Introduction

The purpose of this article is to publish the technical specifications of the telecommunications network interfaces through which telecommunications services of modulus S.A. are provided, in compliance with the obligations arising from Presidential Decree 44/2002 (Government Gazette 44/A/7-3-2002) “Radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity. Adaptation of Greek legislation to Directive 99/5/EC of the European Parliament and of the Council of 9 March 1999” and the HCMC Decision no. ΑΠ 294/55/2003 “Regulation for the publication of technical interfaces of public telecommunications networks, according to PD 44/2002” (Government Gazette 1590/B/03).

Please note that modulus is a provider of access to the public electronic communications network for voice services exclusively through logical, and not physical, circuits. The service is provided through the public Internet, access to which subscribers must secure by their own means. Internet access itself is not provided by modulus. Furthermore, modulus does not provide equipment to its subscribers for receiving the services it offers, while the responsibility for the procurement and maintenance of such equipment lies solely with the subscribers. modulus cannot guarantee the proper operation of the service if the equipment selected by the subscriber or services provided by third parties do not comply with the specifications of this document. The specifications below may not necessarily apply simultaneously in all cases of connection to the logical network of modulus.

L2 Interface Characteristics
 

modulus S.A. provides telecommunications services to end users through the following physical interfaces:

• Indirect interconnection via packet-switched public networks
• Leased Line (Ethernet) at one of the data centres where modulus has a presence

L3 Interface Characteristics
 

• [RFC 791] – Internet Protocol (IP)

  • [RFC 1349] - Type of Service in the Internet Protocol Suite

  • [RFC 2474] - Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

  • [RFC 6864] - Updated Specification of the IPv4 ID Field

• [RFC 792] – Internet Control Message Protocol (ICMP)

  • [RFC 6918] - Formally Deprecating Some ICMPv4 Message Types

  • [RFC 4884] - Extended ICMP to Support Multi-Part Messages

  • [RFC 6633] - Deprecation of ICMP Source Quench Messages

• [RFC 950] – Subnetting

  • [RFC 1812] – Requirements for IP Version 4 Routers

  • [RFC 3168] – The Addition of Explicit Congestion Notification (ECN) to IP

  • [RFC 815] – IP Datagram Reassembly Algorithms

L4 Interface Characteristics
 

• [RFC 9293] – Transmission Control Protocol (TCP)

• [RFC 5246] – The Transport Layer Security (TLS) Protocol Version 1.2

• [RFC 8446] – The Transport Layer Security (TLS) Protocol Version 1.3

• [RFC 1122] – Requirements for Internet Hosts -- Communication Layers

  • [RFC 6298] – Computing TCP's Retransmission Timer

• [RFC 768] - User Datagram Protocol (UDP)

L4+ Interface Characteristics
 

• [RFC 3261] - SIP: Session Initiation Protocol

  • [RFC 3581] - An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing

  • [RFC 4320] - Actions Addressing Identified Issues with the Session Initiation Protocol's (SIP) Non-INVITE Transaction

  • [RFC 5621] - Message Body Handling in the Session Initiation Protocol (SIP)

  • [RFC 5626] - Managing Client-Initiated Connections in the Session Initiation Protocol (SIP)

  • [RFC 5922] - Domain Certificates in the Session Initiation Protocol (SIP)

  • [RFC 6141] - Re-INVITE and Target-Refresh Request Handling in the Session Initiation Protocol (SIP)

  • [RFC 6665] - SIP-Specific Event Notification

  • [RFC 8996] - Deprecating TLS 1.0 and TLS 1.1

• [RFC 3263] - Session Initiation Protocol (SIP): Locating SIP Servers

• [RFC 6086] - Session Initiation Protocol (SIP) INFO Method and Package Framework

• [RFC 3311] - The Session Initiation Protocol (SIP) UPDATE Method

• [RFC 3323] - A Privacy Mechanism for the Session Initiation Protocol (SIP)

• [RFC 3264] - An Offer/Answer Model with the Session Description Protocol (SDP)

• [RFC 3324] - Short Term Requirements for Network Asserted Identity

• [RFC 3325] - Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks

• [RFC 3326] - The Reason Header Field for the Session Initiation Protocol (SIP)

• [RFC 3327] - Session Initiation Protocol (SIP) Extension Header Field for Registering Non-Adjacent Contacts

• [RFC 3362] - Real-time Facsimile (T.38) - image/t38 MIME Sub-type Registration

• [RFC 3515] - The Session Initiation Protocol (SIP) Refer Method

• [RFC 5009] - Private Header (P-Header) Extension to the Session Initiation Protocol (SIP) for Authorization of Early Media

• [RFC 5589] - Session Initiation Protocol (SIP) Call Control - Transfer

• [RFC 3550] - RTP: A Transport Protocol for Real-Time Applications

• [RFC 3711] - The Secure Real-time Transport Protocol (SRTP)

• [RFC 3966] - The tel URI for Telephone Numbers

• [RFC 4028] - Session Timers in the Session Initiation Protocol (SIP)

• [RFC 4694] - Number Portability Parameters for the "tel" URI

• [RFC 4568] - Session Description Protocol (SDP) Security Descriptions for Media Streams

• [RFC 8643] - An Opportunistic Approach for Secure Real-time Transport Protocol (OSRTP)

• [RFC 7714] - AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP)

• [RFC 5761] - Multiplexing RTP Data and Control Packets on a Single Port

• [RFC 4585] - Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)

• [RFC 5124] - Extended Secure RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/SAVPF)

• [RFC 4733] - RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals

• [RFC 3551] - RTP Profile for Audio and Video Conferences with Minimal Control

• [RFC 8866] - SDP: Session Description Protocol

Voice Codecs
 

• ITU-T G.711 (11/1988), General Aspects of Digital Transmission Systems; Terminal Equipment; Pulse Code Modulation (PCM) of Voice Frequencies

• ITU-T G.722 (09/2012), 7 kHz Audio Coding within 64 kbit/s

• ITU-T G.729 (06/2012), Coding of Speech at 8 kbit/s Using Conjugate-Structure Algebraic-Code-Excited Linear Prediction (CS-ACELP)

Voice Configuration
 

• SIP Proxy:

  • A record: voips.modulus.gr or voips-ng.modulus.gr

  • SRV UDP: _sip._udp.voips.modulus.gr

  • SRV TLS: _sip._tls.voips.modulus.gr

  • IP 1: 185.73.43.250/32

  • IP 2: 185.73.42.250/32

• SIP Proxy Ports:

  • UDP: 5060, 6050

  • TLS: 5061

• RTP Proxy Ranges:

  • 185.73.43.248/29

  • 185.73.42.248/29

• RTP Proxy Ports:

  • UDP: 20000-60000

• Supported DTMF Modes:

  • Inband

  • RFC 4733