INTERNET-DRAFT J. Mueller
Intended Status: Informational AT&T Foundry
Expires: August 07, 2017 T. Herbert
Facebook
February 07, 2017
Mobility Management Using Identifier Locator Addressing
draft-mueller-ila-mobility-03
Abstract
This specification describes a new mobile network architecture which
improves mobility management using Identifier Locator Addressing ILA)
in IPv6 for next generation mobile telecommunication networks such as
5G and Mobile Edge Clouds. Identifier-locator addressing
differentiates between location and identity of a addressable network
element, which can be a mobile device or a data center task. The
approach presented in this draft enables mobility management on Layer
3, and provides a simplified, GTP-tunnel-free and more efficient
architecture with less core network utilization compared to
traditional architecture.
Status of this Memo
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Copyright and License Notice
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Copyright (c) 2016 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction and Problem Statement . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Related Work, Protocols and Concepts . . . . . . . . . . . . . 6
2.1. Mobile IPv6 . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Proxy Mobile IPv6 (PMIPv6) . . . . . . . . . . . . . . . . 7
2.3. Host Identity Protocol (HIP) . . . . . . . . . . . . . . . 7
2.4. Locator/ID Separation Protocol (LISP) . . . . . . . . . . . 7
2.5. Identifier-Locator Addressing (ILA) . . . . . . . . . . . . 8
2.6. Comparison of ILA to alternative approaches . . . . . . . . 8
2.6.1. Identifier Locator Network Protocol (ILNP) . . . . . . 8
2.6.2. Locator Identifier Separation Protocol . . . . . . . . 8
3. Mobility Management Architectures Using ILA . . . . . . . . . . 10
3.1. Address format for ILA mobile . . . . . . . . . . . . . . . 10
3.2. Architecture with Functional Elements and Reference
Points . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. Functional Elements . . . . . . . . . . . . . . . . . . . . 12
3.4. Signaling and Data Flows . . . . . . . . . . . . . . . . . 14
3.5.1. Provisioning . . . . . . . . . . . . . . . . . . . . . 14
3.5.2. Attachment . . . . . . . . . . . . . . . . . . . . . . 14
3.5.3. Communication Scenarios for End-to-End Data Transport
Sessions . . . . . . . . . . . . . . . . . . . . . . . 15
3.5.4. Homogeneous Handover . . . . . . . . . . . . . . . . . 20
3.5.5. Heterogeneous Handover . . . . . . . . . . . . . . . . 21
3.5.6. Detachment . . . . . . . . . . . . . . . . . . . . . . 22
3.5.6. Idle-mode and paging . . . . . . . . . . . . . . . . . 22
4. Discussion, Evaluation and Summary . . . . . . . . . . . . . . 22
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.1. Normative References . . . . . . . . . . . . . . . . . . . 23
5.2. Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction and Problem Statement
The Internet Protocol (IP) has been overloaded in its functionality
in the sense that it has been used as service locator and service
identifier at the same time. Since changes of the associated IP
address during a connection-oriented TCP session causes service
interruptions, mobility has become a challenge. Mobility has been a
challenge for IP based network since the area of smart phones began
and has been addressed with Layer 2 and Layer 3 tunneling solutions.
More specifically, uplink and downlink data traffic is encapsulated
with GPRS-Tunneling-Protocol (GTP) headers, which are routed through
the core network between the service and the base stations. One big
challenge of client mobility is to ensure seamless and transparent
mobility (e.g. IP address preservation) for mobile devices among
different geographical locations and in between several Radio Access
Technologies. Due to the deployment of micro-service architectures,
another dimension in the complexity of mobility occurs. Single IP
addressable tasks might change their physical location within a
(virtualized) data center architecture as well. Therefore, mobility
on both ends of the End-to-End (E2E) connection can be observed.
Hereby, mobility requires a large number of service registry (e.g.
DNS) updates and the state synchronizations between registries
perhaps located in different (geographical) locations. In regard to
current research and development on next generation mobile broadband
networks (such as Mobile Edge Cloud and 5G), key requirements such as
high-availability, low-latency and ultra-high-bandwidth are required
to ensure the reachability of the massive number of communicating
instances including from cellular communications, high-definition
multimedia streaming, Internet-of-Things (IoT), critical
infrastructures, etc.
This specification describes a new mobile network architecture which
improves mobility management using Identifier Locator Addressing ILA)
([nvo3]) in IPv6 for next generation (virtualized) fixed and mobile
telecommunication networks such as 5G and Mobile Edge Clouds. ILA
shares many properties of the Identifier-Locator Network Protocol
(ILNP) ([RFC6740], [RFC6741]) which is also a protocol that perform
identifier locator split in IPv6 addresses. Identifier-locator
addressing differentiates between location and identity of a
addressable network element, which can be a mobile device or a data
center task. A network architecture aligned on 3GPP is presented
which evolves existing policy, charging and mobility concepts and
substitutes GTP tunnels with ILA and therefore, improves mobility,
latency, and service placement closer to the edge of the network.
