

10. system as claimed in claim 6, said compressor reducer also can be operated:

Confirm that said context identifier can use;

Said context identifier is distributed to a new stream;

With adding said stream to corresponding to the full header packet of said context identifier; And

Said stream is retransmitted to said decompressor.

11. a system that is used to carry out compression comprises:

Be used for receiving at the compressor reducer place device of the stream that comprises a plurality of groupings, each grouping has a packet identifier, and this packet identifier is associated with predetermined increment;

Be used to ignore the device of the change of the predetermined increment that is associated with said packet identifier;

Be used to compress the device of said a plurality of groupings;

Be used for said stream is sent to the device of decompressor;

The inertia time that is used for confirming to be associated with said stream, said stream had context identifier above the maximum device that allows the inertia time period; And

Be used for having confirmed the device that the context identifier of said stream can be used above the maximum permission inertia time period in response to the inertia time of confirming to be associated with said stream.

12. system as claimed in claim 11 also comprises:

Be used for receiving at said decompressor place the device of said stream, each grouping of said stream has sequence number;

Be used to ignore the device of saltus step of said sequence number of a plurality of groupings of said stream; And

Be used to accept have the device of the said stream of said sequence number saltus step.

13. system as claimed in claim 11 also comprises:

Be used for confirming the device of the grouping of said stream after the position of full header packet comprises compression at said decompressor place; And

Be used to the device of confirming that said full header packet is lost.

14. system as claimed in claim 11 also comprises:

Be used for after compressed packet, being provided with the device of context inactivity timer.

15. system as claimed in claim 11 also comprises:

Be used to the device of confirming that said context identifier can be used;

Be used for said context identifier is distributed to the device of a new stream;

Be used for the device that adds said stream corresponding to the full header packet of said context identifier to; And

Be used for said stream is retransmitted to the device of said decompressor.

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