GB2575027A

GB2575027A - Path selection for content delivery network

Info

Publication number: GB2575027A
Application number: GB201810216A
Authority: GB
Inventors: Hart Jonathan; Cuevas Ramirez Maria; Brown Ruth
Original assignee: British Telecommunications PLC
Current assignee: British Telecommunications PLC
Priority date: 2018-06-21
Filing date: 2018-06-21
Publication date: 2020-01-01
Anticipated expiration: 2038-06-21
Also published as: GB201810216D0; GB2575027B

Abstract

A method of operating a content delivery network (CDN) includes generating a content request for content on the CDN, determining which of a plurality of caches 94-99 of the CDN contains the content, evaluating options for delivering the content to a user device 90 from different caches, selecting the optimal option, instructing the user device to request the content via an access network associated with the selected option, and delivering the requested content. The options may be evaluated based on signal strength, path cost metrics, network load, proximity etc. The user device has one or more access network interface for connection to caches of the CDN via one or more access networks (e.g. 4G). If the requested content is available at a cache of an access point 17 to which the user device is currently connected, the data may be served from that cache, and otherwise the device may be handed over to another access point 14, 15, 16, 18, 19. The method may be performed by a decision processor 12 provided as a network core function or a decision function (190, fig. 8) running on the user terminal. Two access networks may provide requested content in parallel.

Description

Path Selection for Content Delivery Network

This invention relates to improvements in routing for delivering multimedia data stored in a Content Delivery Network (CDN) to user devices. In present 4G and future 5G infrastructures, content can be delivered from a CDN to a user device via a number of different radio access networks such as cellular base stations, Wireless local area networks (WLANs), satellite, personal area networks, etc. A user device having the appropriate network interfaces can be attached to all available access networks simultaneously, subject to battery considerations.

Today’s environments have multiple access networks (e.g. 4G, WiFi), multiple backhaul technologies, content and application instances stored in different places in the network. A device can connect to all those different access networks and move between them (whilst in coverage of one or more access networks at any point in time).

In order to optimise network use and end-user experience the device, with support from the network, needs to select the right access technology at any point in time. In existing arrangements, an appropriate access network to be used for a given data transfer is selected by the device based on frequency priority, signal strength, device preferences, etc. with no involvement from the network operator.

According to the invention, there is provided a method of operating a content delivery network having a plurality of content caches to deliver requested content to at least one user device, the user device having one or more access network interfaces for connection to content caches of the content delivery network via one or more respective access networks, the method comprising:

a. generating a request for an item of content available on the content delivery network;

b. determining which of the plurality of content caches contain the requested content;

c. evaluating candidate options for delivering said requested content to the user device from different content caches ;

d. selecting a candidate option determined to be optimal for delivering said requested content;

e. instructing the user device to request the item of content via an access network associated with the selected candidate option; and

f. delivering the requested content to the user device.

The method may be performed by a network core function interfacing with the content delivery network and the access networks, or by a content delivery route decision function running on a user device interfacing with the content delivery network and the access networks. In the latter case, the user device may maintain a database of neighbour content caches and access network properties, and determine steps b and cfrom the data in the database.

Alternatively, the user device may transmit data requests to one or more content caches in response to the generation of a content request, and identify an optimal cache from the outcomes of those requests. It may transmit data requests to a plurality of caches in a predetermined sequence, selecting for content delivery the first cache identified to have the required content. The sequence may be determined by properties of respective connections between the user device and the respective access points associated with each cache.

The content delivery route decision function may monitor the quality of network paths between a plurality of caches and the user device location, so that when a user device requests data available on the content delivery network, the content delivery route decision function is able to determine the most suitable data source and path.

If the requested content is available at a cache associated with an access node to which the user device is currently connected, the data can be served from that cache, and if it is not available from that cache, and it is determined that the requested content is available at another access point which is in range of the user device, the user device can be handed over to that access point and data served from that cache by way of that access point. To facilitate this, data may be received from the user device relating to associations between access nodes available to the device, and listings of data available in the content caches of the available access nodes. This data may be provided as part of a Content Request message from the user device.

