Ribbon recommends using the Transparency Profile to configure transparency on the SBC Core Core for new deployments, as well as applying additional transparency configurations to existing deployments. Do not use IP Signaling Profile flags in these scenarios because the flags will be retired in upcoming releases.
Refer to the SBC SIP Transparency Implementation Guide for additional information.
The instructions, commands and references in this document apply to the SBC Core (SBC 5000 series, SBC 7000, SBC 5400, and SBC Software Edition Ribbon).
This document does not apply to SBC Edge (SBC 1000 and 2000 systems).
This document provides configuration and provisioning guidance to enable SIP transparency on SBC Core systems. In addition to the configuration examples on the Session Border Controller (SBC), this document provides an introduction to key topics related to SIP headers and bodies on the SBC Core platform.
This document is intended for design engineers, system engineers and operations staff for the purpose of deploying SIP on a SBC Core system. Although this document provides some background on the concepts involved, the reader is expected to have a basic understanding of SIP.
Ribbon Technical Support can be obtained using the following methods:
For some SIP elements, transparency is a frequently-debated topic. When transparency for a SIP header or body is desired, the user may often compare the element against a SIP Proxy which is a typical benchmark for significant transparency. Considered a popular comparison, this topic needs to addressed up front when discussing SIP transparency.
The SIP devices that connect most peers and endpoints are typically a SIP Proxy or Back-to-Back User Agent (B2BUA). The most transparent device is the SIP Proxy; its behaviors are primarily specified in RFC 3261 and are very basic in its message processing capabilities. The required transparency of a Proxy is one of its few strengths when compared to a B2BUA.
SIP Transparency Spectrum
Although an SBC is not defined in any IETF standard, it is most closely associated functionally with a SIP B2BUA (RFC 5853, 7092). Unless otherwise specified, this document will use B2BUA and SBC terms interchangeably.
While RFC 3261 goes into detail describing the required behavior of a SIP Proxy, its description for a B2BUA could be considered somewhat terse: "Since it is a concatenation of a UAC [User Agent Client] and UAS [User Agent Server], no explicit definitions are needed for its behavior." This statement notwithstanding, debate and research into the transparency behavior of a B2BUA continued, but seemingly without consensus. An often referenced IETF draft (draft-marjou-sipping-01) submitted to the SIPPING WG was not accepted as a working group document.
Admittedly, complete SIP transparency is not achievable due to the needs and requirements of changing some headers. Even a SIP Proxy is not completely transparent. In many scenarios the ability to control and even minimize transparency is a strength of a B2BUA/SBC. Some key selling points of an SBC highlight its ability to not be transparent:
Fundamentally, the Ribbon SBC behaves as a SIP Back-to-Back User Agent (B2BUA) and not as a SIP Proxy. (If SIP Proxy behavior is actually needed then use of the Ribbon PSX Policy Server should be considered as it can be deployed specifically as a SIP Proxy or Redirector.) Unlike a standard SIP Proxy, the Ribbon SBC can provide a wide spectrum of SIP message transparency, from fairly transparent to almost completely non-transparent.
This document describes the SBC SIP transparency controls, how they behave, and how they interact. Some configuration examples using these transparency controls is also provided.
Since its inception, the SBC includes two related types of control flags: Relay Flags and Transparency Flags. Relay Flags primarily control SIP at the Request and Response level and are discussed later in a separate section. Transparency Flags control SIP headers and bodies that are generally not modified when received in a SIP message. While these controls are related, there is no direct overlap or precedence between them.
SIP Message Flow
Prior to release 4.0, SIP header and body transparency was controlled primarily by the use of individual Transparency Flags, mostly within the IP Signaling Profile (IPSP; ipSignalingProfile > commonIpAttributes > transparencyFlags) and apply on the egress leg of a session (egress relative to the SIP message).
Maximum of 144 unique unknown headers can be configured across all Header Transparency Profiles.
IP Signaling Profile Transparency Flags
acceptContactHeader | pVisitedNetworkIDHeader |
acceptHeader | qsigBody |
acceptLanguageHeader | reasonHeader |
alertInformationHeader | referredByHeader |
authcodeHeaders | requestURI |
callInfoHeader | resourceListBody |
contactHeader | resourcePriorityOptionTag |
errorInfo | rlmiBody |
externalBody | routeHeader |
fromHeader | serverHeader |
geolocation | serviceRouteHeader |
geolocationError | simpleFilterBody |
geolocationRouting | sipBody |
historyInfo | sipfragBody |
maxForwardsHeader | toHeader |
mwiBody | toneBody |
pAccessNetworkInfoHeader | unknownBody |
passCompleteContactHeader | unknownHeader |
pathHeader | userAgentHeader |
pCalledPartyID | userToUserHeader |
pChargingVectorHeader | viaHeader |
pEarlyMedia | warningHeader |
pidfBody | watcherInfoBody |
pidfDiffBody |
The message bodies are described in blue cells.
