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

# Short note: Soft switching

Telecommunications · Chapter 8: Data Communication

- Asked in: 2081 Bhadra, 4 marks; 2080 Chaitra, 4 marks; 2080 Bhadra, 4 marks (asked 3 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/telecommunications/short-note-soft-switching
- Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-8

## Question

Write a short note on soft switching.

## Short answer

Soft switching separates call control (software on a softswitch) from media hardware. A softswitch handles call setup, routing, and signalling, while media gateways convert TDM voice to IP packets. It uses protocols like H.248/MGCP and SIGTRAN, offering lower cost and faster service introduction.

## Answer

**Soft switching** is a switching technique in which **call control is performed by software** on a server called a **softswitch**, separated from the hardware that carries the voice. It is the core of next-generation (IP-based) networks.

```text
     [Softswitch / Call agent]
      |H.248/MGCP     |SIGTRAN
 [Media gateway] [Signalling gateway]
      |                 |
 PSTN trunks        SS7 network
      \_____ IP / MPLS core ____/
```

**Main elements**

- **Softswitch (Media Gateway Controller):** call setup, routing, signalling and billing records.
- **Media gateway:** converts TDM voice to IP packets (RTP).
- **Signalling gateway:** carries SS7 signalling over IP.
- **Application and media servers:** services, announcements, conferencing.

**Protocols:** SIP, H.323, H.248/Megaco, MGCP, SIGTRAN.

**Advantages**

- Lower cost and space than circuit switches.
- Open, standard interfaces; vendor independence.
- Fast introduction of new services.
- Same network carries voice, video and data.
- Easy to scale by adding servers and gateways.

## Check yourself

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

1. What does the softswitch (MGC) do?
   A. Converts voice to RTP
   B. Handles call setup, routing, signalling and billing records
   C. Only plays announcements
   D. Carries SS7 links
   Answer: B. The softswitch handles call control: setup, routing, signalling and billing records. (Key point: Softswitch role)

2. Which protocols are associated with softswitching?
   A. Only TDM
   B. ARP and DHCP only
   C. SIP, H.323, H.248/Megaco, MGCP, SIGTRAN
   D. FTP and SMTP
   Answer: C. Softswitches use SIP, H.323, H.248/Megaco, MGCP and SIGTRAN. (Key point: Protocols)

3. Which is an advantage of soft switching?
   A. Closed vendor-specific interfaces
   B. Open standard interfaces and quick introduction of new services
   C. Higher space needs than circuit switches
   D. Separate networks for voice and data
   Answer: B. Open interfaces, vendor independence, fast new services and one network are advantages. (Key point: Advantages)

## Related in Telecommunications

- [Soft switching architecture and management](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Asoft-switching-architecture) — Telecommunications, chapter 8, asked 4×
- [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