IPv6 in 3GPP Evolved Packet
System
draft-korhonen-v6ops-3gpp-eps-04
Jouni Korhonen, Jonne Soininen,
Basavaraj Patil, Teemu Savolainen,
Gabor Bajko, Kaisu Iisakkila
V6OPS IETF #79
Overview
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Describes 3GPP Release-8 Evolved Packet
System and Evolved Packet Core architectures.
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And some Release-9 and -10 IPv6 related features.
Explains how IPv6 is supported in the
architecture and the different types of bearers.
Explains some of the basic concepts and
terminology of 3GPP IP access.
Mostly about “what is already there ” not about
all possible enhancements..
Some Common
Terminology..
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EPC = Evolved Packet Core
RAN = Radio Access Network
EPS = Evolved Packet System (EPC + RAN)
eNodeB = evolved NodeB i.e. base station in EPS
3GPP Access = radio system developed by 3GPP
Non-3GPP Access = radio system not developed by 3GPP
UE = User Equipment i.e., a mobile host, wireless device
APN = Access Point Name
PDN = Packet Data Network i.e. an IP network
SGSN = Serving GPRS Support Node
GGSN = Gateway GPRS Support Node
SGW = Service Gateway
PDN-GW = Packet Data Network Gateway
MME = Mobility Management Entity
Release-x = named version of the GPRS/EPS architecture (eg. Rel-8, Rel-9 etc)
Basic Evolved Packet
System Architecture
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Architecture supports EUTRAN and legacy 2G/3G
accesses as well.
PtP link is established between the UE and the P-GW.
User-plane traffic always tunneled over the transport
network.
User-plane addressing independent of transport network
addressing and IP versions.
S1-MME
UE
LTE-Uu
eNodeB
MME
S11
S1-U
Dual-Stack EPS Bearer
SGW
S5/S8
PDN-GW
SGi
PDN / IP
Services
PDN Connection
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A PDN Connection is an association between an UE and a PDN,
represented by one IPv4 address and/or one /64 IPv6 prefix.
A PDN is identified by an APN and a PDN is accessed via a PDN-GW
A PDN is responsible for the IP address/prefix management.
On an UE a PDN Connection is equivalent (or visible to an IP stack) as
a network interface.
Pre-Release-8 “equivalent” for a PDN Connection is the PDP Context
(used in GPRS).
APN points to a
specific PDN-GW
and “names” the
PDN..
Operator
Core & RAN
U
E
Point-to-point connection
UE sees the PDN
Connection as an
interface with an
address/prefix that
belongs to the PDN..
SGi
S5/S8
PDN-GW
PDN-GW is UE’s first-hop
router and mobility
anchor for the
address/prefix..
PDN
Addresses/prefixes
belong topologically
to a PND..
EPS Bearer Model
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A logical concept of a bearer has been
defined as an aggregate of one or more IP
flows related to one or more services.
The EPS bearer is between the UE and the
PDN-GW, and used to transport IP (v4 and/or
v6) packets.
The UE performs the binding of the UL IP
flows and the PDN-GW performs the binding
of the DL IP flows.
Access Point Name concept
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UEs and network use APNs to identify a network
(e.g. internet, corporate intra-network, etc) and to
some extent the associated services in
that network. Example “internet.example.com”
APNs are piggybacked on the administration of the
DNS namespace. Release-8 uses extensively SNAPTR, where are pre-Release-8 was just A/AAAA.
During the connection (bearer) setup, APNs are
used (by SGSN/MME) to discover the gateway
(GGSN/PDN-GW) that provides the IP
connectivity to the network identifier by the APN,
supported protocols, topological location collocation
properties of gateways.
Access Point Name concept
cont’d
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UE would just request an APN e.g. for
“internet” or request nothing..
MME either figures out the “default”
APN for the UE/subscriber.. or
..MME would substitute a full domain
name of the APN received from the
UE
MME would then:
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Query a NAPTR for the domain
Select the NAPTR which matches the
required protocols and such..