If a header or body did not have a specific flag on the SBC, it was treated as unknown, which meant it, along with any other SBC-unknown header, was controlled by the single unknownHeader flag (or unknownBody).
When a transparency flag was added for a header, it meant that the header was now known and that the unknownHeader flag no longer controlled it.
This methodology was problematic as headers transitioned from unknown to known on the SBC. It also meant that the unknownHeader flag was a very coarse control as it would allow any header that was unknown to the SBC.
The SBC introduced a more robust future-proofing mechanism in release 4.0 called the Transparency Profile. Ribbon SBC version 4.2 extends the Transparency Profile with similar support for SIP message bodies and the flexible ability to explicitly exclude some headers and/or methods.
A Transparency Profile is a user-configurable profile allowing the user to transparently pass almost any SIP header/body through the SBC. It is no longer necessary for a user to request SBC to create a specific Transparency Flag for the desired header/body. Both already-known and previously-unknown SIP headers and bodies can be configured in a Transparency Profile. By default, no headers or message bodies are present in a Transparency Profile. If a received Content-Type header value matches any “Message Body” entry configured in the Transparency Profile, the SBC transparently passes the corresponding message body in the outgoing message. The SBC supports configuring up to 256 Transparency Profiles. The following functionality is included:
When configuring a Transparency Profile for specific SIP headers, Ribbon recommends that the unknownHeader flag be disabled (similarly, when configuring a Transparency Profile for specific SIP message bodies, Ribbon recommends that the unknownBody flag be disabled).
The following transparency is not supported by the SBC:
endToEndAck
flag is enabled in the "IP Signaling Profile".For configuration details, see Service Profiles - Transparency Profile (EMA) or Transparency Profile - CLI.
The SBC introduced the Transparency Profile in release 4.0 to configure one or more SIP headers in a single profile to be passed transparently through. Release 4.2 extended the abilities of the Transparency Profile further. It now supported transparency for out-of-dialog messages, the ability to exclude specific headers from transparency and the ability to configure transparency on a per-method basis (e.g. INVITE, REGISTER, SUBSCRIBE, REFER, etc...), where specific methods can be excluded from transparency for that header. If no methods are specified to be excluded, then the configured header will be transparent for all methods.
set profiles services transparencyProfile <profile> sipHeader <SIP Header>
where <SIP Header>
is case insensitive, supports up to 31 characters, and supports an "all" entry to match all headers (see section 3.3 for exceptions).
The ability to exclude specific headers from transparency is primarily intended for use in conjunction with the "all" header option.
SIP headers are also configurable using compact form. When configuring specific headers in a Transparency Profile, Ribbon recommends the configuration of both compact and long forms.
Compact form can be received by the SBC, but the Ribbon SBC never generates the Compact form of any headers.
The Ribbon SBC does not send multiple header instances as a comma separated list; they are always sent as separate headers.
The following SIP headers are not controlled by the Transparency Profile (or any Transparency Flags), and are ignored if configured in a Transparency Profile:
RAck
P-Associated-URI
The transparency of Allow, Supported, and Require headers can be controlled by using SIP Param Filter Profile. For more information, refer to SIP Param Filter Profile.
If Contact Header is specified in a Transparency Profile, then it is treated as full Contact transparency and it will take precedence over other Contact related flags (such as useZoneLevelDomainNameInContact).
Ribbon SBC version 4.2 extends the Transparency Profile with similar support for SIP message bodies. In addition, both message header and body transparency is configurable on a per-method basis (e.g. INVITE, REGISTER, SUBSCRIBE, REFER, etc...), where specific methods can be excluded from transparency for that body. If no methods are specified to be excluded, then the configured body is transparent for all methods.
set profiles services transparencyProfile <profile> sipMessageBody <Content-Type>
where <Content-Type>
is case insensitive, supports up to 127 characters, and supports an "all" entry to match all message bodies except those described in the below list.
The following Content-Types are not controlled by the Transparency Profile and are ignored if configured in a profile:
Multipart/mixed and multipart/alternative are ignored because the SBC automatically matches each component message body contained within a multipart message independently. For example, if "application/qsig" is configured in a profile, the SBC will match it even if it is contained within a multipart/mixed message with no additional configuration needed.
A Transparency Profile cannot control the SDP (application/sdp). The SDP and its controls will be discussed later in this document.
The other exceptions are due to existing Relay Flags (see table below) elsewhere within the SBC.
Relay Flags That Control SIP Message Bodies
Relay Flag | Configuration Location | Content Applicability |
---|---|---|
dtmfBody | IP Signaling Profile | application/dtmf and application/dtmf-relay |
sonusMediaBody | IP Signaling Profile | application/sonus-media |
thirdPartyBodies | IP Signaling Profile | application/broadsoft |
isupMimeBodyRelay | SIP Trunk Group | application/isup |
conferenceEventPackage | IP Signaling Profile | application/conference-info+xml |
dialogEventPackage | IP Signaling Profile | application/dialog-info+xml |
See Relay Flags below for details.
