Traditional SS7 Protocol

1. Message transfer part 2 (MTP2)

MTP2 corresponds to OSI Layer 3 (the data link layer) and such is the lowest protocol in the stack.Sitting on the phisical layer, its provide a realiable means of transfer for siganling information between two direcly connected singaling point (SPs),ensuring that the signaling information is delivered in the sequence and error free

MTP2 performs the following functions:

1.Delimination of signal units
2.Alignment of signal units
3.Siganling link error detection
4.Siganling link error correction by retransmission
5.Signaling link initial alignment
6.Error monitoring and reporting
7.Link flow control

Message transfer part 3 (MTP3)

The primary purpose of this protocol is to route message between SS7 network node in the reliable manner.This responsibility is devided into two categories:

1.Signaling message handling (SMH)

2.Siganling network management (SNM)

SMH is concerned with the routing message to the appropriate network destination.Each node analyzes the incoming message based on its destination point code (DPC) to detemine whether the message is destined for that node.If the receiveing node is the destination, the incoming message is delivered to the appropriate MTP3 user.If the receiving node is not the destination and the message has routing capability, i.e, is an STP, an attempt us made to route the message
SNM is set of message and procedures whose purporse is to handle network failure in a manner that allows message continue to reach their destiantion whenever possible.These procedures work together to coordinates SS7 resource that are becoming available or unavaiable with the demand of user traffic

ISDN user part (ISUP)

ISUP is responsible for setting up and releasing trunk used for inter exchange calls.As its name implies, ISUP was created to provide core network signaling that is compatible with ISDN access siganling.The combination of ISDN access signaling and ISUP network signaling provides end to end transport mechanism for signaling data between subscribers.ISUP provides siganling for both non ISDN and ISDN traffic, in fact the majority of ISUP signaled traffic currently originates from analog acccess signaling like that used by telephone service phone

The primay benefits of ISUP are its speed,increased signaling badwidth and standardization of message exchange.Providing faster call setup times than Channel Associated Signaling (CAS), it ultimately uses trunk resource more effectively.The difference in post dial delay for calls using ISUP trunk is quite noticeable to the subscriber who make a call that traverses several switches
ISUP consists of call processing, suplementary service and maintenance functions.

Signaling Connection Control Part (SCCP)

SCCP sits on top of MTP3 in the SS7 protocol stack.The SCCP provides additional network layer function to provide trandfer of noncircuit-related (NCR) signaling information,appliation management and alternative and more flexible methods of routing
SCCP was developed after the MTP and together with the MTP3 it provides the capabilities corresponding to layer 3 of the OSI references model

SCCP provides the folowing additional capabilities over the MTP:

1.Enhance MTP to meet OSI layer 3

2.Powerfull and flexible routing mechanism

3.Enhance transfer capability, including segmentation/reassembly when message is too large to fit into one Message Signal Unit (MSU

4.Connectionless and connection-oriented data transfer services

5.Management adn addressing of subsystem (primarly database-driven applicaiton)

Transction capabilities applicaiton (TCAP)

TCAP allows service at network to communicate with each other using an agrees upon of data elements.Prior to SS7, one of the problem with implementing swtiching service beyond the boundary of the lcoal switch was the propreitary nature of the switches.TCAP provides a generic interface between service that is based on the concept of componnents.Componnects comprise the instructure that service applications exchange at different nodes Read More..

FMC solution

Telecom convergence on IP networks has been underway for at least a decade, as both carriers and entrprise have sought to replace separate,single purpose infrastructures with integrated,multi service ones.This is evolution is reflected in the convergence of voice and data in enterprise campus IP telephony,consumer VoIP services and local carroer Digital SUbscriber Line (DSL) services.FMC merges service in the fixed line and mobile telecom worlds,as exemplified by voice roaming between a cellular network and a campus voice enable WLAN.
In its ultimate form,FMC reflects a true integration of underlying network and aasociated management infrastructures.But there are several interim steps in the way to the most seamless form of FMC

Broadly speaking,carriers rollouts of converged services begin with simple service bundling,followed by real integration of underlaying network infrastructure,followed by integration in operations support system (OSS). The baby step of carrier servies bundling can be taken without any techincal integration between the fixed and the mobile network, and only a consolidation of previously separate customer interface, e.g, single sales contact instead of two; an integrated support and help desk function and single bill for both mobile and fixed services.

The customers get some modest benefits in terms of consolidated purchasing and discounting leverage as well as fewer carriers to deal with.The carriers get some modest uptick in customer retention and can market its entry into FMC. Such service bundling is already taking place today,but that barely scratches the surface of FMC's potential

The benefits of FMC appear much more compelling to both the enterprise customer and the carrier once the underlying fixed and mobile telecom infrastructures - plus OSS functions for management, provisioning and billing - begin to converge.

The evolution toward true FMC service is projected to proceed through five major phases:

1. Phase 1: Basic network infrastructure convergence

already well underway.The carrier consolidates voice traffic onto its IP WAN using VoIP and the enterprise begins moving its campus voice service to some form of IP telephony, often using a hybrid approach than combines Time Divission Multuplexing (TDM) and VoIP.The main benefits are cost savings through reduction in capital expenditures for network infrastructure for network infrastructure and in operating expenses to maintain it

2. Phase 2: Addition of enterprise wireless LANs, followed by voice over WLANs

Party to well underway at most large enterprise. Enterprise WLANs move from limited deployments serving nomadic users in conference room and lobbies to ubiquitous campu wide coverage, serving as the primay means of network acccess for all users.Greater integration of wire and wireless LAN infrastructure begins , e.g the use of common authentication mechanisms and endpoint security plociy is enforced for both wired and wirelss LAN users,thus deploying voice over the WLAN

3. Phase 3: Early managed FMC services

were underway as of 2006. Carriers and carrier partnership begin to roll out the first managed FMC services, providing mobile users with the ability to roam seamlessly between cellular netwrok and enterprise voice enable WLANs, using dual mode handsets or PDAs equipmed with both Wi-Fi and 3G radios

4. Phase 4: Tighter integration of fixed and mobile network infrastructure and back office system

Begin in late 2007, with broader adoption expected in the beginning of 2009. FMC carriers and their partners began to functionally converge their network signaling and back office system. Consolidation of formely separate control paths for service setup and feature delivery enable new services beyond cellular to voice - over - WLAN roaming - e.g, push to talk voice and application like instant message that exploit a user's presence and availability profile

5. Phase 5: High value FMC application delivery

As the undustry matures and accelerates through 2011. With a truly integrated, multimedia infrastructure in place that supports any combination of information types, end device and access technologies, FMC providers begin to focus their efforts to developing new application services. They take further advantage of converged network' presence awareness, effectively delivering services to specific persons rather than device or via specific access networks.