The key advantages of the presented ILA mobility solution are:
1) Backwards-compatibility within existing IPv6 network
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architectures such as the AT&T network,
2) Enablement of ultra-low-latency Mobile-Edge-Cloud (MEC)
services by locating services closer at the network edge,
3) GTP-Tunnel-free and flatter architecture with less protocol
overhead and less hops on the end-to-end path,
4) Reduce complexity by merging data plane gateways into a single
gateway,
5) Proven applicability of ILA within the Facebook data centers
and related networks at scale.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The following terminology will be referred to in the document.
* SIR: As defined in ([nvo3ila]): "In order to maintain compatibility
with existing networking stacks and applications, identifiers are
encoded in IPv6 addresses using a standard identifier
representation (SIR) address. A SIR address is a combination of a
prefix which occupies what would be the locator portion of an ILA
address, and the identifier in its usual location."
* SIR: Standard Interface Representation.
* SIR Prefix: A sixty-four bit network prefix used to identify a SIR
address.
* SIR Address: An IPv6 address composed of a SIR prefix (upper sixty-
four bits) and an identifier (lower sixty-four bits). SIR addresses
are visible to applications and provide a means to address nodes
independent of their location.
* ILA Identifier (ID): An identifier that identifies an addressable
element in the network independent of its location and type. ILA
identifiers are sixty-four bit values. An ID can be generated on a
per session basis with the effect to secure the privacy of the end
point. The International Mobile Subscriber Identity (IMSI) or the
International Mobile Equipment Identity (IMEI) can be used for ID
generation. The ID is comparable with the Globally Unique Temporary
UE Identity (GUTI) in the mobile space.
* ILA Locator (LOC): A network prefix that routes to a physical host.
Locators provide the topological location of an addressed node. The
locator is represented in the prefix of the SIR address.
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* ILA Host: An end host that is capable of performing ILA
translations for both sending and receiving. An ILA host uses the
ILA resolver protocol to get identifier to locator mappings for
destinations in communication.
* ILA Router: A network device that performs ILA translations and
packet forwarding. ILA router participate in distribution protocol
mapping.
* ILA Node: A network node capable of performing ILA translations.
This can be an ILA router or ILA host.
* User Equipment (UE): A device with an identifier such as a mobile
phone, IoT gateway or another SIM equipped mobile device.
* Access Point (AP) and Base Station (BS): A edge network element
such as evolved-NodeB (eNB) in 4G that bridges the radio network
and fixed network.
* Gateway (GW): A central network element such as Serving-Gateway
(SWG) or Packet-Data-Network-Gateway (PGW) in 4G.
* Application Function (AF): The AF refers to the 3GPP terminology
and stands for any IP addressable endpoint such as service or task.
* EXA: An Internet routable prefix, may be use as a SIR
2. Related Work, Protocols and Concepts
This section provides an overview on the state-of-the-art on
protocols and concepts for mobility management on mobile networks. In
particular the 4th Generation (4G) of mobile telecommunication
networks has been taken into account for this draft on functional and
conceptual comparison.
2.1. Mobile IPv6
The IETF specified the Mobile IPv6 ([MIPv6]) protocol to ensure
connectivity and reachability in case of client mobility within an
IPv6 network. Mobility within a MIPv6 network is solved by assigning
an additional IPv6 address - the Care-of-Address (CoA) - next to the
current IPv6 address that as been assigned in the home network.
Therefore a UE is equipped with a home address together with a
primary CoA in case of foreign network attachment. IPv6 is classified
as host-based mobility protocol, due to the fact that the UE is in
charge of announcing its mobility to the network. In particular it is
the client's responsibility for sending binding updates to the Home
Agent (HA). In order to ensure reachability, the UE communicates its
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new assigned CoA(s) to the HA, which acts as a router and registrar
for UEs. Connection requests are intercepted and re-routed in case
CoA entries for a UE exists. A tunnel is established between the UE
at the CoA and the HA for securely exchanging packets. By default,
the first packet is routed from the correspondent UE towards the CoA
of the UE via the HA. This route is not always the shortest path. All
consecutive packets of the same data stream will follow on the same
path, which might include a detour, but hides the new location of the
UE for privacy reasons. The feature of route optimization allows the
UE to directly contact the correspondent UE, therefore cuts out the
HA from the communication path and forwards packets on a shorter
route. Security of the Mobile IPv6 is enhanced through IPSec for
binding updates to avoid spoofing of CoA for a UE.
2.2. Proxy Mobile IPv6 (PMIPv6)
The IETF specified PMIPv6 ([PMIPv6]) provides network-based mobility
management for UEs and extends the Mobile IPv6 in the way, that host-
based mobility management functionalities in Mobile IPv6 are excluded
from the client into the network. Hereby, the Local Mobility Anchor
(LMA) acts as topological anchor point and manages the UE's binding
state. The Mobile Access Gateway (MAG) manages mobility-related
signaling on behalf of the UE at the access router. It is responsible
for tracking the UE's movements to and from the access link for
signaling the UE's local mobility anchor.
2.3. Host Identity Protocol (HIP)
HIP ([hip]) is providing a secure solution for identifier/locator-
split by adding a new host identity layer into the protocol stack. A
cryptographic namespace build upon a host identity as public key
allows scalability and multi-homing within the network. An extension
of DNS supports rendezvous server functionality for secure host
identity lookup. A secure channel is establishment over Diffie-
Hellmann-key exchange between two communicating entities. The
communication setup is considered as robust against DOS, due to a
riddle solved at the requestor side. On the other side a high
overhead for the secure communication establishment due to key
exchange has to be taken into consideration. HIP requires an
additional protocol layer between L2 and L3 for encapsulation.
