Table Of Contents
Support for IUA with SCTP for Cisco Access Servers
Prerequisites for the Support for IUA with SCTP for Cisco Access Servers Feature
Information About the Support for IUA with SCTP for Cisco Access Servers Feature
Multiple Non-Facility Associated Signaling
IUA and SCTP with the Cisco PGW2200
How to Configure the Support for IUA with SCTP for Cisco Access Servers Feature
Creating NFAS Groups and Binding NFAS Groups to the Application Server
Migrating from RLM to IUA with SCTP
Modifying a PRI Group on an MGC
Configuration Examples for Support for IUA with SCTP for Cisco Access Servers
AS and ASP Example Configuration
Creating a Trunk Group and Binding the Trunk Group to an AS Example
Migrating from RLM to IUA for SCTP Example
Modifying a PRI Group on an MGC Example
show ip sctp association parameters
Support for IUA with SCTP for Cisco Access Servers
This document describes support for the IDSN User Adaptation Layer (IUA) with Stream Control Transmission Protocol (SCTP) for the Cisco AS5x00 network access servers (NASs) and the Cisco 2420, Cisco 2600 series, and Cisco 3600 series using Cisco IOS Release 12.2(15)T. This feature is to be used as an alternative to the existing IP-based User Datagram Protocol (UDP)-to-Reliable Link Manager (RLM) transport between the Cisco PGW2200 and Cisco gateways.
This feature supports the Internet Engineering Task Force (IETF) Signaling Transport (Sigtran) standard, IUA with SCTP, to act as the call signaling IP transport mechanism in a Voice Gateway solution. SCTP and IUA are used for Signaling System 7 (SS7) Interconnect solutions, which allows required flexibility in connecting Inter-Machine Trunks (IMTs) from more than one public switched telephone network (PSTN) switch (multiple trunk groups) to the Cisco AS5x00 series gateways, the Cisco 2460, Cisco 2600 series, and Cisco 3600 series. This feature also allows you to interconnect with multiple carriers on high-capacity Cisco AS5x00 gateways for load balancing and redundancy.
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This feature does not support the Cisco 2600XM or Cisco 2691.
The IUA and SCTP protocols provide the following:
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Feature Specifications for the Support for IUA with SCTP for Cisco Access Servers Feature
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
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Prerequisites for the Support for IUA with SCTP for Cisco Access Servers Feature
You must have Cisco IOS Release 12.2(15)T or later installed and running on your system.
For additional information about IUA with SCTP configuration on the Cisco Media Gateway Controller (MGC), refer to the following feature documents:
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Restrictions
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Information About the Support for IUA with SCTP for Cisco Access Servers Feature
To help you configure the Support for IUA with SCTP for Cisco Access Servers feature, you should understand the following concepts:
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SCTP
SCTP allows you to terminate multiple switches and trunk groups on a gateway to add scalability. Adding trunk groups does not require more memory or processing resources because SCTP supports multiple streams in a single SCTP association. SCTP is a reliable transport protocol for message-oriented communications; SCTP is specifically designed to support PSTN signaling messages over IP networks.
SCTP allows you to configure at least one trunk group per T1 or E1 interface available on a given platform. For example, a gateway platform with four T1 or E1 interfaces can control four unique trunk groups per device. Certain platforms, such as the Cisco AS5800 and Cisco AS5850, can deliver the individual T1 or E1 trunk groups over a high-speed interface, such as T3, which operates at 45 Mbps. Table 1 lists the number of trunk groups supported per gateway platform.
Table 1 SS7 Interconnect for Voice Gateway Solutions Supported Trunk Groups per Gateway1
Cisco AS5300
4
Verify both T1 and E1 cards.
Cisco AS5350
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Verify both T1 and E1 cards. Also, verify with Integrated SLT option. Refer to the Integrated Signaling Link Terminal, Cisco IOS Release 12.2(11)T feature document.
Cisco AS5350 CT3
28
CT3 DS-3 card. Also, verify with Integrated SLT option.
Cisco AS5400
16
Verify both T1 and E1 cards. Also, verify with Integrated SLT option.
