U.S. patent application number 12/738912 was filed with the patent office on 2010-10-28 for signaling of mgw identity in sip-i.
Invention is credited to Philip Hodges, John Kerr, Marcello Pantaleo.
Application Number | 20100274905 12/738912 |
Document ID | / |
Family ID | 40580155 |
Filed Date | 2010-10-28 |
United States Patent
Application |
20100274905 |
Kind Code |
A1 |
Pantaleo; Marcello ; et
al. |
October 28, 2010 |
SIGNALING OF MGW IDENTITY IN SIP-I
Abstract
The invention relates to signaling of MGW identity in SIP-I. A
Call Control Unit of a network includes an Input/Output unit. The
Call Control Unit includes a processing unit in communication with
the input/output unit. The Call Control Unit includes a memory unit
in communication with the processing unit, the processing unit
producing a signal having information which identifies a seized
Media Gateway (MGW) related to a call establishment or one or more
offered Media Gateways, which is sent via Session Initiation
Protocol (SIP) to a Mobile Switching Centre (MSC)-Server in the
network which is in charge to seize a MGW. A computer readable
medium storing a computer program, which, when executed by at least
one processing unit, signals a media gateway (MGW) identity. A
method in a telecommunications node for signaling a Media Gateway
(MGW) Identity.
Inventors: |
Pantaleo; Marcello; (Rome,
IT) ; Kerr; John; (Herzogenrath, DE) ; Hodges;
Philip; (Melbourne, AU) |
Correspondence
Address: |
ERICSSON INC.
6300 LEGACY DRIVE, M/S EVR 1-C-11
PLANO
TX
75024
US
|
Family ID: |
40580155 |
Appl. No.: |
12/738912 |
Filed: |
October 23, 2008 |
PCT Filed: |
October 23, 2008 |
PCT NO: |
PCT/IB08/02837 |
371 Date: |
April 20, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60982880 |
Oct 26, 2007 |
|
|
|
Current U.S.
Class: |
709/227 |
Current CPC
Class: |
H04L 65/1023 20130101;
H04L 65/103 20130101; H04W 80/10 20130101; H04L 65/1069 20130101;
H04L 65/1006 20130101; H04W 72/08 20130101; H04L 67/141
20130101 |
Class at
Publication: |
709/227 |
International
Class: |
G06F 15/16 20060101
G06F015/16 |
Claims
1. A method in a telecommunications node for signaling a Media
Gateway (MGW) Identity comprising the steps of: identifying a
seized MGW; and sending a signal via Session Initiation Protocol
(SIP) having information which identifies the seized MGW.
2. The method according to claim 1 wherein the identifying step
includes the step of identifying one or more offered Media
Gateways; and the sending step includes the step of sending the
signal via SIP having information which identifies one or more of
the offered Media Gateways.
3. The method according to claim 1, wherein the sending step
includes the step of sending the signal from a call control
unit.
4. The method according to claim 1, wherein the sending step
includes the step of sending a P-Header with the information.
5. The method according to claim 1, wherein the sending step
includes the step of sending information contained in an
o-Parameter of a Session Description Protocol (SDP) message.
6. The method according to claim 1, wherein the sending step
includes the step of sending information contained in an
a-Parameter of a Session Description Protocol (SDP) message.
7. The method according to claim 3, including the step of the call
control unit including one session level attribute set to an MGW
identity of the seized MGW, or one or more session level attributes
each one set to an offered MGW within an SDP offer encapsulated in
an initial invite request.
8. The method according to claim 7 including the step of the call
control unit selecting the MGW using the session level attribute
included within an SDP answer in a first response to the invite
request.
9. The method according to claim 8 including the step of using the
session level a=inactive attribute in the SDP offer included in the
initial invite request by the call control unit to indicate a user
plane is not connected.
10. The method according to claim 3 including the step of the call
control unit seizing the MGW.
11. The method according to claim 1 wherein the MGW identity
includes an octet string.
