Table Of Contents
PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer
Cisco AS5850 High Density PRI Business Trunking Gateway
Supported Standards, MIBs, and RFCs
Configuring ISDN Signaling Backhaul
AS and ASP Example Configuration
Configuring ISDN Signaling Backhaul Example
show ip sctp association parameters
show ip sctp association statistics
PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer
Feature History
This feature module describes PRI/Q.921 Signaling Backhaul for Call Agent Applications using IP transport protocol SCTP with the IUA. This feature is supported in Cisco IOS Release 12.2(4)T, 12.2(11)T, and 12.2(11)T1.
This document includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
The PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer feature fulfills the need for a standards based PRI Signaling backhaul that works with third party Call Agents to enable solutions like Integrated Access, IP PBX, and Telecommuter.
This feature provides the following:
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These features do the following:
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PRI Backhaul
The PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer feature provides standards-based ISDN signaling backhaul capability on Cisco IOS Gateways. Signaling backhaul is used in voice network architectures employing a Call Agent (also called Media Gateway Controller or MGC), where the call processing for voice calls is carried out by the call control servers, and the packet network connections are made using protocols such as the Media Gateway Control Protocol (MGCP) and the Simple Gateway Control Protocol (SGCP).
Signaling backhaul facilitates the handling of voice traffic coming from the signaling endpoints, which communicate using facility associated signaling. Facility associated signaling requires the signaling channel (a channel carrying call signaling information) to share a digital facility with the bearer channels. ISDN PRI is one example of facility associated signaling.
This feature implements the Internet Engineering Task Force (IETF) standards-based signaling backhaul protocols. This standards-based signaling transport support enables any third party Call Agent that supports the standards to work with Cisco gateways. ISDN signaling backhaul is required in the MGCP-based call control architecture to enable end-to-end voice solutions.
PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer migrates the proprietary PRI backhaul infrastructure to open standards. The backhauling is carried out using industry standard SCTPs and ISDN IUA protocols as defined by the SIGTRAN working group of the IETF.
This feature supports backhauling of the ISDN-based signaling protocols only.
Figure 1 shows an example of PRI signaling backhaul. The MGC provides call processing and gateway control.
Figure 1 PRI Signaling Backhaul
Ordinarily, signaling backhaul occurs at a common boundary for all protocols. For ISDN, the signaling backhaul takes place at the Layer 2 (Q.921) and Layer 3 (Q.931) boundaries. The lower layers of the protocol (Q.921) are terminated and processed on the gateway, while the upper layers (Q.931) are backhauled to the MGC using SCTP. Signaling backhaul provides the advantage of distributed protocol processing. This permits greater expandability and scalability while offloading lower layer protocol processing from the MGC.
The signaling transport between entities is applied to ensure that the signaling information is transported with the required functionality and performance. The SG/MG receives both the ISDN signaling and bearer channel data. The ISDN signaling is backhauled up to an MGC or Call Agent using the SIG protocol stack. Each SG can be configured to use up to three MGCs within an application server (AS) for redundancy. Multiple application servers can also be supported on an SG. MGCP is then used to control the bearer channels. Figure 2 shows the functional model for PRI signaling transport.
Figure 2 Signaling Transport Model
SCTP is a peer-to-peer protocol, while the IUA is a client-server protocol. Figure 3 shows the protocol flow from an ISDN endpoint, through the SG, and then to a Call Agent or MGC.
Figure 3 Protocol Flow
PRI Backhaul Using the Stream Control Transmission Protocol and the ISDN Q.921 User Adaptation Layer on the Cisco 3660 supports the following:
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SCTP
Stream Control Transmission Protocol (SCTP) is the layer between the SCTP user application and an unreliable end-to-end datagram service such as IP. The basic service offered by SCTP is the reliable transfer of user datagrams between peer SCTP users. It performs this service within the context of an association between two SCTP hosts. SCTP is connection-oriented, but SCTP association is a broader concept than the Transmission Control Protocol (TCP) connection, for example.
SCTP provides the means for each SCTP endpoint to provide its peer with a list of transport addresses during association startup (address and UDP port combinations, for example) through which that endpoint can be reached and from which messages originate. The association spans transfer over all of the possible source and destination combinations that might be generated from the two endpoint lists (also known as multi-homing).
SCTP provides the following services and features:
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IUA
The IUA module creates the associations between the SG and MGC based on configuration requests. It also manages multiple application server processes as defined in the IETF IUA Specification. The IUA performs the following functions.
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Cisco AS5850 High Density PRI Business Trunking Gateway
This feature adds support for the Cisco AS5850 and adds the following:
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Benefits
Third-Party Interoperability
This feature supports interoperability with third-party Call Agents.
Solutions Enabling
This feature supports the following solutions, which require signaling backhaul functionality:
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Restrictions
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Related Documents
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Supported Platforms
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Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.
To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:
Availability of Cisco IOS Software Images
Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.
Supported Standards, MIBs, and RFCs
Standards
IUA draft, Version 4.
MIBs
There are no new or modified MIBs.
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
http://tools.cisco.com/ITDIT/MIBS/servlet/index
If Cisco MIB Locator does not support the MIB information that you need, you can also obtain a list of supported MIBs and download MIBs from the Cisco MIBs page at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
To access Cisco MIB Locator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions found at this URL:
RFCs
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Prerequisites
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Configuration Tasks
See the following sections for configuration tasks for this feature. Each task in the list is identified as either optional or required:
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Caution
Configuring IUA
To configure IUA, you must create the AS and the ASP. Each task in the list indicates if it is optional or required.