Providers begin creatively mixing and matching once disparate services - voice, audio conferencing, video, video conferencing, text based instant messaging, email, games, SIP enabled conferencing and collaboration, broadcast video and audio - to serve an array of new applications and end user needs Read More..

DPI (Deep Packet Inspection)

The rapid growth and popularity of broadband service presents both opportunities and challenge for carriers. On the other hand, the popularization of such service as, P2P,online games,WebTV and VoIP means that many people are now using and enjoying these service and telling their friends abotu them, so the number of usrs is growing larger everyday. On the other hand,carriers now have to resolve a series of problems in relation to bandwidth management,content billing and information security

The most obvious problem has to do with P2P application.P2P technology in effect clears a path through the C/S traffic model.By adopting a non concentrated server mode, it is able to penetrate and break up server bottleneck and so it is now being widely used in many domains including downloading,streaming and VoIP.According to the statistic data, at present, P2P traffic accounts for over 50% of all online traffic and the percentage is growing higher all the time.Many people are even saying that P2P is a killer application or revolutionary technology.However most carriers' network planning and construction mode are not suitable for the P2P applications traffic model

In addition most network equipment is lacking int terms of efficient technical monitoring, so P2P application would not recognized if used. As a result,carriers are unable to properly identify or manage network applications.Hence their networks are always congested and operations are in a state of confusion pr facing some technical dilemma

Another barrier reratding carriers' development is that they are unable to implement content billing.Content billing means that a carrier is able to perform in depth analysis in data packets,differentiate type of user service and set reasonable rates according to service features
At present, as data services and content services have been developing, the lack of complete content billing modes make it virtually impossible to convert service increase into equivalent benefits.

What makes things worse is that the benefits derived from some services have even decreased. In providing voice, IM (instant messageing) and game applications, ISP and ICPs utilize cheap network resource to attract and develop users and recieve a huge portion of the profits. leaving carriers helpless, receiving an insubstantial portion of the profits.

Thus far content billing become an important threshold feature upon which are wireless carriers have started to deploy content billing and fixed netwrok carreirs are also investigating useful steps in this direction

Content security presents another headache for carriers.Over the past few years, intrussions and attacks from online hackers have resulted in huge loss for carriers.Although a firewall can repel some of these attacks, it offers little if any protection againts viruses that are hiden in IP packet net loads.Currently, network attacks have been gradually shifted toward high level application.According to recent statistics released by Gartner, the application layer has been the target of over 70% of network attacks, and the percentage is still increasing steadily.Therefore,content security has become a key focus in information security

While carriers are failing to identify services, implement content billing and not meeting information security demands, they are on the one hand being forced to pay more in terms of operation costs and are recieving lower customer satisfaction in return. Therefore, a major concern for carriers is acquiring the ability to perceive network applications and provide network service control and management measures, so that their networks are both operable and manageable

A positive step in this direction is the recent development of DPI.Deep Packet Inspection is a new technology is comparasion to ordinary message analysis.Ordinary message inspection only analyze contents under layer 4 of each IP packet, which includes the source address, destination address, source port, destination port and protocol type.So on this basis DPI is capable of implementing analysis on the application layer that can identify applications and their contents

In fact, DPI technology has already been applied in the security protection system of intranets.Since its application scope is relatively samll, it has thus far not attracted much attention,However the forces that are currently driving it to center stage are P2P application and content billing Read More..

Metro Transport network

MSTP is based on SDH,can enjoy existing SDH network resource and provides various interface to support data service such as ethernet and ATM.Through the analysis of SDH network operational,maintenance and management experience,MSTP is fully compatible with existing TDM service and can integrate multiple service transport and access to meet upward spiraling data service commands.

Fro traditional carriers with mature SDH network offering a huge quantity of TDM service,MSTP is the most direct and efficient metro transport network solution.

MSTP has been widely applied and most new metro SDH networks are MSTP.To efficienly process and transmit data service,it utilize some key technologies including GFP,VC (virtual connection) and LCAS (Link capacity adjustment scheme).As MSTP is TDM based,the service mode it suits is the provision of traditional TDM service while partially supporting IP and ATM service.

MSTP can be located on the convergence adn access layers of a metro transport network and can integrate service networks into both

The existing network environment bears traditional TDM services, whereas MSTP can reliably bear new,high capaity services such as ethernet leased line,point to multipoint and ring services.Integrated access with convergence from DSLAM to BRAS can be offered to large scale customers and it can also transmit NGN and 3G services

MSTP mainly exist as a layer 1 network and is not suitable for large scale layer 2 and layer 2 services.Ehen introducing MSTP,carriers should ensure that existing networks can coordinate and coorporate.MSTP can mainly offer existing metro network and ATM networks access and convergence functions, and it can be used to expand the ethernet and ATM service coverage.Its data processing function effeciently handles data services but it can not wholly replace data service networks

MSTP related rechnologies have been constantly developed adn optimized.To further improve its perfomance in transmitting ethernet services and balance nodes, some MSTPs adopt embedded RPR (Resilence packet ring),which enables highly efficent data service transport.Given RPR only supports ring network topologies,some MSTPs adopt built in MPLS (multi protocol lable switching) to process inter ring services

As MAN bandwidth demands have been soaring,it is increasingly difficult for SDH based MSTP to cater to MAN developments. A trend for solving the MAN bandwidth bottleneck is to gradually introduce WDM into MAN.WDM represents a mainstream technology in terms of long haul transport, but it has only been recently applied to MAN.Metro WDM embodies another type of driving force and characteristic that are different to those of long haul WDM.When used in long haul transport,WDM can save on expensive long haul optical fiber resources.

In the MAN network with its mostly short transport distance, costs on optical fibers will be much lower than in long haul backbones.Node equipment normally incurs high costs in each metro transport network and while it is beneficial to save optical fibers in some MAN,however service flexibility,manageability and cost effetiveness are more important for MAN applications.

