WO2019141376A1

WO2019141376A1 - Methods and apparatus

Info

Publication number: WO2019141376A1
Application number: PCT/EP2018/051352
Authority: WO
Inventors: Anubhav Srivastava; Mahesh SURYAWANSHI; Nalin VILOCHAN
Original assignee: Nokia Technologies Oy
Priority date: 2018-01-19
Filing date: 2018-01-19
Publication date: 2019-07-25

Abstract

A method comprises causing a request to be sent to a domain name service server. This request may be sent from a client. The request comprises name information and information indicating that the domain name service server is to return a reduced number of record responses. In response to the request, a reduced number of record responses are provided.

Description

METHODS AND APPARATUS

Field

Some embodiments relate to methods and apparatus for use in the context of requests to and responses from domain name service servers.

Background

To contact any NE network element or node in a network, a DNS (domain name service) lookup from a DNS server may be required. Summary

According to one aspect, there is provided a method comprising: causing a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and receiving said reduced number of record responses.

The information indicating that the domain name service server is to return a reduced number of record responses may comprise percentage information.

The information indicating that the domain name service server is to return a reduced number of record responses may be provided in a field in said request.

The field may be dedicated to controlling a number of record responses provided.

The request may comprise a domain name service query.

The request may be for a fully qualified domain name resolution.

The information indicating that the domain name service server is to return a reduced number of record responses may comprise one of a plurality of different options.

The request and said plurality of responses may comprise SIP messages.

The name information may comprise QNAME.

The request may further comprise information as to a type of records to be provided in responses from said domain name service server.

The type of records may comprise one or more of: SRV records, A records, and

AAAA records.

The information indicating that the domain name service server is to return a reduced number of record responses may be configured to control switching from a first site to a second site in dependence on said information. According to another aspect, there is provided a method comprising: receiving at a domain name service server a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and causing said reduced number of record responses to be provided.

The request may comprise a domain name service query.

The request may be for a fully qualified domain name resolution.

The information indicating that the domain name service server is to return a reduced number of record responses comprises one of a plurality of different options.

The request and said plurality of responses may comprise SIP messages.

The name information may comprise QNAME.

The request may further comprise information as to a type of records to be provided in responses from said domain name service server and said method comprises providing the type of records in said responses.

The type of records comprises one or more of: SRV records, A records, and AAAA records.

The method may comprise using said information indicating that the domain name service server is to return a reduced number of record responses to control switching from a first site to a second site in dependence on said information.

The method may comprise selecting records in dependence on a load balancing algorithm, wherein the number of records selected is dependent on said information indicating that the domain name service server is to return a reduced number of record responses.

According to another aspect, there is provided an apparatus, said apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to: cause a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and receive said reduced number of record responses.

The request may comprise a domain name service query.

The request may be for a fully qualified domain name resolution.

The request and said plurality of responses may comprise SIP messages.

The name information may comprise QNAME.

The type of records may comprise one or more of: SRV records, A records, and AAAA records.

The information indicating that the domain name service server is to return a reduced number of record responses may be configured to control switching from a first site to a second site in dependence on said information.

According to another aspect, there is provided an apparatus in a domain name service server, said apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to: receive at a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and cause said reduced number of record responses to be provided.

The information indicating that the domain name service server is to return a reduced number of record responses may be provided in a field in said request. The field may be dedicated to controlling a number of record responses provided.

The request may comprise a domain name service query.

The request may be for a fully qualified domain name resolution.

The request and said plurality of responses may comprise SIP messages.

The name information may comprise QNAME.

The at least one memory and the computer code may be configured with the at least one processor to use said information indicating that the domain name service server is to return a reduced number of record responses to control switching from a first site to a second site in dependence on said information.

The at least one memory and the computer code may be configured with the at least one processor to select records in dependence on a load balancing algorithm, wherein the number of records selected is dependent on said information indicating that the domain name service server is to return a reduced number of record responses.

According to another aspect, there is provided an apparatus, said apparatus comprising: means for causing a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and means for receiving said reduced number of record responses.

