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

Describes 3GPP Release-8 Evolved Packet System and Evolved Packet Core architectures. 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.. 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 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.

PDN-GWSGW

MME

eNodeBUE

S1-MME S11

S1-U S5/S8LTE-Uu

Dual-Stack EPS Bearer

PDN / IP ServicesSGi

PDN Connection 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).

PDN-GWUE

S5/S8

PDN

SGi

Operator Core & RAN

UE sees the PDN Connection as an interface with an

address/prefix that belongs to the PDN..

PDN-GW is UE’s first-hop router and mobility

anchor for the address/prefix..

Point-to-point connection

Addresses/prefixes belong topologically

to a PND..

APN points to a specific PDN-GW and “names” the

PDN..

EPS Bearer Model

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

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 S-NAPTR, 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 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:

Query a NAPTR for the domain Select the NAPTR which matches the

required protocols and such.. Query A/AAAA for both SGW and PDN-GW Push the “selected” PDN-GW address to

“selected“ SGW

PDN-GWSGW

MME

eNodeBUE

S11

S5/S8 PDN / IP ServicesSGi

DNS

$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 A 192.0.2.113 IN A 192.0.2.114 IN AAAA 2001:db8:0:c:0:0:0:0 IN AAAA 2001:db8:0:d:0:0:0:0topoff.b2.gw2.nodes IN A 192.0.2.143 IN A 192.0.2.144 IN AAAA 2001:db8:0:2a:0:0:0:0...

IP configuration and address management

IPv4 Address Configuration. Two methods: DHCPv4 or within the EPS bearer setup

signaling (the common way) DHCP is optional on both the UE and the P-GW.

IPv6 Address Configuration. One method: Stateless Address Autoconfiguration after the

bearer setup. A single /64 prefix is only supported.

Additional configuration either using: Stateless DHCPv[46]; or Using protocol configuration options during NAS signaling

(“layer-2” control signaling).

EPS Bearer Types IPv4 only bearer.

The bearer is configured with one IPv4 address. The link is “IPv4 only”.

IPv6 only bearer. The bearer is configured with one /64 prefix. The link is “IPv6 only”.

IPv4v6 bearer. 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

1. Attach request

2. Auth/AuthZ phase

3. Create Session Request

4. Create Session Response

5. Initial context setup request/Attach accept

6. Radio bearer reconfig

7. Initial context setup response

8. Direct transfer

9. Attach complete

10. UE starts sending UL data

11. Modify bearer request

12. Modify bearer response

13. DL data transmission starts

UE eNodeB MME SGW PDN-GE HSS/AAA

Authentication and Authorization

RB Setup

1)1)

2)

3)3)

4)

5)4)

6)

7)8)

9)

10)

11)

12)

13)

UL Data

DL Data

Address/prefixallocation

Dual-Stack Approach for IP Access

Networks prior to Release-8 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. 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

Release-9 will introduce IPv4v6 PDP Context type also for GPRS (i.e. 3G, HSPA, ..): Means Gn/Gp interfaces and GTPv1 are updated

to understand the new PDP Type. Release-10 will introduce prefix delegation:

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

NodeB/BTS

eNodeB

S-GW

MME

P-GW

DS-PDN

Type v4v6 PDN connection

NodeB/BTS

BS

SGSN

GGSN

IPv4-PDNIPv4-APNIPv4-PDP Context

GGSN

IPv6-APNIPv6-PDN

IPv6-PDP Context

In Rel 8 and beyond networks

In Pre Rel 8 networks