WO2005112415A1

WO2005112415A1 - Method for establishing a communication link

Info

Publication number: WO2005112415A1
Application number: PCT/EP2005/051503
Authority: WO
Inventors: Achim Ackermann-Markes
Original assignee: Siemens Aktiengesellschaft
Priority date: 2004-05-12
Filing date: 2005-04-04
Publication date: 2005-11-24

Abstract

The invention relates to a method for establishing a communication link, a packet-oriented network (NW) being composed of several network areas (LAN1, WAN1, LAN2, WAN2), connected to each other and a first communication terminal (TP1) being connected to a first network area (LAN1). According to said method, a network address of a second communication terminal (TP2) to be called is received by the first calling communication terminal (TP1); the received network address of the second communication terminal (TP2) is compared with the network address, allocated to the first communication terminal (TP1) and with the network mask thereof; a network topological relation of the second network area (LAN1, WAN1, LAN2, WAN2), connected to the second communication terminal (TP2), is evaluated based on the previous comparison and a codec, to be used for establishing the communication link, is selected based on the previous evaluation.

Description

description

Method for establishing a communication connection

The invention relates to a method and a communication terminal for establishing a communication connection. The invention relates in particular to the selection of a codec suitable for the communication link.

To define a compression or decompression algorithm for video or audio information, the abbreviation »Codec« (compression-decompression) is common in the professional world. A codec is understood to mean the principle of compressing uncompressed video and / or audio information according to a defined algorithm and being able to decompress the compressed video and / or audio information again.

Various codecs are used in telecommunications for the compression of video and / or audio information.

For video communication, for example, the codecs H.263 or MPEG-4 are used. Depending on the requirements of the quality of the speech signal, different codecs are used for audio or voice communication. The G.711 codec supports a bandwidth of 64 kB / s and is used to achieve ISDN voice quality. The G.723.1 codec offers less bandwidth, but it also has a longer delay and poorer voice quality. In contrast, the G729a / b codec offers a lower delay. Another codec, G.722, is suitable for supporting a "HiFi quality" of the audio information.

Each codec has its own characteristics with regard to its bandwidth requirements and its transmission quality, but in general the quality of the video deo and / or audio information with the bandwidth requirement and falls with the degree of compression.

In digital telecommunications, codecs are used in particular for the transmission of communication data over packet-oriented networks. Such a transmission is often referred to in the professional world as VoIP (Voice over IP). In the event of a call being set up between a calling first subscriber and a called second subscriber, two end points involved in the communication choose one in consultation with one another and, if appropriate, with a further instance for a transmission of user data - i.e. Audio or video information - appropriate codec.

In today's communication and data processing systems, this choice of the codec used for the encoding and decoding of user data transmitted is predominantly made from the point of view of which codec the other end point of the communication supports. With the constant further development of high-performance codecs, such an agreement is particularly necessary in order to provide an endpoint with "more modern" codecs for communication even with older systems.

In many cases, however, such a codec determined by agreement when a communication connection is set up is not an optimal codec for this communication connection. A codec that is suitable for a first network with a high transmission bandwidth and is characterized by low compression with a simultaneous high bandwidth requirement will cause an incorrect transmission of the user data when used in a communication connection in a second network with a limited transmission bandwidth. Conversely, a codec that is more suitable in this second network with higher compression and thus lower required transmission bandwidth is used with respect to the quality when used for a communication connection in the first network. tat of the transmitted user data lie within a limit specified for this high-compression codec. However, the bandwidth available in the first network would allow the use of a less strongly compressing codec with a higher bandwidth in order to achieve a higher quality of the user data exchanged with the communication link.

The object of the invention is to provide means by which a communication link is set up while avoiding the above-mentioned problems or loss of quality.

The problem is solved with regard to its procedural aspect by a method with the features of patent claim 1 and with regard to its device aspect by a communication terminal with the features of patent claim 11.