The request may comprise a domain name service query. The request may be for a fully qualified domain name resolution.

The request and said plurality of responses may comprise SIP messages.

The name information may comprise QNAME.

According to another aspect, there is provided an apparatus in a domain name service server, said apparatus comprising: means for receiving a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and means for causing said reduced number of record responses to be provided.

The request may comprise a domain name service query.

The request may be for a fully qualified domain name resolution.

The request and said plurality of responses may comprise SIP messages. The name information may comprise QNAME.

The request may further comprise information as to a type of records to be provided in responses from said domain name service server and said method comprises providing the type of records in said responses. The type of records comprises one or more of: SRV records, A records, and AAAA records.

The apparatus may comprise means for using said information indicating that the domain name service server is to return a reduced number of record responses to control switching from a first site to a second site in dependence on said information.

The apparatus may comprise means for selecting records in dependence on a load balancing algorithm, wherein the number of records selected is dependent on said information indicating that the domain name service server is to return a reduced number of record responses.

A computer program comprising program code means adapted to perform the herein described methods may also be provided. In accordance with further embodiments apparatus and/or computer program product that can be embodied on a computer readable medium for providing at least one of the above methods is provided.

According to another aspect, there is provided a non-transitory computer program product comprising computer executable instructions which when executed by at least one processor perform any of the previously discussed methods.

Various other aspects and further embodiments are also described in the following detailed description of examples embodying the invention and in the attached claims.

Brief description of drawings

For a better understanding of some embodiments, reference will now be made by way of example only to the accompanying drawings in which:

Figure 1 shows DNS configuration and record mapping for two example sites;

Figure 2 shows a signal flow in an embodiments;

Figure 3 shows modified IP selection for the sites of the arrangement of Figure

1 ;

Figure 4 shows a system in which embodiments may be used;

Figure 5 shows a system in which embodiments may be used; and

Figure 6 shows an apparatus.

Detailed description Some embodiments are described herein with reference to particular examples. The invention is not, however, limited to such examples.

To contact any NE network element or node in a network, DNS (domain name service) lookup from a DNS server may be required. This look up may provide and/or cause the provision of the protocol, IP (internet protocol) and port of the NE where a request needs to be sent.

In SIP (session initiation protocol) methodology, the following DNS look up queries may be supported:

a) A NAPTR (name authority pointer) query returns a supported protocol; b) A SRV (service record query) returns target hosts and port along with a weight and a priority; and

c) A (associated with IPv4)/AAAA (associated with IPv6) record query returns target IPs.

Consider the following scenario.

There may be two (or more sites) in a network. One may be an active site and one maybe for back up. Each site may have a plurality of nodes. Each node may be mapped to different Internet protocols (IP). If all the nodes from one of the sites, for example the active site, is not available then a request may needs to be tried with all the nodes of another of the sites, for example, the backup site.

In terms of DNS configuration, the active site may be configured with a SRV

(service record) record of higher priority (say 10) than a SRV record of the backup site (say 20). Each SRV record dig up will typically return multiple A/AAAA records (IPs). In a heterogeneous mesh network such as IMS (IP multimedia subsystem), an operator may deploy numerous nodes/sites in the network to deal with a large amount of signalling traffic and to ensure relatively high availability. This may mean that an operator needs to configure substantial number of SRV records and their corresponding A/AAAA record.

A site (for example the active site) may become unavailable. This may be due to planned/unplanned activity. The may mean that means all nodes of that site go out of service. In accordance with DNS configuration logic, a request will be tried on all nodes of the active site before being tried on nodes of the second site. This may add an extra delay in processing the request. As a result of this, there may be a relatively high chance of a transaction being terminated. This may result in call failures and a deterioration in end user experience. In this example only two sites are considered but in practice, a network will generally have many more than two sites.

Some embodiments may provide for faster switchover to another site for processing messages successfully in the network.

Some embodiments will, based on a determination that a plurality of nodes of one site are not reachable that the respective site is down and the message will be tried on the nodes of another site.

Some embodiments may restrict the number of SRV and A/AAAA records from the DNS server itself.