SIP Transparency Profile provides advanced control of the transparency of headers and message bodies. However, customers may continue with the existing (albeit simple) IPSP transparency controls in PSX/e-PSX/ERE.
Using message body transparency as an example:
Header transparency is based on the headers that are present in the Transparency Profile of the egress trunk group for requests and headers that are present in the ingress trunk group for responses. By default, no headers are present in the Transparency Profile.
Headers may be configured in compact form and transparently passed using a Transparency Profile. It is advisable to configure both compact and long formats to ensure both types of received headers in the PDU are transparently passed.
A 'sipHeader' in the Transparency Profile can be composed of:
Some headers are not under the control of transparency flags in relay scenarios. These headers can be classified into three categories as shown in the below table:
SIP Headers not Under Control of Transparency Flags in Relay Scenarios
Header Classifications | ||
---|---|---|
Transparently sent irrespective of transparency settings | Added/modified by the SBC | Not sent at all |
Accept-Language | Also | Allow |
Alert-Info | Anonymity | Max-Forwards |
Authorization | Diversion | Require |
Content-Length | Path | Supported |
Error-Info | P-Charge-Info | RAck |
Event | P-DCS-Billing-Info | P-Associated-URI |
Expires | P-K-Cfl | |
Min-Expires | P-K-Cfo | |
Min-SE | P-Preferred-Identity | |
Proxy-Authenticate | P-Sig-Info | |
Proxy-Authorization | Record-Route | |
Proxy-Require | Remote-Party-ID | |
RAck | Reply-To | |
Reason | Requested-By | |
Refer-Sub | Service-Route | |
Resource-Priority | ||
Retry-After | ||
RSeq | ||
Session-Expires | ||
Subscription-State | ||
Warning | ||
WWW-Authenticate |
The following SIP headers are not supported by a Transparency Profile (or any Transparency flags):
RAck
These SIP headers are entirely added and/or modified by the SBC itself and cannot be transparently passed.
Previously, the following headers were transparently passed by the SBC. From release 4.2 onwards, these headers are controlled using transparency flags.
SBC transparency mechanisms control the initial INVITE, its responses, and other requests/responses within the INVITE dialog, as well as REGISTER, BYE, UPDATE, REFER, INFO, PUBLISH, MESSAGE, OPTIONS, SUBSCRIBE, NOTIFY requests and their responses (this assumes that the request method has been allowed by the applicable Relay Flag: INFO, MESSAGE, etc…).
There are some exceptions to the transparency mechanisms. Some SIP Methods and some SIP headers are not affected by any configurable transparency mechanism, while other headers may not be affected by transparency controls in some scenarios (in-dialog vs. out-of-dialog).
Option tags/methods of the following SIP headers can be transparently passed or blocked by configuring the SIP Param Filter Profile.
For configuration details, see:
Some header behaviors vary depending on whether they are received in or out of an existing dialog. While the Transparency Profile has been extended in 4.2 to apply to out-of-dialog messages, there are some specific headers whose behavior is not under the control of a Transparency Profile (or Transparency Flags) when received in out-of-dialog messages.
A Dialog "represents a peer-to-peer SIP relationship between two user agents that persists for some time. The dialog facilitates sequencing of messages between the user agents and proper routing of requests between both of them. The dialog represents a context in which to interpret SIP messages." (reference: RFC 3261)
The SBC can receive messages within a dialog or outside of a dialog, and treats them differently based upon that relationship (or lack thereof).
If "Session-Expires" header is configured, the SBC passes the "Min-SE" header and their values transparently to the egress remote peer. This behavior is achieved either by configuring “all” header or “Session-Expires” and “Min-SE” header in the Transparency Profile. The Keep-Alive behavior must be disabled by setting “Session-Expires” to “0” in the respective SIP Trunk Group.
For example,
set profiles services transparencyProfile ALL_HEADER sipHeader all set profiles services transparencyProfile SIP_HEADER sipHeader Session-Expires ignoreTransparency no set profiles services transparencyProfile SIP_HEADER sipHeader Min-SE ignoreTransparency no set addressContext default zone Zone1 sipTrunkGroup TG1 signaling timers sessionKeepalive 0
If "all" header in Transparency Profile is configured and SBC supports "Session Keep Alive" mechanism, the "Session-Expiry" and "Min-SE" headers are excluded from the Transparency Profile by setting ignoreTransparency
as “yes”.
