Service Function Chaining Use Cases in Mobile Networks
draft-haeffner-sfc-use-case-mobility-00
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draft-haeffner-sfc-use-case-mobility-00
Service Function Chaining W. Haeffner
Internet-Draft Vodafone
Expires: August 2, 2014 J. Napper
Cisco Systems
January 29, 2014
Service Function Chaining Use Cases in Mobile Networks
draft-haeffner-sfc-use-case-mobility-00
Abstract
This document provides some exemplary use cases for service function
chaining in mobile service provider networks. The objective of this
draft is not to cover all conceivable service chains in detail.
Rather, the intention is to localize and explain the application
domain of service chaining within mobile networks as far as it is
required to complement the problem statement and framework statements
of the working group.
Service function chains typically reside in a LAN segment which links
the mobile access network to the actual application platforms located
in the carrier's datacenters or somewhere else in the Internet.
Service function chains ensure a fair distribution of network
resources according to agreed service policies, enhance the
performance of service delivery, take care of security and privacy or
support application and business support platforms. General
considerations and specific use cases are presented in this document
to demonstrate the different technical requirements of these goals
for service function chaining in mobile service provider networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 2, 2014.
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
1.1. Terminology and abbreviations
Much of the terminology used in this document has been defined by the
3rd Generation Partnership Project (3GPP), which defines standards
for mobile service provider networks. Although a few terms are
defined here for convenience, further terms can be found in
[RFC6459].
Device A physical or virtualized function.
< payload | IP header > IP packet.
UE User equipment like tablets or smartphones.
S-IP Source IP address.
D-IP Destination IP address.
IMSI The International Mobile Subscriber Identity that identifies a
mobile subscriber.
SGi, Gi Egress termination point of the mobile network (SGi in case
of LTE, Gi in case of UMTS/HSPA). The internal data structure of
this interface is not standardized by 3GPP.
PCRF 3GPP standardized Policy and Charging Rules Function.
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1.2. General scope of mobile service chains
Mobile access networks terminate at a mobile service creation point
(Packet Gateway) typically located at the edge of an operator IP
backbone. From the user equipment (UE) up to the Packet Gateway
(P-GW) everything is fully standardized by the 3rd Generation
Partnership Project (3GPP) e.g., in [TS.23.401]. Within the mobile
network, the user payload is encapsulated in 3GPP specific tunnels
terminating eventually at the P-GW. In many cases application-
specific IP traffic is not directly exchanged between the original
mobile network, more specific the P-GW, and an application platform,
but will be forced to pass a set of service functions. Those
application platforms are, for instance, a web server environment, a
video platform, a social platform or some other multimedia platform.
Network operators use these service functions to differentiate their
services to their subscribers. Service function chaining is thus
integral to the business model of operators.
1.3. General scope of mobile service chains
Important use cases classes for service function chains generically
include:
1. functions to protect the carrier network and the privacy of its
users(IDS, FW, ACL, Encryption, Decryption, etc.),
2. functions that ensure the contracted quality of experience using
e.g., performance enhancement proxies (PEP) like video
optimizers, TCP optimizers or functions guaranteeing fair service
delivery based on policy based QoS mechanisms,
3. functions like HTTP header enrichment that may be used to
identify and charge subscribers real time,
4. functions like CG-NAT/PAT, which are required solely for
technical reasons, and
5. functions like parental control or malware detection that may be
a cost option of a service offer.
2. Mobile Network overview
For simplicity we only describe service function chaining in the
context of LTE (Long Term Evolution) networks. But indeed our
service chaining model also applies to earlier generations of mobile
networks.
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2.1. Building blocks of 3GPP mobile networks
The major functional components of a LTE network are shown in
Figure 1 and include user equipment (UE) like smartphones or tablets,
the LTE radio unit named eNB (enhanced NodeB), the serving gateway
(S-GW) which together with the mobility management entity (MME) takes
care of mobility and the packet gateway (P-GW), which finally
terminates the actual mobile service. These elements are described
in detail in [TS.23.401]. Other important components are the home
subscriber system (HSS) and the policy and charging rule function
(PCRF), which are described in [TS.23.203]. The P-GW interface
towards the SGi-LAN is called SGi-interface, which is described in
[TS.29.061] and finally the SGi-LAN is the home of service function
chains (SFC), which are not standardized by 3GPP.