2.4. Locator/ID Separation Protocol (LISP)
LISP is a network-layer-based protocol that enables separation of IP
addresses into two new numbering spaces: Endpoint Identifiers (EIDs)
and Routing Locators (RLOCs). Tunnel router encapsulates and
encapsulates packets.
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2.5. Identifier-Locator Addressing (ILA)
ILA is outlined in detail in ([nvo3]), ([nvo3ila]) as well as in this
document. In a nutshell, the concept of ILA splits IPv6 addresses
into a locator and an identifier, eliminates the need for tunneling
and therefore reduces the header size. ILA routers create and
maintain a mapping table of identifiers of locators.
2.6. Comparison of ILA to alternative approaches
This section compares the ILA approach to some alternatives that have
been discussed in 5gangip list.
2.6.1. Identifier Locator Network Protocol (ILNP)
ILNP ([rfc6741]) is an experimental protocol that splits and IPv6
address into a locator and identifier. ILA is fundamentally based on
ILNP.
The key differences between ILA and ILNP are:
* ILNP requires changes to the transport layer. This limits ILNP
to be used only on hosts and every transport protocol
implementation would need to be modified to use ILNP. Presumably
to overcome the limitation above, some sort of ILNP proxy could
be defined to perform ILNP in a middle-box.
* ILA does not require changes to the transport layer.
* Checksum neutral translation means that transport layer does not
need to be parsed to perform ILA. This also ensures that
existing device offloads (like checksum offload) work
seamlessly.
* ILNP employs IPv6 extension headers which are mostly considered
non-deployable. ILA does not use these.
* Core support for ILA is in upstream Linux, to date there is no
publicly available source code for ILNP.
* ILNP involves DNS to distribute mapping information, ILA assumes
mapping information is not part of naming.
2.6.2. Locator Identifier Separation Protocol
Locator Identifier Separation Protocol (LISP ([rfc6830)) is an IP
encapsulation protocol where the destination address in the outer IP
header is a locator and the destination address in the inner header
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is an identifier.
The key differences between ILA and LISP are:
* ILA is not encapsulation so there is no associated encapsulation
overhead. For instance IPv6/IPv6 in LISP would have fifty-six
bytes of overhead whereas ILA translation has zero.
* LISP may not work with some network device offloads whereas ILA
works with all stateless offloads (ILA is transparent to the
network so that it would just see TCP/IP packets for instance).
* ILA has been accepted into Linux, LISP has not been accepted.
* ILA can run either on end hosts (ILA hosts) or in the network
(ILA routers). ILA maintain a cache of identifier to locator
mappings.
* ILA defines locators and identifiers to be sixty-four bits
whereas LISP allows them to be full 128 bit addresses increasing
the memory needed in mapping table.
* The process of ILA translation is much more efficient than
performing LISP. The translation path is:
1) Parse IP header and extract the destination address
2) Lookup destination in a hash table (obviated with cached
route for ILA hosts)
3) Write new destination address (16 byte copy)
4) Forward to new destination (or receive at final destination).
5) At the final destination, a reverse translation is performed
to restore the originally sent address.
LISP processing is more involved. To do encapsulation:
1) An outer IP header, UDP header and LISP header need to be
inserted in the packet. Tunnel fragmentation and MTU need to
be considered [RFCXXXX] (i.e. increasing the size of a packet
may exceed tunnel MTU).
2) At the remote tunnel end point, the outer IP header must be
validated and a lookup done on the destination address to see
if it is a local address. A lookup must be done on the
destination UDP port to find that it is a LISP port. If the
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UDP checksum is not zero that must also be validated.
3) The LISP header must is processed and validated.
4) Once the encapsulation is verified, the headers are removed
and the inner packet is either forwarded or received.
3. Mobility Management Architectures Using ILA
This section outlines the ILA protocol structure and architecture
supporting ILA in mobile networks. The main functional blocks for
connectivity, mobility support, security and charging are presented.
Message flows for basic use cases executed by the mobile UE such as
attachment, data transport with session handover and detachment are
outlined.
3.1. Address format for ILA mobile
The address format is derived out of the ILA draft in ([nvo3]) and is
used without modifications in this draft.
The IPv6 canonical address format is:
+-----------------------------+-------------------------+
| 64 bits | 64 bits |
+-----------------------------+-------------------------+
| IPv6 Unicast Routing Prefix | Interface Identifier |
+-----------------------------+-------------------------+
The address format using ILA is:
+--------------------------------------------------------+
| 64 bits |3 bits|1| 60 bits |
+-----------------------------+--------------------------+
| Locator | Type |C| Identifier |
+--------------------------------------------------------+
The C bit is used to indicate that checksum-neutral mapping has been
performed ([nvo3]).
3.2. Architecture with Functional Elements and Reference Points
The presented architecture in Fig 1 is aligned on the 3GPP Evolved
Packet System (EPS) ([23401], [23402]) following the separation of
control plane and data plane. Whereas 3GPP EPS addresses mobility
through Layer 3 tunneling with GTP, this approach provides a Layer 3
mobility approach utilizing the ILA concepts for mobility without
tunnels.