The invention is based on a first communication terminal - for example a VoIP telephone or a computer system, e.g. Workstation computer - which is connected to a packet-oriented network for the exchange of data. The packet-oriented network is divided into individual network zones in the usual way. A zone can e.g. consist of one or more iP subnets in an iP network. A characteristic of a zone is that there is enough bandwidth available for real-time communication even without a compression algorithm. A zone can therefore consist of a LAN (Local Area Network) or several LANs that are networked via high-bandwidth WAN connections (Wide Area Network).

The terms “close” or “local” and “far” used in the following do not necessarily correspond to the usual topological view (as far as they can be used in networks), but define a neighborhood to an end point via the transmission hand width, which is assured in communication with it or which can be achieved on average. A zone is local or neighboring, which a communication or. Data connection with high transmission bandwidth permitted.

To establish the communication connection, a network address of a second communication terminal to be called is first obtained from the calling first communication terminal. A comparison of the related network address of the second communication terminal with the network address assigned to the first communication terminal and its network mask enables an assessment of a network topological relationship of the second network zone connected to the second communication terminal. A codec to be used for the communication connection is selected on the basis of the network topological relationship determined.

An essential feature of the method according to the invention is that the codec to be used for the communication connection is selected on the basis of a network topological relationship of the two communication terminals involved in this communication connection. The network topological relationship here means in particular the assignment of the zone of the second communication terminal called in relation to the zone of the first communication terminal calling, on the basis of which a criterion for the selection of the codec is derived. The method according to the invention is based on the idea that more distant zones suggest a codec with higher compression than zones which are in the immediate vicinity or even a logical component of the current zone. The term network topology includes the range of the zone to which the communication link is to be established and the “neighborly” relationship to the current zone.

A particular advantage of the method according to the invention is a codec which is adapted to the conditions of the communication connection and which makes an optimal compromise between the available bandwidth and the highest possible transmission quality.

It is also advantageous to only slightly adapt the internal logic of the communication terminals and to be independent both of the respective communication protocol used in the communication system (for example H.323, SIP, etc.) and of the communication devices or network coupling devices used in the communication system, as is known "Switches" or "routers".

Advantageous developments of the invention are specified in the subclaims.

In one embodiment of the invention, as a result of the assessment of the network topological situation, there is information as to whether the zone in which the second communication terminal is located is identical to the first network zone or whether the second network zone is outside the first network zone. This embodiment of the method according to the invention is advantageously associated with the least effort, since the information required for this, namely the network address of the two communication terminals and the network mask of the first communication terminal must be available for packet-oriented communication anyway, but has not hitherto been available for an assessment of the network topological situation were used to select a suitable codec.

In a further advantageous embodiment of the invention, it is provided that entries are kept in the communication terminals which are used for a more precise analysis of the network topological situation. These entries are used, for example, by a network administration System related. These entries are advantageously obtained when a network address is assigned or transmitted for the respective communication terminal, for example in conjunction with a DHCP method (Dynamic Host Control Protocol). These entries include, for example, a list of network addresses or address ranges, by means of which a more precise assessment of zones is possible which are topologically to be regarded as "close", in which data traffic with a higher bandwidth is therefore possible.

An exemplary embodiment with further advantages and refinements of the invention is explained in more detail below with reference to the drawing.

It shows:

FIG: a structure diagram for the schematic representation of a communication system with individual network zones

The only FIG shows a communication system CSY with a packet-oriented network NW. The packet-oriented network NW is composed of several network zones LAN1, LAN2, LAN3, ANl, WAN2.

In the present exemplary embodiment, a first local network zone LAN1 is connected to a second local network LAN2 via a first connection CN1. The second local area network LAN2 is in turn a zone of a first wide area network WAN1, which is connected to a second wide area network WAN2 via a second connection CN2. A third local area network LAN3 is connected to the second wide area network WAN2 via a third connection CN3 and to the first local area network LAN1 via a fourth connection CN4.