End to end context including all major components of a LTE network.
The actual 3GPP mobile network includes the elements from the user
equipment [UE] to the packet gateway [P-GW].
+--------------------------------------------+
| Control Plane (C) [HSS] | [OTT Appl. Platform]
| | | |
| +--------[MME] [PCRF] | Internet
| | | | | |
| [UE-C] -- [eNB-C] == [S-GW-C] == [P-GW-C] | |
+=====|=========|==========|============|====+ +--------+---------+
| | | | | | | | |
| [UE-U] -- [eNB-U] == [S-GW-U] == [P-GW-U]-+--+----[SGi-LAN] |
| | | | |
| | | | |
| | | [Appl. Platform] |
| | | |
| User Plane (U) | | |
+--------------------------------------------+ +--- IP Backbone --+
|<----------- 3GPP Mobile Network ---------->|
Figure 1: Major components of an LTE network.
The radio-based IP traffic between the UE and the eNB is encrypted
according 3GPP standards. Between eNB, S-GW, P-GW user IP packets as
well as control plane packets are encapsulated in 3GPP-specific
tunnels. In some mobile carrier networks the 3GPP specific tunnels
between eNB and S-GW are even additionally IPSec-encrypted. For more
details see [TS.29.281] and [TS.29.274].
Service function chains act on user plane IP traffic only. But the
way these act on user traffic may depend on subscriber, service or
network specific control plane metadata.
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2.2. General scope of mobile service chains
The original user IP packet including the Source-IP-Address (S-IP) of
the UE and the Destination-IP-Address (D-IP) of the addressed
application platform and leaves the Packet Gateway away from the
mobile network via the so-called Gi-interface (3G service, e.g.,
UMTS) respectively SGi-interface (4G service, e.g., LTE). Between
this (S)Gi-interface and the actual application platform the user
generated upstream IP packets and the corresponding downstream IP
packets are typically forced to pass an ordered set of service
functions, loosely called a service function chain (SFC). The set of
all available service functions (physical or virtualized) which can
be used to establish different service chains for different services
is often called a Gi-LAN for 2G/3G services and SGi-LAN for 4G
services.
The (S)Gi-interface towards the (S)Gi-LAN itself is discussed in
[TS.29.061], but service function chaining is not specified by 3GPP.
The (S)Gi-LAN service functions may use subscriber and service
related metadata delivered from mobile control plane functions like
PCRF to process the flows according to service related policies.
In short, the (S)Gi-LAN service area is presently used by mobile
service providers to differentiate their services to their
subscribers and reflect the business model and of mobile operators.
For different applications (e.g., Appl. 1,2,3) upstream and
downstream user plane IP flows will be forced to pass a sequence of
service functions which is called a service chain specific to a given
application. In the simple example sketched in Figure 2 the service
chains for applications 1,2 and 3 may be just classified by an unique
interface-ID of the egress P-GW interfaces where the service chains
for application 1, 2 and 3 are attached.
Service functions typically observe, alter or even terminate and
reestablish application session flows between mobile user equipment
and application platforms.
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Typical service function chain topologies as seen in many of today's
mobile networks. Control plane metadata supporting policy based
traffic handling may be linked to individual service functions SFn.
Because in this example the P-GW classifies service chains we
consider the P-GW being a component of the service chaining
environment.
+------------------------------------------------------------------+
| Control Plane Environment [HSS] [MME] [PCRF] [others] |
+------------------------------------------------|-----------------+
+--------------------+
+---------------------------|--------------------|-----------------+
| User Plane Environment | | |
| | +------(S)Gi-LAN --+-----+ |
| | | | |
| | | +---[SF1]-[SF3]-[SF5]---[Appl. 1] |
| | | / | |
| [UE]---[eNB]===[S-GW]===[P-GW]-----[SF2]-[SF4]-[SF6]--------+ |
| | \ | | |
| | +---[SF7]-[SF8]-[SF9]-----+ | |
| | | | | |
| +--------------------------+ | | |
| | | |
+----------------------------------------------------------|--|----+
| |
OTT Internet Applications
| |
[Appl. 2] [Appl. 3]
Figure 2: Typical service chain topology.