In some embodiments, flexibility will be provided to a DNS client to request a percentage of records out of overall configured ones from the DNS server.

Some embodiments may provide a field QLIMIT in DNS query along with existing fields QNAME, QTYPE & QCLASS. QLIMIT may take an integer value which will mean a percentage of records that needs to be returned from DNS server. The QLIMIT field may be filled by the node (DNS client) which is performing DNS lookup of the SRV or A/AAAA records. The QLIMIT field may be used by the DNS server to filter out same priority records based on the percentage.

Consider an example where a DNS query is supposed to result in 8 SRV records, 4 with higher priority (10) and 4 with a lower priority (20) records. If QLIMIT has value of say 50 it means 50% of records from each priority will be returned as a response from the server. In the given example, the DNS response will contain 2 higher priority (10) records and 2 (20) lower priority records.

The QLIMIT field may apply to the A/AAAA query alternatively or additionally. For example, if each SRV records is mapped to 4 A/AAAA records and DNS query for fetching A/AAAA records contains QLIMIT as 50 it means, 50% record will be returned as response. So in this case out of 4 mapped A/AAAA record, only 2 records will be returned.

In this way 4 IPs (2 higher priority SRVs each returning 2 IPs) will be tried before switching over to lower priority records. This contrasts to prior proposals where 16 IPs (4 SRV records and each returning 4 IPs) will be tried before any switchover to a lower priority site.

Reference is now made to Figure 1 which shows an example DNS Configurations SRV and A Records Mapping for two example sites according to current proposals. Site 1 DNS records which are to be looked up are referenced 404a and Site 2 DNS records which are to be looked up are referenced by 404b.

For a given target FQDN (fully qualified domain name), a NAPTR record query returns a response 401 in the form sip.tcp.example.com.

After a NAPTR response, a SRV query gets performed which returns 8 SRV records 400a to h which maps to Site-1 and Site-2. The SRV records 400a to d belonging to Site-1 have higher priority (10) as compared to the priority (20) given to the SRV records 400e to h belonging to Site-2. The SRV records serverl .example.com to server4.example.com belong to Site-1 and server5.example.com to server8.example.com belong to Site-2

Each SRV record is mapped to 4 A- records resulting in 16 IPs (IP1...IP16) for Site-1 referenced 402a to 402d and 16 IPs (IP17...IP32) for Site-2 referenced 402e to h.

Now suppose Site-1 is completely down then also before switching to Site-2, all the IPs of Site-1 will be tried to process the message. This will add extra delay in message processing resulting in transaction timeouts in worst cases.

Reference is made to Figure 2 which shows the communication between a DNS client 406 and a DNS server 408 in accordance with an embodiment. This example uses a DNS Query (SRV and A record) with a QLIMIT value.

As described, some embodiments provide the flexibility to the DNS client to request a percentage of records out of overall configured ones from the DNS server

In step S1 , the DNS client sends a DNS query along with fields QNAME, QTYPE, QCLASS and QLIMIT. The QNAME may be in the form of sip.tcp.example.com. The QTYPE is 33 indicating a SRV query. The QCLASS is IN. In this example, QLIMIT will take integer value which indicates the percentage of records that needs to be returned from DNS server. The QLIMIT field will be filled by the node (DNS client) which is doing DNS lookup of the SRV or A/AAAA records. In this example, the QLIMIT VALUE is 50 indicating that 50 percent of the records need to be returned from the DNS server.

In some embodiments, the DNS server may respond the QLIMIT parameter so to return the required number of records in combination with its existing load balancing algorithm and the parameter QLIMIT. Thus in step S2, the DNS server filters out 50% of the SRV records from each priority based on its load balancing algorithms and sends a response to the DNS client. The DNS usually sends the list of IP addresses (any DNS record for SRV/A/AAAA) in a different order each time it responds to a new client. This may be by using a round-robin/random method or algorithm. This algorithm of deriving sequence of records will, based on QLIMIT, cause the appropriate number of records to be selected (using the round- robin/random principles) and returned to the client.