In the CSY communication system, user data e.g. for voice or video communication as well as data for the control and monitoring of communication connections via the packet-oriented network NW. As is well known, packet-oriented networks include LANs (Local Area Network), MANs (Metropolitan Area Network), WANs (Wide Area Network) or the so-called Internet, which enables worldwide access to packet-oriented data. Internet telephony, for example, is often based on packet-oriented telecommunications technology and is often also referred to as “Voice over Internet Protocol” (VoIP).

Furthermore, organizational forms of a so-called virtual LAN are known for the logical zone formation of packet-oriented networks NW. A virtual LAN or VLAN is formed by a group of network nodes that are combined in an autonomous domain or “broadcast domain”. The affiliation of a network node to a VLAN does not depend on the location of the network node. It is determined exclusively by software configuration and can be changed if a network node is to be assigned to a new work group.

To simplify the two structuring of a packet-oriented network NW mentioned above are referred to as a "network zone".

A first communication terminal TP1 is connected to the first local network LAN1 and a second communication terminal TP2 is connected to the third local network LAN3. Although the communication terminals TP1, TP2 mentioned in the present exemplary embodiment are assumed to be VoIP communication terminals or “IP telephones”, the method according to the invention can also be applied to data terminals TP1, TP2, which are used either for communication purposes or for the purpose of Exchanges of data are operated. The method according to the invention according to a first embodiment is described below. It is assumed here that the first communication terminal TP1 knows its assigned network address and its network mask. This requirement is necessary for each packet-oriented communication terminal TP3, TP2 or data terminal TP1, TP2. For the description, it is assumed that communication takes place in accordance with the Internet Protocol, IP. Although this protocol is largely established as the standard in today's data networks, all other protocols can also be used as an alternative for packet-oriented transmission.

The method for establishing a communication connection between the calling first communication terminal TP1 and the called second communication terminal TP2 according to the first embodiment takes place as follows. Via a - not shown - network instance, e.g. a gatekeeper when using the H.323 protocol or a proxy when using the SIP protocol, the first communication terminal TP1 finds out the IP address of the second communication terminal TP2 to be called.

The first communication terminal TP1 assesses the network topological relationship by comparing this related IP address with its own IP address and its subnet mask. After this assessment, the first communication terminal TP1 has knowledge of whether the called communication terminal TP2 is in its IP subnet (LAN) or in another subnet (WAN). Based on this knowledge, the first communication terminal TP1 then selects a suitable codec, for example an audio codec. The choice of a codec follows a preference noted by the first communication terminal TP1, something in the form of "high quality preferential" or "low bandwidth preferred". In the case of a more distant zone, a codec with higher compression is used. selects as for zones that are in the immediate vicinity or a logical part of the current zone.

Both in H.323 and in SIP there is an optional exchange of technical possibilities of the two communication terminals TP1, TP2 to be involved in the communication connection, which is also referred to as the “capabilities exchange”. Such a comparison enables the codec used to be “agreed” on the basis of the codecs available in each case on the other communication terminal.

If the called communication terminal TP2 - as assumed in the present exemplary embodiment - is outside the "own" local network zone LAN1 and both support codec G.723.1, the two communication terminals TP1, TP2 will use this codec due to the preference set for the first communication terminal TPl some, which enables bandwidth-reduced communication.

If, on the other hand, a called - not shown - communication terminal is located within the "own" local network zone LAN1 or the called communication terminal is an external participant with respect to the communication system CSY, who is connected via an "exchange connection" (not shown) present in the local network zone LANl a preference for a codec with optimal speech quality, for example G.711 for the communication connection to be set up, is noted in the first communication terminal TP1.

In the case of large-scale local networks LAN1, organization is often carried out in the form of individual subnets (not shown). Such a subnet corresponds in the broadest sense to the second local area network LAN2, which in turn is part of the first wide area network WAN1. With such an organization of the first local area network LAN1, the situation can arise that a - Called communication terminal (not shown) is located outside the current subnet, although its belonging to the current local network LAN1 means a network topological neighborhood, which speaks in favor of choosing a codec with a higher bandwidth requirement. With the above method according to a first embodiment of the invention, the called communication terminal would, however, be classified as belonging to another zone - that is to say beyond a zone boundary - and thereupon preference would be given to a higher-compression codec with less bandwidth requirement, although a higher transmission bandwidth would certainly be feasible , With the choice of the higher compressing codec, the bandwidth available per se and thus the transmission quality are limited without technical necessity. This slight disadvantage of the first embodiment is eliminated by a method explained below in accordance with a second embodiment.

