Interview Questions.

Question 1. What Is Ss7?

Answer :

Common Channel Signaling System No. 7 (i.E., SS7 or C7) is a global wellknown for telecommunications described via the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The trendy defines the procedures and protocol by using which community factors within the public switched cellphone network (PSTN) exchange statistics over a virtual signaling network to effect wi-fi (mobile) and wireline name setup, routing and control. 

Question 2. What Standards Does The Ss7 Stack Confirm To ?

Answer :

The HSS SS7 stack lets in for countrywide variations which include the American National Standards Institute (ANSI) and Bell Communications Research (Bellcore) requirements used in North America and the European Telecommunications Standards Institute (ETSI) general utilized in Europe. Spanish and British Variants are also supported.

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Question three. What Can The Ss7 Network And Protocol Be Used For?

Answer :

The SS7 network and protocol may be used for: 

basic call setup, management, and tear down 
wireless services such as personal communications offerings (PCS), wi-fi roaming, and mobile subscriber authentication 
nearby number portability (LNP) 
toll-free (800/888) and toll (900) wireline offerings 
superior name features which includes name forwarding, calling party call/number show, and 3-manner calling 
efficient and at ease global telecommunications 
Question 4. What Does The Ss7 Signaling Architecture Look Like ?

Answer :

SS7 messages are exchanged between community elements over 56 or 64 kilobit according to second (kbps) bidirectional channels called signaling hyperlinks. Signaling happens out-of-band on committed channels in place of in-band on voice channels

The Network consist of three varieties of Network Elements

SSP: Signal Switching Points are cellphone exchanges equipped with SS7 capable software. They are responsible for originating, terminating or switching calls
STP: Signal Transfer Points are packet switches that acquire and direction signaling messages to their right destination
SCP: Signaling Control Point is a database that provides information important for advanced call-processing abilities
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Question five. What Are The Layers In A Ss7 Stack ?

Answer :

The SS7 protocol stack has the following underlying layers.

Message Transfer Part 

The Message Transfer Part (MTP) is divided into three degrees. The lowest level, MTP Level 1, is equal to the OSI Physical Layer. MTP Level 1 defines the bodily, electrical, and purposeful characteristics of the virtual signaling hyperlink. Physical interfaces described encompass E-1 (2048 kb/s; 32 64 kb/s channels), DS-1 (1544 kb/s; 24 64kb/s channels), V.35 (64 kb/s), DS-0 (64 kb/s), and DS-0A (fifty six kb/s).

MTP Level 2 guarantees accurate end-to-quit transmission of a message across a signaling hyperlink. Level 2 implements float control, message collection validation, and error checking. When an errors takes place on a signaling hyperlink, the message (or set of messages) is retransmitted. MTP Level 2 is equivalent to the OSI Data Link Layer. 

MTP Level 3 provides message routing among signaling points within the SS7 network. MTP Level three re-routes site visitors faraway from failed links and signaling factors and controls site visitors when congestion occurs. MTP Level 3 is equivalent to the OSI Network Layer. 

ISDN User Part (ISUP): The ISDN User Part (ISUP) defines the protocol used to set-up, control, and launch trunk circuits that carry voice and data between terminating line exchanges (e.G., among a calling party and a known as party). ISUP is used for each ISDN and non-ISDN calls. However, calls that originate and terminate on the same transfer do no longer use ISUP signaling. 

Telephone User Part (TUP): In a few parts of the world (e.G., China, Brazil), the Telephone User Part (TUP) is used to assist basic call setup and tear-down. TUP handles analog circuits simplest. In many nations, ISUP has changed TUP for name control. 

Signaling Connection Control Part (SCCP): SCCP presents connectionless and connection-oriented community offerings and worldwide title translation (GTT) abilties above MTP Level three. SCCP is used as the delivery layer for TCAP-primarily based offerings. 

Transaction Capabilities Applications Part (TCAP): TCAP supports the exchange of non-circuit related statistics among packages throughout the SS7 network the usage of the SCCP connectionless carrier. Queries and responses despatched between SSPs and SCPs are carried in TCAP messages. For example, an SSP sends a TCAP question to decide the routing number related to a dialed 800/888 quantity and to to check the private identification range (PIN) of a calling card person. In cell networks (IS-forty one and GSM), TCAP contains Mobile Application Part (MAP) messages despatched between cellular switches and databases to help consumer authentication, device identification, and roaming. 