In step S3, the DNS client makes a request to the DNS server for A records. The QNAME is of the form of serverl .example.com. QTYPE is 1 representing an A query. The QCLASS is IN (Internet) and in this example the QLIMIT is 50.

In response, in step S4, the DNS filters out 50% of A records based on its load balancing algorithm and sends back a DNS response to the DNS client.

In step S5, the DNS client makes a request to a second DNS server for A records. In this example, the QNAME takes the form server2.example.com, the QTYPE is 1 representing an A query, the QCLASS is IN and the QLIMIT is 50.

In step S6 the second DNS server filters out 50% of A records based on its load balancing algorithm and send the response back to the DNS client.

Figure 3 shows the modified DNS server responses for the first and second sites 404a and 404b.

Consider the example where the DNS query happens for SRV records with a QLIMIT value as 50. This means that 50% records from each priority will be returned as a response from the server. In the given example, DNS response will contain twO higher priority (10) records belonging the first site. These may be serverl .example.com referenced 400a in Figure 1 and server2.example.com referenced 400b. There may be two lower priority (20) records belonging to the second site. These may be server5.example.com referenced 400e and server6.example.com referenced 400f. The SRV records reference 400c, 400d, 400g and 400h will be skipped and DNS server will not return these records in the response.

The QLIMIT field may alternatively or additionally be extended to A/AAAA query. For example, if each SRV records is mapped to 4 A records and a DNS query for fetching A records contains QLIMIT as 50, this means that 50% of the records will be returned as response. So in this case out of 4 mapped record with each SRV record, only 2 A records will be returned. In the given example of Figure 1 , from site- 1 , an A query on serverl .example.com will return IP1 and IP2. An A query on Server2.example.com will return IPS and IP6. From the second site 404b, an A query on server5.example.com will return IP17 and IP18 and a query on Server6.example.com will return IP21 and IP22. The following IPs are skipped and the DNS server will not return them in the response:

IP3, IP4, IP7, IP8, IP9-16, IP19, IP20, IP23, IP24, IP25-32.

In this way before switching to the second site, 4 IPs of the first site are tried in comparison to the 16 of previous proposals.

In some embodiments, the value of QLIMIT may indicate the percentage of responses which are returned.

In some embodiments, the value of QLIMIT may indicate the percentage of responses which are not returned.

In some embodiments, the QLIMT may have one of a plurality of fixed values which control the number of responses returned/not returned. For example in one case, QLIMIT may be defined by a single bit. One value may indicate that there is not limit and the other value may indicate that the particular number of responses are to be returned/not returned.

In some embodiments there may be a set of values defining particular numbers of responses to be returned/not returned. For example QLIMIT may have four values representing 0, 25, 50, 75 and 100 percent. The number of values may be more or less than four. The actual percentage represented by the values may be differ at least partially or completely from the example.

In some embodiments, QLIMIT may have any integer value from 0 to 100 percent.

In some embodiments, QLIMIT may be dependent on the nature of the network which has been provided. The value of QLIMIT may be dependent on one or more of: a) a number of sites and/or regions which have been configured, for example by a particular operator;

b) on a number of servers per site and/or region;

c) a maximum call set-up time required by for example an operator; and d) Maximum message transaction time that operator wants.

One or more of these factors may at least partially control a particular value of QLIMIT in request. One or more of these factors may at least partially control the possible values of QLIMIT which can be used.

Some embodiments may provide one or more of the following advantages: since the number of records returned on the DNS interface may be less, this may result in lower DNS traffic; faster switching to emergency sites may occur in the case of a disaster when one or more nodes/sites are down;

filtering may be done at a central DNS server and may be consistent across clients; and

client performance during processing of messages may be improved at the client may receive already filtered IPs.

In some embodiments, the DNS may return less numbers of records, so that less processing done at client side (which does other call related processes), resulting in less DNS traffic. In other embodiments, the client itself may filter out the records before switching over to a new site.