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+--------------------+ +--------------------+
| Access Network | | Policy Charging |
+------+ Discovery and +-+ and Rules Function |
| | Selection Function | | |
| +------------+-------+ +---------+-----+----+
| | | |
| | | |
| +------+-----+ +---------+--+ |
| | Mobility | | Home | |
| | Management +---+ Subscriber | |
| | Entity | | Server | |
| +-----+------+ +------------+ |
| | |
| +--------------------------+--+
| | |
| +-------+-------------+ |
| | | |
+-+--+ +--+-----------+ +----+----+ +-----+------+
| UE |====| Base Station |====| Gateway |====| IP Service |
+----+ +--------------+ +---------+ +------------+
Fig 1: ILA-Based Architecture for Improved Mobility
Similarities between this new mobile network architecture and the
3GPP EPS are:
1) Split control and data plane.
2) Policy Control and Charging Rules Function (PCRF) architecture
and interfaces.
3) Network-based mobility management using Access Network
Discovery and Selection Function (ANDSF).
4) Home Subscriber Service (HSS) for managing and control dynamic
and static user profile information.
Differences between this new mobile network architecture and the 3GPP
EPS are:
1) Combined gateways and aggregated data plane functions within a
single gateway.
2) Interfaces between the PCRF and ANDSF, HSS.
3) Enhanced mobility support as further outlined in 3.5.3.
Communication Scenarios for End-to-End Data Transport Sessions.
4) Localized traffic handling within the Base Station to transport
traffic among associated clients without core network
involvement.
5) The associated network address is an ILA IPv6 address
+--------+ +--------+
| Mobile +-+ +----| Mobile |
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| Node 1 | | (') | Node 3 |
+--------+ | ................ ( ) +--------+
| +---+--+ . . +---+--+ (_)
| | ILA |--. IPv6 .--| ILA | |
+--|router| . Network . |router|---+
+---+--+ . . +---+--+
/ . .
/ . Ipv6 Overlay . +--+-++--------+
+--------+ / . Network . | ILA|| Mobile |
| Mobile +--+ . .- -|host|| Node 4 |
| Node 2 | . . +--+-++--------+
+--------+ ................
Fig 2: Distributed ILA Network Architecture [nvo3ila]
3.3. Functional Elements
This subsection summarizes the key functional elements of the ILA
based mobility architecture.
* The User Equipment (UE) is the SIM enabled mobile device (cellular,
gateway, etc.) executing services such as apps on the device, binding
apps to the ID as communication endpoints, handling the bindings of
all associated LOC/ID's and performing mobility as described below.
The UE performs security related functions via its (embedded) SIM
handling at least one or multiple identifiers provisioned by one or
multiple network operators. Security related functions include
authentication of the UE towards the network (more specifically the
BS) and certificate management for establishing secure transport
connections. Either the UE supports IPv6 or ILA for handling locator
and ID bindings and updates or the network is handling ILA
functionality on behalf of the UE. Storage and management of multiple
locators for multi-path and multi-homing is supported by the UE.
* The Base Station (BS) or Access Point (AP) are the first point of
contact from the UE when attaching over radio to the network. Its
main purpose are routing, gating and forwarding data and control
packets. The Radio Access Technology (RAT) is independent of the
proposed concept and therefore out of scope of this document. 3G, 4G,
5G or WiFi are applicable RATs for the presented architecture. The BS
is also capable of caching of content and state as close as possible
to the user at the edge of the network. Another aspect of the cache
is to support transparent handovers, during which buffering of
packets at the target BS is required. Therefore, an X2-like
connection between BSs is required. The BS supports a support a
policy enforcement function (PEF) as well as a Event Reporting
Function (ERF) aligned on the 3GPP defined Policy Control and
Charging (PCC) functionality for the EPS in ([23203], [29212]).
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Uplink QoS management is handled by the BS, too. In order to
differentiate between multiple types of data traffic, signaling,
high-priority, real-time and non-real-time connections can be
distinguished and the order of packet processing in the BS can be
influenced for uplink. The same concept applies for downlink in the
GW. Forward Error Correction (FEC), IP header compression, encryption
of user data stream are supported by the BS, too. Traffic filtering,
gating, legal interception on the BS, to include the case, in which
traffic re-routed only by the BS and is not traversing the GW.
* The Gateway (GW) encompasses data and control traffic related
functions. Its main purpose is routing, gating and forwarding data
and control packets. Therefore functionalities such as downlink QoS
enforcement, APN management and charging is performed by each GW.
* The Application Function (AF) or IP Service are an examples of any
IP addressable service in network. Other than in the 3GPP defined
architecture, the IP service does not need to reside in the SGi LAN
reachable only after terminating the GTP tunnel in the PGW.
Furthermore services can be reached directly after the RAN connection
is terminated within the BS.
* The Mobility Management Entity (MME) handles the initial
authentication, authorization and mobility management of UE's over
the control plane. The MME is responsible for tracking the UE's
mobility and is in charge for updating the registries with near real-
time status updates for LOC/ID mapping. ID and LOC assignment are
performed by the MME.