The metro WDM network must support multiple services on the same platform and should be transparent to rates and protocols.Equipment ought to be low in price and the network should feature good expandibility in order to adapt to various metro service demands.Wavelength management capabilities must be strong to facilitate rapid wavelength service deployment.

A solid network self healing capacity that matches SDH network is necessary to offer different levels of protection according to services demands.As transmisiion distances in the MAN are alwasys short, there is no unreasonable demand on network capacity, and some cheaper components can be employed to reduce DWDM equipment cost.Alternatively,the network can adopt CWDM,which enable large inter channel distance.Point to point WDM cannot meet the demands of MAN applications so, as ROADM (reconfigurable optical add drop multiplexer) matures, ROADM can enable optical layer networking and introduce the control plane so that WDM plays greater role in MAN networks

Metro optical networks can provide strong bandwidth support for metro IP networks and ethernet.Compared with pure,direct optical fiber connections,this is network is more flexible,secure and resource efficient.The WDM networkcan deploy some new service such as BoD (bandwidth od demand),wavelength wholesale,wavelength lending,OVPN (optical VPN) and optical multicast.As the SDH network on the electronic layer is gradually replaced by IP/ethernet,future metro transport network will adopt the optocal layer metro WDM network Read More..

Fixed Mobile Convergence (FMC)

Following a long period of development, fixed mobile convergence (FMC) appears ready to arrive in the froms of real carrier services for enterprises.The concept of FMC-the ability to access multimedia application from a variety of end user device while roaming across a range of fixed line and mobile networks-has broad appeal.Enterprise see FMC as a way to improve employee efficiency which may also help reduce telecom costs.Carrier look to help them survive and grow in a world where profits from providing mere connectivity and transport for voice and data rapidly dwindling.

Industry analysts are projecting aggresive uptake of FMC services:global sales of dual mode mobile phones are expected to exceed 100 million units by 2010 (per ABI research).FMC revenues may reach US80 billion worldwide by 2009 (per pyramid research)

FMC promises to provide carriers and their partners with a range of new applications and srevices they can deliver to enterprises to drive revenue, profits and customer retention.The first managed services to offer true convergence will allow enterprises users to roam between cellular networks and voice enabled wireless LANs (WLANs),using dual mode handset equipped with 3G and Wi-Fi radios.Carriers considering their own FMC solutions can learn some important lessons from the innovative carriers who brought these services to market in 2006,such as the new functioanllity that WLANs deliver,making mobile voice practical within the enterprises campus

As with all fundamentally transformative processes,the FMC revolution-from our current collection of disjointed fixed and mobile carrier and enterprise network,toward seamlessly interoperating,converged multimedia applicaiton delivery platform-will take place in a series of incremental steps

Carriers and enterprises that anticipate the critical technology inflection points that accompany each major phase in the evolution toward FMC will be able to make smarter decisions on near-term network infrastructure investments


The Role of WLANs in FMC

One of the critical inflection points in the path to FMC is the advent of WLAN infrastructure capable of supporting mobile voice with sophisticated roaming capabilities.Early carrier rollouts of managed FMC services have identified certain limitations inherent in aging WLAN architectures that use independent access points ( so called "fat APs") or a centralized WLAN gateway (the WLAN switch with thin APs approach)

The WLAN component of managed FMC services will have to implement a third - generation architecture - one that leverages discrete,distributed handling of WLAN transport,control and management functions - in order to deliver the following critical features:

1. Definition and enforcement of very granular WLAN quality of service policies,tunable to broad range of application (notable voice and video),end device capabilities and other characteristic

2. A combination of centralized control and access point intellegence to optimize perfomance along the data path to ensure scalability and consistent perfomance.

3. Seamless roaming (handover) between WLAN access points on the same LAN segment and between WLAN access points on different IP subnets

4. Management tools to help carriers centrally monitor,troubleshoot, and maintain WLAN equioment across an FMC customer base that may extend to thousand of locations

5. Features to support an eventual migration to IP multimedia system, including session initiantion protocl (SIP) based VoIP signaling and other SIP-enabled applications and services

6. Access point features to automatically enable to connection of the broadest possible range of end user device and radio types without the need for any end user configuration work

7. The ablitiy to add WLAN capacity in cost effective increments and planning tools that help carriers anticipate and pre emptively address problems with enterprise WLAN congestion,radio frequency (RF) coverage and infrastructure resilency

8. Thigh integration and interoperation with the wired LAN and its bandwidth management,netwrok security and authentication/authorization/accounting (AAA) infrastructure

Carriers considering their first FMC offerings can benefit greatly from the experiences of FMC pioneers and their customers.Talking to vendor reference customers will provide useful insight into how their WLAN infrastructure choice helped or impeded the rollout of FMC services.
At a minimum,carriers should begin to more closely examine the implications of FMC on WLANs as they consider potential vendor alliances.Identifying a WLA solution that can meet FMC's requirement - for multimedia support,quality of service (QoS), perfomance, scalability, managemeability and security - may help carriers to avoid some potentially costly mistakes. Read More..

P2P (Point to Point)

Online video has emerged as the most badwidth hungry application.Some researches have state that video services ocupy 60% of P2P traffic,which each file averaging around 1GB.
Hence VOD and downloads use huge amounts of network bandwidth and this is exerbated if a video is particularly popular.A singel video report covering 9.11,for instance, had a click rate exceeding 100 million

P2P connects peoples in a network and users can communicate directly via the internet rather than though any intermediary.Its application enable users to directly exchange and share file instead of connecting to servers for file browses and downloads..Significanly P2P alters the reality that the internet is the dominant power core as P2P devolves power to users via decentralization, while greatly enhancing the value of online services

However,the wide range of P2P appplicaitons on the internet describes a trend for which it is complicated for carriers to strategize.Its advantages are fairly evident.Firstly,P2P creates new opportunities as it can attract more users to broadband networks that provide these applications.Secodnly,P2P technologies can be used to optimize existing services and networks to increases perfomance and decrease cost.P2P and online TV for example represent a good combination.