One example of a system in which embodiments may be provided is shown in Figure 4. Figure 4 shows an example of a communication system enabled to offer multimedia services. This is the Internet Protocol (IP) Multimedia network. IP Multimedia (IM) functionalities can be provided by means of an IP Multimedia Core Network (CN) subsystem, or briefly IP Multimedia subsystem (IMS). The IMS includes various network entities for the provision of the multimedia services.

In Figure 4 an IP Multimedia Network 45 is provided for offering IP multimedia services for IP Multimedia Network subscribers. IP Multimedia (IM) functionalities can be provided by means of a mobile communication system. A mobile communication system is typically arranged to serve a plurality of mobile user equipment usually via a wireless interface between the user equipment and at least one base station of the communication system. The mobile communication system may logically be divided between a radio access network (RAN) and a core network (CN).

In the system base stations 31 and 40 are arranged to transmit signals to and receive signals from mobile user equipment 30, 41 of mobile users i.e. subscribers via a wireless interface between the user equipment and the radio access network. Correspondingly, a mobile user equipment is able to transmit signals to and receive signals from the radio access network via the wireless interface.

In the shown arrangement the user equipment 30, 41 may access the IMS network 45 via the access network associated with base station 31 , 40, respectively. It shall be appreciated that, although, for clarity reasons Figure 4 shows two base stations only, a typical communication network system usually includes a number of base stations. A mobile user equipment may comprise any appropriate mobile user equipment adapted for Internet Protocol (IP) communication to connect the network. For example, the mobile user may access the cellular network by means of a Personal computer (PC), Personal Data Assistant (PDA), mobile station (MS), smart phone and so on. The following examples are described in the context of mobile stations.

One skilled in the art is familiar with the features and operation of a typical mobile station. Thus, it is sufficient to note that the user may use a mobile station for tasks such as for making and receiving phone calls, for receiving and sending data from and to the network and for experiencing multimedia content or otherwise using multimedia services. A mobile station may include an antenna for wirelessly receiving and transmitting signals from and to base stations of the mobile communication network. A mobile station may also be provided with a display for displaying images and other graphical information for the user of the mobile user equipment. Camera means may be provided for capturing still or video images. Speaker means are also typically provided. The operation of a mobile station may be controlled by means of an appropriate user interface such as control buttons, voice commands and so on. Furthermore, a mobile station is provided with a processor entity and a memory means.

It shall be appreciated that although only two mobile stations are shown in Figure 4 for clarity, a number of mobile stations may be in simultaneous communication with base stations of a mobile communication system.

The core network (CN) entities typically include various switching and other control entities and gateways for enabling the communication via a number of radio access networks and also for interfacing a single communication system with one or more communication system such as with other cellular systems and/or fixed line communication systems. In some systems the radio access network controller is typically connected to an appropriate core network entity or entities such as, but not limited to, a serving general packet radio service support node (SGSN), see controllers 33 and 39 of Figure 1. The radio access network is in communication with the serving GPRS support node via an appropriate interface, for example on an lu interface. Although not shown, the SGSN typically has access to designated subscriber database configured for storing information associated with the subscription of the respective user equipment. The serving GPRS support node, in turn, typically communicates with a gateway GPRS support node via the GPRS backbone network 32. This interface is commonly a switched packet data interface.

A packet data session may be established to carry traffic flows over the network. Such a packet data session is often referred as a packet data protocol (PDP) context. A PDP context may include a radio bearer provided between the user equipment and the radio network controller, a radio access bearer provided between the user equipment, the radio network controller and the SGSN, and switched packet data channels provided between the serving GPRS service node and the gateway GPRS service node. Each PDP context usually provides a communication pathway between a particular user equipment and the gateway GPRS support node and, once established, can typically carry multiple flows. Each flow normally represents, for example, a particular service and/or a media component of a particular service. The PDP context therefore often represents a logical communication pathway for one or more flow across the network. To implement the PDP context between user equipment and the serving GPRS support node, radio access bearers (RAB) need to be established which commonly allow for data transfer for the user equipment. The implementation of these logical and physical channels is known to those skilled in the art and is therefore not discussed further herein.