2.3. The most common classification scheme
Mobile user equipment like smartphones, tablets or other mobile
devices address use Access Point Names (APNs) to address a service
network or service platform. APNs are DNS host names and comparable
to FQDN host names. While a FQDN refers to an Internet IP address,
an APN (loosely speaking) specifies a P-GW IP address. These APNs
are used to distinguish certain user groups and their traffic, e.g.,
there can be an APN for a mobile service offered to the general
public while enterprise customers get their own APN. For APN details
see [TS.23.003].
Operators often associate a designated VLAN-ID with an APN. A VLAN-
ID n then may classify the service function chain n (SFC n) related
to an application platform n (Appl. n).
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+----------+
| |
| IF-1 O [APN 1 => VLAN-ID 1] ---- [SFC 1] ---- [Appl. 1]
| |
=====| P-GW O . . . .
| |
| IF-n O [APN n => VLAN-ID n] ---- [SFC n] ---- [Appl. n]
| |
+----------+
Figure 3: Association of a service chain to an application platform.
Examples for an APN are:
Vodafone Germany:
+------------+-----------------+
| APN: | web.vodafone.de |
| | |
| User Name: | not required |
| | |
| Password: | not required |
+------------+-----------------+
Table 1
Deutsche Telekom/T-Mobile:
+------------+------------------+
| APN: | internet.telekom |
| | |
| User Name: | t-mobile |
| | |
| Password: | tm |
+------------+------------------+
Table 2
More sophisticated classifications are feasible using UE related,
subscriber and service related, as well as network related metadata.
Typical metadata and their sources are:
UE: terminal type (e.g., HTC one); IMSI (country, carrier, user);
GTP tunnel endpoint: eNB-Identifier; time;
PCRF: subscriber info; APN (service name); QoS; policy rules.
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Mobile operator defined subscriber, service or network specific
policies are typically encoded in the 3GPP-based "policy and charging
rules function" (PCRF), see [TS.23.203]. For instance, a PCRF may
encode the rules that apply to pre-paid and post-paid users, users
with a classification of gold, silver, or bronze, or even as detailed
as describing rules that apply to "gold users, wishing to download a
video file, while these subscribers are subjected to a fair-usage
policy". It is up to the mobile service providers to encode the
precise mappings between its subscriber classes and the associated
service chains.
3. Example use cases specific to mobile networks
Because HTTP via TCP port 80 (or TCP port 443 for HTTPS) is by far
the most common Internet traffic class, we discuss two typical
examples of an associated service function chaining model in some
more detail.
The models presented below are simplified compared to real life
service function chain implementations because we do not discuss
differentiated traffic handling based on different subscriber-
specific service level agreements and price plans or even actual
network load conditions.
3.1. Service chain model for Internet HTTP services
With the increase of Internet traffic in mobile networks mobile
operators have started to introduce Performance Enhancement Proxies
(PEPs) to optimize network resource utilization. PEPs are more or
less integrated platforms that ensure the best possible Quality of
Experience (QoE). Their service functions include but are not
limited to Deep Packet Inspection (DPI), web and video optimizations,
subscriber and service policy controlled dynamic network adaption,
analytics and management support.
A simple service function chain model for mobile Internet upstream
and downstream traffic is shown in Figure 4 below. The function
chain includes Load Balancers (LB), which split HTTP over TCP port 80
away from the rest of the internet traffic. Beside basic web
content, this traffic class includes more and more video. To act on
this traffic type we force this traffic to pass Performance
Enhancement Proxies. The firewall function (FW) protects the carrier
network from the outside and Network Address Translation (NAT) maps
the private IP address space dedicated to user equipment to a public
IP address.
The first application in the service chain caches web content to help
reduce Round Trip Times (RTT) and therefore contribute to improved
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web page load times. This is generally more important for mobile
service providers than reducing Internet peering costs. Similar
arguments hold for cached video content. We avoid potential large
jitter imported from the Internet.
