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LTE: Is it possible SGW and PGW support multiple IPs for GTP tunneling ?

+1 vote

GTP tunnel id is a 32-bit long value over one IP address combination. Suppose there are two nodes A and B which has IP addresses X and Y respectively. Is it possible when first GTP tunnel id range gets exhausted then both the nodes starts using different IP address combination and again GTP tunnel id range can be re-used ? If it is impossible then what could be the reason ?

posted Oct 10, 2017 by Harshita

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1 Answer

+3 votes
Best answer

In LTE, GTP tunnel ID range cannot be reused for other set of IP address.
For example, if any DL data packet received at PGW for specific UE, then PGW will send that packet to UE via SGW through GTP tunnel. This GTP tunnel was selected by PGW based on TFT. if this selected tunnel ID was associated to two SGW IP addresses then to which SGW, this packet is forwarded by PGW?

32-bit value is quite a big to hold 2 power 32 TEID's

on S11 interface - TEID is for UE. Means one pair of TEID's are enough to serve UE - irrespective to how many PDN's were created.
on S5S8c interface - TEID is for PDN. Means one pair of TEID's will serve on PDN.(eg: 3 pair od TEID's will serve 3 PDN's for same UE)

In the above control plane TEID's there is no question of exhausted in case of LTE devices. This is the operator responsibility to deploy enough number of TA's/SGW's based on number of users.
on S1U/S5S8U - TEID per bearer. Means one pair of TEID's will serve on bearer(default/dedicated). Usually PGW will change(but not compulsory) per PDN/APN. So, in this case also TEID's are enough to serve.

In case of IOT devices separate diameter interface(T6a) was defined between MME and SCEF.

answer Jun 27, 2018 by Althi Rajeswararao
Similar Questions
+1 vote

Hi Friends,
I saw somewhere that MME will also do a DNS query for P-GW. As i know S-Gw will do a query for P-Gw address. Is there any situation that MME will do a query for P-GW address using APN? and after this query how MME will use the P-Gw Address.

and is there any possibility of Doing DNS query by P-Gw to get any other nodes Ips and under what conditions P-Gw will do a DNS query?

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