For example,
set profiles services transparencyProfile ALL_HEADER sipHeader all set profiles services transparencyProfile ALL_HEADER sipHeader Session-Expires ignoreTransparency yes set profiles services transparencyProfile ALL_HEADER sipHeader Min-SE ignoreTransparency yes
Out-of-Dialog header behavior irrespective of the Transparency Profile or Flags:
Out-of-Dialog SIP Header Behavior
SIP Header | Out-of-Dialog Behavior |
---|---|
Accept-Language | Sent |
Alert-Info | Sent |
Also | Dropped |
Anonymity | Dropped |
Authorization | Sent |
Content-Length | Sent |
Diversion | Dropped |
Error-Info | Sent |
Event | Sent |
Expires | Sent |
Min-Expires | Sent |
Min-SE | Sent |
P-Charge-Info | Dropped |
P-DCS-Billing-Info | Dropped |
P-K-Cfl | Dropped |
P-K-Cfo | Dropped |
P-Preferred-Identity | Dropped |
P-Sig-Info | Dropped |
Path | Dropped |
Proxy-Authenticate | Sent |
Proxy-Authorization | Sent |
Proxy-Require | Sent |
RAck | Sent |
Reason | Sent |
Record-Route | Dropped |
Refer-Sub | Sent |
Remote-Party-ID | Dropped |
Reply-To | Dropped |
Requested-By | Dropped |
Resource-Priority | Sent |
Retry-After | Sent |
RSeq | Sent |
Service-Route | Dropped |
Session-Expires | Sent |
Subscription-State | Sent |
Warning | Sent |
WWW-Authenticate | Sent |
Message body transparency is based on message bodies that are present in the Transparency Profile of the egress trunk group for requests and content-types/bodies that are present in the ingress trunk group for responses. By default, no message bodies are present in the Transparency Profile.
The allowed range for a "contentType" in the Transparency Profile includes:
The SBC treats constituent parts of a 'multipart/mixed' message body just as it treats any message with a single body. Therefore, a constituent part of a 'multipart/mixed' message body will be transparently passed through only if the Content-Type specified in the MIME envelope of the corresponding part has been configured in the Transparency Profile.
For example, consider a SIP message with content-type 'multipart/mixed' with two parts in its body: the first part is type 'application/foo' and the other type 'application/bar'. If the Transparency Profile is configured to transparently pass 'application/foo', then the first part of the message body is passed transparently in the egress SIP message.
This feature will be supported across Ribbon Gateways (using Ribbon Proprietary GW to GW Signalling) only for SIP INVITE messages.
he SBC supports anchoring the following media types:
For all the above mentioned media types (with the exception of Audio), the SBC consumes (hence does not transparently relay) the following attributes that are required to anchor the media:
SBC supports Secure Real-Time Transport Protocol (SRTP) media pass-through for SRTP and Secure Real-Time Transport Control Protocol (SRTCP) media streams.
For Audio, the SBC does not transparently relay the ptime and maxptime attributes in addition to the above mentioned attributes.
You must enable Video (assign a valid video bandwidth) and Audio transparency to achieve the above described behavior using the below CLI syntax.
Associate the following configuration with both Trunk Groups.
set profiles media packetServiceProfile <packetServiceProfileName> packetToPacketControl transcode transcoderFreeTransparency set addressContext <addressContextName> zone <zoneName> sipTrunkGroup <trunkGroupName> media sdpAttributesSelectiveRelay enabled set addressContext <addressContextName> zone <zoneName> sipTrunkGroup <trunkGroupName> media lateMediaSupport passthru
Make note that the sdpTransparencyState
signaling object within the SIP Trunk Group must not be considered a general use parameter. It is specific to some functionality (mainly ICE) and environments; however, this flag does not apply to all types of call flows.
Do not enable the sdpTransparencyState
flag unless specifically directed to do so by Ribbon Design or Support engineers.
The SBC for the audio m line allows relaying unknown attributes. The SBC allows transparency for subset of the attributes like rtpmap
, fmtp
, and T38
fax
. Audio transparency functionality is used to manage bandwidth for audio stream in the pass-through calls. By enabling this feature, audio codecs that are unknown to the system are available to establish audio calls or streams.
SBC supports audio transparency for known attributes by relaying attributes and codecs transparently in pass-through scenarios for SIP-SIP calls only. However, the following exceptions require system handling:
This feature does not support H323-H323 and GW-GW calls.
Audio Transparency Feature is controlled by two flags:
Bandwidth (b) lines are transparently relayed and do not play any role in calculating the unknown audio codec bandwidth. The following PSP configuration bits for Audio Transparency feature are included for Unknown audio bandwidth reservation to calculate the Unknown audio bandwidth:
unknownCodecBitRate
unknownCodecPacketSize
If the bandwidth is not configured, the default settings (Packet Size—10 ms and Bit Rate—124 KB/s) are used for a pass-through call.
By default for pass-through calls, SBC reserves the worst case common audio codec bandwidth on Trunk Groups and IP interfaces, and polices for the same bandwidth. To facilitate pass-through calls scenarios/cases, where media uses the preferred common codec the flag reserveBwForPreferredAudioCommonCodec
is added to reserve the bandwidth associated with the preferred common codec (instead of the worst case common codec) on the Trunk Groups and IP interfaces. When this flag is enabled, bandwidth of the first common codec from Answer (SIP) is used for reservation and bandwidth of the heaviest common codec is used for policer.
