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GTP (GPRS Tunneling Protocol)

 

When a data is transferred from Radio Stack(eNB) to Core Network it goes through various Interfaces as illustrated in Figure 1 of Network Architecture and Interface page. When the data go through these interface, they get encapsulated by various tunnel protocol as in Figure 2 of Network Architecture and Interface page. GTP is a specific type of tunneling protocol by which U-plane data (user data) go through as illustrated below. In 3GPP, GTP is specified in 29.281.

 

 

 

Following is the GTP Header format. User Data (usually IP data) is encapsulated by a GTP packet following this header as shown in example section.

 

< 3GPP 29.281 - Figure 5.1-1: Outline of the GTP-U Header >

 

 

Examples :

 

Example 1 :  GTP - IP - ICMP (Echo Request)

 

 

 

Example 2 :  GTP - IP - ICMP (Echo Reply)

 

 

 

 

Reference :