Based on existing services, carriers can explore new P2P operation and profit models to render these application managable and profitable, and allows them to develop in a constructive,sustaibale way that caters to user requirements

The most obviously negative aspect is that if P2P applications are all interconnected in parralel, network bandwidth increase tremendously.In extreme cases, this may result in network congestion and the perfomance degradation of other internet application.Moreover, P2P based voice communicaiton technologies such as Skype have direclly threatened carrier's traditional voice communicaiton services

Given these considerations,carriers are left with two broad strategies:Prevent the use of P2P or develop and guide sustainable usage.Since P2P represents an irreversible trend,logic dictates that usage guidance is the better long term option,despite the fact that the challenges currently outweigh the opportunities.Correct decision making and implementation will be the tool to heighten the potential benefits

Many carrier have in fact started developing solutions for P2P apllication.Carriers should prevent illegal network resource usage,while exploting P2P applications' inherent advantages and transform then into something useful

Three strategies can be followed to reach this goal.The first is to limit overall bandwidth.Traffic should be localized to reduce pressure on the backbone network.The second is to employ P2P technologies to reconstruct existing networks,thereby increasing perfomance and reducing cost.Thirdly,P2P technologies can be used as a platform to develop new services and increase income.Some carriers have already started expanding network bandwidth


Adjust MAN architecture


Both P2P software download such as Bit Torrent, and live broadcast P2P software including PPLive are executed via applicaiton layer duplcations between node.In the present MAN architecture,users exist in a dual layer separation mode in the acces network.

Application layer duplication between users can only occur through the core convergence layer of the MAN or the backbone network and the bandwidht consumed on the MAN core convergence is proprotionate to the numbers of users

The present MAN see data traffic passing the convergence swtiches and BRAS before arriving at the MAN egress.No fixed bandwidth is reserved for each users from the access layer to the MAN egress and whenever a large amount of traffic exists on the access layer,much bandwidth will occupied on the convergence layer or the backbone network.Moreover ADSL bandwidth in the access network is asymmetrical as uplink bandwidth is fast less than downlink bandwidth.If application layer duplications are implemented,uplink bandwidth demands are increased,which would exeed present access network capacities.

If P2P services become mainstream services over present network architecture,badwidth on the MAN core convergence netwrok will see the greatest bottleneck,while access layer bandwidth will be continously occupied.In terms of online TV applications, P2P duplications on the application layer are not cost effective in term of bandwidth usaged compared with multicast.Network access can only adjust MAN architecture so that it can adapt to the P2P application layer duplication model and reduce pressure on the MAN convergence layer's P2P derived bandwidth demands.

To make the MAN architecture suitable for P2P applications layer duplications, the following principles should be obsreved:

1. Selecting symmetrycal access equipment

DSLAM is continously used by carriers but possesses asymmetrical access equipment that cause significanly more downlink abdwidth than uplink. It is rather suitable for C/S model than P2P.Therefore a shift toward symmetrical access technologies such as LAN,ADSL2+ or EPON is recommended

2. Flattering the access network

The nature P2P traffic means that placing the layer 3 gateway closer to users will increase bandidth saving on the MAN core convergence layer

3. Building a full meshed structure at the core convergence layer

MAN currently adopts a dual start,tree structure.All traffic passing MAN must cross two routers at he MAN core.This is unsuitable for P2P traffic,adaptation to which necessitates the adoption of multi node architecture at the MAN core layer under which different nodes network via the full meshed Read More..

Building a secure network

The internet begans as an experiments in 1969 by ARPA of the US Departement of defence.ARPA's intention was to create a very reliable digital communications network that could be used in wartime, so communication could be maintain even if the stations or physical links were targetted during attacks.Early researches into this area adopted an innovative and powerfull idea - packet switching- to build the ARPANET.Subsequencely the new technology proved to be highly successful.In the following years, more research networks were created and the ARPANET evolved into the NSFNET, before finally becoming the Internet we know today.

The internet began into rouse the interests of the public during the 1990s, partly due to the wide applications of PC and WWW.Soon access to the internet became a popular services of the residential customers as well as enterprises and the number of internet users has increase exponentially over the years, so much so, that as of the end of 2006, the number of people using the internet has sky rocketed to 1 billion worlwide.

As a public communcaiton service, the internet access has to reliable.However the kind of reliability that ARPA was looking for was actually robustness,that is, the capability to function correcly under negative impacts, so commands can be delivered to the outposts to coordinate attacks, even after some stations had been destroyed.In comparasion, the kind of reliability that the public needs is high availability.That is the proportion of the time whe the service is available, which is this instance, should be most of the time

Accoring to the Infocomm Development authority of Singapore, the availability of internet service provide by major ISPs in Singapore about 99.99%.In other words, internet service is unavailable and cannot be accessed for a little than a hour each year
Since the most people use the internet for seding email, browsing news sites,searching for information,etc, and for basically nothing very critical, then most people are satisfied with the service.

The new millenium has withnessed the coming of network convergence.A fair portion of long haul calls had been packetisez nad routed to the internet and now ILECs are beginning to replace PSTN with IMS.Succesful deployments of IPTV by pioneer telecom operators have helped to showcase the revenue and profit potential and triple play service and triggered a new wave of expansion of IP networks globally.As a result, more and more enterprises are switching to IP VPN to replace the expensive frame relay ceoonections.As the telecommunication network is heading into an all IP era, the internet will become the common IP bearer network for all kinds of new services.

Glory is always accompanied by a heavier sense of responsibility.Telecom operators established the availability standarad for PSTN and leased circuits long ago, five 9s (99,999%) which translate into 5 minutes downtime per year.Cable operator have a similar availability satandard for cable TV.In order to bear the traffic multy-play or VPN services, the IP bearer network has to be revolutionized,hence,improving availability from four 9s, to five 9s

To make the task even harder,some services are session based such as voice service. If the call is broken then the call is dropped and customers have to dial again.To effectively deal with this issue,the IP bearer network has to provide a fast automatic oath swichover mechanism to re reroute the traffic,like,SDH or PSTN, which are able to provide 50 milliseconds automatic protection

Is summary, as the common IP bearer network in All-IP era, the IP bearer network needs to be able to provide four 9s for internet access, five 9s for voice,IPTV and VPN, as well as a fast path switchover mechanism for session based services Read More..

