Radio Link Control Packet Analysis

RLC typically be any data type e.g. Programming language C ,which decide the length, size, type of information dependent on situation or requirements.

So Let's Explore RLC like never done before.

Architecture 

What is SDU & PDU?

Service Data Unit: A unit of data passed down in a Protocol stack from Upper layer to lower layer. Efficiently called as ‘Payload’.

Protocol Data Unit: A protocol specific control information with specified headers and associated detailing along with Payload.

 So the below given segment will see how to deal with Payload size and different types of PDU formats as per given architecture.

RLC Analysis is the focus so all the given references below will be towards the same direction.

1st step : Signaling Packets

During call processing we have to validate the status packets & statistics for signaling data.

Let's First start discuss about Downlink

RLC Configured with SRB1: Post to RRC Connection setup the RLC DL config confirms the activation for SRB -1/AM mode 

The RLC RB info packet confirms the configurations presented at RRC Connection setup.

As the AM mode information is just initialized and in RRC Setup we use TM mode, the RLC Statistics will be as mentioned.

As we move on towards Attach/Signaling process

The above given I have taken example for two DL SRB Packets sent to UE

1. RRC DL Information Transfer >>{Piggybacked NAS info: Identity Request }

2. RRC DL Information Transfer >> {Piggybacked NAS info :Authentication Request }

Do write down in comment section why we need Identity Request ....

As the data carried by SRB 1,Surely will have the RLC Data for the given information.

So same as follows for the

3. RRC DL Information Transfer >>{Piggyback NAS Info: Security Mode Command}

and So on for the rest of the signaling.

With above picture Follow the call flow too....

As we reach to the part of call flow where we get the RRC Connection Reconfiguration

We get to establish with new SRB-2 & DRB-ID :depends upon ASN.1

To know more play around with the given website. Click here:ASN.1

With RLC configuration we can clearly see the activation for SRB-2 & DRB respectively.

So from here the complexity and fun arises.

We will see 3 different information data mapped to 3 different ID's at difference instances

which may can increase in number as we are establishing new DRB for different QCI's

The best way to map is to follow the RB config-Idx.

Here Comes the Uplink

Quick checks are Uplink Configuration and UL packet stats.

above given is SRB1 Establishment and below given is so on for SRB2,DRB and so on..

whereas UL Stats are mandatory too . Below given for UL Data during SRB1 only

For SRB-2, DRB-1 uplink stats

With the given logs and detailing is just basic part of RLC analysis been covered for signaling .

RLC type , Debugging the RLC with data packets will be covered with next Blog.

And for the beginners have attached the call flow . Click here: Call-flow

Will comeback with more exclusive log analysis content soon till then be positive!!

See yeah!!