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Question 6. What Is Global Title Translation?

Answer :

A global name is an address (e.G., a dialed 800 range, calling card range, or mobile subscriber identity wide variety) that is translated by way of SCCP right into a vacation spot point code and subsystem number. A subsystem range uniquely identifies an software at the vacation spot signaling point.

Question 7. What Is Meant By The Statement - "ss7 Stack Can Work In Both Single-threaded And Multi-threaded Systems"?

Answer :

The SS7 Stack entities (MTP2, MTP3, ISUP SCCP& TCAP) can be compiled and run as a single thread. This is feasible because of the coding pointers which make sure distinctiveness of feature names and international variables.

In addition, every SS7 Stack Entity can execute as a separate thread. This is feasible due to the fact every stack entity is independent and does not percentage any facts systems with other stack entities. Communication between  stack entities is thru a message based interface.

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Question 8. What Does Porting The Stack Onto A System Involve?

Answer :

Porting the stack onto a machine entails the subsequent :

Porting the OS calls
Porting mistakes handler & printing of hint messages
Porting System Management Entity 
Porting redundancy
Porting the OS calls is dependent on the Operating System & entails :

Memory management
Timer management
IPC mechanism between stack entities / stack entity & provider user
Porting mistakes handler is dependent on the User’s System & is based totally on how the errors are to be mentioned.

Porting the printing is dependent on the User’s System & is primarily based on how / in which the hint messages are to be displayed.

Porting System Management Entity entails growing an User Interface (GUI / different) for dealing with the stack entities the usage of the Layer Management APIs (Provisioning, Statistics, Controlling Error Reporting and Traces and many others.). 

SS7 stack can be ported unto any patron platform 

Question nine. What Can I Configure Using The Layer Management Entity Interface?

Answer :

Given below are a few examples of parameters configurable from LME 

Linksets configuration
Link configuration
Route configuration
Timer configuration
Trace Levels
E1/T1 card configuration
Congestion levels
Other parameters e.G. Call Control configuration parameters, CICs provisioning / unprovisioning and so forth can be included as in keeping with the client's necessities

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Question 10. What Is The Functionality Of The Client Code?

Answer :

The patron codes parses all the APIs coming to the stack. It paperwork an interface among the stack and the user / service layer.

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Question eleven. How Does Mtp2 Handle Multiple Links ?

Answer :

MTP2 has a properly described interface (within the shape of purposeful calls) with the hardware, that's to be ported. This is defined in detail, in the MTP2 Porting Guide. 

The a couple of SS7 links are handled by the hardware in any style (polling in round robin or another way/ interrupt pushed) – MTP2 places no restriction on this.

MTP2–hardware interface consists of a fixed of functions, that are invoked through the hardware as wanted :

Whenever the hardware is ready to transmit, it's going to invoke a properly-described MTP2 function.
Whenever the hardware has received a signaling unit, it will invoke any other MTP2 feature.
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Question 12. Can Multiple Instances Of The Same Stack Entity Run On One Processor ?

Answer :

This relies upon upon the working system.

In OS like Solaris, Windows NT and so on., wherein each instance / execution of the stack entity has its personal information vicinity, this is feasible. 

In RTOS like VxWorks and so forth., the worldwide variables are mapped to a set location in reminiscence (flat memory shape). Hence, more than one instances of the stack entity get entry to the identical data region for globals, leading to clash. 

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Question 13. What Compiler Do We Use For Ss7 ?

Answer :

The SS7 improvement environment is Solaris, with GNU C (gcc) compiler.

We also collect our source code the use of the following compilers, before a launch :

Microtek MCC68K compiler
Borland C compiler
If a client is making plans to use a distinct compiler than the above, the source code may be compiled using that compiler earlier than the discharge. 

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Question 14. Is Any Global Data Referenced By The Stack Entity? What Are The Implications ?

Answer :

The database and a few different variables maintained by way of each stack entity are described as international definitions. This has no implication in OS like Unix, which do no longer share memory across duties. However, in case of RTOS (like Vxworks, PSOS) that have a flat memory space, there's best one replica of this information regardless of variety of tasks or methods started. E.G. If two times of ISUP are strolling on the equal board they'll be regarding the identical copy of facts.

