Friday 24 August 2007

Next Generation Networks (NGN)

Next Generation Networks (NGN)

Next Generation Networks are based on Internet technologies including Internet Protocol (IP). For voice applications one of the most important devices in NGN is a Softswitch (The Softswitch also acts as an MGC) a programmable device that controls Voice over IP (VoIP) calls. It enables correct integration of different protocols within NGN. The most important function of the Softswitch is creating the interface to the existing telephone network, PSTN, through Signalling Gateways (SG) and Media Gateways (MG). However, the Softswitch as a term may be defined differently by the different equipment manufacturers and have somewhat different functions.

Media gateway controller (MGC)

MGC is residing on the control layer of Next Generation Network architecture, providing multi-service and packet voice connection control, routing, management of network resource, billing, authentication and all other functions. Secondly, MGC should interworking with other network elements such as trunking gateways, signaling gateway, multimedia application servers, other MGC and the existing/others SCP (for IN services) using standard protocols. MGC has to be able to support basic class 4 and class 5 functionality such as basic SPC services, some of advanced IP services, management & control of IP phone (both SIP and H.323) and Integrated Access Device (IAD) as well.
MGC has to support the following item.

Interfaces:
The MGC shall support the following interfaces:
-IEEE 802.3x with 100 Base TX Ethernet for carriage of MGCP and ITU-T H.248 and SIP and SIP-T and H.323 signaling to core packet network.
-IEEE 802.3x with 100 Base TX Ethernet for communication to NMC and any OAM terminal.
-IEEE 802.3x with 100 Base TX Ethernet for Input/Output functions including download of billing data, operational measurements, traffic statistics, logs and alarm information.
-All 100 Base TX Ethernet inter must comply with IEEE 802.3x full duplex mode operation.
-E1 physical G.703 attached to STP exchanges in case of integrated functional of SS7 gateway.

Redundancy and Reliability
-MGC must be a fault tolerant design. MGC should be highly reliable and highly stable. It should be built around a hardware platform delivering carrier grade, that is ‘five nines’ 99.999% availability.
-Essential components of MGC such as main processor board, communication board, power supply and so on must follow redundant design and be able to support insertion or removal with power on (hot swappable).
-The active to standby and vise versa switchover of main control part of MGC either causes from automatically by the MGC itself or manually switchover by the operator shall not affect any services and current calls and any call detail record (CDR) running in progress.
-MGC platform should adopt the dual-host system, work as hot backup mode. When the active host is faulty, the standby host will automatically switch over and take charge of the original active host’s function. And the switchover time should be less than 15 seconds to ensure the system reliability.
-All data storage devices should be mirrored disks or configured as RAID.
-MGC platform should adopt hot-backup mode based on highly reliable system with hardware and software fault tolerance design.

Major Functionality
-The MGC shall have integrated function of SIP proxy server, SIP redirect server and SIP registrar in order to comply with IETF RFC 2543 to be able to manage and control the difference SIP endpoints, e.g. SIP user agent or SIP phone.
-The MGC shall be able to support the H.323 trunk side so the MGC shall be interoperable with others gatekeeper in H.323 network.
-The MGC shall be able to support managing and controlling of its own difference H.323 endpoints, e.g. H.323 phone and H.323 softphone by using H.323 and its protocol suites.
Protocol supported
-IETF SIP
-IETF SIP-T (SIP for Telephony)
-MGCP and H.248
-H.323 V.4
-PARLAY API V 3.0
-JAIN
-CORBA
-SIGTRAN
-SCCP/TCAP/INAP(CS1&CS2) in case of integrated SS7 signalling gateway to interconnect to others SCP.
-SNMP
-ITU-T Standard White book ISUP
-ITU-T ISUP (TOT’s version).
-The MGC shall be able to support PARLAY or JAIN (Java Application for Integrated Network) or CORBA (Common Object Request Broker Architecture) or SIP (Session Initiation Protocol) for Application Program Interface to inter-operate with the third party server who is providing variety of IP services/features.
-The MGC shall support Time of Day synchronization via an NTP server
-As a minimum the MGC must effect call set-up, control and tear down using MGCP (RFC 2705) or ITU-T H.248 signaling to:
Access Gateway
Trunk Gateway
Media Server
-If the present MGC – TG call setup protocol is IETF MGCP, bidder shall offer the option for upgrading overall system (MGCs, TGs and NMS) to ITU-T H.248 (MEGACO)
-The MGC shall also support ISDN signaling using IUA over the packet network to Trunk Gateways supporting connection of ISDN PRI services.
-MGC shall be able to effect call set-up and tear down between any of the following network elements:
Recorded announcement on Media Server.
ISUP Trunks supported on Trunk Gateway.
PRI Trunks supported on Trunk Gateway.
Tones or recorded announcements on Trunk Gateway
-The MGC shall be able to decode and generate all ISUP messages, perform any functions indicated by an ISUP message, and create any suitable response.
-The MGC shall support, and be compliant to, Blue Book ITU-T Recommendations E.164 addressing schemes.
-The MGC must support termination of call to tones or recorded voice announcement on trunk gateway according to the nature of the failure of the call.
-MGC must have a management of IAD and IP phone, SIP Phone, H.323 soft phone.
-MGC must have a management of IAD and IP phone, SIP Phone, H.323 soft phone.
-MGC software upgrading should be conducted online without any interruption of the running services, and online services loading should also be possible.
-MGC shall have traffic management function and self-adaptive overload control capability. According to overload cause and conditions, the corresponding algorithms should be dynamically used to carry out different degrees of filtration of service calls, to ensure safety of network operation.
-MGC shall control TG or Access gateway (via MGCP/H.248 protocol) even though the TG and Access gateway is another supplier’s.
-MGC must be able to support at least basic SPC functions such as :
Call Waiting
Caller Identification Presentation/Restriction
Caller ID Presentation on Call Waiting
Multiple numbering/identification on same device.
Call Conferencing
Selective Incoming Caller ID Restriction
Outgoing Call Barring
Call Forwarding
Close User Group
Anonymous Call Rejection
Carrier Pre-Selection
Abbreviate Dialing
Access to operator for assistance and information
Access to recorded announcements
Access to community services (public utilities and emergency calls)
Payphone service
Private branch exchange
Malicious call identification service
Interception service
Line observation service
Call barring service
Priority service
Hot line service
Do not disturb service
Automatic call repetition service
Subscriber with private meter service
Centrex service
Virtual private network (vpn) service
Absent subscriber service
Reminder (alarm) call service (call wake up)Last

