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Table Of Contents
Cisco SS7 Interconnect for Voice Gateways Solution Configuration Options and Components
Cisco SS7 Interconnect for Voice Gateways Solution Configurations
Simplex and Redundancy Options
Signaling Network Connection Options
Control Signaling Network Options
Cisco SS7 Interconnect for Voice Gateways Solution Components
Cisco SS7 Interconnect for Voice Gateways Solution Configuration Options and Components
This chapter briefly describes the various Cisco SS7 Interconnect for Voice Gateways Solution configuration options and the required and optional components:
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Cisco SS7 Interconnect for Voice Gateways Solution Configurations
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Cisco SS7 Interconnect for Voice Gateways Solution Configurations
The Cisco SS7 Interconnect for Voice Gateways Solution provides the following configuration options:
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Simplex and Redundancy Options
You can deploy the Cisco SS7 Interconnect for Voice Gateways Solution in one of three ways:
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Simplex Configuration
A simplex configuration is an SC zone that consists of a single SC host (E450 or Sun Netra t 112x) operating with one or more Cisco SLTs. The SC application is run on the SC host and the SS7 signaling links are terminated on the Cisco SLT. An IP control LAN is used to interconnect the host server with the Cisco SLTs. One or more access gateways are required for bearer channel termination. See Figure 2-1.
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Figure 2-1 Simplex Configuration Example
Continuous Service Configuration
A continuous service configuration is an SC zone that consists of a pair of SC hosts running in a primary (active) and secondary (standby) mode, operating with one or more access gateways and one or more Cisco SLTs. An error-checking function runs continuously between the two SC hosts, monitoring the primary SC host. When the function detects an error condition on the primary SC host, responsibility for call processing is switched to the secondary SC host. The secondary SC host now becomes the primary SC host; call preservation is maintained.
Figure 2-2 shows an example of a continuous service configuration with redundant signaling links terminating on a pair of Cisco SLTs with bearer traffic terminating on the access gateway.
Figure 2-2 Continuous Service Configuration Example
Signaling Network Connection Options
The Cisco SS7 Interconnect for Voice Gateways Solution performs functions to exchange telephone control messages between the following components that support the end user's signaling network connection:
Cisco Signaling Controller—Provides a signaling protocol conversion and network Q.931 call control to communicate with the access gateways. One signaling controller might provide signaling and call-processing services for multiple access gateways in geographically distributed locations, over redundant IP links used for ISDN signaling.
Cisco SLT—Handles the incoming and outgoing SS7 messages (MTP layer 1 and 2) from the A-links (access links) connected to Signal Transfer Points (STPs) or F-links connected to Service Switching Points (SSPs). Also, when used in Drop and Insert mode, the Cisco SLT grooms off the terminating signaling link from F-links (fully associated links) and then hairpins the bearer channels (ISUP) to the access gateway.
Cisco Access Gateway—Provides termination for PSTN trunks. An access gateway functions as a server to the SS7 bearer links. The access gateway has at least two IP network interfaces: one to carry IP packet data onto one or more of the ISP's backbones and another to connect to the ISP's secure management, signaling, and Q.931 control network.
Your Cisco SS7 Interconnect for Voice Gateways Solution can be deployed in three ways, as described in "Simplex and Redundancy Options", with the following SS7 signaling network connections.
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A-Link with Cisco SLT
An A-link with Cisco SLT signaling connection is an access link from the PSTN Signal Transfer Point (STP) connected to the Cisco SLT of the SC node, through RS-449, RS-530, V.35, and T1/E1 interfaces. This option can be used with simplex and continuous service host configurations. Each interface supports a single signaling channel.
In the A-link SLT signaling connection, the Cisco SLT processes the two lowest-level SS7 signaling protocols, MTP1 and MTP2. The upper layer protocols are then forwarded to the SC host over the control signaling network. Each Cisco SLT supports two signaling network connections. Multiple Cisco SLTs can be used to support additional signaling channels or provide redundant signal paths between the signaling network and the control signaling network, as illustrated in Figure 2-3.
Figure 2-3 A-Link SLT Signaling Configuration
F-Link with Cisco SLT
An F-link with Cisco SLT signaling connection is a fully associated link from the SS7 network to the Cisco SLT of the SC node. F-links connect the SC host directly to a Service Switching Point (SSP) or a Service Control Point (SCP) in the SS7 network; they do not make an intermediate connection through STPs.
The F-link SLT signaling configuration supports RS-449, RS-530, V.35, and T1/E1 interfaces that are installed in the Cisco SLT. The F-link SLT configuration can be used with simplex and continuous service SC host configurations. Each interface supports a single DS0 signaling channel.
A-Link or F-Link with Cisco SLT (Drop and Insert)
An A-link or F-link with Cisco SLT (Drop and Insert) signaling connection is similar, respectively, to an A-link or F-link SLT signaling connection. Fully associated links directly connect an SSP or SCP to the Cisco SLT. The difference is that the A-link and F-link Drop and Insert configurations support a single DS0 signaling channel per link and additional bearer traffic channels up to the capacity of the T1 or E1 link as shown in Figure 2-4.