The communication systems may be such that services are provided for the user equipment by means of various functions of the data network that are handled by controller entities, such as servers. For example, several different servers providing various control functions are used for the service provision control. These may include functions such as the call state control functions (CSCFs). The call state control functions may be divided into various categories such as a proxy call state control function (P-CSCF), interrogating call state control function (l-CSCF), and serving call state control function (S-CSCF). It shall be appreciated that similar functions may be referred to in different systems with different names. For example, in certain applications the CSCFs may be referenced to as the call session control functions.

A user who wishes to use services provided by the IMS system may need first to register with a serving controller, such as the serving call session control function (S-CSCF) 36. As shown in Figure 4, communication between the S-CSCF 36 and the user equipment may be routed via at least one proxy call session control function (P- CSCF) 35. The proxy CSCF 35 is thus for proxying messages from the GGSN 34 to a serving call session control function 36. The serving controller, i.e. CSCF 36 in Figure 4, in turn, provides the control entity the user equipment 30 needs to be registered with. The registration is required to enable the user equipment to request for a service from the communication system.

A policy control entity 37 may also be provided. The policy control entity 37 may be configured to store required policy information in a database 38 thereof. The network entities may query the policy control entity for various purposes, such as for obtaining information regarding the media policy of a particular user. The policy control entity may be provided by means of a policy decision function (PDF), which is connected to P-CSCF and GGSN.

Figure 4 shows also an application server 50. The user equipment may connect, via the GPRS network, to the application server that is connected to one or more data networks such as, but not limited to, the exemplifying Internet Protocol (IP) network. It shall be appreciated that a great number of application servers may be connected to each data network.

Some embodiments may be used in the Serving Call State Control Function (S-

CSCF) selecting an Application Server (AS) node from the given FQDN which resolves in multiple IPs. The SCSF would query the DNS 53.

Reference is made to Figure 5 which schematically shows some other functions of the IMS network.

Figure 5 shows a S-CSF 800, an Interconnection Border Control Function

(IBCF) node 802, a Breakout Gateway Control Function (BGCF) node 804 and a Media Gateway Control Function (MGCF) node 806. The MGCF may provide call control protocol conversion. The BGCF may act as a proxy which processes requests for routing from an S-CSCF. The IBSF may provide a gateway to other networks. The DNS is referenced 808.

Some embodiments may be used in the S-CSCF selecting an IBCF node from the given FQDN which resolves in multiple IPs.

Some embodiments may be used in the S-CSCF selecting a BGCF node from the given FQDN which resolves in multiple IPs.

Some embodiments may be used in the BGCF selecting a MGCF node from the given FQDN which resolves in multiple IPs.

It should be appreciated that the embodiments may be applied broadly. Embodiments are not limited to SIP entities. Rather embodiments, may be used in any network element which uses a DNS server for routing the requests. Figure 6 shows an example of an apparatus 300 provided in or associated with any of the DNS client or server entities discussed. The apparatus comprises at least one memory 301 , at least one data processing unit or at least one data processor 302, 303 and an input/output interface 304.

Some embodiments may be provided with any entity which uses DNS to resolve any server’s FQDN. For example, one common use may be where a computer is contacting a web server from a computer using a HTTP message. In this example, the client uses a DNS server to resolve a web site FQDN which can be mapped to multiple IPs.

The required data processing apparatus and functions may be provided by means of one or more data processors. The described functions may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. The data processing may be distributed across several data processing modules.

A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. One or more of the steps discussed in relation to Figure 2 may be performed by one or more processors in conjunction with one or more memories.

An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded or otherwise provided on an appropriate data processing apparatus. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

It is noted that whilst embodiments have been described in relation to certain architectures, similar principles can be applied to other systems. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted that different combinations of different embodiments are possible. It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the spirit and scope of the present invention.

Claims

1 . A method comprising:

causing a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

receiving said reduced number of record responses.

2. The method as claimed in claim 1 , wherein said information indicating that the domain name service server is to return a reduced number of record responses is configured to control switching from a first site to a second site in dependence on said information.

3. A method comprising:

receiving at a domain name service server a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

causing said reduced number of record responses to be provided.