In a second embodiment, additional configurations are provided for the communication terminals TP1, TP2 on the basis of entries held there and optionally further local procedures for manual or remote-controlled setting of the configuration.

To distinguish it from zones viewed as "remote" from the network topology, locally stored, for example list-like, entries of zones are provided which are considered to be adjacent or local to the network topology, i.e. Zones in which a high bandwidth communication link is possible.

The network topological relationship continues to be subject to dynamic changes in the design of the network NW. In the drawing, a larger bar width indicates a higher transmission bandwidth for the first three connections CN1, CN2, CN3 than for the fourth connection CN4 between the first and third local area networks LAN1, LAN3. The called communication terminal TP2, which is connected to the third local area network LAN3, is therefore to be characterized as local via the first three connections CN1, CN2, CN3, provided that there are also zones in between, ie the first and the second wide area network WAN1, WAN2 appropriate transmission bandwidth is guaranteed. If, on the other hand, one of these first three connections CN1, CN2, CN3 fails, the third local network, which can now only be reached via the narrowband fourth connection CN4, is to be regarded as remote from the network topology. The narrowband connection CN4 is shown in the drawing as compared to the broadband first three connections CN1, CN2, CN3 with a smaller stroke width.

Communication setup according to this second embodiment is as follows.

Via a - not shown - network instance, e.g. a gatekeeper when using the H.323 protocol or a proxy when using the SIP protocol, the first communication terminal TP1 finds out the IP address of the second communication terminal TP2 to be called.

In an assessment of the network topological relationship, this IP address is compared with entries held in the first communication terminal TP1, and thus the list of nearby or local zones. As a result of this assessment, a statement is made as to whether the second communication terminal TP2 is located in a zone close to the network topology or in a zone distant from the network topology.

If no local zone area matching the related IP address is found in the entries of the first communication terminal TP1 and the second communication terminal TP2 is not in the local subnet of the first communication terminal TP1, the network topology characterized the relationship of the second communication terminal TP2 as "remote". A codec with high compression is then selected in a subsequent method step, which is then noted as a preference in a subsequent capabilities exchange.

If, on the other hand, there was a - not shown - called communication terminal within the local subnet of the first communication terminal TP1 or if a local zone area matching the related IP address was found in the entries of the first communication terminal TP1, the network topological relationship of this called communication terminal would be found be characterized as "local" and a codec with low compression selected.

In the capabilities exchange provided by both H.323 and SIP, a codec, which both support, is “negotiated” between the called and the calling communication terminal TP2, TP1.

The method according to the second embodiment differs from that of the first embodiment in that entries are kept in the respective communication terminal TP1, TP2 which support an assessment of the network topological relationship to the respective communication partner. The entries can be stored in the respective communication terminal TP1, TP2, as well as transmitted by one or more central entities (not shown) assigned to the respective communication terminal, if required.

In the event that no entries are available for any reason, the respective communication terminal behaves according to the above method according to the first embodiment, which is necessary in many applications.

provides an optimal assessment of the network topological relationship.

The configuration of entries is either done manually, via an application - e.g. a so-called »IP Phone Deployment Tool« - or via a management system.

An effective method of handing over the entries held to the respective communication terminal TP1, TP2 is to hand over the corresponding entries during a DHCP process in accordance with documents RFC 1533 and RFC 2131 (Request for Comment) of the IETF (Internet Engineering) Task Force).

A method for supporting an automatic configuration of a communication device was proposed in the DE application filed on April 29, 2003 with the registration number 10319322.7, which describes a method for transmitting voice VLAN information using a DHCP method. In using and expanding this method, both a request and a transmission of the entries kept can be carried out by means of the present invention. This also gives the full mobility of a communication terminal TP1, TP2 in the communication system CSY. Whenever a communication terminal TP1, TP2 requests an IP address via DHCP, the entries kept are transmitted.