The user terminal may periodically perform a query to the cache associated with each available access node, to determine if it has the requested content. Alternatively, a database of available content associated with the decision function may be periodically updated by interrogating the content delivery network caches.

The decision function may obtain path cost metrics of the proximity between each candidate cache and the user device via an access network, and uses the metrics to calculate the performance and financial cost of delivering the content via each access network.

If no local cache is identified, access may default to delivery from a centralised content delivery network cache.

As well as availability of the required content, suitability may be determined according to signal strength and any one or more of the following factors:

a. proximity between the user terminal and the cache,

b. network load,

c. latency,

d. CPU Load,

e. Network Type,

f. time of day,

g. contention rate

h. bandwidth,

i. operator metrics,

j. quality of service parameters,

k. security.

Two or more separate access networks may be selected to deliver requested data to the user device in parallel.

The invention also extends to a computer system including a processor and a memory storing computer program code for performing the process of the invention, and to a computer program element comprising computer program code to, when loaded into a computer system and executed thereon, cause the computer to perform the steps of the process.

This invention relates to functionality in the core network to direct a user device to select an access network at a given time, and based on the content location, that provides the best user experience and maximises efficiency to the operator, and to direct the device to connect to that access network.

A Content Delivery Route Decision Function (CDRDF) is provided as a network core function, located on the edge of the network core, to interface with the CDN and the access networks. The CDRDF monitors the quality of the network paths between the CDN caches and user device locations, so that when a user device requests data available on the CDN, the CDRDF is able to determine the most suitable data source and path.

In an embodiment to be described in detail later, the currently connected access node’s local cache is checked and if the requested content is available, the data is served. If it is not available locally, the process determines whether the requested content is available at any other access point which is in range. To enable this step, the CDRDF uses data received from the user device, associations between access nodes available to the device and the access node’s local CDN cache, and listings of data available in each CDN cache. These listings may be look-up tables maintained by each individual cache, interrogated at the time a request is made, or a centrally-maintained look-up table, periodically updated by each cache reporting its content to the database. The CDRDF maintains, or obtains, path cost metrics of the proximity between the CDN candidate cache to the user device via an access network and uses that to calculate the performance and financial cost of potentially delivering the content via each access network. The process can default to a conventional CDN delivery, if that path is not identified in the earlier steps.

In some embodiments, only content availability and signal strength are used to determine suitability. Other embodiments take into account other factors, such as proximity to the CDN, network load, etc. Two or more separate access networks may be selected to deliver requested CDN data to the user device in parallel.

Embodiments of the invention may make use of existing features of the converged network architecture, which can play a role in determining to which access node a User Equipment (UE) should be connected. Such features include the “Access network discovery and selection function” (ANDSF), which is an entity within an LTE Core Network. The purpose of the ANDSF is to assist the UE to discover non-3GPP access networks (WiFi) that can be used for data communications in addition to 3GPP access networks (LTE) and to provide the UE with rules policing the connection to these networks. Operators define per-user policies to control how and when WLAN and cellular networks are used. The ANDSF consists of a standard XML based policy format and OMA-DM based network transport protocol. Policies tend to be relatively static and typically updated weekly or monthly.

The equivalent function in the proposed 5G standard is the access traffic steering, switching and splitting (ATSSS) function, which makes decisions on access node connectivity for the user terminal.

An embodiment of the invention will now be described by way of example, with reference to the drawings, in which

Figure 1 is a schematic representation of a first embodiment of a CDN Path Selection Architecture

Figure 2 is a flow chart depicting a Content Delivery Route Decision Function

Figure 3 depicts a CDN Path Selection Call Flow in a first embodiment when a first condition applies

Figure 4 depicts a CDN Path Selection Call Flow in the first embodiment when a second condition applies

Figure 5 depicts a CDN Path Selection Call Flow in the first embodiment when a third condition applies

Figure 6 is a consolidated and simplified flow diagram depicting the three flows illustrated in Figures 3, 4 and 5

Figure 7 depicts a CDN Path Selection Call Flow, similar to Figure 4, in a second embodiment when the second condition applies

Figure 8 is a schematic representation of a second embodiment of a CDN Path Selection Architecture

Figure 9 is a consolidated flow diagram depicting a CDN Path Selection Call Flow in the second embodiment

Figure 1 depicts a Network Architecture for an embodiment of this invention. A core system 1 manages the process. The converged core 1 also has a content delivery network cache 91 associated with it.