Service function chain to control, steer and manipulate HTTP traffic
over TCP port 80. An example for non HTTP:80 traffic is IPsec
traffic, which is dedicated to port 10000. Note that in a real
environment not only port 80 but for example additional traffic via
port 8080, 25 for SMTP, 110 for POP3 or 143 for IMAP may be forced to
pass a service chain.
[Cache]
|
[P-GW]---[LB]-----------[PEP]--[LB]--[FW]---[NAT]---[Internet]
| HTTP:80 |
| |
| |
| non HTTP:80 |
+---------------------+
Figure 4: Service function chain for HTTP traffic over TCP port 80.
A second application is video optimization. Video content from the
Internet may not fit in the size of mobile device displays or simply
would overload the mobile network when used natively. Therefore
mobile operators adapt internet-based video content to ensure the
best Quality of Experience.
Video content optimization very often is also an additional premium-
related component in service offers and price plans.
Our PEP environment for video optimization consists of three basic
service functions shown in Figure 5: A steering proxy which is able
to redirect HTTP traffic, a DPI-based controller which checks for
video content and an optimizer which transcodes videos to an
appropriate format on the fly in real time.
[PEP for video] ==>> [Steering Proxy]---[DPI Contr.]---[Optimizer]
Figure 5: Service functions required for video optimization.
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In Figure 6 we show the detailed HTTP flows and their redirection in
some more detail. The intention here is to show every elementary
functional step in a chain as a separate physical or virtualized item
but this state diagram must not necessarily reflect every existing
vendor-specific proprietary implementation.
[UE]----[Steering Proxy]----[DPI Contr.]----[Optimizer]----[Content]
|-- HTTP GET ->|-------------- HTTP GET ----------------------->|
|<------------- HTTP Response -------------------|
|-- Is it Video? ->|
|<-- Video found --|
|<--- HTTP ----|
Redirect
|-- HTTP GET ->|-----HTTP GET ---------------->|
|-- HTTP GET -->|
Video
|<--- HTTP -----|
Response
Orig. Video
{Optimize}
|<------- HTTP Response --------|
Transcoded Video
|-- Is it Video? ->|
|<-- Video found --|
|<--- HTTP ----|
Response
Transcoded Video
Figure 6: Flow diagram between UE and video optimization PEP.
3.1.1. Weaknesses of current approaches
This use case model highlights the weakness of current service
deployments in the areas of traffic selection, reclassification, and
multi-vendor support. Traffic is classified after the P-GW and
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separated into separate flows based on whether it is (in this
example) TCP traffic destined to port 80. This classification could
be done initially if the load balancer can classify the traffic and
initiate service chain selection, or the traffic can be reclassified
at the load balancer if it is already embedded in a service chain
(e.g., when combined with other functions such as the TCP
optimization in the following use case). Multi-vendor support is
needed because every element in the use case can be provided by a
different vendor: load-balancer, http proxy, firewall, and NAT.
3.1.2. Requirements from use case
This use case imposes the following requirements on a service
function chaining (SFC) solution:
REQ1. SFC solutions MUST support service functions that
differentially steer traffic.
REQ2. SFC solutions MUST support service functions that terminate or
originate sessions.
REQ3. SFC solutions SHOULD allow traffic to, from, and between
service functions that are remote to the original service
chain.
REQ4. SFC solutions MUST support service functions that change
payload and IP header data of traffic.
REQ5. SFC solutions SHOULD allow service functions to be members of
multiple service chains.
REQ6. SFC solutions SHOULD allow the dynamic adaptation to changing
network and computing loads by adding or removing edges in the
graph.
3.2. Service chain for TCP optimization
The essential parameters influencing TCP behavior are latency, packet
loss and available throughput.
Content servers are mostly attached to fixed networks. These are
characterized by high bandwidth and low latency. Therefore content
servers often experience large TCP window sizes. In fixed networks,
end-to-end TCP window size mismatches do not have that much negative
impact on data flows.