When using an organizational form of the network structure also known as “IP Supernettmg” according to document RFC 1338, the number of IP subnets to be administered in the entries kept can be minimized.

In a method according to a third embodiment, in addition to the above method according to the second embodiment, it is provided that a network management system (for example HP OpenView, Tivoli or HiPath Management) which Knowledge of the network topology and its changes, which are reported by the active components (routers, switches), which map the network topology and which are used to generate individual entries for each communication terminal TP1, TP2. These entries are then forwarded to a terminal device configuration tool (eg deployment tool, DHCP server, ...) and, as in the above description for the second exemplary embodiment, are transmitted to the communication terminals TP1, TP2.

Claims

claims

1. Method for establishing a communication connection, with a packet-oriented network (NW) consisting of several interconnected network zones (LAN1, WAN1, LAN2, WAN2), with a first communication terminal (TP1) connected with a first network zone (LAN1), comprising the following steps: a ) Obtaining a network address of a second communication terminal (TP2) to be called by the calling first communication terminal (TP1), b) Comparison of the related network address of the second communication terminal (TP2) with the network address assigned to the first communication terminal (TP1) and its network mask , c) Assessment of a network topological relationship of the second network zone (LAN1, WAN1, LAN2, WAN2) connected to the second communication terminal (TP2) on the basis of the comparison of method step c) d) Selection of a codec to be used for the communication connection based on the assessment of Process step c).

2. The method according to claim 1, characterized in that as a result of the assessment of the network topological relationship after method step c), there is information as to whether - the second network zone lies within the first network zone, or, the second network zone is identical to the first network zone, or , the second network zone is outside the first network zone.

3. The method according to any one of claims 1 to 2, characterized in that the selection of the codec according to method step d) takes place after an information exchange of the respectively available options between the first and the second communication terminal (TP1, TP2). , Method according to one of the preceding claims, characterized in that codecs supporting higher compression rates are preferred for the selection of the codec according to method step d) if the assessment according to method step c) has at least one zone boundary between the first network zone (LAN1) and the second network zone (LAN1 , WA 1, AN2, AN2) results.

5. The method according to any one of claims 1 to 3, characterized in that for the selection of the codec according to step d) low compression rates supporting codecs are preferred if the assessment according to step c) no zone boundary between the first network zone (LANl) and the second Network zone (LANl, WANl, AN2, AN2) results.

6. The method according to any one of claims 1 to 3, characterized in that for the selection of the codec according to method step d) low compression rates supporting codecs are preferred if the assessment according to method step c) at least one zone boundary between the first network zone

(LAN1) and the second network zone (LAN1, ANl, LAN2, WAN2), which are assessed as non-critical on the basis of entries held in the first communication terminal in method step c).

7. The method according to claim 6, characterized. that the entries held in the first communication terminal comprise network addresses identifying network zones, by means of which logical subnets of the first network zone (LAN1) are defined.

8. The method according to any one of claims 6 or 7, characterized in that the entries held in the first communication terminal are obtained from a network management system.

9. The method according to any one of claims 6 to 8, characterized in that the entries held in the first communication terminal are obtained with a transmission of a network address.

10. The method according to any one of the preceding claims, characterized in that an audio and / or video codec is used as the codec.

11. Communication terminal connected to a first network zone (LAN1) in a packet-oriented network (NW) consisting of a plurality of interconnected network zones (LAN1, WAN1, LAN2, WAN2) comprising: a) means for obtaining a network address of a second communication terminal (TP2) to be called ), b) means for comparing the related network address of the second communication terminal (TP2) with the network address assigned to the first communication terminal (TP1) and its network mask, c) means for assessing a network topological relationship of the second network zone connected to the second communication terminal (TP2) ( LAN1, ANl, LAN2, WAN2) d) means for selecting a codec to be used for the communication connection on the basis of the information provided by the means for assessment.