* The Home Subscriber Server (HSS) stores and manages user profile
information. These include the static information such as the
assigned ID, security credentials as well as dynamic information LOC
and the current Tracking Area.
* The Policy Charging and Rules Function (PCRF) controls data flows
in the network architecture according to pre-defined rules. Such
rules can be created by the network operator such as rate limiting or
traffic shaping. Other rules differentiate between class of services
for various traffic flow types identified on their Traffic Flow
Template (TFT) characteristics such as source, destination, port and
protocol information. The PCRF is handling charging for traffic flows
using online (pre-paid) and offline (post-paid) charging. Both
charging modes include a modes of operations with metrics such as
service invocations, online time, data transferred, or no-charging.
Out of credit events may influence the current connectivity for
online charging, whereas offline charging is accumulating charging
records which are usually processed in a monthly period.
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* The Access Network Discovery and Selection Function (ANDSF) is an
operator controlled database used for mapping the user location with
available (radio) access networks. With this information, the ANDSF
is capable of signaling suggestions for handovers to UE's. A UE is
therefore able to operate only on one interface at a time to save
resources. In case of the availability of adjacent RAT and after
reception of a handover suggestion from the ANDSF, the UE is able to
enable the suggested interface, perform a scan and finally decide
whether or not to attach to the new targeted RAT. The database can be
filled using device monitoring/telemetry statistics signaled from the
UE to the network or by active measurements of the environment.
3.4. Signaling and Data Flows
3.5.1. Provisioning
A Subscriber Identity Module (SIM)-card is provisioned by the network
operator with a unique and secure identifier that is comparable to
the IMSI in 3GPP telco architectures (2G, 3G and 4G). This draft does
not differentiate between a physical or an embedded SIM. In addition,
security credentials and preferred network identifier are provisioned
for authentication as well as network selection are provisioned. The
matching information to the SIM card is stored in the HSS.
3.5.2. Attachment
After powering on the device, a scan for available radio networks is
performed on the device, which selects the initial network (e.g. with
the strongest signal) and performs a network attachment procedure
aligned on ([23401], [23401]) towards the BS using security
parameters, ID, last MME associated with (GUMMEI) and last GUTI
assigned by MME with ID GUMMEI - the Packet Temporary International
Mobile Subscriber Identity (M-TSMI). A secure identifier on the SIM
is used to generate a temporary ID (the ILA ID), which is only valid
for one session, hides the privacy of the UE in the network and
unambiguously identifies the UE within the global network. This ID is
used for identification, authentication, authorization and charging
purposes.
For each network attachment, and due to privacy concerns for not
revealing the identify of the UE towards the public, a new unique and
temporary ID is generated. This ID is valid for a single session and
is renewed afterwards.
The BS derives the last MME association out of the network attachment
request sent by the UE and queries the last or a new MME based on
availability of information for UE authentication. The MME performs a
lookup in the user database of the network operator, which is the
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Home Subscriber Server (HSS) and/or Home Location Register (HLR) and
receives a profile in return. Hereby the MME is able to query the
mapping database for existing mappings or to retrieve a unique ID for
the UE.
In the following, the MME selects and configures the BS and GW
according to the profile received and signals the profile including
the ID towards the BSs of a certain tracking area and GW.
The BS allocates a LOC for the UE, binds the ID-LOC combination
locally in a cache, publishes its binding in the MME/NVA and signals
the ID-LOC towards the client.
Quality of Service (QoS) and charging related policies are installed
in the BS and GW. The BS handled uplink and the GW downlink related
traffic shaping functions. Charging can be performed in both
functional elements (BS or GW), whereas a centralized charging in
case of multi-path streaming is preferred.
After the successful attachment, a service can be invoked.
3.5.3. Communication Scenarios for End-to-End Data Transport Sessions
After the successful attachment, applications can start communicating
in the network using its assigned ILA by constructing IPv6 packets
with the SIR source information (ID+LOC) and the mandatory target ID.
The target LOC can be either set directly or can be defined as a
broadcast message, in which the target LOC will be determined at the
edge of the target.
The following main high level use cases have been defined. The use
cases can be distinguished into the following cases:
1) UE accessing a service in the AF,
2) UE is communicating with another UE attached to a different
base station via a gateway,
3) UE is communicating with another UE attached to a different
base station,
4) UE is communicating with another UE attached to the same base
station,
5) Mobile Edge Cloud for localized traffic handling and low-
latency communication,
6) Gateway mobility for enhanced mobility use cases
The example use cases are outlined below in details and the
differences compared to today's networks are discussed. Fig. 3
depicts the network elements and control and data flows related to
those use cases. The communication form can be multicast, broadcast,
anycast or unicast.
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+------------+
| UE 1 |
| +--------+ +---+
| | Task 1 | | | +------------+
| +--------+ | | +------+ +----+ | Host H1 |
+------------+ | | | | | | +--------+ |
+---+ BS A +---+ GW +---+ | Task 0 | |
+------------+ | | | | | | +--------+ |
| UE 2 | | +------+ +-+--+ +------------+
| +--------+ +---+ |
| | Task 2 | | |
| +--------+ | |
+------------+ |
|
+------------+ +------+ |
| UE 3 | | | |
| +--------+ +-------+ BS B +---+
| | Task 3 | | | |
| +--------+ | +------+
+------------+
Fig 3: UE attachment over multiple base stations
1) E2E connection between the UE to AF (Task to Internet)
Considering a communication scenario in which a UE (source) queries a
web site (target) e.g. "http://about.att.com/innovation/foundry" in a
browser represented by T1.