A content delivery route decision processor 12 is provided, with an associated content delivery network controller 13. The content delivery route decision processor 12 is provided as a network core function, located on the edge of the network core 1 to interface with the Content delivery network (CDN) 91, 94, 95, 96, 97, 98, 99 and the access networks 83, 84, 85, 86, 87, 88. The content delivery route decision processor monitors network path quality between the individual CDN caches and the location of the user devices, so that when a user device 90 requests data available on the CDN, the content delivery route decision processor is able to determine the most suitable data source and path. Initially, the currently connected access node’s local cache 97 is checked and if the requested content is available, the data is served. If the local cache does not have the required data the CDRDF determines whether the requested content is available at any other access point 14, 15, 16, 18, 19 which is in range. In Content availability and signal strength are used to determine suitability, and other factors may be considered such as proximity to the CDN, network load, etc. If no local cache has the required content, the system defaults to a conventional CDN delivery.

To enable the determination of available local caches, the content delivery route decision processor 12 may use data received from the user device 90, associations between access nodes available to the device and the access node’s local CDN cache, listings of data available in each CDN cache, and cost metrics, for example if connection to another operator’s network is required.

Figure 1 depicts three macrocell base stations 14, 15, 16, and three more localised base stations 17, 18, 19 (depicted as a microcell 17 and two WLAN access points 18, 19). Each of these cells has a respective associated CDN cache 94, 95, 96, 97, 98, 99. The core network 1 is connected to these access points 14, 15, 16, 17, 18, 19 by associated respective backhaul links 84, 85, 86, 87, 88, 89. As depicted for the links 87, 88, some of these links may connect to an intermediate connection point 82 with a common backhaul connection 83. A user terminal 90 is depicted, initially in communication with an access point 17.

Control connections are depicted in Figure 1 by dashed lines.

When a user terminal 90 transmits a request for a piece of content, the network makes a decision as to which Cell or Access Point the terminal should connect to, in order to be connected to the optimum CDN cache and therefore improve the user’s quality of experience for the session. The optimum cache will normally be the topologically closest cache to the user terminal that has the required content, but this selection may be modified subject to considerations such as bandwidth. To achieve this, a new function is required in the network herein referred to as the ‘Content Delivery Route Decision Function.’ This function is managed by a Content Delivery Route Decision processor 12 which determines where the UE is to be connected for delivery of a particular piece of content, based both on information received from the UE request, and information about each CDN node.

As shown in Figure 1, the ‘Content Delivery Route Decision processor’ 12 is part of the Mobile Core Network, but it could be located at the edge of the Core Content Delivery network as a decision entry point to the CDN. In the example, each Macrocell 14, 15, 16, Small Cell 17, and WiFi AP 18, 19 has a respective local CDN cache 94, 95, 96, 97, 98, 99 within close proximity. The Core Network 1 also has a Core CDN 91 cache.

The user terminal 90 may have a number of options available in regard to which access node and local CDN cache to connect to for a particular content request and the Content Delivery Route Decision processor 12 directs the User terminal 90 to connect to the best one available.

In an alternative embodiment, depicted in Figures 8 and 9, the content delivery route decision processing can be implemented in individual user terminals 90, embodying a processor 190.

The embodiments can be adapted to both LTE and 5G implementations.

It is assumed in the discussion to follow that there is a pre-existing relationship between the content provider (the operator of the content delivery route decision processor 12 and the associated content delivery network controller 13) and the network operator (the operator of the core network 1, such that the content can be hosted and served by the operator.