Cisco AS5400 CT3
28
CT3 DS-3 card. Also, verify with Integrated SLT option.
Cisco AS5850
112
Verify E1 cards and CT3 DS-3 cards.
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1 There is no degradation or change in the number of circuit identification codes (CICs) supported on any of the gateways listed.
In a typical network topology, there is only one SCTP association configured between a signaling controller and a gateway. Multiple IP addresses on either side can be designated to the same association for the purpose of link redundancy, or multihoming. On a gateway, signaling messages for all trunk groups are carried over on the same SCTP association to the same signaling controller. Trunk groups on a gateway can also be controlled through different signaling controllers. In such cases, multiple associations can be configured on a gateway and directed to different signaling controllers.
SCTP is based on RFC2960 and offers the following support:
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Figure 1 shows the IUA with SCTP transport stack supported by this feature.
Figure 1 IUA with SCTP Transport Stack
IUA
IUA is the adaptation layer that makes SCTP services available to Q.921 services users, such as Q.931, Q Signaling (QSIG), and National ISDN-2 with Cisco extensions (Cisco NI2+). IUA supports the standard inter-layer primitives provided by Q.921. As a result, an upper layer protocol (ULP) that typically used Q.921 services can be easily migrated to IUA.
IUA service points are represented to the upper-layer protocol as application servers (ASs). Each AS is bound to an SCTP local endpoint managed by an SCTP instance. A remote signaling controller is known as an application server process (ASP). An ASP is connected to the local endpoint through a single SCTP association.
To use IUA services, the AS and ASP should be made available, and a trunk group must be bound to an AS for its Layer 2 server. For more information, see the configuration tasks in the "How to Configure the Support for IUA with SCTP for Cisco Access Servers Feature" section.
Multiple Non-Facility Associated Signaling
If all interfaces on a gateway are controlled through a single signaling controller, all interfaces are bound to the same AS. On a gateway, trunk groups are defined as Non-Facility Associated Signaling (NFAS) groups. An NFAS group is a group of ISDN PRI trunks with a single dedicated D channel. In a Voice Gateway solution, the D channel in a trunk group is symbolic because SS7 is used as the signaling mechanism. The D channels defined for each NFAS group are actually DS0 bearer channels for voice or modem calls. Therefore, each NFAS has a corresponding D channel for which it is allocated.
A symbolic D channel interface is dedicated to a trunk group. Each D channel interface is bound to an AS and a dedicated stream is associated with this interface. Thus, the NFAS group identification can be recovered on each side of the SCTP association through this two-stage mapping as long as both sides share the same configuration information. The multiplexing of multiple trunk groups through a single association is accomplished this way, for example.
The SCTP stream is a logical identification of the grouping of messages and consumes little additional memory and processing power. Each association can support as many as 65,355 streams.
Figure 2 shows the mapping between the trunk group, D channel interface, and SCTP stream.
Figure 2 Mapping Between Trunk Group, Interface, and Stream
Figure 3 shows the NFAS group and SCTP association.
Figure 3 NFAS Group and SCTP Association
See the "Creating NFAS Groups and Binding NFAS Groups to the Application Server" section.
IUA and SCTP with the Cisco PGW2200
This feature enables support of the IUA transport protocol using SCTP on the Cisco PGW2200. The Cisco PGW2200 can now use IUA to communicate with Cisco access servers.
IUA and SCTP on the Cisco PGW2200 provides the following:
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For more information about IUA and SCTP on the Cisco PGW2200, refer to the Support for IUA with SCTP feature document on Cisco.com
How to Configure the Support for IUA with SCTP for Cisco Access Servers Feature
This section contains the following procedures:
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Configuring IUA
An AS and the ASP should be configured first to allow an NI2+ to be bound to the IUA transport layer protocol. The AS is a logical representation of the SCTP local endpoint. The local endpoint can have more than one IP address but must use the same port number.
To configure IUA, you must create the AS and the ASP by using the following commands.
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enable
Example:Router> enable
Enables higher privilege levels, such as privileged EXEC mode.
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configure {terminal}
Example:Router# configure terminal
Enters global configuration mode.