Step 1
(Required) The iua command specifies backhaul using SCTP and enters IUA configuration mode.
Step 2
(Required) Defines an Application Server (AS). To disable, enter the no form of this command.
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Step 3
(Required) Defines an Application Server Process (ASP). To disable, use the no form of this command.
The asp-name argument is the name for this ASP. The as-name argument is the name of the AS to which this ASP belongs.
The remoteip keyword specifies the remote IP addresses for this SCTP association. The remote-sctp-port keyword specifies a connection to a specific remote SCTP port other than the IUA well-known port.
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Step 4
(Optional) Specifies the IP address to enable and disable keep alives. Specifies the keep alive interval (in milliseconds) when an IP address has been selected. Controls SCTP keepalives on destination IP addresses. To disable, use the no form of this command. Keepalives are enabled by default.
The asp-name argument specifies the name of the ASP. The remote-ip-address argument specifies the IP address of the remote end point (the address of MGC, for example).
Step 5
(Optional) Specifies the IP precedence level for protocol data units (PDUs). To disable, use the no form of this command.
You can configure the precedence value in IUA in the range of 0 through 7 for a given IP address. Within IUA, the upper three bits representing the IP precedence in the ToS byte (used in the IP header) are set based on what you input before passing down the value to SCTP. In turn, SCTP passes the ToS byte value to IP. The default value is 0 for normal IP precedence handling.
The asp-name argument specifies the name of this ASP. The ip-precedence keyword sets the precedence and ToS field. The remote-ip_address argument specifies the IP address of the remote end-point (the address of MGC, for example). The number argument can be any IP precedence bits in the range 0 through 7.
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Step 6
(Optional) Changes the failover timer value (1 to 10 seconds) in milliseconds. Valid ranges are from 1000-10000 msec. Default is 4000 msec. Find the failover timer value by examining the show iua as all command output.
If the failover timer is not set, it assumes its default value of 4000 msec. Once you have set the failover timer to a value, you can return it to its default of 4000 msec by using the no form of this command.
The as-name argument specifies the name of this AS. The time argument can be any value between 2000 and 10000 milliseconds. IUA waits for this amount of time for one ASP to take over from another ASP during failover.
Step 7
Exits IUA configuration mode.
Configuring ISDN Signaling Backhaul
Use the commands in this section to configure ISDN signaling backhaul.
Verifying Configuration
Use the following show commands in privileged EXEC mode to verify your configuration.
Step 1
Displays the current state of the active AS and shows the PRI interfaces configured on the AS. If the all keyword is specified, information about all the configured AS are shown.
Step 2
Displays the current state of the active ASP and shows information about the SCTP association being used by this ASP. If the all keyword is specified, information about all the configured ASPs are shown.
Step 3
Displays status of ISDN backhaul. If the connection to the MGC is lost, the router shuts down Layer 2 so that it cannot receive more calls. When the MGC connection is back up, you can use this command to verify that Layer 2 was also brought back up correctly.
The following typical output for show iua as all shows that the current state of the AS (as1) is active and that there are four PRI interfaces configured to use this AS:
Router# show iua as allName of AS :as1Total num of ASPs configured :2Current state : ACTIVEActive ASP :asp1Number of ASPs up :1Fail-Over time : 4000 milli secondsLocal address list : 10.21.0.2Local port 9900Interface IDs registered with this ASInterface ID stream #256 (serial1/0:23) 1257 (serial1/1:23) 2512 (serial2/0:23) 3513 (serial2/1:23) 4The following typical output for show iua asp all shows that the current state of the ASP (asp1) is active. This command also gives information about the SCTP association being used by this ASP.
Router# show iua asp allName of ASP :asp1Current State of ASP:ASP-ActiveCurrent state of underlying SCTP Association IUA_ASSOC_ESTAB , assoc id0SCTP Association information :Local Receive window :9000Remote Receive window :9000Primary Dest address requested by IUA 10.23.0.16Effective Primary Dest address 10.23.0.16Remote address list : 10.23.0.16Remote Port :9900Statistics :Invalid SCTP signals Total :0 Since last 0SCTP Send failures :0Name of ASP :asp2Current State of ASP:ASP-DownCurrent state of underlying SCTP Association IUA_ASSOC_INIT , assoc id0Remote address list : 10.23.0.16Remote Port :9911Statistics :Invalid SCTP signals Total :0 Since last 0SCTP Send failures :0The following is typical output for the show isdn status command. In this example, Layer 2 status is defined by the MULTIPLE_FRAME_ESTABLISHED message, which indicates that Layer2 is up. The L3 protocol and State status are highlighted:
Router# show isdn statusGlobal ISDN Switchtype = primary-5essISDN Serial1/0:23 interfacedsl 0, interface ISDN Switchtype = primary-5essL2 Protocol = Q.921 L3 Protocol(s) = IUA BACKHAULLayer 1 Status:ACTIVELayer 2 Status:TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHEDLayer 3 Status:0 Active Layer 3 Call(s)Active dsl 0 CCBs = 0The Free Channel Mask: 0x807FFFFFISDN Serial1/1:23 interfacedsl 1, interface ISDN Switchtype = primary-5essL2 Protocol = Q.921 L3 Protocol(s) = IUA BACKHAULLayer 1 Status:ACTIVELayer 2 Status:TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHEDLayer 3 Status:0 Active Layer 3 Call(s)Active dsl 1 CCBs = 0The Free Channel Mask: 0x807FFFFFISDN Serial2/0:23 interfacedsl 2, interface ISDN Switchtype = primary-5essL2 Protocol = Q.921 L3 Protocol(s) = IUA BACKHAULLayer 1 Status:ACTIVELayer 2 Status:TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHEDLayer 3 Status:0 Active Layer 3 Call(s)Active dsl 2 CCBs = 0The Free Channel Mask: 0x807FFFFFISDN Serial2/1:23 interfacedsl 3, interface ISDN Switchtype = primary-5essL2 Protocol = Q.921 L3 Protocol(s) = IUA BACKHAULLayer 1 Status:ACTIVELayer 2 Status:TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHEDLayer 3 Status:0 Active Layer 3 Call(s)Active dsl 3 CCBs = 0The Free Channel Mask: 0x807FFFFFTotal Allocated ISDN CCBs = 0Troubleshooting Tips
This section describes the debug commands available for SCTP. For more information, refer to the Stream Control Transmission Protocol (SCTP), Release 2 feature.
