07 Messages in Roaming Cases
Transcript of 07 Messages in Roaming Cases
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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
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GPRS network
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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)
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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
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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 )
Operator 2Operator 1
Backbone Backbone
Without IPSec:
… This is a message …
With IPSec:
… h.j$hFj=kXja,zedf…
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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.
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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).
Operator 2Operator 1
Backbone Backbone
GRX network
BG
FW
BG
FW direct line: static routing
Via GRX:BGP-4 for routing
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Inter-PLMN Interconnection Possibilities2) GPRS Roaming Network (GRX) – BGP4 routing – Dynamic routing
Impact on DNS architecture and messages:
Operator 2Operator 1
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
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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
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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.
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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 A: LABAPN1.OP2.COM.mnc002.mcc230.gprs
Standard query response NS: please ask TLD
Standard query A: LABAPN1.OP2.COM.mnc002.mcc230.gprs
Standard query response NS: please ask op2 home dns
Standard query A: LABAPN1.OP2.COM.mnc002.mcc230.gprs
Standard query response A=192.168.20.21
Standard query response A=192.168.20.21
Create PDP
context request
DNS
client
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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
Standard query A: LABAPN1.OP2.COM.mnc002.mcc230.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
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Roaming Messages Exercises
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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.gprsHome PLMN
mnc002.mcc230.gprs
Visited PLMN
mnc009.mcc262.gprs
RAS/RAN
Gb/Iu-PS
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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
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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.gprsHome PLMN
mnc002.mcc230.gprs
Visited PLMN
mnc009.mcc262.gprs
RAS/RAN
Gb/Iu-PS
E t dR i
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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 A LABAPN1.OP2.COM.mnc002.mcc230.gprs
Standard query response: NS 192.168.200.65 (TLD)
Standard query A LABAPN1.OP2.COM.mnc002.mcc230.gprs
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 request
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
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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.gprsHome PLMN
mnc002.mcc230.gprs
Visited PLMN
mnc009.mcc262.gprs
RAS/RAN
Gb/Iu-PS
Roaming
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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 A BASIC1.NOKIA-OCD.COM.mnc002.mcc230.gprs
Standard query response: NS 192.168.20.60 (home dns)
Standard query A BASIC1.NOKIA-OCD.COM.mnc002.mcc230.gprs
Standard query response A 192.168.20.21Standard query response A 192.168.20.21
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