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Router(config)# iuaEnters IUA configuration mode and specifies backhaul using SCTP. There are no arguments for this command.
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as as-name {localip1 [localip2]} [local-sctp-port]
Example:Router(config-iua)# as as5400-3 10.1.2.34 10.1.2.35 2577Defines an application server (AS) on a gateway.
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Defines an application server process (ASP). To disable, use the no form of this command.
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(Optional) IP address to enable and disable keep alives and control SCTP keepalives on destination IP addresses.
Step 7
(Optional) IP precedence level for protocol data units (PDUs). To disable, use the no form of this command.
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(Optional) Changes the failover timer value (1 to 10 seconds) in milliseconds. Valid values range from 1000 to 10000 ms. Default is 4000 ms.
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Router(config-iua)# exitExits IUA configuration mode and completes IUA configuration.
Configuring SCTP
To configure the SCTP T1 initiation timer, use the following commands.
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DETAILED STEPS
Step 1
enable
Example:Router> enable
Enables higher privilege levels, such as privileged EXEC mode.
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Step 2
configure {terminal}
Example:Router# configure terminal
Enters global configuration mode.
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Router(config)# iuaEnters IUA configuration mode and specifies backhaul using SCTP. There are no arguments for this command.
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as as-name {localip1 [localip2]} [local-sctp-port]
Example:Router(config-iua)# as as5400-3 10.1.2.34 10.1.2.35 2577Defines an application server (AS) on a gateway.
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(Optional) Changes the failover timer value (1 to 10 seconds) in milliseconds. Valid values range from 1000 to 10000 msec. Default is 4000 msec.
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as as-name sctp-startup-rtx number
Example:Router(config-iua)# as as5400-3 sctp-startup-rtx 8
Configures the SCTP maximum startup retransmission timer.
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as as-name sctp-streams number
Example:Router(config-iua)# as as5400-3 sctp-streams 56
Configures the number of SCTP streams for this AS.
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as as-name sctp-t1init number
Example:Router(config-iua)# as as1 sctp-t1init 1000
Configures the SCTP T1 initiation timer.
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asp asp-name as as-name ip-address
Example:Router(config-iua)# asp asp1 as as1 10.4.8.68 10.4.9.68
Creates an ASP and specifies to which AS this ASP belongs.
Step 10
Specifies the IP precedence level for protocol data units (PDUs). To disable, use the no form of this command.
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Defines an application server process (ASP).
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(Optional) Specifies the IP address to enable and disable keep alives and control SCTP keepalives on destination IP addresses.
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asp asp-name sctp-max-association ip-address number
Example:Router(config-iua)# asp asp1 sctp-max-association 10.10.10.10 20
Sets the maximum association retransmissions for this ASP.
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asp asp-name sctp-path-retransmission ip-address number
Example:Router(config-iua)# asp asp1 sctp-path-retransmission 10.10.10.10 2Sets the SCTP path retransmissions for this ASP.
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asp asp-name sctp-t3-timeout ip-address number
Example:Router(config-iua)# asp asp1 sctp-t3-timeout 10.10.10.10 60000Sets the SCTP T3 retransmission timeout for this ASP.
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Exits IUA-SCTP configuration mode and completes the configuration.
Creating NFAS Groups and Binding NFAS Groups to the Application Server
Use the procedure in this section to configure two T1 interfaces into two NFAS groups, or trunk groups, that are served by the same AS with two different SCTP streams (ASPs). These steps allow you to configure the NFAS primary D channel and bind the D channel to an IUA AS.
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SUMMARY STEPS
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enable
Example:Router> enable
Enables higher privilege levels, such as privileged EXEC mode.
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configure terminal
Example:Router# configure terminal
Enters global configuration mode.
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controller t1 1/0/0
Example:Router(config)# controller t1 1/0/0
Enters controller configuration mode on the first T1 controller.
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pri-group timeslots 1-23 nfas-d primary nfas-int 0 nfas-group number iua as-name
Example:Router(config-controller)# pri-group timeslots 1-23 nfas-d primary nfas-int 0 nfas-group 1 iua as-1
Configures the NFAS primary D channel on one channelized T1 controller, and binds the D channel to an IUA AS.
