2001: Homework assignment 15

• General instructions
• Material
• Assignment
• Returning

• Deadline: Tuesday 4.12.2001 at 4pm

Material

If you use other sources than the material mentioned below, add a reference list to your homework assignment!

• Introduction to teletraffic modeling and theory
• Network management - What it is and what it isn't
• The handouts.

Important information for all: Copyright basics for Web authors and users by Jukka Korpela

Assignment:

1. Signalling and IP (8 points)

Read this first. Think about the signalling gateway for VoIP.

Now, imagine that you would like to implement a IP based PBX to control your own company's telephones. Your PBX SSP understands ISUP and INAP. You want to generate a WWW server accessible in your Intranet which is capable of controlling the SSP.

Consider a signalling gateway that is able to support the system.

1. What interfaces (I/O cards or software interfaces) are needed? (2 p)

   - for the intranet, Eth
   - for the SSP side, T1/E1 line interface card
   
   standard software interfaces
   

2. Show the protocol stacks required. (4 p)

   W-app.			GW			SSP
   ----			------------------	----
   
   A			A   |  INAP | ISUP	INAP,ISUP
   UDP			UDP |  TCAP |		TCAP
   IP			IP  |  SCCP		SCCP
   Eth			Eth |  MTP-3...1	MTP-3...1
   			    |  T1/E1		T1/E1
   
   here, A is a self-made protocol.  As an alternative, mapping INAP/ISUP
   messages on UDP might be applicable.  For security, A might use some
   security features.
   
   

3. Describe how the WWW server interacts with your SSP.(2 p)

   
   here one possible scenario
   
   - someone calls to someone's number in the company
   - the recipient wants to redirect the call, so he uses the
     WWW server (normal HTTP activity)
   - The recipient selects the call redirect function, and the
     cgi-script sends a request to the GW using the A protocol
   - GW:s software makes the necessary requests for the SSP and
     sends them as ISUP messages
   
   

2. Network dimensioning (5 points)

1. What is the required capacity (bps) of the link from the concentrator to the exchange, if the target call blocking probability is 0.5% ? (3 p)

   Use Erlang's formula to calculate call blocking probability with different numbers of channels, see image:

   

   The value given will be 120 or 121 channels. Each PCM channel is 64kbps, so the resulting bitrate will be 7680bps or 7744bps. Do not forget signalling, which requires at least 64kbps extra to this! This capacity is then needed by both concentrators.

2. What PDH multiplex or SDH containers should be used? (2 p)

   • PDH: E2 for both is roughly enough, but it is safer to use E3 for both concentrators.
   • SDH: C-3/VC-3 for both concentrators

3. Write open and explain the meanings of these network management-related acronyms briefly (6 points)

1. CMISE

       Common Management Information Service Element, provides access to
   information in the managed objects, uses CMIP to issue requests for
   management services 
   

2. MIB

       Management Information Base, a network's managed information and the
   rules by which that information is presented and managed
   

3. SNMP

       Simple Network Management Protocol, IP-version for reading and manipulating MIBs 
   

4. EML

       Element-management layer, one of the TML logical layers, manages each
   network element
   

5. KPI

       Key Performance Indicator, presents some vital information regarding the
   network. Network performance can be evaluated based on it. 
   

6. QA

       Q-adapter, one of the TMN functional components. Enables the TMN to
   manage NEs that have non-TMN interfaces.
   

4. Feedback

1. How many hours did you spend doing this assignment?
2. Was the assignment too hard or too easy? Why?
3. What topics should this assignment cover next year?

Returning your answer