Caution
Note
Debugs are often used with time stamps enabled to see the relevant timing of the events indicated. Use the service timestamps commands to add time stamps to debug output in the format MMM DD HH:MM:SS, which indicates the date and time according to the system clock. If the system clock has not been set, the date and time are preceded by an asterisk (*) to indicate that the date and time are probably not correct. To activate millisecond time stamps for debugs, use the following commands in global configuration mode:
Router(config)# service timestamps debug datetime msecRouter(config)# service timestamps log datetime msecFor more information, see the service timestamps command reference entry in the "Troubleshooting and Fault Management Commands" chapter in the "System Management Commands" part of the Cisco IOS Configuration Fundamentals Command Reference, Release 12.2.
The following debug commands are available for SCTP:
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In a live system, the debug commands for performance, state, signal, and warnings are the most useful. These debug commands show any association or destination address failures and can be used to monitor the stability of any established associations.
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Configuration Examples
The following section shows configuration examples for this feature:
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AS and ASP Example Configuration
The following is an example of an AS configuration on a gateway:
AS as-name 10.4.8.69 10.4.9.69 2577In the configuration above, an AS named as-name 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.
An ASP can be viewed as a local representation of an SCTP association since it specifies a remote end point that will be in communication with an AS local end point. An ASP is defined for a given AS. For example, the following configuration defines a remote signaling controller asp-name at two IP addresses for AS as-name. The remote SCTP port number is 2577:
AS as-name 10.4.8.69 10.4.9.69 2477ASP asp-name AS as-name 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 start-up 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 start-up 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 start-up 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. 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 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 shows sample SCTP configuration options using using the help menu for the as and asp commands:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# iuaRouter(config-iua)# as as1 ?A.B.C.D Specify (up to two) Local IP addressFail-Over-Timer Configure the Fail-Over timer for this ASsctp-startup-rtx Configure the SCTP max startup retransmission timersctp-streams Configure the number of SCTP streams for this ASsctp-t1init Configure the SCTP T1 init timerRouter(config-iua)# as as1 sctp-startup-rtx ?<2-20> Set SCTP Maximum Startup Retransmission IntervalRouter(config-iua)# as as1 sctp-streams ?<1-56> Specify number of SCTP streams for associationRouter(config-iua)# as as1 sctp-t1init ?<1000-60000> Set SCTP T1 init timer (in milliseconds)Router(config-iua)# asp asp1 as as1 ?A.B.C.D Specify (up to two) IP addresses of the call-agentRouter(config-iua)# asp asp1 ?AS Specify which AS this ASP belongs toIP-Precedence Set IP precedence bits for a IP address in this ASPsctp-keepalives Modify the keep-alive behaviour of an IP address in thisASPsctp-max-assoc Set SCTP max association retransmissions for this ASPsctp-path-retran Set SCTP path retransmissions for this ASPsctp-t3-timeout Set SCTP T3 retransmission timeout for this ASPRouter(config-iua)# asp asp1 sctp-keep ?A.B.C.D specify the IP address to enable/disable keep alivesRouter(config-iua)# asp asp1 sctp-keepalive 10.10.10.10 ?<1000-60000> specify keep alive interval (in milliseconds)Router(config-iua)# asp asp1 sctp-max-assoc ?A.B.C.D specify the IP addressRouter(config-iua)# asp asp1 sctp-max-assoc 10.10.10.10 ?<2-20> specify maximum associationsdefault use default value of max associations for this addressRouter(config-iua)# asp asp1 sctp-path-retran ?A.B.C.D specify the IP addressRouter(config-iua)# asp asp1 sctp-path-retran 10.10.10.10 ?<2-10> specify maximum path retransmissionsdefault use default value of max path retrans for this addressRouter(config-iua)# asp asp1 sctp-t3-timeout ?A.B.C.D specify the IP addressRouter(config-iua)# asp asp1 sctp-t3-timeout 10.10.10.10 ?<300-60000> specify T3 retransmission timeout (in milliseconds)default use default value of T3 for this addressThe following example shows a running AS configuration with IUA configured with one AS (as1) and two ASPs (asp1 and asp2). Four T1s (T1 1/0, 1/1, 2/0, 2/1) are configured to use IUA backhaul.