4. The method as claimed in claim 3, comprising using said information indicating that the domain name service server is to return a reduced number of record responses to control switching from a first site to a second site in dependence on said information.

5. The method as claimed in claim 3 or 4, comprising selecting records in dependence on a load balancing algorithm, wherein the number of records selected is dependent on said information indicating that the domain name service server is to return a reduced number of record responses.

6. The method as claimed in any preceding claim, wherein said information indicating that the domain name service server is to return a reduced number of record responses comprises percentage information.

7. The method as claimed in any preceding claim, wherein said information indicating that the domain name service server is to return a reduced number of record responses is provided in a field in said request.

8. The method as claimed in claim 7, wherein said field is dedicated to controlling a number of record responses provided.

9. The method as claimed in any preceding claim, wherein said request comprises a domain name service query.

10. The method as claimed in any preceding claim, wherein said request is for a fully qualified domain name resolution.

1 1 . The method as claimed in any preceding claim, wherein said information indicating that the domain name service server is to return a reduced number of record responses comprises one of a plurality of different options.

12. The method as claimed in any preceding claim, wherein said request and said plurality of responses comprise SIP messages.

13. The method as claimed in any preceding claim, wherein said name information comprises QNAME.

14. The method as claimed in any preceding claim, wherein said request further comprises information as to a type of records to be provided in responses from said domain name service server and said method comprises providing the type of records in said responses.

15. The method as claimed in claim 14, wherein said type of records comprises one or more of:

SRV records, A records, and AAAA records.

16. An apparatus, said apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to:

cause a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

receive said reduced number of record responses.

17. The apparatus as claimed in claim 16, wherein the information indicating that the domain name service server is to return a reduced number of record responses is configured to control switching from a first site to a second site in dependence on said information.

18. An apparatus in a domain name service server, said apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to:

receive at a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

cause said reduced number of record responses to be provided.

19. The apparatus as claimed in claim 18, wherein the at least one memory and the computer code are configured with the at least one processor to use said information indicating that the domain name service server is to return a reduced number of record responses to control switching from a first site to a second site in dependence on said information.

20. The apparatus as claimed in claim 18 or 19, wherein the at least one memory and the computer code are configured with the at least one processor to select records in dependence on a load balancing algorithm, wherein the number of records selected is dependent on said information indicating that the domain name service server is to return a reduced number of record responses.

21 . The apparatus as claimed in any of claims 16 to 20, wherein said information indicating that the domain name service server is to return a reduced number of record responses comprises percentage information.

22. The apparatus as claimed in any of claims 16 to 21 , wherein said information indicating that the domain name service server is to return a reduced number of record responses is provided in a field in said request.

23. The apparatus as claimed in claim 22, wherein said field is dedicated to controlling a number of record responses provided.

24. The apparatus as claimed in any of claims 16 to 23, wherein said request comprises a domain name service query.

25. The apparatus as claimed in any of claims 16 to 24, wherein said request is for a fully qualified domain name resolution.

26. The apparatus as claimed in any of claims 16 to 25, wherein said information indicating that the domain name service server is to return a reduced number of record responses comprises one of a plurality of different options.

27. The apparatus as claimed in any of claims 16 to 26, wherein said request and said plurality of responses comprise SIP messages.

28. The apparatus as claimed in any of claims 16 to 27, wherein said name information comprises QNAME.

29. The apparatus as claimed in any of claims 16 to 28, wherein said request further comprises information as to a type of records to be provided in responses from said domain name service server and said method comprises providing the type of records in said responses.

30. The apparatus as claimed in claim 29, wherein said type of records comprises one or more of: SRV records, A records, and A AAA records.

31. A non-transitory computer program product comprising computer executable instructions which when executed by at least one processor perform the method of any one of claims 1 to 15.

32. An apparatus comprising:

means for causing a request to be sent to a domain name service server comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

means for receiving said reduced number of record responses.

33. An apparatus in a domain name service server, said apparatus comprising:

means for receiving a request comprising name information and information indicating that the domain name service server is to return a reduced number of record responses; and

means for causing said reduced number of record responses to be provided.