12. A Call Control Unit of a network comprising: an Input/Output
unit, a processing unit in communication with the input/output
unit, and a memory unit in communication with the processing unit,
the processing unit producing a signal having information which
identifies a seized Media Gateway (MGW) related to a call
establishment or one or more offered Media Gateways, which is sent
via Session Initiation Protocol (SIP) to a Mobile Switching Centre
(MSC)-Server in the network which is in charge to seize a MGW.
13. The Call Control Unit according to claim 12, wherein the
information in the signal is contained in an a-Parameter of a
Session Description Protocol (SDP) message.
14. The Call Control Unit according to claim 12, wherein the
processing unit includes one session level attribute set to an MGW
identity of the seized MGW, or one or more session level attributes
each one set to an offered MGW within an SDP offer encapsulated in
an initial invite request.
15. The Call Control Unit according to claim 14, wherein the
processing unit selects the MGW using the session level attribute
included within an SDP answer in a first response to the invite
request.
16. The Call Control Unit according to claim 14, wherein the
processing unit uses a session level a=inactive attribute in the
SDP offer included in the initial invite request to indicate a user
plane is not connected.
17. The Call Control Unit according to claim 14, wherein the MGW
identity includes an octet string.
18. A computer readable medium storing a computer program which
when executed by at least one processing unit signals a media
gateway (MGW) identity, the computer program comprising
instructions for the processing unit generated steps of:
identifying a seized MGW or one or more offered Media Gateways; and
sending a signal via Session Initiation Protocol (SIP) having
information which identifies the seized MGW or one of more of the
offered Media Gateways.
19. The computer readable medium according to claim 18, wherein the
sending step includes the step of sending the information contained
in an a-Parameter of a Session Description Protocol (SDP)
message.
20. The computer readable medium according to claim 19, including
the step of including one session level attribute set to an MGW
identity of the seized MGW, or one or more session level attributes
each one set to an offered MGW within an SDP offer encapsulated in
an initial invite request.
21. The computer readable medium according to claim 20, including
the step of selecting the MGW using the session level attribute
included within an SDP answer in a first response to the invite
request.
22. The computer readable medium according to claim 20, including
the step of using the session level a=inactive attribute in the SDP
offer included in the initial invite request to indicate a user
plane is not connected.
23. The computer readable medium according to claim 18, including
the step of seizing the MGW.
24. The computer readable medium according to claim 18, wherein the
MGW identity includes an octet string.
Description
TECHNICAL FIELD
[0001] The invention relates to the field of telecommunication, and
more specifically, to a communication system using layered
architecture and SIP-I like protocols. (As used herein, references
to the "present invention" or "invention" relate to exemplary
embodiments and not necessarily to every embodiment encompassed by
the appended claims.)
BACKGROUND
[0002] This section is intended to introduce the reader to various
aspects of the art that may be related to various aspects of the
present invention. The following discussion is intended to provide
information to facilitate a better understanding of the present
invention. Accordingly, it should be understood that statements in
the following discussion are to be read in this light, and not as
admissions of prior art.
[0003] With 3GPP Rel'8 there is now the inclusion of SIP-I on the
Nc interface, where BICC protocol would be replaced as the call
control protocol within PLMN, further reference hereto may be found
in 3GPP TS 23.231 and TR 29.802 and ITU Q.1902.4, incorporated by
reference herein. Such a system is displayed exemplary in FIG. 1
showing the functional split into a user plane comprising the UTRAN
and GERAN with respect to their Interface (A-Interface) towards the
MediaGateway (MGW) and among MediaGateways (Nb-Interface) and a
signaling plane comprising the UTRAN and GERAN with respect to
their Interface (Iu-Interface) towards the Mobile Switching Center
Server (MSC-S) and among MSC-Server (MSC-Server, Gateway MSC) with
the Nc Interface. As shown, the signaling plane is indicated by a
dashed line, whereas the User Plane is indicated by a solid
line.