Figure 2 is a flow chart depicting the decision logic used by the Content Delivery Route Decision processor 12.

It will be seen that there are three possible outcomes 22, 25, 28 of this process, depending on two decision points 21,23.

If the requested content is identified by the decision processor 12 as being available in a cache 97 located at the access point 17 to which the user terminal is currently connected (step 21, outcome 21 y), streaming can be initiated from that access point (step 22).

If the requested content is identified by the decision processor 12 as being available in one or more caches 94, 95, 96, 98, 99 located at access points 14, 15, 16, 18, 19 other than that to which the user terminal is currently connected, but within range (outcomes 21x, 23y), the most appropriate of those access points is selected (step 24), and the user terminal handed off to that terminal (step 25) so that streaming can be initiated from that access point (step 27). If no local access point has the requested content (outcomes 21 x and 23x), the terminal connects, through its existing connection 17, to the default cache 91 (step 28).

It should be noted that a negative outcome (21x, 23x) may result at steps 21,23 either because a cache associated with the relevant access point does not have the required content, or because the access point has no associated caching facility.

The processes initiated by these outcomes will now be discussed in more detail with reference to Figures 3 to 7. Figures 3 to 5 illustrate the process applied to the LTE standard architecture. In the LTE standard the access nodes 17 are known as “enhanced nodes B” (eNB)

As seen in Figures 3 to 5, an initial attachment process 200 of the user terminal 90 to a packet gateway 102 in the core network 1 takes place in a conventional manner. When a user requires content to be downloaded from the content delivery network, the user terminal 90 generates a content request message 20. This message includes address data (e.g a url) for the content, the terminal’s current access identity (e.g an SSID), and a neighbour list of additional networks in range. It may also specify other data such as bandwidth capabilities of the currently serving access point 17.

In addition to the information that the Content Delivery Route Decision processor 12 receives from the UE 90, it also needs information about the association between each access node 14, 15, 16, 17, 18, 19 and its respective local CDN cache 94, 95, 96, 97, 98, 99, and also a list of content stored at each local CDN cache. Such information may be provided as part of the ‘Content Request’ message 20 from the UE. The user terminal may periodically perform a query to each access node’s local CDN cache to enquire if it has the requested content. Alternatively, the Content Delivery Route Decision processor 12 may store this information in a database 120, periodically updated by interrogating all the CDN caches associated with access points under its control. Data relating to signal strength and other channel properties are also stored in the database 120.

When a ‘Content Request’ message 20 is received from the UE, the Content Delivery Route Decision processor 12 performs an initial check 21 to establish whether the requested content is available at a CDN cache 13 associated with the access node 17 to which the user terminal 90 is currently connected.

The checking process 21 may also include assessment of the currently connected access node 17 to determine whether it meets a minimum required signal strength, using data specified by the user terminal 90 in the ‘Content Request’ message 20.

Figure 3 and Figure 6 (outcome 21Y), depict the process when requested content is identified as being available at a cache 97 associated with the currently-connected access node 17 (outcome 21Y in Figure 2). If it is, then the request is forwarded to the local CDN cache 13 (step 22) and content is streamed from the local CDN cache 97 to the user terminal 90 (step 29).

Figure 4 and Figure 6 (outcomes 21x, 23y), depict the process when the Content Delivery Route Decision processor 12 identifies that the requested content is not identified as being available at a cache 97 associated with the currently-connected access node 17 (outcome 21X in Figure 2). In this case, it performs another check 23 to establish whether the requested content is available at any additional network nodes 14, 15, 16, 18, 19 which is in range of the UE 90, using information provided by the UE 90 in the ‘Content Request’ message 20. If the requested content is available at any of the access nodes within range (outcome 23y) , then the ‘Content Delivery Route Decision Function’ 12 compares the signal strengths of potential access nodes (step 24) and chooses the node with the strongest signal (node 14 in this example), subject to any constraints such as a minimum signal strength requirement.

Other parameters may also be taken into account such as Proximity to CDN, Signal Strength Latency, CPU Load, Network Type, Time of Day, Number of other Users (contention rate) Cell Bandwidth, Operator Metrics (Cost of Route), Quality of service parameters, and security.