This flag can be used independently or in conjunction with Audio Transparency feature and/or policeOnHeaviestAudioCodec
flag. This functionality is currently supported for SIP-SIP call scenarios only. In the event that policeOnHeaviestAudioCodec
and reserveBwForPreferredAudioCommonCodec
are both configured, the following behavior applies:
reserveBwForPreferredAudioCommonCodec
impacts the bandwidth reservation policy. That is, first common codec from Answer (SIP) and,policeOnHeaviestAudioCodec
impacts the policer configuration. That is, heaviest codec in the offer or answer.The flag reserveBwForPreferredAudioCommonCodec
is active for a call when both the PSPs have this flag enabled. If this flag is disabled in any of the PSPs, the flag is not applied.
By default for pass-through calls, the SBC reserves the worst case common audio codec bandwidth on trunk groups and IP interfaces, and polices for the same bandwidth. To facilitate asymmetric pass-through calls scenarios/cases and to police on the heaviest codec in the offer or answer, the flag policeOnHeaviestAudioCodec
is used in the PSP.
This flag can be used independent of or in conjunction with Audio transparency feature and/or reserveBwForPreferredAudioCommonCodec
flag. This functionality is currently supported for SIP-SIP call scenarios only.
Configuring the basic audio transparency feature contains:
sdpAttributesSelectiveRelay
Parameter on Both Ingress and Egress Trunk GroupstranscoderFreeTransparency
Parameter on Packet Service ProfileEnabling the sdpAttributesSelectiveRelay
Parameter on Both Ingress and Egress Trunk Groups
set addressContext default zone ZONE1 sipTrunkGroup TG_SBX_INT media sdpAttributesSelectiveRelay enabled set addressContext default zone ZONE2 sipTrunkGroup TG_SBX_EXT media sdpAttributesSelectiveRelay enabled
Configuring the transcoderFreeTransparency
Parameter on Packet Service Profile
set profiles media packetServiceProfile PSP_INT packetToPacketControl transcode transcoderFreeTransparency set profiles media packetServiceProfile PSP_EXT packetToPacketControl transcode transcoderFreeTransparency
Configuring AudioTransparecy Parameter on Packet Service Profile
set profiles media packetServiceProfile PSP_INT audioTransparency unknownCodecBitRate 124 set profiles media packetServiceProfile PSP_EXT audioTransparency unknownCodecBitRate 124 set profiles media packetServiceProfile PSP_INT audioTransparency unknownCodecPacketSize 10 set profiles media packetServiceProfile PSP_EXT audioTransparency unknownCodecPacketSize 10 set profiles media packetServiceProfile PSP_INT flags reserveBwForPreferredAudioCommonCodec enable set profiles media packetServiceProfile PSP_EXT flags reserveBwForPreferredAudioCommonCodec enable
For configuring Bit Rate (kbps), Packet Size (ms) and Reserve BW For Preferred Audio Common Codec for pass-through calls flags on PSX, refer to PSX Documentation.
As discussed previously, the Transparency Profile does not deprecate any existing Transparency Flag. Those flags continue to function as designed. When a header/body is specified in a Transparency Profile, then the profile takes precedence over any applicable Transparency Flag. For headers/bodies not specified in a transparency profile, the setting of existing Transparency Flags continues to determine the transparency of that header.
When configuring a Transparency Profile for specific SIP headers, SBC recommends disabling the unknownHeader flag (similarly, when configuring a Transparency Profile for specific SIP message bodies, SBC recommends disabling the unknownBody flag).
There are three modes of using Transparency Profile:
In this mode, only headers/bodies explicitly configured in the Transparency Profile are allowed to pass-through.
For example, the following scenario allows only the headers "p-asserted-identity" and "xyzHdr" and message bodies of type "application/simple-message-summary" and "xyzContentType" to pass transparently.
set profiles services transparencyProfile ALLOW_SPECIFIC_HDRS_BODIES sipHeader p-asserted-identity set profiles services transparencyProfile ALLOW_SPECIFIC_HDRS_BODIES sipHeader xyzHdr set profiles services transparencyProfile ALLOW_SPECIFIC_HDRS_BODIES sipMessageBody application/simple-message-summary set profiles services transparencyProfile ALLOW_SPECIFIC_HDRS_BODIES sipMessageBody xyzContentType set profiles services transparencyProfile ALLOW_SPECIFIC_HDRS_BODIES state enabled commit
Complete or maximum transparency is occasionally desired, especially during initial integration testing to determine if specific headers are required for the success of certain call flows.
set profiles services transparencyProfile MAX_TRANSPARENCY sipHeader all set profiles services transparencyProfile MAX_TRANSPARENCY sipMessageBody all set profiles services transparencyProfile MAX_TRANSPARENCY state enabled commit set addressContext <AC> zone <ZONE> sipTrunkGroup <TG> services transparencyProfile MAX_TRANSPARENCY commit
Additional Relay Flags also need to be enabled to maximize the transparency of the Trunk Group for testing. See Relay Flags above.
All headers/bodies are allowed to pass-through unless they are explicitly disallowed by Transparency Profile configuration. The ignoreTransparency
header option within the Transparency Profile is primarily used for excluding one or more specific headers when paired with the "all" header option. In the example below, the user wishes to pass all SIP headers except for the History-Info header.