This can be constant in future releases of stack – the answer will be as determined in the Protocol Development framework, which might be one of the following :

Keep worldwide database listed via the instance number of the module.
Define the database as nearby to the stack entity and pass the connection with it with every name of stack and right down to all tiers. All the database references will be completed with admire to this reference.
Question 15. On A 64bit Processor, Do Checksums And Crcs Calculation In The Stack Get Impacted ?

Answer :

All the checksums calculated in SS7 (i.E. CRC in MTP2) are 16-bit CRC. They will now not be affected by a sixty four-bit processor.

All the stack entities operates on following fundamental sorts : 

U8bit
U16bit
U32bit
S8bit
S16bit
S32bit 
(wherein U is for unsigned and S for Signed)   These definitions are defined in a header document & can be modified if needed. 

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Question sixteen. Is Any System Requirement Functionality Assumed From An External Db?

Answer :

Database maintained via each stack entity is local to it and has got no external dependency. The database maintained by using every entity has were given a static part (that's initialized by provisioning) and a dynamic part (that is updat5ed at run-time with the aid of the stack entity).

The interface of each stack entity with its database module is a nicely defined practical interface (read/write/access/modify). If there may be a want to apply an outside database, this practical interface has to be ported.

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Question 17. What Are The Performance Requirements That The Hss Ss7stack Has Been Designed To Meet?

Answer :

The protocol stack (and each constituent entity) might be so designed with the intention to permit porting at the target platform with minimum real-time overload on the consumer’s thread of manipulate (calling utility). This means that on every occasion viable, the stack code ought to be carried out within the stack’s thread of control.
Keeping in thoughts the sturdy time and reminiscence constraints in telecom systems, the stack layout and code can be advanced for optimum time and reminiscence efficiency.
Wherever messages need to be exchanged across entities, stack architecture will be so designed in an effort to limit the bandwidth requirement.
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Question 18. How Is Error Handling Implemented ?

Answer :

All mistakes are indicated thru an uniform interface. Handling of errors is the obligation of the machine management entity. All feasible mistakes that would occur in processing (which include SS7 protocol procedural errors) is numbered and globally described. All the SS7 protocol processing entity modules keep a international mistakes flag (global to a module) which displays final blunders encountered inside the processing.

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Question 19. What Is The Functionality Of The System Management Entity?

Answer :

The SS7 stack consists of a primitive System Management entity. The capability of gadget management entity consists of the subsequent: 

Provisioning, initialization and upkeep of SS7 stack entities.
Debug and trace management of SS7 stack entities.
Solicited and periodic statistics collection/reporting.
Redundancy management of SS7 stack entities.
Question 20. What Is Meant By 'redundancy Management'?

Answer :

Redundancy management if applied shall mean the following

SS7 stack shall have two working states ONLINE and STANDBY.
An interface shall be furnished for redundancy records updation.
A mechanism shall be furnished to indicate to the system management entity for triggering the redundancy information updation to all of the redundant components.
System control entity shall have the control for converting the country of the SS7 stack.
Compile time flag to control the inclusion/exclusion of redundancy functions will be provided. 
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Question 21. How Many Links Are Possible Between 2 Ss7 Links?

Answer :

Two links are viable among 2 ss7 hyperlinks.

High Speed Links (HSL).
Low Speed Links (LSL).
Question 22. What Is The Difference Between Mtp3 And Mtp3b?

Answer :

MTP3 is used for Narrowband signaling and is the traditional TDM based totally transmission system.
On the other hand MTP3b is used for Broadband signaling and basically designed for helping ATM functions on the premise of MTP3.

Question 23. Do You Know What Is The Address Of One Node In Isup?

Answer :

SPC, Signalling factor code.

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Question 24. Explain Devices That Operate At The Different Layers Of The Osi/tcp/ip Model Clearly Stating Their Functions At The Respective Layers?

Answer :

bodily layer : all phsical devices like wires, connectors, hubs repeaters,electric alerts
Datalink layer : transfer ,briges.
Network layer: routers or broutertransport-gateways.
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Question 25. What Is Difference Between Osi Layer And Tcp/ip Suite?

Answer :

In OSI reference model, there are seven layers which are Application layer, Presentation layer, Session layer, Transport layer, Network layer, Datalink Layer, and Physical layer. It is special version for the switch of information from one vacation spot from other. While the TCP/ IP suite changed into extremely compact, it changed into now not as certain.