[0004] Currently, within a BICC based Public Land Mobile Network
(PLMN) as an example of a mobile communications network the media
gateway selection procedures enable a node to select a media
gateway (MGW) which is most suitable for a given traffic case,
thereby offering the operator the ability to optimize user plane
resources and also enabling flexible routing of the actual
payload.
[0005] Although in the following, the problems are explained with
respect to a mobile communication network, the same problems may
arise in a fixed mobile network.
[0006] However, the above networks suffer certain problems which
will be explained in the following.
[0007] In order to have almost the same level of functionality as
currently applied to 3GPP BICC layered architecture, in this case
optimized MGW selection, SIP-I needs to offer some means of
signaling the identity of MGW(s). The MGW could be identified by
using either the sent or received user plane connection's Internet
Protocol (IP) address. But this assumes all (G)MSC servers know all
IP addresses of every MGW and can thus map this to an actual MGW.
This is inefficient and unnecessarily complicates the network
configuration. This is somewhat analogous to the handling of the
Bearer Control Unit Identifier (BCU-Id) in BICC. When BICC is run
over IP, it is the BCU-Id that is used for MGW selection, not the
connection IP addresses which are swapped via the IP Bearer Control
Protocol (IPBCP).
[0008] Currently, the concept of MGW identity (or BCU-Id) is not
specified in SIP-I; thereby MGW selection optimization is not
possible. Without such indication, each (G)MSC server would need to
select and use locally configured MGW(s), without utilizing any
network knowledge. Further, from a 3GPP perspective, external
networks shall always select their own MGW. Thus the GMSC and
interworking MSC servers shall also seize a MGW at the network
border. In order to offer MGW at the Edge, call establishment
procedures need to allow deferred (for mobile originating) or
optimized (for mobile terminating) MGW selection.
Deferred MGW Selection
[0009] FIG. 2 explains an example of deferred MGW selection that
could be applied to SIP-I. In this case, a Session Description
Protocol (SDP) offerer is an originating MSC Server which does not
signal any MGW identity.
[0010] The SDP answerer is an interworking MSC Server which seizes
the MGW at its network border and returns its MGW identity to the
originating MSC Server. The originating MSC Server now has the
ability to select the same MGW. It seizes a bearer termination,
indicating in a new second SDP offer to the interworking MSC Server
a user plane connection address without any MGW identity.
Optimised MGW Selection
[0011] In FIG. 3 is explained an example of optimized MGW selection
that could be applied to SIP-I. In this case, the SDP offerer is a
GMSC Server which has seized a MGW at the network border. The
initial SDP offer indicates that a MGW is connected by including a
MGW identity. The SDP answerer is a terminating MSC Server which is
able to connect to the same MGW. It seizes a bearer termination in
this MGW and returns in the SDP answer both a user plane connection
address and used MGW identity.
MGW Negotiation
[0012] Not all MGWs may be controlled by all MSC Servers; if this
were the case there would be a heavy burden on the operator to
configure the network and there would also be the need for a fully
meshed transport and GCP signaling network which might not be the
case in a network with large geographical coverage and varying
traffic densities across the network. Further, not all MGWs, even
if they are controlled by all MSC Servers, may support all the same
features; pooling of resources may occur in certain MGWs.
[0013] It is therefore desired to be able to signal a recommended
set of MGWs that would be suitable for a given call and allow the
succeeding node or terminating node to select the most suitable MGW
that fulfills the requirements of the given call.
SUMMARY
[0014] The present invention pertains to a Call Control Unit of a
network. The Call Control Unit comprises an Input/Output unit. The
Call Control Unit comprises a processing unit in communication with
the input/output unit. The Call Control Unit comprises a memory
unit in communication with the processing unit. The processing unit
produces a signal having information which identifies a seized
Media Gateway (MGW) related to a call establishment or one or more
offered Media Gateways related to a call establishment, which is
sent via Session Initiation Protocol (SIP) to a Mobile Switching
Centre (MSC)-Server in the network which is in charge to seize a
MGW.