Next Generation Network (NGN) architecture

The converged world of next generation networks (NGN) brings with it the promise of voice,video and data over a single broadband netwrok.This transition from the traditional circuit switched to packet switched networks has been underway for many years and Voice Over IP (VoIP) is now leading the transition

One NGN architecture for VOIP with centralised call processing decomposes the functional elements of a traditional circuit switch into specialized componnect with open interfaces.
Following are the key logical element of this reconstruction are the following:

1. THe MG handle the media or beared, interface.It converts media from the format used in one network to the format required in the another network.For example it can terminate the TDM trunk from the PSTN,packetize and optionally compress the audio signals an then deliver the packet to the IP network using real time protocol (RTP)

2. The MGC (also known as a call agent) contains the call processing.In addition it manage the resource of the MGs that it controls.The MGC controls the MG using a control protocol to set up the RTP connections and control the analog or TDM end point in the MG

3. THe SG sits at the edge of an IP network and terminates circuit-switched network signaling such as SS7 or ISDN from the circuit switched network.It transport or backhauls, this signaling to the MGC or other IP based application endpoint

MGCP can also be used as a control protocol between an MGC MGCU (TG) and an MG. While MGCP is defined by an informational (versus standard track) RFC, it is commonly used in many product today because the specification was available before Megaco and H.248 were finished.Both MGCP and Megaco/H.248 assume that the call control intelligence is outside the MGs and that the MGC handles it

Closely related to the MGCP protocol are the Packet Cable protocol, network based call signaling (NCS) and PSTN gateway call signaling protocol (TGCP).These protocol provide functionality similat to MGCP for cable based network


Sigtran

The IETF SigTran working group was founded after a Bird of a Father (BOF) session which was held at he Chicagi 1998 IETF meeting, to discuss transport of telephony sigaling over packet networks.The SigTran working group define the framework architecture and perfomance require in RFC 2719(126).The framework include the conceptof the reconstructing the traditional circuit switch into MGC,MG nad SG elements, thereby separating the signal and the media control plane

The framework document identified three necessary components for the SigTran protocl stack:

1. A set of adaptation layes that support the primitice of SCN telephony signaling protocol

2.A common siganling transport protocol that meets the requirement of transporting telephony signaling

3.IP network protocol

The three layers of the protocol stacks are:

1.Adaptation layer

2.Common Transport protocol

3.Internet protocol (IP) Read More..

Mobile Station at GSM

GSM refers to the cellular handsets as MS.PCMCIA cards are also available for laptop to allow data transfer over GSM network, without the need for a voice-centric handset.
The MS consists of typical equipment that the subscriber uses to access a PLMN and a removable smart card, knows as the SIM to identify the subscriber.

GSM was uniqueto use the SIM card to break the subscriber ID apart from the equipment ID.The SIM card is fully portable between Mobile Equipment (ME) units.This allows many features that we take for granted usch as being able to swap MS simply by swapping our SIM car over.All functionally continues seamless, including billing and the telephone number remains the same

An MS has several associated identities including the International Mobile Equipment Identity (IMEI), the International Mobile Subscriber Identity (IMSI), the Temporary Mobile Subscriber Identity (TMSI) and the Mobile Station ISDN (MSISDN) number


IMEI

Each ME has a unique number known as the IMEI, stored on it permanently.The IMEI is not only a serial number, it is also indicates the manufacturer, the country in which it was produced and the type approval. It is assigned at the factory

The IMEI is used so actions can be taken againts stolen equipment or to reject equipment that it cannot accept for technical and/or safety reason.The IMEI allows tracing and prevention of fraudulent use and in some circumtances,special network handling of specific MS types

Structures of the IMEI:

1.TAC (type approval code)

2.FAC (Final assembly code)

3.SNR (Serial number)


IMSI

Each subscriber is assigned a unique number,which is known as the IMSI.The IMSI is the only absolute identity a subscriber has within GSM and such as it is stored on the SIM.The SIM is a credit size or quarter-credit card size smart card that containts the subscriber's subscription details and grants the subscriber service when placed into a piece of ME.Among other purpose it is used for subscriber billing, identification and authentication when roaming

The structure of IMSI are

1. MCC ( Mobile Country Code)

2.MNC (Mobile Network Code)

3.MSIN (Mobile Station Identification Number)


TMSI

A TMSI is an alias used by the VLR ( and the SGSN in GPRS) enabled networks) to protect subscriber confidentiality.It is temporaily used as a substitute for the IMSI to limit the number of times the IMSI is broadcast over the air interface because intruders could ise the IMSI to identify a GSM subscriber


MSISDN

MSISDN is the number the calling party dial to reach the called party-in other qords it is the mobile usbscriber's directory number.This parameters refer to one of the ISDN number that assigned to a mobile subscriber in accordance with ITU recommandation

The structures of MSISDN are:

1.NDC (National destination code)

2.CC (Country code)

3.SN (Serial number) Read More..

Message Transfer Part (MTP)

MTP acts as the carrier for all SS7 message, providing reliable transfer of message from one signaling point to another.This function include levels one, two and three. In addition to providing signaling point to signaling point communication, the MTP also provide error detection and correction

The methodology of MTP are very similar to those used in other bit oriented protocol (BOPs), such as X.25.Sequence numbering and error checking mechanism are very similar
The signal unit structure used in all SS7 message provides all the information required by MTP level two and three.Flow control is provided through the use of a special signal unit called the Link Status Signal Unit (LSSU)

MTP provides all functions of layers one,two and three.Level two of MTP provides error detection/correction, as well as error checking through the cjeck bit field.In addition to these two fundamental functions, the following is provided:

1.Signal unit delimitation
2.Signal unit alignment
3.Signal unit error detection
4.Signal unit error correction
5.Signal unit initial alignment
6.Signal unit error monitoring
7.Flow control


Structure of MTP level two


The backward sequence number and the forward sequence number are used for sequencing packet and are used by level two to ensure tha all transmitted packets are received.They are also used for positive and negative acknowledgements.The indicator bits are used to request a retransmission.The lenght indicator allows level two to determine the type of signal unit being sent and the cyclic redundancy check (CRC) field is used to detect data errors in the signal unit


Flag

flag is used to indicates the beggining of a signal and the end of a signal unit.The flag in US network is used to indicate both beginning of the signal unit and the end another.In some other networks there can be both an opennung and closing flag


Sequence numbering

The SS7 protocol used sequence numbering like many other layer two bit oriented protocols.The SS7 technique is just a little different from, say X.25 but the principle is the same.Both a forwars sequence number (FSN and a backward sequence number (BSN) are provided


Indicator bits

The indicator bits are used to request a retransmission.There are two indicator bits; a forward indicator and a backward indicator bit.During normal conditions, both indicator should be of the same value (0 or 1).When a retransmission is being requested, the signal unit being sent by the signal point requesting the restransmission will have an intervet backward indicator bit.The forward indicator bit retains its original value.This indicates to the distant signaling point that an error occured and retransmission must take place.