Router# show runBuilding configuration...Current configuration :2868 bytes!version 12.2no service single-slot-reload-enableservice timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname iua_3660_b!logging rate-limit console 10 except errors!!!memory-size iomem 30voice-card 1!voice-card 2!voice-card 3!voice-card 4!voice-card 5!voice-card 6!ip subnet-zero!!no ip domain-lookup!no ip dhcp-client network-discoveryiuaAS as1 10.21.0.2 9900ASP asp1 AS as1 10.23.0.16 9900ASP asp2 AS as1 10.23.0.16 9911isdn switch-type primary-5ess!!!!!!fax interface-type modemmta receive maximum-recipients 0!!controller T1 1/0framing esfclock source line primarylinecode b8zspri-group timeslots 1-24 service mgcp!controller T1 1/1framing esflinecode b8zspri-group timeslots 1-24 service mgcp!controller T1 2/0framing esflinecode b8zspri-group timeslots 1-24 service mgcp!controller T1 2/1framing esflinecode b8zspri-group timeslots 1-24 service mgcp!controller T1 3/0framing sflinecode ami!controller T1 3/1framing sflinecode ami!controller T1 4/0framing sflinecode ami!controller T1 4/1framing sflinecode ami!controller T1 5/0framing sflinecode ami!controller T1 5/1framing sflinecode ami!controller T1 6/0framing sflinecode ami!controller T1 6/1framing sflinecode ami!!!interface FastEthernet0/0ip address 10.21.0.3 255.255.0.0 secondaryip address 10.21.0.2 255.255.0.0speed 10half-duplex!interface FastEthernet0/1no ip addressshutdownduplex autospeed auto!interface Serial1/0:23no ip addressip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice voiceisdn bind-l3 iua-backhaul as1no cdp enable!interface Serial1/1:23no ip addressip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice voiceisdn guard-timer 3000isdn T203 10000isdn bind-l3 iua-backhaul as1no cdp enable!interface Serial2/0:23no ip addressip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice voiceisdn guard-timer 3000isdn T203 10000isdn bind-l3 iua-backhaul as1no cdp enable!interface Serial2/1:23no ip addressip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice voiceisdn T203 10000isdn bind-l3 iua-backhaul as1no cdp enable!ip classlessip route 10.0.0.0 255.0.0.0 10.21.0.17ip route 11.0.0.10 255.255.255.255 FastEthernet0/0ip route 172.0.0.0 255.0.0.0 172.18.194.1ip http server!!!!snmp-server manager!call rsvp-sync!voice-port 1/0:23!voice-port 1/1:23!voice-port 2/0:23!voice-port 2/1:23!no mgcp timer receive-rtcp!mgcp profile default!dial-peer cor custom!!!!line con 0transport input noneline aux 0line vty 0 4login!!endConfiguring ISDN Signaling Backhaul Example
Enter the show isdn status command to verify successful ISDN configuration for backhaul. The following output shows that Layers 1, 2, 3 are enabled and active. Layer 3 shows the number of active ISDN calls.
In the example below, notice that the Layer 2 protocol is Q.921, and the Layer 3 protocol is BACKHAUL. This verifies that it is configured to backhaul ISDN. Also, if you are connected to a live line, you should see Layer 1 status is active, and layer 2 state is MULTIPLE_FRAME_ESTABLISHED. This means that the ISDN line is up and active.
Router# show isdn status*00:03:34.423 UTC Sat Jan 1 2000Global ISDN Switchtype = primary-net5ISDN Serial1:23 interfacedsl 0, interface ISDN Switchtype = primary-net5L2 Protocol = Q.921 L3 Protocol(s) = BACKHAULLayer 1 Status:ACTIVELayer 2 Status:TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHEDLayer 3 Status:NLCB:callid=0x0, callref=0x0, state=31, ces=0 event=0x0NLCB:callid=0x0, callref=0x0, state=0, ces=1 event=0x00 Active Layer 3 Call(s)Activated dsl 0 CCBs = 0Number of active calls = 0Number of available B-channels = 23Total Allocated ISDN CCBs = 0Router#Command Reference
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.
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as
To define an application server for backhaul, use the as command in IUA configuration mode. To disable, use the no form of this command.
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as as-name {localip1 [localip2]} [local-sctp-port]
no as name
Syntax Description
Defaults
No default behavior or values.
Command Modes
IUA configuration
Command History
Usage Guidelines
A maximum of two local IP addresses can be specified. (Note that SCTP has built-in support for multihomed machines.)
Examples
The following output shows that the AS (as1) is defined for backhaul:
AS as1 10.21.0.2 9900Related Commands
asp
To define an application server process (ASP) for backhaul, use the asp command in IUA configuration mode. To disable, use the no form of this command.
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asp asp-name as as-name {remoteip1 [remoteip2]} [remote-sctp-port] [ip-precedence [sctp-keepalives] [sctp-max-associations] [sctp-path-retransmissions] [sctp-t3-timeout]
no asp asp-name
Syntax Description
Defaults
No default behavior or values.
Command Modes
IUA configuration
Command History
Usage Guidelines
Examples
An ASP can be viewed as a local representation of an SCTP association because it specifies a remote endpoint that will be in communication with an AS local endpoint. An ASP is defined for a given AS. For example, the following configuration defines a remote signaling controller asp-name at two IP addresses for AS as1. The remote SCTP port number is 2577:
as as1 10.4.8.69, 10.4.9.69 2477asp asp1 as as1 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 ASPs are inactive and only become active after fail-over.