[0015] The present invention pertains to a computer readable medium
storing a computer program which when executed by at least one
processing unit signals a media gateway (MGW) identity. The
computer program comprises instructions for the processing unit
generated steps of identifying a seized MGW or one or more offered
Media Gateways. There is the step of sending a signal via Session
Initiation Protocol (SIP) having information which identifies the
seized MGW or one of more of the offered Media Gateways.
[0016] The present invention pertains to a method in a
telecommunications node for signaling a Media Gateway (MGW)
Identity. The method comprises the steps of identifying a seized
MGW. There is the step of sending a signal via Session Initiation
Protocol (SIP) having information which identifies the seized
MGW.
[0017] To ensure MGW at the Edge in similar manner to that using a
BCU-ID in BICC, three alternatives are given as examples on how to
signal either a single or multiple ID(s) for MGW. These
alternatives either use or update existing SIP mechanisms of
carrying information. Within all of these alternatives, it is not
intended to alter or change the technique of deferred or optimized
MGW selection. Also the use of single or multiple MGW-Id(s) is
considered as being the same from a signaling perspective.
[0018] In a first embodiment, a new P-Header is introduced.
[0019] This P-Header (Private-Header) Definition is simulated to
some extent by P-headers as defined in RFC (Request for Comment)
3455. Within the application, this newly introduced P-header is
referred also as "P-MGW-ID".
[0020] The new P-Header extension allows a (G)MSC server node to
signal the identity of the seized MGW or the identity of one or
more offered MGWs for usage within a 3GPP CS domain.
[0021] In the following, short examples thereof are presented:
Examples
[0022] P-MGW-ID=no-mgw-selected
[0023] P-MGW-ID=mgw1.operator.net, mgw2.operator.net
[0024] P-MGW-ID=127.124.65.78
[0025] P-MGW-ID=0111000 0101000 1101011 0011011
[0026] In a second embodiment an origin line (o=) is used for the
purpose within SDP.
[0027] This origin parameter is originally defined in SDP according
to RFC 4566. However, then the MGW identity should be carried
within the <unicast-address> field.
[0028] This would allow the (G)MSC server to set the
<unicast-address> of the origin ("o=") line to the MGW
identity of the seized/offered MGW or to a reserved string
indicating that no MGW identity is provided.
[0029] In the following short examples thereof are presented:
Examples
[0030] o=-2890844526 2890842807 IN IP4 no-mgw-selected
[0031] o=-2890844526 2890842807 IN IP4 mgw1.operator.net
[0032] o=-2890844526 2890842807 IN IP4 10.47.16.5
[0033] In a third embodiment an attribute line (a=) is used for the
purpose within SDP.
[0034] Such a new <attribute> is to be registered for use in
existing `session level` attribute ("a=") line in SDP, as defined
in RFC 4566.
[0035] It could be assigned in the same manner as BCU-ID in BICC;
i.e. 4 octets for representing Network ID field and the Local
BCU-ID field.
[0036] A (G)MSC server node shall include one `session level`
attribute (a=3gMGWid) set to the MGW identity of the seized MGW.
Alternatively one or more (a=3gMGWid) attributes for each offered
MGW may be offered.
[0037] In the following, a short example thereof is presented:
Example
[0038] a=3gMGWid: 0x07 0xA6 0xD2 0x35
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] In the accompanying drawings, preferred embodiment of the
invention and preferred methods of practicing the invention are
illustrated in which:
[0040] FIG. 1 shows an exemplary 3GPP Layered Architecture.
[0041] FIG. 2 shows an exemplary deferred MGW Selection.
[0042] FIG. 3 shows an exemplary optimised MGW Selection.
[0043] FIG. 4 shows an exemplary signal flow when MGW and user
plane bearer termination is seized according to one embodiment of
the invention.
[0044] FIG. 5 shows an exemplary signal flow when one or more
offered MGW(s) exist according to one embodiment of the
invention.
[0045] FIG. 6 shows an exemplary signal flow when there is no
indication of a selected MGW according to one embodiment of the
invention.