For example, in the following scenario, the rules are configured and all the headers and message bodies except "history-info" and "application/resource-lists+xml" are passed transparently. The "xyzHeader" is passed transparently in all methods except INFO and REGISTER. The "xyzContentType" is passed transparently in all methods except INVITE.
set profiles services transparencyProfile ALMOST_ALL_TRANSPARENCY sipHeader all set profiles services transparencyProfile ALMOST_ALL_TRANSPARENCY sipMessageBody all set profiles services transparencyProfile ALMOST_ALL_HDRS sipHeader history-info ignoreTransparency yes set profiles services transparencyProfile ALMOST_ALL_HDRS sipMessageBody application/resource-lists+xml ignoreTransparency yes set profiles services transparencyProfile ALMOST_ALL_HDRS sipHeader xyzHeader excludedMethods info,register set profiles services transparencyProfile ALMOST_ALL_HDRS sipMessageBody xyzContentType excludedMethods invite set profiles services transparencyProfile ALMOST_ALL_HDRS state enabled commit
The excludedMethods
parameter indicates the list of methods for which the transparency is not allowed and is common to both header and body entries.
set profiles services transparencyProfile TP1 sipHeader all set profiles services transparencyProfile TP1 sipHeader all excludedMethods bye,info,notify commit
If a specific header is configured, ignoreTransparency
and excludedMethods
are exclusive. Once ignoreTransparency
is configured, excludedMethods
no longer displays. Likewise, once excludedMethods
is configured, ignoreTransparency
no longer displays.
Use the ignoreTransparency
flag in a configuration to allow all SIP headers, or use it when one of the SIP header transparency flags is enabled in the IP Signaling Profile.
Existing deployments will likely utilize Transparency Flags, and those that must pass proprietary or otherwise SBC unsupported SIP headers will most likely make use of the unknownHeader transparency flag in an IP Signaling Profile.
While a Transparency Profile can be configured to completely overlap with any existing Transparency Flags settings, it is not required. A Transparency Profile can be configured to simply augment existing Transparency Flags settings with a more surgical configuration and allowing unknownHeader to be disabled.
For example, a user may wish to have the SBC transparently pass RFC 4474 identity headers. Prior to the introduction of the Transparency Profile, the user would have had to enable the unknownHeader transparency flag.
Rather than continue to allow all unknown headers through the SBC, the user can configure a Transparency Profile that only allows the RFC 4474 identity headers (configured in standard and compact forms) and disable the unknownHeader transparency flag.
set profiles services transparencyProfile IDENTITY_HDRS sipHeader Identity set profiles services transparencyProfile IDENTITY_HDRS sipHeader y set profiles services transparencyProfile IDENTITY_HDRS sipHeader Identity-Info set profiles services transparencyProfile IDENTITY_HDRS sipHeader n set profiles services transparencyProfile IDENTITY_HDRS state enabled commit set addressContext <AC> zone <ZONE> sipTrunkGroup <TG> services transparencyProfile IDENTITY_HDRS commit set profiles signaling ipSignalingProfile <IPSP> commonIpAttributes transparencyFlags unknownHeader disable commit
SBC supports SRTP media pass-through for SRTP and SRTCP media streams. SBC does not terminate the SDP security description or SRTP media streams and passes them through without authenticating, decrypting, and encrypting. In this pass-through mode of operation, SBC treats SRTP media as plain text RTP pass-through media.
The following diagram illustrates the media flow for an SRTP pass-through call.
SRTP Packet to Packet Media Call Flow
To control this SRTP media pass-through, the allowPassthru
flag is available from the secureRtpRtcp
parameter of the PSP. When allowPassthru
flag is enabled along with the security enableSrtp
flag, it allows SBC to pass-through SRTP media without authenticating, decrypting, and encrypting it internally. When selected, this flag prioritizes SRTP pass-through media over terminated SRTP media. When disabled, this flag terminates all SRTP and SRTCP media for authentication, encryption, or decryption. This flag is disabled by default.
Relay Flags exist mostly within the IP Signaling Profile (IPSP; ipSignalingProfile > commonIpAttributes > relayFlags) and apply on the ingress leg of a session (ingress relative to the SIP message).
Relay Flags are intended mainly for SIP Methods (Requests) and Responses (and some SIP message bodies) that normally get consumed or modified by the SBC when received in the incoming SIP message.
Albeit imprecise, a good method to contrast Relay Flags and Transparency Flags/Profiles is to consider that Relay controls whether a SIP request/response is sent through the SBC, while the Transparency controls whether a header/body in a SIP request/response is sent through the SBC.