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exit
Example:Router(config-controller)# exit
Exits controller configuration mode on the first controller.
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controller t1 1/0/1
Example:Router# controller t1 1/0/1
Enters controller configuration mode on the second T1 controller.
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pri-group timeslots 1-23 nfas-d primary nfas-int 0 nfas-group number iua as-name
Example:Router(config-controller)# pri-group timeslots 1-23 nfas-d primary nfas-int 0 nfas-group 1 iua as-1
Configures the NFAS primary D channel on another channelized T1 controller, and binds the D channel to an IUA AS.
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Returns to global configuration mode and completes the configuration.
Migrating from RLM to IUA with SCTP
To migrate from RLM to IUA with SCTP, you must perform the following tasks in privileged EXEC mode. You must link to IUA instead of RLM.
Restrictions
The following changes have been made between RLM and IUA with SCTP:
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See the "Migrating from RLM to IUA for SCTP Example" section for more information about this migration task.
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Modifying a PRI Group on an MGC
Before you can modify a PRI group on an MGC, you must first shut down the D channel beginning in global configuration mode.
Restrictions
The isdn bind commands must be removed from the D channel. The binding of the NFAS groups now takes place when you use the pri-group commands for IUA with SCTP. See the "Modifying a PRI Group on an MGC Example" section.
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Troubleshooting Tips
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Configuration Examples for Support for IUA with SCTP for Cisco Access Servers
This section contains the following configuration examples:
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AS and ASP Example Configuration
The following is an example of an AS configuration on a gateway:
as as5400-3 10.4.8.69 10.4.9.69 2577In the configuration above, an AS named as-named as5400-3 is configured to use two local IP addresses and a port number of 2577. IP address values that are set apply to all IP addresses of the ASP.
The following configuration example defines a remote signaling controller asp1 at two IP addresses for the AS named as5400-3. The remote SCTP port number is 2577:
Router(config-iua)# as as5400-3 10.4.8.69 10.4.9.69 2477Router(config-iua)# asp asp1 as as5400-3 10.4.8.68 10.4.9.68 2577Multiple ASPs can be defined for a single AS for the purpose of redundancy, but only one ASP can be active. The other ASP is inactive and only becomes active after fail-over.
In the Cisco MGC solution, a signaling controller is always the client that initiates the association with a gateway. During the initiation phase, you can request outbound and inbound stream numbers, but the gateway only allows a number that is at least one digit higher than the number of interfaces (T1/E1) allowed for the platform.
The number of streams to assign to a given association is implementation dependent. During the initialization of the IUA association, you need to specify the total number of streams that can be used. Each D channel is associated with a specific stream within the association. With multiple trunk group support, every interface can potentially be a separate D channel.
At startup, the IUA code checks for all the possible T1, E1, or T3 interfaces and sets the total number of inbound and outbound streams supported accordingly. In most cases, there is only a need for one association between the GW and the MGC. For the rare case that you are configuring multiple AS associations to various MGCs, the overhead from the unused streams would have minimal impact. The NFAS D channels are configured for one or more interfaces, where each interface is assigned a unique stream ID.
The total number of streams for the association needs to include an additional stream for the SCTP management messages. So during startup the IUA code adds one to the total number of interfaces (streams) found.
You have the option to manually configure the number of streams per association. In the backhaul scenario, if the number of D channel links is limited to one, allowing the number of streams to be configurable avoids the unnecessary allocation of streams in an association that will never be used. For multiple associations between a GW and multiple MGCs, the configuration utility is useful in providing only the necessary number of streams per association. The overhead from the streams allocated but not used in the association is negligible.
If the number of streams is manually configured through the CLI, the IUA code cannot distinguish between a startup event, which automatically sets the streams to the number of interfaces, or if the value is set manually during runtime. If you are configuring the number of SCTP streams manually, you must add one plus the number of interfaces using the sctp-streams keyword with the as command. Otherwise, IUA needs to always add one for the management stream, and the total number of streams increments by one after every reload.
When you set the SCTP stream with the CLI, you cannot change the inbound and outbound stream support once the association is established with SCTP. The value takes effect when you first remove the IUA AS configuration and then configure it back as the same AS or a new one. The other option is to reload the router.