The ‘Content Delivery Route Decision processor 12 then instructs the serving mobility management entity 100 in the core network 1 to manage a handover of the UE 90 to hand over to this node 14 (steps 25, 26, 261, 262, 263). The content request 20 can then be forwarded to that access node’s local CDN cache 94 (step 27) for delivery of the content (step 29)

If it is not possible to identify a local access point having a cache with the required content (outcome 23x), the content delivery route decision processor 12 sends the request to the Core

CDN 91 (step 28) and the streaming session is established in the usual manner (step 29), as shown in figure 5 and Figure 6 (outcomes 21X, 23X) .

If the user terminal 90 has a dual connectivity capability, it may use two or more access nodes in order to receive the content from multiple CDN sources. Following a content request 20, the Content Delivery Route Decision processor 12 determines which of the local caches 94, 97, 98 have the required content. The Content Delivery Route Decision processor then selects two Access Nodes (or more, if the user terminal can support more than two links) with the strongest signals (step 24) to deliver the content to the UE. No distinction is made in the selection process 23 between the currently-serving access point 17 and any other local access points 14, 18, and thus in this dual connectivity embodiment step 21 in Figure 2 can be omitted.

The user terminal 90 then attaches to both all of the access points selected (step 25). It is of course unnecessary to reattach to the currently serving access point 17, if that is one of those selected, as it has already been attached (step 200).

The UE would need the capability to synchronise I buffer the received packets from the multiple CDN sources.

Figures 3 to 6 illustrate the process applied to LTE technology, but the invention can be applied to other architectures. The call flows defined in this invention could be applied to other architectures. Figure 7 is a representation of the same process as figure 4, but implemented in 5G architecture. The handover process 25, 26, 261,262 is mediated in the core network by an access and mobility function 600, analogous to the process performed by the mobility management entity 100 in the embodiment of Figure 4. Other elements 601, 602 perform their usual functions, including the original attachment process 200, which is handled by a service management function 601.

In the embodiment of Figure 8, the decision processor 190 is embodied in a user terminal 90, together with an associated database 192 storing data on the content stored in each of the local caches 94, 95, 96, 97, 98, 99. The resulting decision tree is similar to that in Figure 2, and the information flows similar to those depicted in Figures 3 to 7. The database 192 may be populated by data broadcast from a central co-ordinating content delivery network controller 13, or by periodic updates broadcast by each local CDN cache 94, 95, 96.... within range of the cell 17 serving the user terminal.

In an alternative embodiment, the route decision processor 190 assesses the content of each local cache at the time a request is made. The information flows in this embodiment are depicted in Figure 9, which should be compared with Figure 6.

In this embodiment, the user terminal 90 initiates a request for content by sending a request 922 for the content to the local cache 97 associated with the currently-serving base station 17. If the local cache 97 has the requested content (step 921) it delivers the content requested (step 933) to the user terminal 90.

In this embodiment it, if the content is not available at the local cache (922), or the local base station 17 has no associated cache, the user terminal 90 transmits a request to each other cache, either as a broadcast to all cells in range, or in a sequence determined from data stored in a database 191 relating to properties of the connections between the user terminal 90 and the individual base stations 14, 15,16, 18, 19, such as network topology and signal quality. The user terminal selects the first cache in the sequence which reports that it has the required content.

In the example depicted in Figure 9, if the local cache 97 does not have the requested content (step 922) the user terminal checks the database 191 (step 923) and transmits enquiries to one or more caches 98 associated with access points 18 on the same local area network, served by a common access point 82 (step 924). If the local cache(s) 98 has the requested content (step 925) it delivers the content requested (step 933) to the user terminal 90. If the content is not available at the local cache 98, or the local base station 18 has no associated cache, a report is returned that the content is not available (step 926).