Configuration Locations of Relay Flags
Relay Flags | Configuration Location |
---|---|
conferenceEventPackage | IP Signaling Profile > Common IP Attributes |
dialogEventPackage | IP Signaling Profile > Common IP Attributes |
dtmfBody | IP Signaling Profile > Common IP Attributes |
force503to500Relay | IP Signaling Profile > Common IP Attributes |
info | IP Signaling Profile > Common IP Attributes |
message | IP Signaling Profile > Common IP Attributes |
notify | IP Signaling Profile > Common IP Attributes |
options | IP Signaling Profile > Common IP Attributes |
publish | IP Signaling Profile > Common IP Attributes |
refer | IP Signaling Profile > Common IP Attributes |
referToHeaderRelay | IP Signaling Profile > Common IP Attributes |
regEventPackage | IP Signaling Profile > Common IP Attributes |
sonusMediaBody | IP Signaling Profile > Common IP Attributes |
statusCode3xx | IP Signaling Profile > Common IP Attributes |
statusCode4xx6xx | IP Signaling Profile > Common IP Attributes |
thirdPartyBodies | IP Signaling Profile > Common IP Attributes |
updateWithoutSdp | IP Signaling Profile > Common IP Attributes |
isupMimeBodyRelay | SIP Trunk Group > Signaling |
relayUpdatewithSdp | SIP Trunk Group > Signaling |
The SBC is enhanced to relay REFER request, even though the refer
relay flag is disabled. To support this enhancement, Conditional Relay Matching criteria is provided by the SBC. Using this criteria, SBC decides whether to relay and process the REFER request message or not.
If the refer
relay flag is disabled, the Call Control (CC) mechanism forwards the REFER request to Digital Signaling (DS). DS exchanges information with the PSX to check the match criteria set in Conditional Relay Matching.
Starting with SBC SWe release 8.1, the D-SBC supports REFER (without Replaces) in relay and local processing mode for audio pass-through calls.
The matched criteria includes call parameters such as Username, Directory Number (DN), or Fully Qualified Domain Name (FQDN).
If a REFER request is sent after a switchover and:
refer
relay flag is enabled, SBC relays REFER request.refer
relay flag is disabled and DN/username/FQDN match, SBC relays the REFER request.This feature is supported only for Blind/Unattended Transfer calls and not for Attended Transfer (refer with replaces) calls.
The following figure shows the enhanced REFER request processing call flow:
To configure this feature, perform the following steps:
Create SIP_MSG_TYPE_REFER call parameter filter profile (CPFP) in the PSX. Execute the following command to view the CPFP SIP_MSG_TYPE_REFER. This profile is already present in ERE.
For more information on creating CPFP, refer to PSX Documentation.
> show table profiles callParameterFilterProfile Description: Profile used for routing based on SIP message type. Possible completions: SIP_MSG_TYPE_INFO - SIP Message Type is Info SIP_MSG_TYPE_MESSAGE - SIP Message Type is Message SIP_MSG_TYPE_NOTIFY - SIP Message Type is Notify SIP_MSG_TYPE_REFER - SIP Message Type is Refer SIP_MSG_TYPE_REGISTER - SIP Message Type is Register SIP_MSG_TYPE_SUBSCRIBE - SIP Message Type is Subscribe none - seed data for provisioning support
All > Profiles > Call Parameter Filter Profile
Call Parameter Filter Profile List showing SIP_MSG_TYPE_REFER profile
A new script SONS_SIP_REFER_RELAY is seeded in both ERE and PSX.
Disable the Refer relay flag in IPSP.
set profiles signaling ipSignalingProfile DEFAULT_SIP commonIpAttributes relayFlags refer disable
Enable the Notify relay in Egress side on IPSP to relay REFER for DN/Username/FQDN match.
set profiles signaling ipSignalingProfile DEFAULT_SIP commonIpAttributes relayFlags notify enable
All > Profiles > Signaling > Ip Signaling Profile > Common Ip Attributes > Relay Flags
Notify and Refer relay flags
Create a new routing label with the script SONS_SIP_REFER_RELAY to trigger process refer request feature.
The routing label action must be set as script.
set global callRouting routingLabel <routing_label> script SONS_SIP_REFER_RELAY action script
All > Global > Call Routing > Routing Label
Creating a Routing Label
Routing Label screen
Configure a DN criteria in the standard route and attach the SIP_MSG_TYPE_REFER profile to the standard route by executing the following command:
set global callRouting route none Sonus_NULL Sonus_NULL standard <Matched_DN or FQDN> 1 all ALL SIP_MSG_TYPE_REFER Sonus_NULL routingLabel <routing_label>
For DN (Directory Number) or username
set global callRouting route none Sonus_NULL Sonus_NULL standard <Matched_DN or Username> 1 all ALL SIP_MSG_TYPE_REFER Sonus_NULL routingLabel <routing_label>
For FQDN with DN or username
The corresponding Sip domain group must be configured in SBC.
set global sipDomain <Matched_domain_name> set global callRouting route none Sonus_NULL Sonus_NULL standard <Matched_DN or Username> 1 all ALL SIP_MSG_TYPE_REFER <Matched_domain_name> routingLabel <routing_label>
All > Global > Call Routing > Route
Creating a Route
Route screen
Execute the following commands to view the call detail status and call media status.
show status global callDetailStatus or show status global callMediaStatus
The SBC is enhanced to support SIP Param Filter Profile to allow the operator to create a profile defining a set of SIP header tags and methods to transparently pass or block, and then assign that profile to a trunk group. The SIP headers configured in this profile for pass-through are transparently passed to the Egress trunk group if received in the Ingress SIP message.