The following is an example of an AS configuration on a gateway. The configuration shows that an AS named as5400-3 is configured to use two local IP addresses and a port number of 2577:
Router(config-iua)# as as5400-3 10.1.2.34 10.1.2.35 2577The following example sets the failover time (in milliseconds) between 1 and 10 seconds. Entering a value of 1000 would equal one second. Entering a value of 10000 would equal 10 seconds. In this example, the failover timer has been set to 10 seconds:
Router(config-iua)# as as5400-3 fail-over 10000The following example specifies the number of SCTP streams for this association. In this example, 57 is the maximum number of SCTP streams allowed:
Router(config-iua)# as as5400-3 sctp-streams 57The following example sets the SCTP maximum startup retransmission interval. In this example, 20 is the maximum interval allowed:
Router(config-iua)# as as5400-3 sctp-startup 20The following example sets the SCTP T1 initiation timer in milliseconds. In this example, 60000 is the maximum time allowed:
Router(config-iua)# as as5400-3 sctp-t1init 60000The following example specifies the IP address to enable and disable keepalives:
Router(config-iua)# asp asp1 sctp-keepalive 10.1.2.34The following example specifies the keepalive interval in milliseconds. Valid values range from 1000 to 60000. In this example, the maximum value of 60000 ms is used:
Router(config-iua)# asp asp1 sctp-keepalive 10.10.10.10 60000The following example specifies the IP address for the SCTP maximum association and the maximum association value. Valid values range from 2 to 20. The default is 20, which is the maximum value allowed:
Router(config-iua)# asp asp1 sctp-max-association 10.10.10.10 20The following example specifies the IP address for the SCTP path retransmission and the maximum path retransmission value. Valid values range from 2 to 10. The default is 10, which is the maximum value allowed:
Router(config-iua)# asp asp1 sctp-path-retransmissions 10.10.10.10 10The following examples specifies the IP address for SCTP T3 timeout and specifies the T3 timeout value in milliseconds. Valid timeout values range from 300 to 60000. Default is 60000, which is the maximum timeout value allowed:
Router(config-iua)# asp asp1 sctp-t3-timeout 10.10.10.10 60000The following example configuration is described below. Figure 4 shows the configuration in diagram form.
Router(config-iua)# as as5300-17 10.0.0.07 10.1.1.17 2097Router(config-iua)# asp pgwa AS as5300-17 10.0.0.00 10.1.1.10 2097Router(config-iua)# asp pgwb AS as5300-17 10.0.0.06 10.1.1.16 2097•
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Figure 4 Specific ASP Example Configuration
The following sample is how the output from the above configuration would look:
iuaAS as5300-17 10.0.0.07 10.1.1.17 2097ASP pgwa AS as5300-17 10.0.0.00 10.1.1.10 2097ASP pgwb AS as5300-17 10.0.0.06 10.1.1.16 2097!!controller E1 0framing NO-CRC4clock source line primarypri-group timeslots 1-31 nfas-d primary nfas-int 0 nfas-group 1 iua as5300-17!controller E1 1framing NO-CRC4clock source line secondary 1pri-group timeslots 1-31 nfas-d none nfas-int 1 nfas-group 1!controller E1 2framing NO-CRC4pri-group timeslots 1-31 nfas-d primary nfas-int 0 nfas-group 2 iua as5300-17!controller E1 3framing NO-CRC4pri-group timeslots 1-31 nfas-d none nfas-int 1 nfas-group 2!!interface Ethernet0description the ip is 10.0.0.06 for interface e0ip address 10.0.0.06 255.255.255.0no ip route-cacheno ip mroute-cache!interface FastEthernet0description the primary ip is 10.1.1.16 for interface f0ip address 10.1.1.10 255.255.255.0no ip route-cacheno ip mroute-cacheduplex autospeed auto!interface Dchannel0no ip addresstrunk-group 11isdn timer t309 100isdn timer t321 30000isdn incoming-voice modemisdn T303 20000isdn negotiate-bchan resend-setupno cdp enable!interface Dchannel2
Guest