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Figure 2-4 F-Link Drop and Insert Configuration
The F-link drop and insert signaling configuration supports T1 and E1 interfaces using signaling interface cards installed in the Cisco SLT. The Drop and Insert cards are special two-port cards designed for this application. Signal and bearer traffic enter one port together, then the Cisco SLT separates the bearer traffic and routes it out the second port.
The F-link Drop and Insert configuration can be used with simplex and continuous service host configurations. Each interface card supports a single DS0 signaling channel.
Control Signaling Network Options
Designing your network to handle control signaling is a complex and sophisticated task beyond the scope of this document. This section briefly describes what control signaling network options are available and some network engineering guidelines to consider.
Customer-Provided Equipment
Your control network consists of a number of hubs, switches, or routers configured together to support the number of ports in your point of presence (POP), the traffic characteristics of incoming calls, the geographic location of the Cisco SS7 Interconnect for Voice Gateways Solution components, and the level of redundancy that you require. Other factors to consider are:
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Control traffic (signaling) should be segregated from the bearer data IP traffic (towards the internet/intranet) onto a different network. This optimizes control traffic latency and provides added security. Redundancy in your control network can be provided by duplicating your Cisco SS7 Interconnect for Voice Gateways Solution components. In the event that the control network fails or connectivity to it fails, the data network is used for signaling.
In the simplest case, your Cisco SS7 Interconnect for Voice Gateways Solution components are co-located and a pair of LAN switches serve as your control network. However, it is also possible that Cisco SLTs, and access gateways, are geographically separate from the SC hosts, requiring a control network with WAN links and separate routers to provide the WAN connection.
IP Connectivity with LAN
Figure 2-2 shows a sample continuous configuration with a mated Cisco SLT pair (for redundancy) on the control signaling network. Redundant signaling controllers support two or four Fast Ethernet connections each.
In this continuous configuration example, the control network functions are:
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The QoS packet network functions are:
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IP Connectivity with WAN
Distributed IP control networks operating over a WAN is necessary when:
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IP Control Network Combinations
The following IP control network combinations are recommended:
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Engineering Considerations
When engineering your network, you must consider the following issues:
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Cisco SS7 Interconnect for Voice Gateways Solution Components
The Cisco SS7 Interconnect for Voice Gateways Solution contains the following components:
Figure 2-5 displays the components of the Cisco SS7 Interconnect for Voice Gateways Solution.
See the "SS7 Technology Overview" appendix for information about how the solution components operate within the SS7 hierarchy.
Figure 2-5 Cisco SS7 Interconnect for Voice Gateways Solution Components
SC Node Products
The SC node is the combination of hardware and software that provides the signaling controller function and transports the signaling traffic between the SC hosts and the SS7 signaling network. The SC node in the Cisco SS7 Interconnect for Voice Gateways Solution consists of one or more SC hosts, one or more Cisco SLTs, the signaling controller software, and ancillary equipment.
SC Hosts
An SC host is a Sun hardware platform running signaling controller software.
Table 2-1 lists supported SC hosts for the Cisco SC2200 product.
SC Host Features
The primary functions of the signaling controller is performing protocol conversion and call screening. The signaling controller is responsible for:
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Table 2-2 lists the features for the SC host.
Cisco SS7 Interconnect for Voice Gateways Solution Software
The Cisco SS7 Interconnect for Voice Gateways Solution SC2200 product requires the following software release levels listed in Table 2-3.
Cisco SLTs
The Cisco SLT handles the incoming and outgoing SS7 messages (MTP layer 1 and 2) that arrive from the PSTN Signal Transfer Points (STPs) or Service Switching Points (SSPs). When used in the proper configurations, the Cisco SLTs improve fault tolerance by providing for multiple communications paths between the SS7 signaling network and multiple SC hosts.
Cisco SLT Features
Table 2-4 lists the features for the Cisco SLT.
Access Gateways
The access gateway terminates the PSTN trunks, also referred to as bearer channels, that carry the call traffic. The PSTN trunks are T1 or E1 PRI interfaces. In addition, the access gateway performs call control (including originating and terminating call processing/signaling).
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Table 2-5 lists the features for the Cisco AS5x00.
Table 2-5 Cisco AS5x00 Features
Continuity testing
Automated diagnostic procedure
Redundant Link Manager
Virtual link management
LAN Switches (Optional)
The control signaling network for the Cisco SS7 Interconnect for Voice Gateways Solution often consists of a LAN switch and the cabling required to interconnect the solution components in an SC zone. This solution supports a LAN switch from the Cisco Catalyst switch family. This switch can extend VLANs across platforms through backbone Fast Ethernet, Gigabit, or ATM connections, when necessary.
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Posted: Thu Oct 21 10:02:45 PDT 2004
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