Query A/AAAA for both SGW and PDNGW
Push the “selected” PDN-GW address to
“selected“ SGW
$ORIGIN epc.mnc123.mcc345.3gppnetwork.org.
...
internet.apn
IN NAPTR 10 1 "a" "x-3gpp-pgw:x-s5-gtp" "" topoff.b1.gw1.nodes
IN NAPTR 20 2 "a" "x-3gpp-pgw:x-s5-pmip” "" topoff.b1.gw2.nodes
...
topoff.b1.gw1.nodes IN
IN
IN
IN
topoff.b2.gw2.nodes IN
IN
IN
...
A 192.0.2.113
A 192.0.2.114
AAAA 2001:db8:0:c:0:0:0:0
AAAA 2001:db8:0:d:0:0:0:0
A 192.0.2.143
A 192.0.2.144
AAAA 2001:db8:0:2a:0:0:0:0
DNS
S11
MME
U
E
eNodeB
SGW
S5/S8
PDN-GW
SGi
PDN / IP
Services
IP configuration and
address management
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IPv4 Address Configuration.
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IPv6 Address Configuration.
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Two methods: DHCPv4 or within the EPS bearer
setup signaling (the common way)
DHCP is optional on both the UE and the P-GW.
One method: Stateless Address Autoconfiguration
after the bearer setup.
A single /64 prefix is only supported.
Additional configuration either using:
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Stateless DHCPv[46]; or
Using protocol configuration options during NAS
signaling (“layer-2” control signaling).
EPS Bearer Types
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IPv4 only bearer.
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IPv6 only bearer.
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The bearer is configured with one IPv4 address.
The link is “IPv4 only”.
The bearer is configured with one /64 prefix.
The link is “IPv6 only”.
IPv4v6 bearer.
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The bearer is configured with both IPv4 address and one
/64 prefix.
New bearer type since Release-8.
The link is “dual-stack”.
V4v6 bearer type is the default in Rel-8 and beyond
Rel 9 has also introduced the DS PDP context type for
UTRAN and EDGE
PDN Connection
Establishment
UE
MME
eNodeB
SGW
PDN-GE
HSS/AAA
1.
1)
2.
1)
3.
Authentication and Authorization
2)
4.
5.
3)
3)
6.
4)
7.
4)
5)
6)
Address/
prefix
allocation
RB
Setup
7)
9.
8)
9)
10.
UL Data
10)
11)
12)
13)
DL Data
8.
11.
12.
13.
Attach request
Auth/AuthZ phase
Create Session Request
Create Session Response
Initial context setup
request/Attach accept
Radio bearer reconfig
Initial context setup
response
Direct transfer
Attach complete
UE starts sending UL data
Modify bearer request
Modify
response
DL data transmission starts
Dual-Stack Approach for IP
Access
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Networks prior to Release-8
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Dual-stack connectivity possible by opening two
parallel PDP Contexts of types IPv4 and IPv6.
Shows up as two separate layer-2 connections.
Networks from Release-8 onwards.
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A single IPv4v6 PDN Connection in addition to
having separate v4 and v6 PDN connections.
Shows up as one layer-2 connection with both
IPv4 and IPv6 addresses to the IP stack.
A peek to Release-9 and -10
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Release-9 will introduce IPv4v6 PDP Context
type also for GPRS (i.e. 3G, HSPA, ..):
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Means Gn/Gp interfaces and GTPv1 are updated
to understand the new PDP Type.
Release-10 will introduce prefix delegation:
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Based on RFC3633.
Due 3GPP link model and architectural decisions
some more work in IETF is needed.
See draft-ietf-dhc-pd-exclude.
Dual-stack approach
In Rel 8 and beyond networks
DS-PDN
NodeB/BTS
eNode
B
S-GW
P-GW
MME
Type v4v6
PDN
connection
In Pre Rel 8 networks
IPv4-PDP Context
NodeB/BTS
IPv4-APN
IPv4-PDN
GGSN
BS
SGSN
IPv6-APN
IPv6-PDN
GGSN