Related CommandsSCTP Send failures:0
clear ip sctp statistics
To clear statistics counts for SCTP, enter the clear ip sctp statistics command in privileged EXEC mode.
clear ip sctp statistics
Syntax Description
There are no arguments or keywords for this command.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
This command clears both individual and overall statistics.
Examples
The following command shows how to empty the buffer that holds SCTP statistics. No output is generated from this command.
Router# clear ip sctp statisticsRelated Commands
debug iua as
To display debug messages for the IUA AS, use the debug iua as command in privileged EXEC mode. To disable, use the no form of this command.
debug iua as {user | state} {all | name as-name}
no debug iua as
Syntax Description
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
Examples
The following example shows debug output when an ISDN backhaul connection is initially established:
Router# debug iua as state allIUA :state debug turned ON for ALL AS00:11:52:IUA:AS as1 number of ASPs up is 100:11:57:IUA:AS as1 xsition AS-Up --> AS-Active, cause - ASP asp1Related CommandsActive
debug iua asp
To display debug messages for the IUA ASP, use the debug iua asp command in privileged EXEC mode. To disable, use the no form of this command.
debug iua asp {pak | peer-msg | sctp-sig | state} {all | name asp-name}
no debug iua as
Syntax Description
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
Examples
The following example shows debug output when an ISDN backhaul connection is initially established.
Router# debug iua asp peer-msg allIUA :peer message debug turned ON for ALL ASPsRouter#00:04:58:IUA :recieved ASP_UP message on ASP asp100:04:58:IUA:ASP asp1 xsition ASP-Down --> ASP-Up , cause - rcv peermsgASP-UP00:04:58:IUA:sending ACK of type 0x304 to asp asp100:05:03:IUA:recv ASP_ACTIVE message for ASP asp100:05:03:IUA:ASP asp1 xsition ASP-Up --> ASP-Active, cause - rcv peermsgASP-ActiveRelated Commands00:05:03:IUA:sending ACK of type 0x403 to asp asp1
isdn bind-L3 iua-backhaul
To specify ISDN backhaul using Stream Control Transmission Protocol (SCTP) for an interface, use the isdn bind-L3 iua-backhaul command in interface configuration mode. To disable the backhaul capability, use the no form of this command.
isdn bind-L3 iua-backhaul [application-server-name]
no isdn bind-L3 iua-backhaul
Note
Syntax Description
application-server-name
(Optional) Name of the application server (AS) to use for backhauling the interface.
Defaults
No default behavior or values
Command Modes
Interface configuration
Command History
Examples
The following example shows IUA backhaul on the application server "as1":
interface Serial1/0:23no ip addressip mroute-cacheno logging event link-statusisdn switch-type primary-5essisdn incoming-voice voiceisdn bind-L3 iua-backhaul as1Related Commandsno cdp enable
iua
To specify backhaul using Stream Control Transmission Protocol (SCTP) and to enter IDSN User Adaptation Layer (IUA) configuration mode, use the iua command in terminal configuration mode.
iua
Syntax Description
There are no arguments or keywords for this command.
Defaults
No default behavior or values.
Command Modes
Terminal configuration
Command History
Usage Guidelines
You must first enter IUA configuration mode to access SCTP configuration mode. First enter IUA configuration mode by using the example below and then enter sctp at the Router(config-iua)#prompt to bring up SCTP configuration mode. See the sctp command.
Examples
The following example shows how to enter iua configuration mode:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# iuaRouter(config-iua)#Related Commands
Specifies ISDN backhaul using SCTP for an interface.
Shows information about the current condition of an AS.
Shows information about the current condition of an ASP.
show ip sctp association list
To display identifiers and information for current Stream Control Transmission Protocol (SCTP) associations and instances, use the sctp-association list command in privileged EXEC mode.
show sctp-association list
Syntax Description
There are no arguments or keywords for this command.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use this command to display the current SCTP association and instance identifiers, the current state of SCTP associations, and the local and remote port numbers and addresses that are used in the associations.
Examples
The following is sample output from this command for three association identifiers:
*** SCTP Association List ****AssocID:0, Instance ID:0Current state:ESTABLISHEDLocal port:8989, Addrs:10.1.0.2 10.2.0.2Remote port:8989, Addrs:10.6.0.4 10.5.0.4AssocID:1, Instance ID:0Current state:ESTABLISHEDLocal port:8989, Addrs:10.1.0.2 10.2.0.2Remote port:8990, Addrs:10.6.0.4 10.5.0.4AssocID:2, Instance ID:0Current state:ESTABLISHEDLocal port:8989, Addrs:10.1.0.2 10.2.0.2Remote port:8991, Addrs:10.6.0.4 10.5.0.4Table 2 describes significant fields in this output.
Related Commands
show ip sctp association parameters
To display configured and calculated parameters for the specified Stream Control Transmission Protocol (SCTP) association, use the show ip sctp association parameters command in privileged EXEC mode.
show ip sctp association parameters [assoc-id]
Syntax Description
assoc-id
(Optional) Association identifier. Shows the associated ID statistics for the SCTP association.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show ip sctp association parameters command displays parameter values for the specified association. It requires an association identifier as an argument. Association identifiers can be obtained from the output of the show ip sctp association list command.
This command provides information to determine the stability of SCTP associations, dynamically calculated statistics about destinations, and values to assess network congestion.