SIR:T1,Iaddr -> // Transport endpoints at T1
L1:T1,Iaddr -> // On the wire in data center
EXA:T1,Iaddr // In the Internet
The request is forwarded to the BS, which performs ILA router
functionality. In case a broadcast address has been selected as a
target LOC, a cache lookup in a local lookup table is performed.
Depending on finding an entry in the local cached lookup table, the
routing is influenced and the packet is redirected. Otherwise the
packet is routed on to the destination ILA SIR address (LOC/ID).
2) UE 1 to UE 3 are attached to distinct BSs via gateway
Considering a communication scenario in which one task (T1) mobile
device of UE 1 is contacting a second task (T3) on mobile device of
UE 3. Both UEs are connected to different BSs. ILA routing is done in
the BS.
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The transport endpoints for task to task between UE's communication
are the SIR addresses for the tasks. When a packet is transported
through the ILA network, the locators are set in source and
destination addresses of the packet. On reception the source and
destination addresses are converted back to SIR representations for
processing at the transport layer.
If task T1 on UE 1 is communicating with task T3 on UE 3, the ILA
translation sequence would be:
SIR:T1,SIR:T3 -> // Transport endpoints on T1
UE1:T1,UE3:T3 -> // ILA used on the wire
SIR:T1,SIR:T3 // Received at T3
3) UE 1 to UE 2 are attached to distinct but interconnected BSs An
extension of the scenario will happen, when If task T1 on UE1 is
communicating with task T2 on UE 2 via interconnected BSs, the ILA
translation sequence would be:
SIR:T1,SIR:T2 -> // Transport endpoints on T1
UE1:T1,UE2:T2 -> // ILA used on the wire
SIR:T1,SIR:T2 // Received at T2
4) UE 1 to UE 2 attached to the same BS
Considering a communication scenario in which two communicating
entities are attached to the same BS and therefore are in close
proximity. The solution for routing traffic in today's network is the
establishment of the data path from the UE over the access network
(e.g. eNB) through the core network (e.g. EPC) into the AF (any IP
addressable service or task) and backwards to the access network and
finally terminated at the UE. Charging needs to be performed in the
BS for this data flow. This communication pattern in today's networks
creates a delay caused by the bearer concept of 3GPP network, which
encapsulate and de-capsulate data in GTP-tunnels between the eNB and
the PGW.
A practical use case is the communication between autonomous vehicles
(e.g. self-driving cars or self-organized and autonomous drone
swarms) through a telecommunication infrastructure. A very low delay
is required for the interaction and precise management. In order to
reach such a low delay, the communication needs to stay local in
order to result in a low delay.
The presented solution on ILA mobility allows to keep traffic local
for the case in which the communicating parties attached to the same
BS.
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Due to a lower amount of hops between UE 1 and UE 2, a lower latency
can be achieved which results in a lower delay.
5) Low-latency Mobile Edge Cloud (MEC) Service
Considering a use case in which a UE is accessing a service with
ultra-low latency requirements in the network such as image
recognition, Augmented Reality (AR), Virtual Reality (VR) or other 5G
low-latency and/or high throughput services. Other examples include
vehicle control (drone or fleet management, traffic information,
robot or power grid). In order to provide a high quality of
experience for the user and customer, latency in the communication
between the mobile device and the service has to be reduced in order
to achieve a lower delay. Where multimedia streaming has an
acceptable latency requirement of ~100ms, ultra-low latency services
have strict requirements on the communication with under ~10ms or
even close to 1ms. Classic cloud approaches that concentrate services
centralized in the network are not applicable for ultra-low delay
services due to the fact, that E2E latency is even too high.
Violations of latency requirements result in motion sickness for VR
users, outdated traffic information for autonomous self-driving cars,
accidents with robotics in factories and the development of a new
type of MEC services is hindered.
Therefore, a request is created and addressed with the source LOC/ID
and targeted towards the destination LOC/ID.
+------------+ +------------+ +------------+
| UE 1 | | MEC | | Host H1 |
| +--------+ | | +--------+ | | +--------+ |
| | Task 1 | | +----+ | | Task 2 | | +----+ | | Task 0 | |
| +--------+ | | BS | | +--------+ | | GW | | +--------+ |
+------------+---+----+---+------------+---+----+---+------------+
Fig 4: Mobile Edge Computing architecture with ILA
The innovative point in this use case depicted in Fig. 4 is the fact
that the URL invocation may result in a redirect to a local service
or content rather then a remote object. Hereby, the request may
trigger a (third party) service or content deployment at the network
edge instructed by the MEC_orchestrator and a policy decision. The
policy decision is the outcome of the reasoning process within the
MEC_orchestrator which takes context, user behavior, system load
(throughput, latency, packet-loss, etc.), network topology map,
distance between UE and service measured in hops, and other available
metrics into account. Geographical load-balancing is therefore
possible and enabled. Even when the first set packets of the
connection are exchanged with a remote service over a longer
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geographical network distance, a context handover during the active
session away from the remote and towards a closer service instance
(out of the same type or load-balancing group) can be applied.
