telecom • networking • design

an EventHelix.com blog


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Debugging software crashes 2

This article continues our discussion on Debugging software crashes. Here we focus on memory corruption crash symptoms. We will also look at the special considerations in debugging C++ code crashes. Finally we will look at techniques to simplify crash debugging.

global-memory-corruptionstack-corruption

The article covers the following topics:


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S1AP View of Inter-MME S1 Handover

Here we look at the S1 handover that involves an MME change. The S1 handover is analyzed at the S1AP interface. S1AP messages involved in S1 handover are shown just before the message. The messages show a high level structure of the complex messages involved in the interaction.

Inter-MME-S1-handover

Additionally, you can click on any S1AP message to see the complete field level details like the one shown below.

PDCP-transfer


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LTE Network Design and Planning Videos

Learn about LTE network design and planning from this video series. Issues involved in RF planning and resource allocation are covered in detail.

The video tutorial series is divided into the following videos:

  1. dimensioning user traffic in 4G networks
  2. overhead in LTE dimensioning
  3. customer experience in wireless network design
  4. measurements in LTE
  5. downlink parameter dimensioning in LTE
  6. uplink parameter dimensioning in LTE
  7. LTE spectrum analysis

Frequency reuse in LTE

 

 


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DHCP: Dynamic Host Configuration Protocol

Dynamic Host Configuration Protocol (DHCP) is used to dynamically provide IP addresses and configuration information to client nodes. DHCP provides greater flexibility by leasing out IP addresses to host nodes. DHCP supports mechanisms that can be used by hosts to renew their lease.
This sequence diagram describes the DHCP interactions between a Laptop and the DHCP servers in the intranet. Four different cases are covered.
  1.    Laptop boots up for the first time and requests an IP address.
  2.    Laptop’s IP address lease is renewed.
  3.    Laptop reboots and confirms the IP address settings
  4.    Laptop is disconnected from Subnet 1 and reconnected in Subnet 3.

DHCP sequence diagram


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BGP peering and route updates

BGP peering and route update messaging is explored in detail in this flow.

This message flow shows how two BGP routers:

  1. Peer by establishing a TCP connection and exchanging BGP OPEN messages.
  2. Exchange Keep Alive messages to ensure that the routers are reachable.
  3. Exchange routes using BGP UPDATE messages.
  4. Release the BGP connection on operator command.
All messages in this sequence diagram may be clicked to see complete field level details of every BGP message.

BGP peering and route update


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Tracking Area Updates in an LTE Network

LTE Tracking Area Update signaling flow describes how mobiles keep the network updated about their location.

A Tracking Area Update takes place if:

  • UE detects it has entered a new Tracking Area that is not in the list of TAIs that the UE registered with the network;
  • the periodic Tracking Area update timer has expired;
  • UE was in UTRAN PMM_Connected state (e.g. URA_PCH) when it reselects to E UTRAN;
  • UE was in GPRS READY state when it reselects to E UTRAN;
  • the TIN indicates “P-TMSI” when the UE reselects to E-UTRAN (e.g. due to bearer configuration modifications performed on
    GERAN/UTRAN);
  • the RRC connection was released with release cause “load re-balancing TAU required”;
  • a change of the UE Core Network Capability and/or UE Specific DRX Parameters information of the UE.

Tracking area update in LTE


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Generate sequence diagrams from PCAP files that carry tunneled GTP traffic

VisualEther 6.1.103 now supports generating sequence diagrams from tunneled messages in PCAP files. You can create filters that will ignore the outer GTP message and extract the fields from the inner message.
Capture inner and outer messages is GTP


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SIP call setup with authentication

This call flow shows the SIP call setup between a SIP client (192.168.0.10) and a SIP server (216.234.64.8). The flow also shows the RTP message flow between the SIP client and the Media Gateway (216.234.64.16).
The example covers the following:

  1. SIP invite from the client.
  2. The SIP server challenges the client to authenticate.
  3. The client responds to the authentication challenge.
  4. The call is connected.
  5. The call enters the conversation phase with RTP traffic.
  6. The SIP call is cleared.

SIP call flow with authentication


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More Object Oriented Design Tips

We have already covered object oriented design tips in a previous article. Here we will look at more tips that will help you improve your object oriented design skills:

  1. Class with just get-set methods points to missed delegation
  2. Replace an array of structures with an array of objects
  3. Delegate work to helper class
  4. Multi-dimensional arrays point to incomplete class identification
  5. Multiple nested loops point to incomplete delegation
  6. Class with very large numbers of methods points to incomplete class identification
  7. Don’t go overboard with inheritance
  8. Prefer delegation to inheritance
  9. Don’t scatter the abstraction
  10. Consider group of objects to split work amongst team members
  11. Use nested classes for lightweight helper classes
  12. Use templates to improve type safety and performance
  13. Divide your code into framework and application parts