There are many parameters that are defined for each association. Some are configured parameters, and others are calculated. There are three main groupings of parameters displayed by this command:
•
•
•
The association configuration section displays information similar to that in the show ip sctp association list command, including association identifiers, state, and local and remote port and address information. The current primary destination is also displayed.
The destination address parameters section displays information associated with each destination address. Many of the address parameters are dynamically calculated and therefore give an indication of the state of the network for each destination. The state of the destination address is either ACTIVE or FAILED, depending on whether this destination address is currently accessible. The heartbeats and timeout are configured values (configured by the application using SCTP), as is the TOS (type of service, or IP precedence) value. The TOS value shows the bits that are used in the IP header of each datagram sent out. The maximum transmission unit (MTU) field shows the currently configured MTU value from the corresponding interface that is used to reach the destination address. The values for congestion window (cwnd), slow-start threshold (ssthresh), and retransmission timeout (RTO) are calculated values, continually updated based on feedback from the network, as specified in RFC2960. The cwnd parameter indicates how much data can be outstanding in the network for that particular destination. The RTO parameter is the retransmit timeout value. Finally, the num retrans and num times failed parameters give the current number for how many times data has been retransmitted to that address and how many times the address has been marked as failed, respectively. These parameters give an indication of how steady that particular address is and has been.
The third group of parameters are boundary parameters that usually don't change over the life of an association, although the calling application can change some of them if it wants. The verification tags (vertags) are chosen during association initialization and don't change. The number of inbound and outbound streams also don't change. The max retrans numbers show the maximum number of times chunks are retransmitted. The association retransmit limit is the number of times any particular chunk are retransmitted before a declaration is made that the association failed. The declaration indicates that the chunk could not be delivered on any address. Init retrans is the number of times the chunks for initialization are retransmitted before a declaration that the attempt to establish the association failed. And the path retrans value is the maximum number of times that chunks are transmitted to any particular destination address before that address is declared failed. The cumulative SACK (cumsack) timeout specifies the maximum time that a SACK is delayed while waiting to bundle with data chunks. The bundle timeout value is the maximum time that data chunks are delayed during attempts to bundle with other data chunks. And finally, the min and max RTO values define the minimum and maximum retransmit timeout values that are allowed for the association.
Examples
The following example shows the IP SCTP association ID parameters:
Router# show ip sctp association parameters 0*** SCTP Association Parameters ****AssocID: 0 Context: 0 InstanceID: 1Assoc state: ESTABLISHED Uptime: 19:05:57.425Local port: 8181Local addresses: 10.1.0.3 10.2.0.3Remote port: 8181Primary dest addr: 10.5.0.4Effective primary dest addr: 10.5.0.4Destination addresses:10.5.0.4: State: ACTIVEHeartbeats: Enabled Timeout: 30000 msRTO/RTT/SRTT: 1000/16/38 ms TOS: 0 MTU: 1500cwnd: 5364 ssthresh: 3000 outstand: 768Num retrans: 0 Max retrans: 5 Num times failed: 010.6.0.4: State: ACTIVEHeartbeats: Enabled Timeout: 30000 msRTO/RTT/SRTT: 1000/4/7 ms TOS: 0 MTU: 1500cwnd: 3960 ssthresh: 3000 outstand: 0Num retrans: 0 Max retrans: 5 Num times failed: 0Local vertag: 9A245CD4 Remote vertag: 2A08D122Num inbound streams: 10 outbound streams: 10Max assoc retrans: 5 Max init retrans: 8CumSack timeout: 200 ms Bundle timeout: 100 msMin RTO: 1000 ms Max RTO: 60000 msLocalRwnd: 18000 Low: 13455 RemoteRwnd: 15252 Low: 13161Congest levels: 0 current level: 0 high mark: 325Table 3 describes significant fields in this output.
Related Commands
show ip sctp association statistics
To display statistics that have accumulated for the specified Stream Control Transmission Protocol (SCTP) association, enter the
show ip sctp association statistics privileged EXEC command.show ip sctp association statistics associd
Syntax Description
associd
(Optional) Association identifier. Shows the associated ID statistics for the SCTP association.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show ip sctp association statistics command requires an association identifier argument. The association identifier can be obtained from the output of the show ip sctp association list command.
This command shows only the information that has become available since the last time a clear ip sctp statistics command was input.
This command displays various statistics about the specified association. The first numbers show the total number of chunks, both data and control, sent and received. The second group of numbers focuses on just the data chunks, showing the following statistics:
•
•
•
•
The average chunks bundled shows how many chunks have been bundled together in each datagram on average. The last section indicates how many datagrams have been sent, have been received, and are ready to be received by the calling application or Upper Layer Process (ULP). The ULP statistics may be different from the chunk statistics if the datagrams are large and have been segmented by SCTP.
The second group of statistics focuses on the data chunks sent, showing the total number sent, the number retransmitted, the number that were ordered and unordered, the average number that were bundled together, and the total bytes sent. The third group of statistics focuses on the data chunks received. It displays the total number received and the number discarded (due to duplicates), the number of ordered and unordered chunks received, the average number of chunks that were bundled, the number of bytes received, and the number of sequenced chunks that were received out of order. The last section indicates how many datagrams have been sent, received, or are ready to be received by the calling application or ULP. The ULP statistics may be different from the chunk statistics if the datagrams are large and have been segmented by SCTP.