On the other hand, mobile networks show a different behavior. While
the (S)Gi-side of the network typically exhibits low latency, low
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packet loss, high bandwidth and minimal congestion, the Radio Access
Network (RAN) tends to have higher latency, packet loss, and
congestion. Therefore mobile devices normally experience much
smaller TCP window sizes.
One way to mitigate these different environments, i.e., the LAN and
the mobile wireless part, is to use split TCP. However, this leads
to the case that the mobile wireless part can experience a different
TCP window size than the fixed LAN part.
In mobile networks, these TCP window size mismatches may result in
poor end-to-end throughput and bad user experience.
Therefore mobile operators very often use TCP optimization proxies in
the data path. These proxies monitor latency and throughput real-
time and dynamically optimize TCP parameters for each TCP connection
to ensure a better transmission behavior.
A rudimentary service chain setup for TCP optimization is shown in
Figure 7. Examples of non TCP flows are UDP/RTP voice or video
traffic.
[P-GW]---[LB]----------[TCP Opt.]---[LB]---[FW]---[NAT]---[Internet]
| TCP |
| |
| non-TCP |
+--------------------------+
Figure 7: Optimizing TCP parameterization in a mobile network.
3.2.1. Weaknesses of current approaches
This use case highlights weaknesses of current service deployments in
the areas of traffic selection, reclassification, and multi-vendor
support as in the previous use case presented in 4.1.
3.2.2. Additional requirements from use case
This use case imposes the following additional requirements on a
Service Function Chaining solution.
REQ7. SFC solutions MUST support service functions that can adapt
TCP traffic to the local networking needs.
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4. Remarks on QoS in mobile networks
As indicated in Figure 2, service functions may be linked to the
control plane to take care of additional subscriber or service
related metadata. In many cases the source of metadata would be the
PCRF and the link would be a Diameter-based Gx interface. Diameter
is specified in [RFC6733] and Gx in [3GPP].
Service functions within the SGi/Gi-LAN are less focused on the
explicit QoS steering of the actual mobile wireless network. QoS in
mobile networks is based on the 3GPP "Bearer" concept. A Bearer is
the essential traffic separation element enabling traffic separation
according different QoS settings and represents the logical
transmission path between the User Equipment (UE) and the Packet
Gateway (P-GW).
5. Weaknesses of current implementations
In many operator environments every new service introduction may
result in a further dedicated (S)Gi-LAN service chain.
5.1. Granularity of the classification scheme
Often the coarse grained classification according APNs is not fine
enough to uniquely select a service function chain or a processing
scheme within a service function chain required to support the
typical user-, service- or network- related policies which the
operator likes to apply to a specific user plane flow.
It is very likely that an APN, such as shown as example in
Section 2.3, is carrying an extremely diverse set of user traffic.
This can range from HTTP web traffic to real-time traffic.
5.2. Service chain implementations
In many carrier networks service chain LANs grow incrementally
according product introductions or product modifications. This very
often ends in a mix of static IP links, policy based routing or
individual VRF implementations etc. to enforce the required sequence
of service functions. Major weak points seen in many carrier
networks are:
o Very static service chain instances, hard-wired on network layer
leads to no flexibility with respect to reusing, adding, removing
service nodes, and reprogramming service chains.
o High complexity to manage or maintain evolutionary grown
"handcrafted" connectivity models.
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o Basic implementation paradigm based on APNs (that is service
types) only and
o Granularity down to user/service level by individual injections of
context-related metadata.
o No natural information exchange on network status between services
and network. This would be fine to manage finite network
resources based on subscriber profiles more easily.
o Practically impossible to implement automated service provisioning
and delivery platform.
o Scaling up flows or service chains with service or subscriber
related metadata may not work.
6. Operator requirements
Mobile operators use service function chains to enable and optimize
service delivery, offer network related customer services, optimize
network behavior or protect networks against attacks and ensure
privacy. Service function chains are essential to their business.
Without these, mobile operators are not able to deliver the necessary
and contracted Quality of Experience or even certain products to
their customers.