[0046] FIG. 7 is a block diagram of a call control unit of the
invention.
DETAILED DESCRIPTION
[0047] Referring now to the drawings wherein like reference
numerals refer to similar or identical parts throughout the several
views, and more specifically to FIG. 7 thereof, there is shown a
call control unit 10 of a network. The call control unit 10
comprises an input/output unit 100. The call control unit 10
comprises a processing unit 300 in communication with the
input/output unit 100. The call control unit 10 comprises a memory
unit 400 in communication with the processing unit 300. The
processing unit 300 produces a signal having information which
identifies a seized Media Gateway (MGW) related to a call
establishment or one or more offered Media Gateways related to a
call establishment, which is sent via Session Initiation Protocol
(SIP) to a terminating Mobile Switching Centre (MSC)-Server in the
network.
[0048] Preferably, the information in the signal is contained in an
a-Parameter of a Session Description Protocol (SDP) message. The
processing unit 300 preferably includes one session level attribute
set to an MGW identity of the seized MGW, or one or more session
level attributes each one set to an offered MGW within an SDP offer
encapsulated in an initial invite request.
[0049] Preferably, the processing unit 300 selects the MGW using
the session level attribute included within an SDP answer in a
first response to the invite request. The processing unit 300
preferably uses a session level a=inactive attribute in the SDP
offer included in the initial invite request to indicate a user
plane is not connected. Preferably, the MGW identity includes an
octet string. The call control unit 10 can be, for example, an MSC
server, as more fully described below.
[0050] The present invention pertains to a computer readable medium
storing a computer program which, when executed by at least one
processing unit 300, signals a media gateway (MGW) identity. The
computer program comprises instructions for the processing unit 300
generated steps of identifying a seized MGW or one or more offered
Media Gateways. There is the step of sending a signal via Session
Initiation Protocol (SIP) having information which identifies the
seized MGW or one of more of the offered Media Gateways.
[0051] Preferably, the sending step includes the step of sending
the information contained in an a-Parameter of a Session
Description Protocol (SDP) message. There can be the step of
including one session level attribute set to an MGW identity of the
seized MGW, or one or more session level attributes each one set to
an offered MGW within an SDP offer encapsulated in an initial
invite request. Preferably, there is the step of selecting the MGW
using the session level attribute included within an SDP answer in
a first response to the invite request. There is preferably the
step of using the session level a=inactive attribute in the SDP
offer included in the initial invite request to indicate a user
plane is not connected. Preferably, there is the step of seizing
the MGW. The MGW identity preferably includes an octet string.
[0052] The present invention pertains to a method in a
telecommunications node for signaling a Media Gateway (MGW)
Identity. The method comprises the steps of identifying a seized
MGW. There is the step of sending a signal via Session Initiation
Protocol (SIP) having information which identifies the seized
MGW.
[0053] Preferably, the identifying step includes the step of
identifying one or more offered Media Gateways; and the sending
step includes the step of sending the signal via SIP having
information which identifies one or more of the offered Media
Gateways. The sending step preferably includes the step of sending
the signal from a call control unit 10. Preferably, there is the
step of the call control unit 10 seizing the MGW.
[0054] In one embodiment, the sending step can include the step of
sending a P-Header with the information. In another embodiment, the
sending step can include the step of sending the information
contained in an o-Parameter of a Session Description Protocol (SDP)
message. In a preferred embodiment, the sending step can include
the step of sending the information contained in an a-Parameter of
a Session Description Protocol (SDP) message.
[0055] Preferably, there is the step of the call control unit 10
including one session level attribute set to an MGW identity of the
seized MGW, or one or more session level attributes each one set to
an offered MGW within an SDP offer encapsulated in an initial
invite request. There is preferably the step of the call control
unit 10 selecting the MGW using the session level attribute
included within an SDP answer in a first response to the invite
request. Preferably, there is the step of using the session level
a=inactive attribute in the SDP offer included in the initial
invite request by the call control unit 10 to indicate a user plane
is not connected. The MGW identity preferably includes an octet
string.