Examples
The following example was taken from a network with known dropped packets in one direction. The number of total chunks sent and received is larger than the number of data chunks sent and received because it also includes the control chunks sent. The number of chunks received out of sequence and the number of chunks discarded indicate that there are problems in the network. Some chunks are being dropped and multiple copies of others are being received. However, no chunks have been retransmitted, indicating that traffic in that direction is running much more cleanly. If the network is completely clean, you see zero chunks received out of sequence and zero chunks discarded or retransmitted.
Router# show ip sctp association statistics 0*** SCTP Association Statistics ****AssocID/InstanceID: 0/0Current State: ESTABLISHEDChunks Sent: 74596995Chunks Rcvd: 74049518Data Chunks Rcvd In Seq: 61627732Data Chunks Rcvd Out of Seq: 8555308Data Chunks Sent: 70183891Data Chunks Rcvd: 70200197Data Bytes Sent: 2723421804Data Bytes Rcvd: 2725052404Data Chunks Discarded: 17157Data Chunks Retrans: 0Average chunks bundled: 10ULP Dgrams Sent: 70183040ULP Dgrams Ready: 70183040ULP Dgrams Rcvd:70183040Table 4 describes significant fields in this output.
Related Commands> > > >ULP Dgrams Rcvd: 3088
show ip sctp errors
To show the error counts logged by SCTP, enter the show ip sctp errors privileged EXEC command.
show ip sctp errors
Syntax Description
There are no arguments or keywords with this command.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
This command displays all errors across all associations that have been logged since the last time that the SCTP statistics were cleared with the clear ip sctp statistics command. If no errors have been logged, this is indicated in the output.
Examples
The following output shows one example in which no errors have been logged, and another in which there have been several different types of errors.
Router# show ip sctp errors*** SCTP Error Statistics ****No SCTP errors logged.Router# show ip sctp errors*** SCTP Error Statistics ****Communication Lost: 95Unknown INIT params rcvd: 8Missing parameters: 18Related Commands
show ip sctp instances
To display information for each of the currently configured Stream Control Transmission Protocol (SCTP) instances, enter the show ip sctp instances privileged EXEC command.
show ip sctp instances
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show ip sctp instances command displays information for each of the currently configured instances. The instance number, local port, and address information is displayed. The instance state is either available or deletion pending. An instance enters the deletion pending state when a request is made to delete it but there are currently established associations for that instance. The instance cannot be deleted immediately and instead enters the pending state. No new associations are allowed in this instance, and when the last association is terminated or fails, the instance is deleted.
The default inbound and outbound stream numbers are used for establishing incoming associations, and the maximum number of associations allowed for this instance is shown. Finally, a snapshot of each existing association is shown, if any exist.
Examples
The following example shows available IP SCTP instances. In this example, two current instances are active and available. The first is using local port 8989, and the second is using 9191. Instance identifier 0 has three current associations, and instance identifier 1 has no current associations.
Router# show ip sctp instances*** SCTP Instances ****Instance ID:0 Local port:8989Instance state:availableLocal addrs:10.1.0.2 10.2.0.2Default streams inbound:1 outbound:1Current associations: (max allowed:6)AssocID:0 State:ESTABLISHED Remote port:8989Dest addrs:10.6.0.4 10.5.0.4AssocID:1 State:ESTABLISHED Remote port:8990Dest addrs:10.6.0.4 10.5.0.4AssocID:2 State:ESTABLISHED Remote port:8991Dest addrs:10.6.0.4 10.5.0.4Instance ID:1 Local port:9191Instance state:availableLocal addrs:10.1.0.2 10.2.0.2Default streams inbound:1 outbound:1No current associations established for this instance.Max allowed:6Related Commands-
show ip sctp statistics
To display the overall statistics counts for Stream Control Transmission Protocol (SCTP) activity, enter the show ip sctp statistics privileged EXEC command.
show ip sctp statistics
Syntax Description
There are no arguments or keywords with this command.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
This command displays the overall SCTP statistics accumulated since the last clear ip sctp statistics command. It includes numbers for all currently established associations, as well as for any that have been terminated. The statistics indicated are similar to those shown for individual associations.
Examples
The following example shows IP SCTP statistics and are similar to those shown for individual associations:
Router# show ip sctp statistics*** SCTP Overall Statistics ****Total Chunks Sent: 2097Total Chunks Rcvd: 2766Data Chunks Rcvd In Seq: 538Data Chunks Rcvd Out of Seq: 0Total Data Chunks Sent: 538Total Data Chunks Rcvd: 538Total Data Bytes Sent: 53800Total Data Bytes Rcvd: 53800Total Data Chunks Discarded: 0Total Data Chunks Retrans: 0Total SCTP Dgrams Sent: 1561Total SCTP Dgrams Rcvd: 2228Total ULP Dgrams Sent: 538Total ULP Dgrams Ready: 538Total ULP Dgrams Rcvd: 538:
Related Commands
show iua as
To show information about the current condition of an application server (AS), use the show iua as command in privileged EXEC mode.
show iua as {all | name name as-name}
Syntax Description
all
Output displays information about all configured ASs.
name as-name
Name of a particular AS. Output displays information about just that AS.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use the show iua as all command to find the failover timer value. You will need to know the failover timer value currently set before you use the as as-name fail-over-timer command to set the failover timer value to fit your application.
