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This chapter briefly describes the various Cisco SS7 Interconnect for Access Servers Solution configuration options and the required and optional components:
The Cisco SS7 Interconnect for Access Servers Solution provides the following configuration options:
You can deploy the Cisco SS7 Interconnect for Access Servers Solution in one of three ways:
A simplex configuration is an SC node that consists of a single SC host (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 network access servers provide for bearer channel termination. See Figure 2-1.
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Note Simplex configurations provide no fault tolerance and are typically used for solution testing or validation or noncritical installations. If the host fails, calls are dropped, and service is discontinued. |
A fault-tolerant configuration is similar to a simplex configuration; however, the SC host must be a Sun Netra t 1400 server platform providing redundant components. If any redundant component fails, the backup component takes over; established calls are maintained.
A continuous service configuration is an SC zone that consists of a pair of SC hosts running in active mode and standby mode, operating with one or more network access servers and two 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, and 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 network access server.
The Cisco SS7 Interconnect for Access Servers 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 NASs. One signaling controller might provide signaling and call-processing services for multiple NASs in geographically distributed locations.
Cisco SLT---Handles the incoming and outgoing SS7 messages (MTP layer 1 and 2) from the A-links connected to Signal Transfer Points (STPs) or F-links connected to other 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 sends the bearer channels to the NAS.
Cisco Network Access Server---Provides termination for bearer trunks. A NAS functions as a server to the bearer links. The NAS 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 Access Servers 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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Note Type of connection would depend on your specific network requirements. |
In the A-link SLT signaling configuration, the Cisco SLT processes the two lowest-layer SS7 signaling protocols, MTP1 and MTP2. The upper layer protocols are then forwarded to the Cisco MGC host over the control signaling network. Each SLT supports two signaling network connections,and multiple SLTs can be used to support additional signaling channels or provide redundant signal paths between the signaling network and the control signaling network.
The A-link SLT signaling configuration supports V.35, T1, and E1 interfaces using signaling interfaces installed in the Cisco SLT. The A-link SLT configuration can be used with simplex and continuous service configurations. Each interface supports a single DS0 signaling channel, as illustrated in Figure 2-3.
F-link SLT signaling configurations are similar to A-link SLT configurations. The SS7 network connection is made through fully associated links that connect an SSP or SCP to the Cisco SLT.
The F-link SLT signaling configuration supports V.35, T1, and E1 interfaces using signaling interfaces installed in the Cisco SLT. The F-link SLT configuration can be used with simplex and continuous service host configurations. Each interface supports a single DS0 signaling channel.
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 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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Note The A-Link and F-link Drop and Insert techniques are also known as time-division multiplexing (TDM) cross-connect. |
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, the Cisco SLT grooms the bearer traffic and then 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.
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.
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 Access Servers Solution components and the level of redundancy that you require. Other factors to consider are:
Control traffic (signaling) should be segregated from the bearer traffic on the QoS packet network (towards the Internet/intranet). This optimizes control traffic latency and provides added security. Redundancy in your control network can be provided by duplicating your Cisco SS7 Interconnect for Access Servers Solution components. In the event that the control network fails or connectivity to it fails, the QoS packet network is used for signaling.
In the simplest case, your Cisco SS7 Interconnect for Access Servers Solution components are co-located, and a pair of LAN switches serves as your control network. However, it is also possible that Cisco SLTs, and NASs, are geographically separate from the SC hosts, requiring a control network with WAN links and separate routers to provide the WAN connection.
Figure 2-2 shows a sample continuous service 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 service configuration example, the control signaling network functions are:
The QoS packet network functions are:
Distributed IP control networks operating over a WAN is necessary when:
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Note The NAS is equipped with serial ports providing WAN termination. |
The following IP control network combinations are recommended:
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Note The subnet mentioned in your IP control network can be a dedicated hub or switch running at 10 or 100 Mbps (10 Mbps for SLTs) or a VLAN configured in a switch sharing backplane bandwidth with other VLANs. |
When engineering your network, you must consider the following issues:
Figure 2-5 displays the components of the Cisco SS7 Interconnect for Access Servers Solution.
See the "SS7 Technology Overview" appendix for information about how the Cisco SS7 Interconnect for Access Servers Solution components operate within the SS7 hierarchy.