[0056] As previously indicated, three embodiments to carry
MGW-Id(s) are considered; where in the following the (G)MSC server
is associated to the use of SIP UAC/UAS (User Agent Client/User
Agent Server) terminology. Although the embodiments are addressed
separately, there may exist also combinations thereof which might
provide further advantages, such as being able to provide MGw list,
prioritization of MediaGateways, etc.
[0057] With respect to the first embodiment, the behavior of the
UAC and the UAS is highlighted in the following.
[0058] UAC Behavior:
[0059] A (G)MSC server may include a P-MGW-ID header within the
initial INVITE request encapsulating an SDP offer. The P-MGW-ID
header either includes the identity of the seized MGW or the
identity of one or more offered MGWs.
[0060] To select a MGW, (G)MSC server may use the MGW identity
within a P-MGW-ID header optionally included in the first reliable
response that encapsulates the SDP answer.
[0061] UAS Behavior:
[0062] A (G)MSC server that receives P-MGW-ID header including one
or more MGW identities within the initial INVITE request
encapsulating an SDP offer may use the P-MGW-ID header to select a
local MGW.
[0063] A MSC server may include the identity of the locally seized
MGW in a P-MGW-ID header within the first reliable response that
encapsulates the SDP answer.
[0064] Therefore, a corresponding header syntax is proposed:
[0065] P-MGW-ID Header Syntax:
P-MGW-ID="P-MGW-ID" HCOLON
[0066] p-mgw-id-spec*(COMMA p-mgw-id-spec)
p-mgw-id-spec=host/mgwid-param mgwid-param=*OCTET/token
TABLE-US-00001 Table of the new P-MGW-ID header: Header field where
proxy ACK BYE CAN INV OPT REG P-MGW-ID R -- -- -- .smallcircle. --
P-MGW-ID 18x -- -- -- .smallcircle. -- -- P-MGW-ID 2xx -- -- --
.smallcircle. -- -- Header field SUB NOT PRA INF UPD MSG REF
P-MGW-ID -- -- -- -- -- -- --
[0067] With respect to the second embodiment, using the o=line, the
behavior of the UAC and the UAS is highlighted in the
following.
[0068] The existing origin ("o=") line in SDP is defined in RFC
4566 as:
o=<username><sess-id><sess-version><nettype><a-
ddrtype><unicast-address> where the
<unicast-address> is the address of the machine from which
the session was created.
[0069] For an address type of IP version 4 (IPv4), this is either
the fully qualified domain name of the machine or the
dotted-decimal representation of the IPv4 address of the machine.
For an address type of IP version 6 (IPv6), this is either the
fully qualified domain name of the machine or the compressed
textual representation of the IPv6 address of the machine. For both
IPv4 and IPv6, the fully qualified domain name is the form that
SHOULD be given unless this is unavailable, in which case the
globally unique address MAY be substituted. It is best not to use a
local IP address in any context where the SDP description might
leave the scope in which the address is meaningful (for example, a
local address MUST NOT be included in an application-level referral
that might leave the scope).
[0070] UAC Behavior:
[0071] A (G)MSC server shall set the <unicast-address> of the
origin ("o=") line to the MGW identity of the seized/offered MGW or
to reserved string indicating that no MGW identity is provided.
[0072] To select a MGW, a (G)MSC server may use
<unicast-address> of the origin ("o=") within the SDP answer
in the first reliable response to INVITE.
[0073] UAS Behavior:
[0074] A MSC server may use the <unicast-address> of the
origin ("o=") line within the SDP offer encapsulated in the initial
INVITE request, to select a MGW.
[0075] A MSC server node shall set the <unicast-address> of
the origin ("o=") line to either the MGW identity of the seized MGW
within the SDP answer of the first reliable response to INVITE.
[0076] With respect to the third embodiment, using the a= line, the
behavior of the UAC and the UAS is highlighted in the
following.
