07 messages in roaming cases

8/17/2019 07 Messages in Roaming Cases

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2 © Nokia Siemens Networks CN3203EN01GLN00

Objectives

After the module, the participants will be able to:

• Explain Roaming Concepts

• Describe the interface between the visited SGSN and thevisited/home GGSN

• Debug a packet switched call set up in a roaming case




GPRS network




General Requirements of the Inter-PLMN BackboneIP addressing

GSN (GPRS Serving Node) addresses are advertised in tunneled

messages, so

• Public addressing should be applied in all GPRS backbone

networks.

•

NAT is not feasibleExample Message:

Frame 88 (160 bytes on wire, 160 bytes captured)

Ethernet II,

Internet Protocol, Src Addr: 192.168.250.111, Dst Addr: 192.168.20.21

User Datagram Protocol, Src Port: 2123 (2123), Dst Port: 2123 (2123)

GPRS Tunnelling Protocol v1

.

Message Type: Create PDP context request (0x10).

GSN address : 192.168.250.111

GSN address : 192.168.250.131

These addresses areused by GGSNs forreplies(Control/User plane)




General Requirements of the Inter-PLMN BackboneSecurity and Screening

• Operators should implement Firewalls adjacent to Border Gateways

• Generally operators should allow only routing information, such as

BGP, GTP traffic and signalling and DNS traffic in addition to some

diagnostic tools, such as ´ping´

Operator 2Operator 1

Backbone Backbone

Allowed Services:BGP, GTP, DNS, ICMP




General Requirements of the Inter-PLMN Backbone

IPSec• GPRS operators may use IPSec

• Inter-PLMN backbone, if implemented on unsecured public

networks, should support the use of IPSec including Public Key

Infrastructure (PKI, algorithm for decoding encrypted info and used to

verify the identity of the user by a public key )


Backbone Backbone

Without IPSec:

… This is a message …

With IPSec:

… h.j$hFj=kXja,zedf…




General Requirements of the Inter-PLMN Backbone

Quality of Service (QoS) is privided by:

• Inter-PLMN backbon e defined by physical characteristics of leased

lines (Layer 1 and Layer 2) and by IP (Layer 3) parameters

• GPRS QoS classes and parameters that define the quality of service

in terms of radio resources etc.

Integration of Inter-PLMN QoS and GPRS QoS classes and parameters

should remain for further study and may be implemented in

forthcoming GPRS releases.




Interconnections of the Inter-PLMN Backbone

Dynamic IP Routing

• Dynamic exchange of routing information between different networks may use BGP-

4 (RFC 4271) routing protocol via GPRS Roaming Exchange network (hub for GPRS

connections from roaming users).

Static IP Routing

• Static exchange of routing information between different networks using direct

leased line (dedicated link between each GPRS service provider).


Backbone Backbone

GRX network

BG

FW

BG

FW direct line: static routing

Via GRX:BGP-4 for routing




Inter-PLMN Interconnection Possibilities2) GPRS Roaming Network (GRX) – BGP4 routing – Dynamic routing

Impact on DNS architecture and messages:


Backbone Backbone

GRX network

BG

FW

BG

Root DNS

OP1DNS OP2DNS

GGSN

BG

FW

BG

FWFW

1) DNS root server is queried for the IP address in OP2 domain to find the APN2) Answer: OP2DNS will tell more

3) OP2DNS is queried about APN

4) Answer: IP address of GGSN




Inter-PLMN Interconnection Possibilities3) GPRS Roaming Network (GRX) including Central Exchange Point – Dynamic routing

Local Operator 1

Backbone

Central Exchange Point

BG

Switch

OP1DNS

GPRS roaming networks can be complemented with local peering

implementations (Central Exchange Points) for regional traffic

Local Operator 2

Backbone

OP1DNSRouter

Router

Router Router

GRX




Services of the Inter-PLMN Backbone

GTP Tunnelling• Inter-PLMN backbone shall support GTP tunnelling on both TCP

and UDP.

Domain Name Service

• Inter-PLMN backbone shall provide a transport of DNS queries

between PLMNs. In addition, Inter-PLMN backbone may provideroot DNS services.




Services of the Inter-PLMN Backbone (1)Root DNS queries - iterative

visited backbone

sgsn

ggsn

RAN

Gb/Iu-PS

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

op2

home dns

Visitor of

mnc002.mcc230.gprsHome PLMN

mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

Standard query A: LABAPN1.OP2.COM.mnc002.mcc230.gprs


Standard query response NS: please ask TLD


Standard query response NS: please ask op2 home dns


Standard query response A=192.168.20.21

Standard query response A=192.168.20.21

Create PDP

context request

DNS

client




Services of the Inter-PLMN Backbone (2)Root DNS queries - recursive

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of

mnc002.mcc230.gprsHome network

mnc002.mcc230.gprs

Visited network

mnc009.mcc262.gprs


?A: LABAPN1.OP2.COM.mnc002.mcc230.gprs

?A: LABAPN1.OP2.COM.mnc002.mcc230.gprs

?A: LABAPN1.OP2.COM.mnc002.mcc230.gp

response A=192.168.20.21

response A=192.168.20.21

response A=192.168.20.21

response A=192.168.20.21

Create PDP

context request

DNS

client

RAN

Gb/Iu-PS




Roaming Messages Exercises




RoamingVPLMN=Y, APN in visited network

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of


mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS




ExpectedResult

Standard query A BASIC31.NOKIA-OCD.COM.MNC009.MCC262.GPRS

RoamingVPLMN=Y, APN in visited network

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of

mnc002.mcc230.gprs

Create PDP

context request

Standard query response A 192.168.30.21

Create PDP context request

Create PDP context responseCreate PDP

context response

Home PLMN

mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS

R i




RoamingVPLMN=Y, APN not available in visited network

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of


mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS

E t dR i




ExpectedResult

RoamingVPLMN=Y, APN not available in visited network

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of

mnc002.mcc230.gprs

Standard query A LABAPN1.OP2.COM.MNC009.MCC262.GPRS

Standard query response, No such name

Standard query A LABAPN1.OP2.COM.mnc002.mcc230.gprs


Standard query response: NS 192.168.200.65 (TLD)


Standard query response: NS 192.168.20.60 (home dns)

Standard query A LABAPN1.OP2.COM.mnc002.mcc230.gprsStandard query response A 192.168.20.21

Standard query response A 192.168.20.21


Create PDP context response

Create PDPcontext request

Create PDP

context response

Home PLMN

mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS

Roaming




RoamingVPLMN=N, same APN in visited network and home network available

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of


mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS

Roaming




ExpectedResult

RoamingVPLMN=N, same APN in visited network and home network available

visited backbone

sgsn

ggsn

cndns1

bg

home backbone

home ggsn

op2bg

GRX DNSs:

ROOT TLD

home dns

Visitor of

mnc002.mcc230.gprs

Create PDP

context request Standard query A BASIC1.NOKIA-OCD.COM.mnc002.mcc230.gprs

Standard query A BASIC1.NOKIA-OCD.COM.mnc002.mcc230.gprs

Standard query response: NS 192.168.200.65 (TLD)


Standard query response: NS 192.168.20.60 (home dns)


Standard query response A 192.168.20.21Standard query response A 192.168.20.21


Create PDP context responseCreate PDP

context response

Home PLMN

mnc002.mcc230.gprs

Visited PLMN

mnc009.mcc262.gprs

RAS/RAN

Gb/Iu-PS

07 messages in roaming cases

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