The SIP Param Filter Profile includes the following characteristics:
The SIP Param Filter Profile Behavior table explains the SIP Param Filter Profile behavior when using the Allow, Supported and Require headers.
SIP Param Filter Profile Behavior
Header | SIP Param Filter Profile Processing |
---|---|
Allow | Ingress leg: The Allow header in the received message is processed after Ingress SIP Message Manipulation (SMM) processing but before any other SBC processing occurs.
Egress leg: The Allow header in the message to be egressed by SBC is processed after all SBC processing but before Egress SMM processing is performed.
|
Require/Supported | Ingress leg: The Require/Supported header in the received message is processed after Ingress SMM processing but before any other SBC processing occurs.
Egress leg: The Require/Supported header in the message to be egressed by SBC is processed after all SBC processing but before Egress SMM processing occurs.
If an option tag present in the received Ingress request is dropped due to Require transparency settings, and if |
The SIP Filter Profile is a collection of the configurable filter settings of individual SIP headers. Depending on the filter settings of each of the SIP headers in the SIP Filter Profile, the SBC either relays the SIP messages without parsing the header, or parses the headers of the messages.
For every SIP message associated with the ingress leg of the call, the SBC first checks the SIP Filter Profile for the filter setting of the SIP header. If the SIP Filter Profile indicates that a particular SIP header needs filtering, the SBC stores it without parsing.
The SIP header of the egress leg is populated on the basis of the configuration in the IP Signaling Profile and the Transparency Profile. In the egress leg of a call, the transparency bit mask is set to identify the headers that are transparently passed. If the transparency settings of all unknown headers in the IP Signaling Profile is enabled, all the stored headers (including the ones filtered in the ingress leg), is copied to the SIP header of the egress leg.
If the Transparency Profile attached with the Egress Trunk Group indicates that specific headers are allowed to pass transparently, and those headers are present as filtered headers, they are individually copied to the SIP header of the egress leg. In this case, the transparency bits are enabled, either by the IP Signaling Profile or through the flexible header transparency.
The SIP Filter Profile is not used for the egress leg of a call.
The mandatory headers which are not part of the sipFilterProfie
are as follows:
From
To
Via
Call-id
Cseq
Max-Forwards
Avoid filtering headers pertaining to SIP call routing/protocol processing, as it may cause unexpected results such as call failures. Some of the headers that should not be filtered are as follows:
Contact
RSeq
RAck
Record-Route
Route
Content-Type
Content-Length
WWW-Authenticate
Perform the following:
Creating a new SIP Filter Profile
set profiles signaling sipFilterProfile doc_FILTER2
Changing the Transparency Setting of a Header Under a SIP Filter Profile
set profiles signaling sipFilterProfile doc_FILTER2 header Also enabled
If sipFilterProfile
is used for Allow
, Require
, and Supported
headers, their transparency cannot be achieved using sipParamFilterProfile
.
Configuring the Zone ID for the Selected Zone
set addressContext default zone doc_ZONE_IAD id 10
Configuring the Media IP Interface Group Name for the SIP Trunk Group
set addressContext default zone doc_ZONE_IAD sipTrunkGroup doc_SBX10_IAD media mediaIpInterfaceGroupName LIF1
set addressContext default zone doc_ZONE_IAD sipTrunkGroup doc_SBX10_IAD signaling sipFilterProfile doc_FILTER2
disabled
. To filter a particular SIP header, change the setting to enabled
.disabled
, the SBC transparently relays the SIP messages containing that header in the following cases:enabled
in the IP Signaling Profile.A new flag anonymizeHostIpAddress
is introduced for the privacy
parameter of the IP Signaling Profile to enable or disable this feature. When this flag is activated, the SBC anonymizes the incoming host IP portion of the private headers (P-AID, P-PID, RPID) by replacing it with the IP address of the SBC, before sending it to the egress leg of a call.
This feature supports anonymizing the host IP address for the following message types:
This feature currently supports only in-dialog messages, and not out-of-dialog messages.
anonymizeHostIpAddress
is available for configuration only when the transparency
flag is enabled for egressIpAttributes
of an ipSignalingProfile
. For more information on Privacy Transparency of Egress IP Attributes, refer to Privacy Parameters - Egress IP Attributes.transparency
and anonymizeHostIpAddress
are set to disable
.Perform the following:
Enabling the transparency
Flag
To enable the transparency
flag for an ipSignalingProfile
, enter the following command:
set profiles signaling ipSignalingProfile DEFAULT_SIP egressIpAttributes privacy transparency enable
Enabling the anonymizeHostIpAddress
Flag
To enable the anonymizeHostIpAddress
flag to activate this feature, enter the following command:
set profiles signaling ipSignalingProfile DEFAULT_SIP egressIpAttributes privacy anonymizeHostIpPortion enable