[0077] UAC Behavior:
[0078] A (G)MSC server shall either include one `session level`
attribute (a=3gMGWid) set to the MGW identity of the seized MGW, or
one or more `session level` attributes (a=3gmgwid) each one set to
an offered MGW within the SDP offer encapsulated in the initial
INVITE request.
[0079] To select a MGW a (G)MSC server may use the `session level`
attribute (a=3gMGWid) optionally included within the SDP answer in
the first reliable response to INVITE.
[0080] UAS Behavior:
[0081] A MSC server that receives one or more `session level`
attributes (a=3gMGWid), may use this parameter to select a MGW.
[0082] A MSC server may include one `session level` attribute
(a=3gMGWid) set to the MGW identity of the seized MGW within the
SDP answer of the first reliable response to INVITE.
[0083] In the following, exemplary signal flows will be explained
with respect to the above mentioned embodiments.
[0084] The procedures specified below are based on the capability
to indicate one or more MGW identities in SIP as for one of the
embodiments.
[0085] Moreover there is also foreseen the need for the originator
of the initial INVITE request to indicate to the receiver of the
INVITE whether the user-plane is connected.
[0086] For this purpose, the session level a=inactive attribute is
used in the SDP offer included in the initial INVITE request. The
use of the a=inactive is considered the most appropriate manner to
indicate user-plane is connected, though other means may be
used.
[0087] To offer the possibility for deferred MGW selection, at
least the following combinations are possible for the originating
MSC server:
[0088] 1. MGW seized and termination within the MGW seized, where
the MGW-ID is included in the initial INVITE. With this case
deferred MGW selection is not used. This allows optimised MGW
selection i.e. the succeeding node may connect to this MGW.
[0089] 2. One or more MGW(s) are offered, where the MGW-ID(s)
is/are included in the initial INVITE. No user plane bearer Mb
termination is seized within the MGW.
[0090] Additionally the session level a=inactive in the SDP offer
and the connection address in the SDP offer is set to a
preconfigured value not associated to a termination in MGW.
[0091] 3. No MGW is selected or indicated in the initial INVITE,
where no user plane bearer Mb-termination is seized. Additionally
the session level a=inactive in the SDP offer and the connection
address in the SDP offer is set to a preconfigured value not
associated to a termination in MGW.
[0092] These examples for the originating traffic are further shown
in the call-flows according to FIGS. 4 to 6, where SIP
preconditions are not shown to simplify the signaling.
[0093] In the first signal flow shown in FIG. 4, the MGW and User
Plane Bearer termination is seized as is explained in further
detail.
[0094] First, an originating MSC-Server (O-MSC-S) seizes a
termination within an originating MediaGateway (O-MGW) in step 1.
Thereafter, the O-MSC-S sends in step 2 an INVITE with an SDP Offer
and includes the identity of O-MGW. For embodiments 2 and 3
described in this application, the identity of O-MGW will be
embedded in the SDP Offer. Then, the Terminating MSC-Server
(T-MSC-S) receives the identity of the O-MGW and may use it, in
step 3, for selecting an optimal terminating MediaGateway
(T-MGW).
[0095] Thereafter, and with respect to steps [4]-[10] the signaling
continues as per normal SIP session establishment.
[0096] In the second signal flow shown in FIG. 5 it is assumed that
one or more offered MGW(s) exist and no User Plane Bearer
termination is seized. First, an O-MSC-S does not seize a MGW
before sending the INVITE. Instead it includes one or a list of MGW
identities in step 1. Since O-MSC-S has not seized a MGW, it
indicates that no user plane termination is available for payload
setting the a=inactive session attribute. Thereafter, in a second
step, a T-MSC-S receives one or a list of MGW identities and from
the presence of a=inactive attribute the T-MSC-S understands that
O-MSC-S has not seized a MGW. T-MSC-S can use it for selecting an
optimal T-MGW. In a third step, due to received a=inactive
attribute T-MSC-S returns the identity of T-MGW in the first
reliable response containing the SDP answer. This is followed by a
fourth step where the O-MSC-S receives the identity of T-MGW and
can use it for selecting the same MGW. Now, in a fifth step, the
O-MSC-S modifies in step 6 the attribute depending on
through-connection handling.