6.1. Simplicity of service function chain instantiation
Because product development cycles are very fast in mobile markets,
mobile operators are asking for service chaining environments which
allow them to instantly create or modify service chains in a very
flexible and very simple way. The creation of service chains should
be embedded in the business and operation support layers of the
company and on an abstract functional level, independent of any
network underlay. No knowledge about internetworking technology
should be required at all. The mapping of the functional model of a
service chain onto the actual underlay network should be done by a
provisioning software package as shown in Figure 8. Details of the
architecture and design are subject of forthcoming standards and
proprietary implementation details.
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+------------------------------------------------------------------+
| Creation of an abstract service function chain |
+------------------------------------------------------------------+
|
V
+------------------------------------------------------------------+
| +----------------------------------------------------+ |
| | Service function chain compiler | |
| +----------------------------------------------------+ |
| | |
| V |
| +----------------------------------------------------+ |
| | Mediation device | |
| +----------------------------------------------------+ |
+------------------------------------------------------------------+
|
V
+------------------------------------------------------------------+
| Physical network underlay |
+------------------------------------------------------------------+
Figure 8: Creation and provisioning system for service function
chains.
Service functions can be physical or virtualized. In the near future
the majority of mobile service functions will typically reside in the
local cloud computing environment of a mobile core location.
Nevertheless, the architecture and design should allow and support
also remote service functions if applicable.
6.2. Extensions
A service function chain should be generalized by a directed graph
where the vertices (nodes) represent an elementary service function.
This model allows branching conditions at the vertices. Branching in
a graph could then be triggered by typical 3GPP specified mobile
metadata (see Section 2.3) and allow for more sophisticated steering
methods in a service chain. Typically this data will be injected by
the mobile control plane, commonly by the PCRF via a Diameter-based
3GPP Gx interface.
Service chain behavior and output should additionally depend on
actual network conditions. For example, the selection of a video
compression format could dependent on the actual load of the mobile
network segment a mobile user is attached to.
To avoid Diameter signaling storms in the (S)Gi-LAN, individual
service functions should probably not be attached individually to the
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control plane. A mechanism where metadata information is carried by
extensions to the user IP packet may be more appropriate, provided
these extensions do not increase the original payload size too much.
6.3. Delimitations
A clear separation between service chaining functionality and 3GPP
bearer handling is required. This may be subject of forthcoming
studies.
7. Security Considerations
TBD.
8. IANA Considerations
This document has no actions for IANA.
9. Acknowledgments
We thank Peter Bosch and Martin Stiemerling for valuable discussions
and contributions.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[RFC6459] Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
Partnership Project (3GPP) Evolved Packet System (EPS)",
RFC 6459, January 2012.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012.
[TS.23.003]
"Numbering, addressing and identification", 3GPP TS 23.003
12.1.0, December 2013.
[TS.23.203]
"Policy and charging control architecture", 3GPP TS 23.203
12.3.0, December 2013.
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[TS.23.401]
"General Packet Radio Service (GPRS) enhancements for
Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) access", 3GPP TS 23.401 12.3.0, December 2013.
[TS.29.061]
"Interworking between the Public Land Mobile Network
(PLMN) supporting packet based services and Packet Data
Networks (PDN)", 3GPP TS 29.061 12.4.0, December 2013.
[TS.29.274]
"3GPP Evolved Packet System (EPS); Evolved General Packet
Radio Service (GPRS) Tunnelling Protocol for Control plane
(GTPv2-C); Stage 3", 3GPP TS 29.274 12.3.0, December 2013.
[TS.29.281]
"General Packet Radio System (GPRS) Tunnelling Protocol
User Plane (GTPv1-U)", 3GPP TS 29.281 11.6.0, March 2013.
Authors' Addresses
Walter Haeffner
Vodafone
Vodafone D2 GmbH
Ferdinand-Braun-Platz 1
Duesseldorf 40549
DE
Phone: +49 (0)172 663 7184
Email: walter.haeffner@vodafone.com
Jeffrey Napper
Cisco Systems
Cisco Systems, Inc.
Haarlerbergweg 13-19
Amsterdam 1101 CH
NL
Email: jenapper@cisco.com
Haeffner & Napper Expires August 2, 2014 [Page 17]