Examples
The following typical output for show iua as all shows that the current state of the AS (as1) is active and that there are four PRI interfaces configured to use this AS:
Router# show iua as allName of AS :as1Total num of ASPs configured :2Current state : ACTIVEActive ASP :asp1Number of ASPs up :1Fail-Over time : 4000 milli secondsLocal address list : 10.21.0.2Local port 9900Interface IDs registerd with this ASInterface ID stream #256 (serial1/0:23) 1257 (serial1/1:23) 2512 (serial2/0:23) 3513 (serial2/1:23) 4Table 5 shows important fields in the output.
Related Commands
show iua asp
To provide information about the current condition of an application server process (ASP), use the
show iua asp privileged EXEC command.show iua asp {all | name name asp-name}
Syntax Description
all
Output displays information about all configured ASPs.
name asp-name
Name of a particular ASP. Output displays information about just that ASP.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Examples
The following typical output for show iua asp all shows that the current state of the ASP (asp1) is active. This command also gives information about the SCTP association being used by this ASP.
Router# show iua asp allName of ASP :asp1Current State of ASP:ASP-ActiveCurrent state of underlying SCTP Association IUA_ASSOC_ESTAB , assoc id0SCTP Association information :Local Recieve window :9000Remote Recieve window :9000Primary Dest address requested by IUA 10.23.0.16Effective Primary Dest address 10.23.0.16Remote address list : 10.23.0.16Remote Port :9900Statistics :Invalid SCTP signals Total :0 Since last 0SCTP Send failures :0Name of ASP :asp2Current State of ASP:ASP-DownCurrent state of underlying SCTP Assocaition IUA_ASSOC_INIT , assoc id0Remote address list : 10.23.0.16Remote Port :9911Statistics :Invalid SCTP signals Total :0 Since last 0SCTP Send failures :0Table 6 describes significant fields shown in this output.
Related Commands
Glossary
API—Application Programming Interface.
AS—application server. A logical entity serving a specific application instance. An example of an application server is an MGC handling the Q.931 and call processing for D channels terminated by the signaling gateways.
ASP—application server process. A process instance of an application server. Examples of application server processes are primary or backup MGC instances.
backhaul—A process in which telephony signaling is passed from a gateway to a separate control for processing. With such a scheme, the gateway does not need to interpret the signaling information.
BRI—Basic Rate Interface. ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data.
DS-0—digital signal level 0. Framing specification used in transmitting digital signals over a single channel at 64-kbps on a T1 facility. Compare with DS-1 and DS-3.
failover—The capability to re-route signaling traffic as required between related ASPs in the event of failure or if the currently used ASP is unavailable (from primary MGC to backup MGC, for example). Failover also applies to the return to service of a previously unavailable process.
IETF—Internet Engineering Task Force. Task force consisting of over 80 working groups responsible for developing Internet standards. The IETF operates under the auspices of ISOC.
ISDN—Integrated Services Digital Network.
IUA—ISDN Q.921 User Adaptation Layer. Provides for the transport of signaling protocol between a SG and MGC including transporting Q.921/Q.931 boundary primitives, communication between layer management modules, and management of active associations.
Layer 1—physical layer of the OSI reference model defined in ITU X.200. It is responsible for the electric signal being sent and received. This can be viewed as a bit stream coming in, and going out, of the system. Scope must be considered when using this term. For example, Layer 1 on a T1 is 1.544 Mbps but Layer 1 on a DS-0 timeslot in the T1 is 64 kbps.
Layer 2—datalink layer of the OSI reference model defined in ITU X.200. It is responsible for point-to-point delivery of a PDU. Layer 2 protocols have two basic classes: reliable (meaning delivery is guaranteed or an error is reported) and unreliable (meaning delivery might not occur with no indication to the upper layers).
Layer 3—network layer of the OSI reference model defined in ITU X.200. It is responsible for the network routing and delivery of messages. Examples of Layer 3 protocols include the X.25 packet level protocol and the Internet Protocol. Q.931 is not considered a Layer 3 protocol because it does not route or deliver messages.
MG—media gateway. A media gateway terminates PSTN facilities (trunks), packetizes the PCM stream into IP/ATM and/or forwards packets into the IP/ATM network. Optionally, media gateways can provide signaling backhaul.
MGC—Media Gateway Controller. A Media Gateway Controller provides call control capability to handle signaling traffic from a variety of sources. It also manages connections and resources of its media gateways. Can also be called a Call Agent.
MGCP—Media Gateway Control Protocol.
NFAS—Non-Facility Associated Signaling. This is a classification of signaling protocols that provide the signaling channel in a separate physical line from the bearer channels.
PRI—Primary Rate Interface.
Q.921, Q.931—ITU-T specifications for the ISDN UNI data link layer.
SAP—Service Access Point.
SCN—Switched Circuit Network. A network that carries traffic within channelized bearers of pre-defined sizes.
SCTP—Stream Control Transmission Protocol. General IP transport protocol defined by the SIGTRAN working group of the IETF.
SG—signaling gateway. A signaling gateway transmits PSTN signaling at the edge of an IP/ATM network. It backhauls the signaling to a Media Gateway Controller.
SGCP—Simple Gateway Control Protocol.
SIGTRAN—One of the working groups of the IETF.
SM—session manager.
TCP—Transmission Control Protocol.
TEI—terminal endpoint identifier.
T1-CAS—T1 Channel Associated Signaling.
UAL—User Adaptation Layer.
ULP—Upper Layer Protocol. The logical higher-layer application which uses the services of SCTP.
VoIP—Voice over IP. The ability to carry normal telephone-style voice over an IP-based internet with POTS-like functionality, reliability, and voice quality.