[0097] Thereafter, and with respect to steps [7]-[9] the signaling
continues as per normal SIP session establishment.
[0098] This scenario applies also to the case where O-MSC-S selects
a MGW without selecting a termination within the MGW.
[0099] In the third signal flow shown in FIG. 6 it is assumed that
no indication of a selected MGW is given and that no User Plane
Bearer termination is seized.
[0100] This signal flow shown in FIG. 6 is similar to the Signal
Flow shown in FIG. 5 with the difference that O-MSC-S does not
include any MGW identities in INVITE and sets the a=inactive
session attribute to inform T-MSC-S that it has not selected a MGW.
T-MSC-S will return its selected MGW in order to allow O-MSC-S to
select the same MGW.
[0101] The above described embodiments offer several advantages
which will be described in further detail below.
[0102] The techniques described herein offer at least the same
functional level for MGW optimization within 3GPP PLMN; as done by
BICC today; namely:
[0103] 1. to indicate in a SIP-I network when signaling a forward
direction if a MGW has been selected and identify the selected MGW
so that the succeeding node has the possibility to connect to the
same MGW;
[0104] 2. to return the identity of the selected MGW in a SIP-I
network when signaling in the backward direction to permit the
preceding node to connect to the same MGW.
[0105] 3. The mechanism to negotiate the optimal MGW for a given
call from a list of MGWs; this is a further advantage over what is
possible today with BICC or other call control protocols used by a
3GPP PLMN.
[0106] 4. The mechanism to indicate if the user plane connection is
seized at the time of signaling forward the initial offer, thus
permitting the sender to defer configuring its associated bearer
resources at the time of the offer and configure them when
receiving a complete answer with associated bearer termination
properties.
[0107] Hence, a MSC-S is therefore provided with one or more
Input/Output Unit(s) (I/O) 100 as shown exemplary in FIG. 7 for
receiving and sending messages towards Media Gateways and other
Call Control Nodes such as a terminating MSC-S and with a
processing unit (PU) 300 for evaluating SIP messages as defined
above. Said means are further arranged for selecting a MediaGateway
accordingly. Furthermore, said MSC-S may further comprises a
storage unit (MU) 400 for storing values for later-on reuse, e.g.
selecting, as defined in the methods above. An I/O unit (I/O) could
be embodied by any kind of Network Interface Card or unit, while
the Processing Unit (PU) 300 could be any kind of a processor
including a Digital Signal Processor (DSP) or controller or may
even be embodied in an ASIC or a FPGA Furthermore, the storage unit
(MU) may be embodied in different kind of memory either as a
electronic memory such as RAM, EPROM, EEPROM, or storage device
such as any kind of optical or magnetic storage medium.
[0108] All the methods as presented above may be embodied in
hardware, software enabled hardware and software offering the
corresponding program logic itself when run on a corresponding
programmable device, either in part or as a whole.
[0109] Abbreviations
[0110] BCU-ID--Bearer Control Unit Identifier
[0111] BICC--Bearer Independent Call Control
[0112] GMSC--Gateway Mobile Switching Centre
[0113] IPBCP--IP Bearer Control Protocol
[0114] MGW--Media Gateway
[0115] MSC--Mobile Switching Centre
[0116] SDP-A--SDP Answer
[0117] SDP-O--SDP Offer
[0118] SIP-I--Session Initiation Protocol (ISUP)
[0119] UAC--User Agent Client
[0120] UAS--User Agent Server
[0121] Although the invention has been described in detail in the
foregoing embodiments for the purpose of illustration, it is to be
understood that such detail is solely for that purpose and that
variations can be made therein by those skilled in the art without
departing from the spirit and scope of the invention except as it
may be described by the following claims.
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