If no local access point has a cache with the available content, the CDN and cell data 191 are checked again (step 923) for other cellular access points 14, 15, 16 within range. A handover 927 is arranged to one of them (access point 15 in this example) and a request to the (or each) cache 95 associated with that access point is made (step 928) for the required content. If the cache 95 has the required content (step 929) it delivers it (step 933) or otherwise it reports the content is not available (step 930). The steps 927-930 may be repeated, with further handovers, until a cache having the required content is identified, or all local access points have been attempted, or until a maximum number of attempts have been made.

If no cache has been identified as having the required content, user terminal 90 arranges a handover (step 931) back to the originally serving access node 17 (as this is would be the one with the best signal qualities) and a request is sent to the central cache 91 (step 932) for delivery of the content (step 933).

It should be noted that in all these embodiments, a handover is only required if the content is to be delivered from a cache associated with a neighbour cell. If the content is available at the currently serving cell 17, or only at the core cache 91, it is delivered using the currently serving cell, without the need for a handover.

Claims

1. A method of operating a content delivery network having a plurality of content caches to deliver requested content to at least one user device, the user device having one or more access network interfaces for connection to content caches of the content delivery network via one or more respective access networks, the method comprising:

f. delivering the requested content to the user device.

2. A method according to Claim 1, in which the method is performed by a network core function interfacing with the content delivery network and the access networks.

3. A method according to Claim 1, in which the method is performed by a content delivery route decision function running on a user device interfacing with the content delivery network and the access networks.

4. A method according to claim 3, in which the user device maintains a database of neighbour content caches and access network properties, and determines steps b and cfrom the data in the database.

5. A method according to Claim 3, in which the user device transmits data requests to one or more content caches in response to the generation of a content request, and identifies an optimal cache from the outcomes of those requests

6. A method according to Claim 5, wherein the user device transmits data requests to a plurality of caches in a predetermined sequence, selecting for content delivery the first cache identified to have the required content.

7. A method according to Claim 6, wherein the sequence is determined by properties of respective connections between the user device and the respective access points associated with each cache.

8. A method according to any of claims 2 to 7, in which the content delivery route decision function monitors the quality of network paths between a plurality of caches and the user device location, so that when a user device requests data available on the content delivery network, the content delivery route decision function is able to determine the most suitable data source and path.

9. A method according to any preceding claim, in which if the requested content is available at a cache associated with an access node to which the user device is currently connected, the data is served from that cache, and if it is not available from that cache, and it is determined that the requested content is available at another access point which is in range of the user device, the user device is handed over to that access point and data is served from that cache by way of that access point.

10. A method according to Claim 9, in which data is received from the user device relating to associations between access nodes available to the device, and listings of data available in the content caches of the available access nodes.

11. A method according to claim 10, in which the data is provided as part of a Content Request message from the user device.

12. A method according to claim 10 or claim 11, in which the user terminal periodically performs a query to the cache associated with each available access node, to determine if it has the requested content.

13. A method according to claim 10 or claim 11, in which a database of available content associated with the decision function is periodically updated by interrogating the content delivery network caches.

14. A method according to any preceding claim, in which the decision function obtains path cost metrics of the proximity between each candidate cache and the user device via an access network, and uses the metrics to calculate the performance and financial cost of delivering the content via each access network.

15. A method according to any preceding claim, in which access defaults to delivery from a centralised content delivery network cache, if no local cache is identified.

16. A method according to any preceding claim, in which content availability and signal strength are used to determine suitability.

17. A method according to claim 16, in which one or more of the following factors are also used to determine suitability:

a. proximity between the user terminal and the cache,

b. network load,

c. latency,

d. CPU Load,

e. Network Type,

f. time of day,

g. contention rate

h. bandwidth,

i. operator metrics,

j. quality of service parameters,

k. security.

18. A method according to any preceding claim, in which two or more separate access networks are selected to deliver requested data to the user device in parallel.

19. A computer system including a processor and a memory storing computer program code for performing the steps of the process of any preceding claim.

20. A computer program element comprising computer program code to, when loaded into a computer system and executed thereon, cause the computer to perform the steps of a process as claimed in any of Claims 1 to 18.