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 Access Servers Solution consists of one or more SC hosts, one or more Cisco SLTs, the signaling controller software, and ancillary equipment.
An SC host is a Sun hardware platform running signaling controller software.
Table 2-1 lists supported SC hosts for the Cisco SC2200 product
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| SC Host | Description | |||
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Sun Ultra Enterprise 450 (E450) | The Sun Ultra Enterprise 450 is a high-performance, shared-memory, multiprocessing, general-purpose
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Sun Netra t 1120/1125 | The Sun Netra t 112x is a general-purpose Sun Ultra SPARC server. The Sun Netra t 112x is rack-mountable and is NEBS and ETSI compliant. The Sun Netra 1120 uses DC power and the | |||
Sun Netra t 1400 | The Sun Netra t 1400 is a fault-tolerant, dual modular, redundant architecture. Additional lockstep operations give this host the ability to isolate and recover from hardware failure.The | |||
The primary functions of the signaling controller is performing protocol conversion and call screening. The signaling controller is responsible for:
Table 2-2 lists the features for the SC host.
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| Feature | Support for ... |
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Call performance per signaling controller |
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Management interfaces |
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Signaling protocols |
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Scaling of point codes | 250+ DPCs and 6 OPCs |
Faults and alarms management | SNMP traps |
Millisecond time stamp | Millisecond time stamps on log records of diagnostic messages, set and clear alarm messages (sets and clears), alarm messages recorded by the Data Dumper, and alarm messages in the responses for the MML commands "rtrv-alms" and "rtrv-alms:CONT" |
Enhanced logging facility |
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Configuration management |
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Accounting | CDR (CSV format) support for international carrier requirements |
Resource management |
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Performance measurements and statistics | Supports carrier requirements |
Security | Structured system of passwords |
Operating system | Sun Solaris 2.6.x |
The Cisco SS7 Interconnect for Access Servers Solution SC2200 product requires the following software release levels listed in Table 2-3.
| Software Release Level | Support for... |
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Cisco MGC Software Release 7.3 | Signaling controller software running on the SC host |
Cisco IOS Release c2600-ipss7-mz | Software running on the Cisco SLT |
Cisco IOS 12.0(7)XR or later releases | Cisco IOS release running on the network access server |
Sun Solaris 2.6.x | Operating system running on the SC host |
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.
Table 2-4 lists the features for the Cisco SLT.
| Feature | Support for... |
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SS7 link termination on a high-availability platform | SS7 network access and interconnection requires a high degree of reliability in the signaling links and associated equipment. The Cisco SLT provides the reliability of a dedicated signaling link termination device and maximizes the availability of the SS7 signaling links. |
Distributed SS7 MTP processing | Processor-intensive parts of the SS7 Message Transfer Part (levels1 and 2) are offloaded from the signaling controller to the Cisco SLT. This distributed MTP model allows the signaling controller to better utilize its resources to provide optimal call control. |
Call control | Signaling backhaul provides a means for integrating the Cisco Signaling Link Terminals into a virtual switch with the call control intelligence centralized in the signaling controller system. |
Standard Physical Interfaces | Interconnection with SS7 network elements is supported using the most popular SS7 physical interface standards: T1, E1, V.35, RS-449, and RS-530. |
Drop and Insert | Cisco T1/E1 Multiflex Voice/WAN interface cards (VWICs) support Drop and Insert (also called TDM Cross-Connect), which allows individual T1/E1 channels to be transparently passed, uncompressed, between T1/E1 ports. This feature enables direct termination of SS7 F-links in T1 or E1 carriers, while the remaining bearer channels are hairpinned back to a gateway device for processing. |
The NAS terminates the PSTN trunks, also referred to as bearer channels, that carry the call traffic. The PSTN trunks are T1 or E1 PRI interfaces.
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Note Cisco IOS 12.0(7)XR or later releases run on the network access server. |
Table 2-5 lists the features for the Cisco AS5x00.
The control signaling network for the Cisco SS7 Interconnect for Access Servers Solution often consists of a LAN switch and the cabling required to interconnect the solution components in an SC zone. The Cisco SS7 Interconnect for Access Servers 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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Note The Catalyst LAN switch is not provided with the Cisco SC2200 product. |
Posted: Thu Jun 15 14:46:26 PDT 2000
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