Trunk gateway (TG)
Trunk gateway provides the direct translation to/from the TDM media of traditional (legacy) carrier infrastructures such as voice, fax DTMF, special tone, modem call to/from packet media.
TG has to support the following item.

Major Functionalities
- TG shall be able to correctly compatible with the existing PSTN and VOIP network.
- TG shall be able to support completely remote software upgrading from centralize unit such as MGC.
- TG shall be able to comply with SDP Protocol (Session Description Protocol, RFC 2327) in order to communicate with MGC by using MGCP Protocol.
- TG shall be able to automatically detect all types of traffic such as: Voice, Fax DTMF and Modem call and must be able to serve these traffic by using any port.
- TG shall be able to support VoIP – modem relay function in order to carries modem traffic from ingress to egress gateways over IP network according to standard ITU-T V.150.0 and V.150.1
- TG shall be able to support voice activity detection (VAD) which will detect and suppress the silence in voice call of the caller at sender trunk gateway.
- TG shall be able to support Comfort Noise Generator (CNG) which is complementary function to VAD expressed. Its function is to insert some signal to called subscriber line to give them pleasant impression that the conversation still active even during the sender TG sending nothing.
- TG shall be support SIGTRAN (ITU-T Signalling System No.7 over IP),
- The TG shall support IUA (ISDN User Adaptation) to carry ISDN Dchannel signaling information from connecting E1 PRI to the MGC.
- TG shall support at least IETF MGCP and must be able to upgrade to fully support ITU-T H.248 signaling from the MGC to effect voice path connection across the core packet (IP) network.
- TG shall support at least the following CODECs (the conversion of TDM voice to packet):
ITU-T G.711 (u-law and A-law) Compression rate 64 kbps
ITU-T G.723.1 Compression rate 5.3and 6.3 kbps
ITU-T G.726 (ADPCM) Compression rate 16 , 24 , 32 , and 40 kbps
ITU-T G.729A (CS-ACELP) Compression rate 8 kbps
ITU-T G.729B (CS-ACELP) Compression rate 11.8 kbps
- TG shall support ability to pre-define type of CODEC respect to type of traffic or user administrator’s decision.
- TG shall support ITU-T G.168 echo cancellation with at least 128 milli-second tail.
- The TG shall support DTMF tone detection, generation, collection and transmission of the decoded information.
- The TG shall have the ability to modify packetization rate as 10 ms, 20 ms and 30 ms respect to the using CODEC.
- TG shall be able to deliver announcements/tones to connecting TDM trunks under instruction from the MGC.
- TG shall have ability to dynamic programmable of jitter buffer.
- TG shall be able to support both T.37 and T.38 Fax transport over IP network.
- TG shall support time synchronization using an NTP (Network Time Protocol) client. At boot and thereafter on a regular basis the TG should synchronize its date and time with a network NTP server.
- TG must support synchronization/clocking to an external timing source. At least three levels of synchronization must be supported with the final level being an internal clock source of Stratum 3 performance or better.
- TG shall be controlled by the MGC (via H.248 protocol) even though the MGC is another supplier’s.
- TG shall support feature DTMF delay according to RFC 2833.

Traffic Management
- TG shall support the RSVP (ReSource Reservation Protocol – RFC 2205) architecture to establish path between endpoints (source and destination TG or IAD) together with core routers, with the goal of delivering high QoS on a media stream along the path.
- TG shall support the DiffServ (Differentiated Services - RFC 2475) architecture that source endpoint shall be able to specify TOS(Type of Services) bits in standard IP packet header to define classes of service that is method by which packet of a classification will be queued , forwarded and/or considered for discard during congestion when those packets reach DiffServ Node, core routers.
- TG shall support ability to manage the size of jitter buffer to preserve a good quality of packet voice at receiving endpoint.
- TG shall support IP/UDP/RTP/RTCP header compression function for reduce end-to-end packet overhead.

Maintainability & Reliability
- The TG shall have the ability to accept the request for a graceful shutdown of the entire gateway, completing all active calls before the gateway is taken off-line for maintenance.
- The TG shall offer real time reporting of performance related information (i.e., performance threshold crossing alerts related to service affecting conditions on individual connections). The statistics to include the following and the information is to be sent to the MGC.

Interface
- The TG shall support the following interfaces to narrow-band PSTN network for carriage of ITU-T Signaling System number 7, ISUP signaling,
- The TG shall support the E1 interfaces to a narrow band TDM network for the carriage of ISDN PRI trunks
- The electrical interfaces to PSTN side shall be complied with ITU-T G.703
- The TG shall support the multiple ethernet IEEE 802.3x (full duplex flow control with 100 Base-TX) to a communicate with IP core network for the carriage of converted IP packets traffic

Redundancy
- shall support 1:1 redundancy on primary controller.
- TG shall support 1:1 redundancy on packet network interfaces, with automatic changeover in the event of the detection of a circuit failure.
- TG shall support 1:1 or N:1 redundancy on voice processing circuits