Length indicator

it is used by level two to determine which type of signal unit is being sent.The value of the length indicator can be:
1. 0 (Fill in signal unit)
2. 1 or 2 ( link status signal unit)
3. 3 or more (message signal unit)


Cyclic redundancy check (CRC)

it is the last field in the signal unit.This field is calculated using the fields immediatly following the flag, up to the chek bit field itself Read More..

Essential understaning of MAN

Deployments in DWDM have stimulated huge capaciti level in long haul backbones nad large scale ethernet in LAN applications bandwidth.The subsequent bandwidth bottlenecks in MAS (Metropolitan Area Network) and AN (access network) have become increasly problematic.IP based voice and video service usch as NGN and IPTV have placed higher demand on MAN and AN functions and perfomance,rendering the condition of these two networks a significant concern to carriers

The concenpt of MAN initially describes a computer network concept corresponding to LAN and now it has been applied intelecom networks as a publice multiservice bearer network that provides broadband data and multimedia services in cities or suburbs with no strict definition.According to the NGN hierarchical architeture recommended by ETSI and ITU-T,NGN comprises two basic strata:service and transport.The transport layer refers to the service-supporting bearer network

A bearer network can be devided into three horizontal constituent parts:backbone netwrok,MAN and AN.The key factor in selecting bearer netwrok techonolies is the features of the services to the borne and these should be reflected in the technical developments of MAN.MAN services can be currently characterized as follows:

1.Compicated services.In additionto traditional TDM and internet, MAN has to bear nascent service usch as IPTV,NGN,3G,P2P and internet broadband applicaiton

2.Mainstream IP services.Essential to a new-type MAN construction is efficeint IP service bearing capability and suitably high QoS and security features.

3. Service inovations.New innovation rich services have been rapidly hitting the market, meaning that it is more adn more difficulty to cater the user demands since MAN require to possess sufficient flexibility,expandability and responsiveness in order to adapt to constantly changing requirements

4.Bandwidht hungry services.THe number of service necessitating high bandwidth coupled with increased users has placed upon MAN considerable badwidth and service management pressures

5.P2P applicaiotions.Large scale P2P applicaitons have changed traditional network traffic structure

6.Traditional service.Including TDM,FR and ATM these still occupy a place in the market.PSTN servie will exist long term and NGN and 3G service developments still rely on certain TDM circuits.The financial adn political sectors have special QoS and securiy demands and currently stick to traditional dedicated line services since doubts remain about the integrity of IP networks

7.Cost.MAN features a short service transport distance compared with the backbones, so cost is of great importance.Carrier can adopt low cost phisical layer technologies to enable short distance transport including ethernet direct connection and CWDM

Traditional networking concept comprises relively independent transport and data networks that provide different functions and so different applications are not carried over the sam network.Traditional carrier's MAN network include metro SDH,metro IP and occasionally ATM,FR and DDN which are siin to be replaced

SDH previously supported PSTN and PLMN and offered physical layer circuits to data networks.The metro IP networks was mainly used to provide internet service but the increase incarrie class IP application requires MAN to offer high quality IP bearing services.SDH networks have consequently developed into MSTP (multi service transport platform) that offer ethernet service and an IP bearing functions.The metro IP netwrok has also been developed into a carrier class by using MPLS and optimized ethernet technologies.For additonal carriers most MAN network will soon include metro MSTP and metro IP network.These two type of network are mmuttualy compelemtary but do compere with each other.They should be deployed in different area according to the conditions of subsequent phases with varied services domains.The gradual decrease in TDM services and the rapid growth of IP services means that the SDH based MSTP will offer fewer functions,while metro IP networks and ethernet will offer more Read More..

CN2: Akey step toward All-IP

A forecasted by Wei Leping the chief engineer for Chine Telecom,the future telecom inddutry might withness voice services as internet applications while mobile and broadband services will become two ipmportant trends for the future.The development direction will focus on a range of full service and all IP

Using this all IP strategy as a guide, CHina telecom had already completed its five phase expansion and reconstructions on ChinaNet which is its internet service bearer network by 2003.However the capacity,perfomance and QoS if ChinaNet were still not able to meet the needs for few services,especially from key account and commercial customers as well as from softswitch and video services

The teelcom industry once attempted to use an IP network designed in the internet mode ot bear telecom service, but the attempt failed to be practicable.A senor telecom expert once said,'the two end mode of telecom service does not comply with internet applications and carriers cannot interfere with internet service.As the result the telecom network adn the internet network will be two parreled servicee which will never meet'

In fact, most bearer networks in the internet era were telecom networks, which were not designed for the internet.Subsequently, many conflict nad problems have arisen because of this.During its developments, the IP network has destroyed the business mode of the telecom network,making it contradictive to the basic economic order.This has resulted in the badwidth growth being faster than traffic growth and traffic growth being faster than the cost growth and the cost growth is faster than income growth

In ht profite mode, business model of telecom comprises of three layers.The first layer is utilized to the sell basic network resource such as badnwidth traffic and VPN.THe second layer is used to lease the service platform.The third layer,which constitutes the highest layer in the value cahin of each telecom carrier, is used to provide basic and value added service.

As we all know, the internet is typical application of the separation of services from services bearer.In order to effectively achieve the above described business model in IP telecom networks,cosideration should be made toward both IP network system structure and the network service structure.New idea must be used in designing IP telecom networks, thus freeing us from the shackles of conventional ideas concerning the internet

With such consideration in mind,starting in 2003,China telecom gradually abonded the idea of reconstructing ChinaNet and instead decided to construct CN2(China Telecom's Next carriying Network),which is a new IP backbone bearer network.THe new network is expected to meet the demands for bearer networks from carrier class service like 3G or NGN.It is also expected to manage and control IP data, and help to lay a solid foundation for China telecom in developing into a first class carrier in the coming 10 to 20 years

In 2006,the CN2 was completed adn put into operation,at cost of 1.3 billion Yuan.As CHina's first independent IP backbone network,which is able to bear NGN,3G as well as other key account service,CN2 is laying a solid foundation for China Telecom's transmission ot providing telecom IP services. Read More..