In case service, task or content are available in MEC, ILA
translation on the wire at the BS changes the locator to the closest
point of presence. The following ILA steps are performed.
SIR:T1,Iaddr_T0 -> // Transport endpoints at T1 invokes Task 0 (T0)
L1:T1,Iaddr_T2 -> // Optional ILA translation from T0 to T2
EXA:T1,Iaddr // In mobile edge cloud data center
Finally, the number of hops between UE and AF are reduced and a lower
delay on the data path is achieved. Otherwise, in case the Edge Cloud
capabilities cannot be utilized, basic routing is applied as outlined
example 1) E2E connection between the UE to AF (Task to Internet)
above.
6) Base Station or Gateway Mobility This use case covers situations
in which the user stays connected to a BS but the core network is
mobile and changes its location and connectivity to the
service/Application Function. One example would be a BS that is
attached to a vehicle (drone, car/bus, train, cargo ship, etc). The
user facing side provides cellular service, backhaul is either WLAN,
satellite, laser, MMWave or temporary a fixed connection. The AF
facing side changes connection with each change of a transport
connection such as WiFi, cellular or satellite.
Gateway mobility requires the update of forwarding entries in related
BS and AF to continuously forward the packets on the data path.
The network setup is depicted in Fig.5 and Fig. 6 with both gateways
(GW 1 and GW 2) both have connections to the same BS and AF.
+------------+
+------+ +------+ | Host H1 |
| | | | | +--------+ |
+---+ BS A +---+ GW 1 |+---+ | Task 0 | |
+------------+ | | | | | | +--------+ |
| UE 1 | | +------+ +------+ +-----+------+
| +--------+ +---+ |
| | Task 1 | | +------+ |
| +--------+ | | | |
+------------+ | GW 2 +----------+
| |
+------+
Fig 5: Gateway mobility with attached UE via GW 1
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The difference between Fig. 5 and Fig.6 is that BS A changes its
association with the network by handing over its connectivity from GW
1 towards GW 2. Due to the use of ILA, and the related address-space
translation capabilities, no GTP tunnels need to be updated and only
the address translation between the gateway and the service space is
updated. All attached UE's preserve their ILA IPv6 address and
continue to be addressable in the network.
+------------+
+------+ | Host H1 |
| | | +--------+ |
| GW 1 |+---+ | Task 0 | |
+------------+ | | | +--------+ |
| UE 1 | +------+ +-----+------+
| +--------+ +---+ |
| | Task 1 | | | |
| +--------+ | | +------+ +------+ |
+------------+ | | | | | |
+---+ BS A +---+ GW 2 +----------+
| | | |
+------+ +------+
Fig 6: Gateway mobility with attached UE via GW 2
Service interruptions may occur during the time of detaching from GW
1 and attaching to GW 2 when using a single radio interface for
wireless back hauling. The capabilities of the 3GPP MME are extended
with the ability to select the target GW for the BS, management of
the BS-GW handover by reserving resources on the target GW 2 and
releasing resources on the source GW 1. GW 1 caches packets during
handover and forwards them to GW 2 (in case a connection exist
between them) until packets are transported on the new uplink and
downlink paths.
3.5.4. Homogeneous Handover
Client mobility in homogeneous networks is usually caused by physical
location changes, changes in the received radio signal strength or
network based handover due to network policies such as UE load
balancing on the BSs.
The status information (the list of signals received from adjacent
BSs including their signal strength) signaled from the UE towards the
BS enables positioning via triangulation as well as the selection of
alternative BS's to which the UE may connect to alternatively.
Reasons for handovers may be evacuation/preemption of resources on
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the BS due to emergency scenarios or higher priority calls,
UE/BS/service load balancing or physical mobility of the UE among the
network. Current resource utilization (e.g. data rates) of the UE or
historical traffic pattern may influence the handover and the BS
selection process.
Mainly the MME selects a target BS (BS_target) as target for the
handover of the UE away from the current BS (BS_source). The decision
is signaled to related BS's and the UE. BS_source starts de-
allocating resource blocked by the UE and BS_target blocks resources
required by the UE. Since most UE's are considered to have only a
single RAT of each type (one WLAN or one LTE interface) an
interruption in the connection while handover is to be expected. In
order to avoid packet loss at the UE, buffering at the BS_target as
well as packet forwarding from BS_source to BS_target are supported.
Only after UE successfully establishes connectivity at the BS_target,
previously blocked resources at BS_source are freed up, which are
used as handover role-back in case of failure. Finally the MME
announces the new ILA ID (BS_target_LOC)/ID for the UE as an update
at GW and in the ILa registry.
New incoming connections are forwarded directly towards the UE over
BS_target using the proclaimed ILA ID (LOC/ID).
Homogenous handovers with one radio technology interface supported
have interruptions during the handover. Nevertheless those
interruptions are relatively small due to techniques such as improved
handovers in WiFi (802.11x, 802.11k, 802.11r, and 802.11v) or context
handover via X2 in 4G.
