---
title: "Soft switching architecture and management"
subject: "Telecommunications"
chapter: 8
key: "semester_8/telecommunications:soft-switching-architecture"
source: https://www.bctengineer.com/q/semester_8/telecommunications/soft-switching-architecture
site: BCT Engineering
---

# Soft switching architecture and management

Telecommunications · Chapter 8: Data Communication

- Asked in: 2081 Chaitra, 2+4 marks; 2080 Baisakh, 2+4 marks; 2078 Bhadra, 2+6 marks; 2073 Shrawan, 2+6 marks (asked 4 times)
- Video: [Tutorial: What is a Softswitch?](https://www.youtube.com/watch?v=qsiOb8Xazfw) — Teracom Training Institute
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/telecommunications/soft-switching-architecture
- Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-8

## Question

What is soft switching? Describe its architecture, functions and management.

## Short answer

Soft switching separates software-based call control (softswitch) from hardware media gateways. The architecture includes a softswitch controlling media and signalling gateways via H.248/MGCP and SIGTRAN over an IP core. Functions include call control, routing, signalling interworking, and CDR generation. Management uses FCAPS for fault, configuration, accounting, performance, and security.

## Answer

#### Soft switching

**Soft switching** is a switching method in which **call control is done by software** on a general-purpose server (the **softswitch** or call agent), separate from the hardware that carries the media. The softswitch controls media gateways over an IP network, so one software platform can handle PSTN, VoIP and mobile calls. It is the core of next-generation networks (NGN).

#### Architecture

```text
+---------------------------------------------+
| Application layer: app servers, IN, billing |
+----------------------+----------------------+
                       | SIP / APIs
+----------------------+----------------------+
| Control layer: SOFTSWITCH (call agent/MGC)  |
+-----+----------------+---------------+------+
      | H.248/MGCP     | SIGTRAN       | SIP
+-----+-----+   +------+-----+   +-----+-----+
|  Media    |   | Signalling |   | IP phones |
|  gateway  |   |  gateway   |   | / SIP UA  |
+-----+-----+   +------+-----+   +-----------+
      |  transport layer: IP/MPLS core   |
   PSTN trunks       SS7 network
```

1. **Softswitch / Media Gateway Controller (MGC):** call control, routing, signalling interworking, number analysis.
2. **Media Gateway (MG):** converts TDM voice (PSTN) to RTP/IP packets and back, under the control of the MGC via **H.248/Megaco** or **MGCP**.
3. **Signalling Gateway (SG):** converts SS7 signalling to IP (SIGTRAN, M3UA/SCTP) for the softswitch.
4. **Application server:** value-added services (voicemail, prepaid, conference, IN services).
5. **Media server:** tones, announcements, IVR, conference mixing.
6. **Transport (IP/MPLS) network** that carries both media and signalling.

#### Functions

- Call setup, supervision and release (call control).
- Signalling interworking: SS7, ISUP, SIP, H.323, H.248.
- Routing and number translation.
- Control of media gateways and allocation of resources.
- Service invocation through application servers.
- Generation of CDRs for billing; authentication and authorisation.

#### Management

The softswitch network is managed by an OSS/NMS using FCAPS:

| Area | Task |
|---|---|
| Fault | alarms, failover, redundancy |
| Configuration | gateways, routes, numbering, users |
| Accounting | CDR collection, billing |
| Performance | traffic, QoS, delay, packet loss |
| Security | access control, encryption, firewalls |

Management uses SNMP and web/CLI interfaces, often remotely.

**Advantages:** lower cost, open interfaces, easy addition of new services, scalability, and one platform for voice and data.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What defines soft switching?
   A. Call control done in software on a server, separate from the hardware carrying media
   B. Switching using analog crossbars
   C. All media carried by the controller
   D. Call control inside each gateway
   Answer: A. The softswitch performs call control and controls media gateways separately. (Key point: Definition of soft switching)

2. What does the media gateway do under MGC control?
   A. Converts SS7 to IP
   B. Provides billing
   C. Converts TDM voice to RTP/IP packets and back
   D. Plays announcements only
   Answer: C. The MG converts PSTN TDM voice to IP, controlled by H.248/Megaco or MGCP. (Key point: Media gateway)

3. Which element carries SS7 signalling to the softswitch over IP?
   A. Media server
   B. Application server
   C. Media gateway
   D. Signalling gateway using SIGTRAN
   Answer: D. The SG converts SS7 to IP via SIGTRAN (M3UA/SCTP). (Key point: Signalling gateway)

4. In FCAPS management of a softswitch network, which area covers CDR collection and billing?
   A. Accounting
   B. Fault
   C. Security
   D. Performance
   Answer: A. Accounting covers CDR collection and billing. (Key point: FCAPS management)

## Related in Telecommunications

- [Short note: Soft switching](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Ashort-note-soft-switching) — Telecommunications, chapter 8, asked 3×
- [IP and soft switching for PC-to-PSTN calls](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aip-soft-switching-skype-pstn) — Telecommunications, chapter 8
- [Switching functions and three-stage crosspoints](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aswitching-functions-crosspoints-4x4) — Telecommunications, chapter 4, asked 2×
- [Conventional exchange functions; PCM switching advantages](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aconventional-exchange-pcm-advantages) — Telecommunications, chapter 4
- [Digital switching system and its functions](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Adigital-switching-functions) — Telecommunications, chapter 4
- [NTA functions; IP switching structure](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Anta-functions-ip-switching) — Telecommunications, chapter 7

## Related in other subjects

- [Define management; functions of management](https://www.bctengineer.com/question.md?key=semester_7%2Forganization_and_management%3Amanagement-functions) — Organization and Management, chapter 2, asked 3×
- [Personnel management and its functions](https://www.bctengineer.com/question.md?key=semester_7%2Forganization_and_management%3Apersonnel-mgmt-functions) — Organization and Management, chapter 7, asked 3×
- [Spectrum management and regulatory functions](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Aspectrum-management-regulatory) — Wireless Communication, chapter 1, asked 2×
- [Importance and functions of management](https://www.bctengineer.com/question.md?key=semester_7%2Forganization_and_management%3Amanagement-importance-functions) — Organization and Management, chapter 2