Telecommuncation Standards Organizations

Standards such as SS7 adn ISDN does not happen quickly. They are the result of many years of research adn development conducted by standards committeees.These organization are ussueally composed of goverment agencies or industry represemtatives from manufacture and service providers

To understand various standards available today, one must first understand the purpose of new standards and how they are developed.There are two differents type of standards: de yure and de facto

The de jure standard is formed by committee.These standards take many years to develop because the proccess used in committees are long and bureaucratic.Nonetheless, many of standards used today are the result of standards committees

A defacto standard is the result of manufacture or service providers monopolizing a market.
De jura and de facto standards can be voluntary or regulatory standards.Voluntary standards are adopted by companies ona voluntary basis.There are no rule that say that all manufacture and srvice providers must comply with voluntary standards.However the advantages are many.Voluntary standards help ensure that everyone developing products for networking build their product for interconnectivity.Without this intrconnectivity and interoperability, only a few equipments would win the market-those with largest intall base

Regulatory standards are created by goverment agencies and must be confirmed to by the industry.These standards do not hold any major advantage to the service provider or the manufacturer but are in place in most cases to protect the customer

Regulatory standards are monitored by goverment agencies susch as the Federal Communication Commission (FCC).These agencies ensure the protection of public and other network users by enforcing standards covering safety,interconnectivity and in some case health (i.e, radiation emission from computer terminals and cellular phones)

SS7 network use standards from a variety of organizations and standards committee.Some of standards used in SS7 network were developed for other applications as well not specifically for SS7.
The following organization have written standards direcly related to SS7:

1.International Telecommunication Union_telecommunication Standarization Sector (ITU-TS)

2.American National Standards Institute (ANSI)

3.Cell Communication Research (Bellcore)

The following standards organization have contributed to the SS7 network with standards not written specifically for SS7 but used by equipment in the network:

1.Electronic Industries Association (EIA)

2.ATM forum

3.Federal COmmunication Commission (FCC)

4.Underwriters Laboratories (UL)

5.Canadian Standards Association (CSA)

6.International Organization for Standardization (ISO) Read More..

Current trends in telecommunication technology

Today's telecommunication industry has changed dramatically.Data communicationand voice networking have been merged to provide a variety of servives that leave even the most educated somewhat confused and baffled.These serivices all revolve around the backbone of the new intelegent network, SS7

Because of SS7, these new technologies can be supportedin the public switched telephone network (PSTN) rather than having to have separate network for each type of service ( as previously done to support packet swithcing jn the '70s and '80s).In fact all of data and voice commnunication will be simplified to the point that the subscriber does something but dial a number adn get connected.The signaling network will handle the rest

The goal of the telephone network is to provide seamless service to all subscribers, regardless off the information being sent through the network.As previously discussed, the intelegent network (IN) will provide this capability.But before the IN is ful;y deployed, there are many different pieces that must first be put into place.

The telephone network of today willnot support the types of the services that subscribers are asking for.If there is a need for high speed data, a special cisrcuit must be installed from customer premise to othner end of the ciscuit.If video is to be transmitted through the telephone network, special high capability circuit must be installed from the studio through the telephone network to anather high capability circuit at the tarsmitter

The ultimate goal is to provide one network capable of tranfferring all kinds of information regardless of the bandwidth necessary and sending it trhough the network just as if placing a telephone call.To support this level of service, the network must be changed

Introduction to Intelligent Network


The IN has been under development for many years, with the goal of allowing all types of information to pass through the telephone network without special circuitsor long installation cycles

The concept of being able to access all kind of informationis not new.The network to support this type of service is new.The IN provides the backbone to support and define these services
As the need for new feature and services becomes more important to customers, the need to deliver this service and feture is economical way becomes equally important.The problem facing telephone company today is being able to provide these features and services quickly and efficiently.Ordering 800 line for two weeks usage is now easy and can be implemented within hours instead days

The IN make is easier, because now when subscriber order new services, technicians do not have to be dispatched to add programming to the swtiching equipment and cross-connect the circuits

In IN everithing is contrrolled or configured by workstation with user friendly software interface.Telephone service representatives can create new services and tailor a subscriber's service from the terminal while talking with the customer.The change are immediatly implemented in the swithces.Circuit are cross-connected using digital cross-connect system, which are also controlled by workstation

The IN relies on SS& network, which forms its backbone.SS7 provide basic infrasturcture need for Service Switching Point (SSP), which provide local acces as well as an ISDN interface for the Signaling Tranfer Point (STP), which provide packet switching of message-based signaling protocol for use in the IN and for the Service Control Point, which provide acces to IN database
The SCP is connected to a Service Management System (SMS), which provide a human interface to the database, as well as the capability to the database when needed.The SMS using command line interface and man to machine language to build service and manage the network

One additional node used in IN that is not seen in the SS7 architecture is the Intelligent Peripheral (IP).The IP provide resource management of device such as voice response units,voice annoucement,and DTMF sensor for caller-activated services.THe IP is accessed by the Service Control Point (SCP) when service demand its interaction.IPs provide the IN with the functionally to allow customers to define their network needs themselves, without the use of telephone company personal

The following features are just a sampling of the features of an IN.As the IN evolves, new service will become availaible. Features include:

1. Find Me service
This service allows call to be forwarded to another location

2. Follow me Service
Similar to call forwarding, this allows a number to be forwarded on the time schedule

3. Computer Security Service
This service prevents unauthorized callers from accessing a computer via modem

4. Call pickup Service
When a call is placed to a number and i unanswered, the called party can be paged via radio pager

5. Store Locator Service
Businesses can advertise one number and callers are automatically tranfered to the nearest location based on their own telephone number

6. Call Routing Service
This allows businesses to reroute calls when congestion occur or after business hours

7. Multilocation Extension Dialing
THis allows the usage of abbreviated extension number to reach personnel regardless of their location and without PBX equipment

8. Name Delivery
A a call rings the tepelhone, the callers name is displayed on a digital display

9. Outgoing Call Restriction
Allows the restriction of specific numbers or prefixses and area codes, allowing customers to restrict long distance calls and service number such as 900 and 976 from being dialed on their phones Read More..