3.5.5. Heterogeneous Handover
Client mobility may involve various Radio Access Technologies (RAT),
in which the client is handed off from RAT_1 to RAT_2. The client is
not required to move physically for heterogeneous mobility. Instead
measurements on the UE or suggestion from the network (signaled over
the ANDSF) may trigger handovers to alternative networks even when
the UE is physically not moving. Such a handover can be done between
WiFi, 4G and 5G.
Heterogeneous handovers are motivated for optimizing connectivity
between UE and AF/service to move a multimedia connection with high
bandwidth requirements from cellular (4G/5G) towards WLAN, a security
sensitive bank transaction from WLAN towards cellular or simply a
better transport-cost-per-bit-ratio.
Heterogeneous (compared to homogenous) handovers may be performed
seamlessly with establishing a second alternative connection in
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parallel to the existing active connection and tearing down the old
connection only, after successfully establishing the new connection.
Usually this is possible, because more then one interface is
available on the client, which can be used in parallel to establish
connectivity in parallel. In order to provide higher bandwidth over
multi-path, both connections may be kept open in parallel. In this
regard, the MME adds another LOC'/ID as update to the existing entry
LOC/ID in the registry on the gateways and DNS.
3.5.6. Detachment
A detachment from the network can happen gracefully by shutting down
the phone and de-registering it from the BS or suddenly due to a loss
of connection. In both situations, a de-registration from the UE out
of the list of active users attached to the BS is done directly or
indirectly (after inactivity for a predefined time). Resource
reservations are freed up again after detachment and opened up for
other connections.
3.5.6. Idle-mode and paging
Power saving methods are working transparent to the ILA mobility
concept such as described in ([23401], [23402]). The device toggles
from active to inactive mode in idle-mode in order to reduce the
communication interval between device and antenna. Resource
reservations in the network are kept alive in order to allow a fast
weak-up and connection re-establishment caused by paging of the BS
towards the device.
4. Discussion, Evaluation and Summary
New low-delay services are appearing with AR/VR, drone communication,
self-driving cars and robotic control that have new requirements on
the network, which cannot be fulfilled by today's network and cloud
architectures. New ultra-low latency is a key requirement on
connectivity that is enabling a new services. One way of improving
the End-to-End (E2E) connectivity is to substitute the underlying
technology with a new generation and to improve the performance. Part
of this improvement is described in Moore's-law, which highlights
that the number of components per integrated circuit is doubling
every 18 month. Another approach is to reduce the E2E latency by
reducing the physical distance between device and service measured in
number of hops and at the same time provide a backwards compatible
solution for WiFi and 4G networks.
This draft is addressing the above mentioned challenges and provides
a solution in form of a new mobile network architecture based on
Identifier-Location Addressing (ILA) mobility. ILA decouples the
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identity from locator within an IPv6 address. Therefore mobility can
be achieved by preserving the same ID at the endpoint and only
adapting the locator used routing in case of mobility. The
implications are improved mobility with less control signaling and a
more efficient tunnel-free core network architecture.
ILA applied on mobile networks and the gained improved mobility
enables multiple new and innovative use cases compared to legacy
telecommunication networks. Summarizing, the above presented
Communication Scenarios for data transport for an End-to-End session
outlines ways to improve connectivity, optimize routing and enable a
new type of service: Mobile Edge Cloud services. Firstly, the
improved data path requires less hops to traverse between UE <-> AF
enabled by Mobile Edge Computing or locally between UE_1 <-> UE_2 due
to the flatter architecture. Secondly, less overhead is created due
to the reduction of GTP tunnels between network elements. Thirdly,
the presented approach of ILA mobility is backwards compatible with
today's IPv6 based fixed and mobile telecommunication networks.
5. References
5.1. Normative References
[rfc6741] Identifier-Locator Network Protocol (ILNP) Engineering
Considerations, Jan 2013, https://tools.ietf.org/html/rfc6741
[nvo3ila] Identifier-locator addressing for network virtualization,
draft-herbert-nvo3-ila-02, Tom Herbert, Mar 2016,
https://tools.ietf.org/html/draft-herbert-nvo3-ila-02#page-17
5.2. Informative References
[rfc6830] The Locator/ID Separation Protocol (LISP), D. Farinacci,
Jan 2013
[MIPv6], Mobility Support in IPv6, C. Perkins, Ed. et al., Jul 2011,
https://tools.ietf.org/html/rfc6275
[PMIPv6] S. Gundavelli, Ed. et al., Aug 2008,
https://tools.ietf.org/html/rfc5213
[23401] 3GPP TS 23.401 V13.7.0 (2016-06), General Packet Radio
Service (GPRS) enhancements for Evolved Universal Terrestrial Radio
Access Network (E-UTRAN) access (Release 13)
[23402] 3GPP TS 23.402 V14.0.0 (2016-06), Architecture enhancements
for non-3GPP accesses (Release 14)
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[23203] 3GPP TS 23.203 V14.0.0 (2016-06), Policy and charging control
architecture (Release 14)
[29212] 3GPP TS 29.212 V14.0.0 (2016-06), Policy and Charging Control
(PCC); Reference points (Release 14)
Authors' Addresses
Dr.-Ing. Julius Mueller
260 Homer Ave
Palo Alto, CA 94301
US
EMail: jmu@att.com
and
Tom Herbert
Facebook
1 Hacker Way
Menlo Park, CA 94052
US
Email: tom@herbertland.com
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