Question 26. What Is Continuity Test In Ss7 And Why It Is Performed?

Answer :

COT is an automatic diagnostic method carried out inside the Signaling System 7 (SS7) PublicSwitched Telephone Network (PSTN) between switches to ensure that circuits are in carrier and notexperiencing excessive signal loss. This validation is executed with the aid of sending tones across the bearer channel. Itis carried out on a sampling foundation. For instance, on 10 percent of the calls.

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Question 27. What Is The Difference Between Sccp And Mtp3?

Answer :

In MTP3 The routing label details like Servive indicator ,servive network kind ,OPC and DPC information are aviable.The SCCP is the Transport layer for Tcap Based programs.The SCCP Placed over the MTP3 layer.

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Question 28. What Are The Different Functionalities Of Mtp3 Layer?

Answer :

Message Transfer Part degree 3 (MTP3) is the network layer inthe SS7 protocol stack. It routes SS7 signalling messages topublic community nodes by using Destination Point Codes,and to the proper signalling entity inside a node bymeans of a Service Info Octet. MTP3 is designated as a part of the SS7 protocol and is also referred to as part of theB-ICI interface for ATM. MTP3 sits between MTP2 and the userparts (ISUP, TUP, SCCP and TCAP) of the SS7 protocol stack.B-ISUP is an Application Layer protocol run over MTP3.

Question 29. If There Is No Rlc In Response To Rel What Will The Intermediate Switch Will Do?

Answer :

After timeout intermediate switch will launch the decision.

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Question 30. What Are The Different Links In A Ss7 Network?

Answer :

There are 6 links

A-Access hyperlink
B-Bridge hyperlink
C-Crossover hyperlink
D-Diagonal link
E-Extended hyperlink
F-Fully Associated link.
Question 31. What Is The Difference Between Iam And Sam?

Answer :

IAM(Initial Address Message)consists of the records requried for setup call.For a basic call it is a first message ship to Destination.SAM(subsequent address message)precisely it is overlap calls cope with.SAM message must be sent in the scenario when suppose a subscriber dialed a number of 9321353536.SSP ship the IAM message to there destination with out studying the 353536. I.E originating SSP seems 9321 and sends the IAM message to their respective Destination.And SAM to be ship with relaxation dialed digit.

Question 32. What Is The Full Form Of D-hyperlink?

Answer :

full shape of D-hyperlink is diagonal hyperlink . This hyperlink in reality used to connect the STP pairs inside the equal network .

Question 33. Explain How Many Types Tcp/ip Protocol?

Answer :

Two forms of tcp/ip protocol is  kinds tcp/ipv4 & tcp/ipv6.Tcp/ipv4 it's miles 32 bit now a days it's far used. Tcp/ipv6 it's miles 128 bits it's far advancd era.

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Question 34. What Are 4 Parameters Between Node A And Node B, To Bring A Pcm Link Up Between Them?

Answer :

The four parameters between node A and node B, to convey aPCM link up among them are

DPC(Destination Point Code) and OWNSP
Signaling Link set.
Network ID(NAT0 & NAT1)
PCM channel on which hyperlink is growing.
Question 35. Data Can Be Stored Permanently In Computer Through What?

Answer :

Computer records storage, regularly called storage or reminiscence, refers to pc. Memory can talk over with different forms of speedy however brief storage. ... The CPU continuouslyreads commands stored there and executes them as required. ... The CPU first off sends a range of through an address bus, a variety of referred to as reminiscence deal with...

Question 36. Why Are Cd And Dvd Media Better Than Floppy Disks?

Answer :

Floopy Disc keep information Less than 200MB CD,DVD's are morethan 200MBCD-700MBDVD-4.3to 8.5GB.

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Question 37. Explain The Booting Process Of A General Computer?

Answer :

Computer is powered on -> Power On Self Test (POST) is doneto take a look at all of the hardware -> BIOS (detects the devices like,tough-disk, units the date and time and so forth.) -> MBR (locates thefirst vicinity of boot-loader and starts booting theboot-loader) -> boot-loader (locates the OS and startsloading the OS).

Question 38. What Is File Fragmentation In Disks?

Answer :

Some instances known as 'document system ageing'is the lack of ability of a record gadget to lay out related statistics sequentially (contiguously), an inherent phenomenon in storage-sponsored record structures that permit in-vicinity amendment of their contents. It is a special case of statistics fragmentation.