Broadband data communications

Broadband standards are still being defined today, with ATM receiving the bulk of attention.SS7 will not carry the actual user data, but will provide the services neccesary to connect the end to end telephone network company facilities required for data transfer between two end points.The specific requirements of SS7 are still being defined.The trial network using ATM do not require SS7, because the trials being performed with broadband ISDN and ATM are currently permanent virtual circuits (PVC) and are not switched. However as the new services are not deployed for public access, SS7 will provide the signaling for ATM

ATM is a transport protocol which relies on upper layer protocols for functions above adn beyond the layer three.The ATM technology was created for support broadband ISDB but has found favor with a number of other nnetworking protocols as well..Frame realy with speed up to 155 Mbps will most likely serve as a good solution for those requiring a PVC service.These work much like a dedicated special circuit adn are not typically swithced.However there are plans to provide switched frame relay, making it a viable service for switched data network.

Narrowband ISDN (1.554 Mbps) is being suggested by many services providers as a cheaper acces to broadband services,while broadband ISDN (155 Mbps) is being targeted at a mega network who need much more bandwidth

Broadband ISDN (BISDN) will provide fast data transmission for service such as video dialtone.With the bandwidth of BISDN video and audio can be transmittedsimulatneosly on the same facility.This willprove to be an imortant feature for the information highway.

A point that often gets lost among all the marketing hype over ATM is the purpose of this technology.Talk of a new telephone network is nothing new.Telephone company officials have been palnning for many years to upgrade their old analog networks to support the services and applicaitions under much demand.Subscribers are not longer complacent with slow data transmission and expensive special circuit for sending data and other information through the network

ATM was developed to support the broadband ISDN interface being defined for customer premise.Many vendor have placed ATM switch inthe hands of customers (philosopically), thinking this will meet the need of every businness and become a necessity in office buolding everywhere.Some have even been so bold as to claim that ATM will replace the local area network.

In reality ATM will only be found at customer premises where nothing else will deliver to the bandwidth required for video service.ATM would be much too expensive for the average business to deploy in place of a LAN, and certainly consitutes overkill for most daily business activities.But for university needing the 600 Mbps of badwidth and the hospital using the telephone network to send high resolution medical image, ATM and broadband ISDN are likely to be an integral part of their networks.

Narrowband ISDN will serve as the customer interface for the majority of subscribers, while ATM and broadband ISDN will become the transport mechanism within the telephone network to the destination.

ATM require a transmission facility capable of carrying the bandwidth (600 Mbps and higher).Syncronous optical network (SONET) is being deployed as the physical medium for ATM Read More..

Introduction to telephony signaling

Even since the begging of the telephone, signalling has been an integral past of the telephone communications.The first tepehone devices depended on the receiving party standing next to the receiver. Early telephone did not have ringers like today's telephone, and used crude speakre to reject the caller's voice in the the room. If the party being called was not eithin close proximity of the speaker, he or she would have no identication of the incoming call

Later, after the formation of the Bell Telehone Company, Alexander Graham Bell's faithfull assitant Watson invented the telephone ringer.This new signalling method served one purpose:to alert the called party of an incoming call. When the called pasrty lifted the receiver, another form of signalling used DC battery and ground. Although not having an immediate impact, this method became important when the first telephone exchange was created.By lifting the receiver and allowing DC current to flow through hte phone and back through the return of the circuit, a lampt would be lit on the exchange operator's swhichboard. This signalled the operator when someone needed telephone service and was often accompanied by buzzer

Signalling has evolved over decades to include significantly more information then this early methods could.Consider the typical long distance telephone call today. When the caller dials the area code and prefix of the telephoe number, the local exchange must determine how to route the call.In addtion, billing information must be passed to central database.If the caller is using contemporary digital facility (such as T-1 or ISDN), information regardign digitization of the linemust also be provided.

Early signalling methods were limited because they used the same ciscuit for both signalling and voice.They were also analog adn had limitation number of states or values, which could be represented.The ciscuit would be busy from the time the caller started dialling until the caller went on hook.To compoun the probelm the companies were quickly running out of facilities and were in desperate need of additional facilities

Many telephone companies in metropolitan areas sucnh as Los Angeles were facing subtantial invesments to add new facilities to support the million of customers that were creating an enourmous amoutn of traffic.The telephone companies had to find a way to consolidate their facilities, making more economical use of what they had. In addition, they need a service that would vastly improve that network's capability and support the many new services being demanded by subscribers

Europe had already begun the procces of digitazing the network in the early '60s.One of the first step to removing signalling from the voice network adn place the signalling to the network all its own.This way, the call setup and tear down procedures required with every call could be faster than the previous methods and voice and data circuits could be reserved for use when a connection was possible, rather than maintaining the connection even when the destination was busy.Common Channel Signalling (CCS) paved the way for services the early pioneers of signaling never dreamed of.CCS is the technology that makes ISDN adn SS7 possible.

The concept behind SS7 is simple.Rather than use voice trunks for signaling they are used only when a connection is established.For isntance, when a call is placed to a distance party using conventional signaling, the signaling for that call begins from the time the caller lifts the receiver and goes off hook until the caller goes back on hook.After the end office has received the diald digits, an putgoing trunk to the destination end office is seized, based in a routing table entry and the digits dialed

The voice cisrcuits remains busy even if the distant party never answers the call until the calling party hangs up.Meanwhile, other subscribers are trying up other voice circuits by placing call of their own.This is not good utilization of voice circuit and it placed immediate limitations on the networks.But if the signaling could be place over a different network and the voice circuit used only when the called dial party answered, the voice circuit would remain available for a longer period of time.This meant availaibility of voice circuits would be higher and the need for additional circuit would decrease

When a caller is to receive an intercept recording (all circuits are busy), the same trunk used for the voice is also used for the recording.This recording is sent by the distant office.Busy tones and other service tones would be sent over the trunk by the distant office to the caller.With SS7,the caller's local office provides these tones and recordings at the command of the distant office.These commands are received via the signalling network.The voice trunk is left unconnected

The procedure for tearing down a circuit is much faster in Common Channel Siganling (CCS) than in convetional singaling and is not as erroe prone.Even if voice circuits do get donnected with the speed of the siganling network, circuit can be disconnected and wuickly connected again for a new call.While a call is in progress, information regarding the call can be sent through SS7 network (for instance, information from a database requested during an interactive multimedia call) Read More..