Internet DRAFT - draft-zhang-i2rs-mbb-usecases
draft-zhang-i2rs-mbb-usecases
Network Working Group L. Zhang
Internet-Draft Z. Li
Intended status: Informational Huawei Technologies
Expires: August 18, 2014 D. Liu
China Mobile
S. Hares
Hickory Hill Consulting
February 14, 2014
Use Cases of I2RS in Mobile Backhaul Network
draft-zhang-i2rs-mbb-usecases-01
Abstract
In a mobile backhaul network, traditional configuration and diagnoses
mechanisms based on device-level management tools and manual
processing are ill-suited to meet the requirements of today's
scalable, flexible, and complex network. Thanks to the new
innovation of Interface to the Routing System's (I2RS) programmatic
interfaces, as defined in [I-D.ietf-i2rs-architecture], an
alternative way is available to control the configuration and
diagnose the operational results. This document discusses the use
case for I2RS in mobile backhaul network.
Requirements Language
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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
and may be updated, replaced, or obsoleted by other documents at any
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 18, 2014.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Application Configuration . . . . . . . . . . . . . . . . . . 4
3.1. Application Configuration . . . . . . . . . . . . . . . . 4
3.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 5
4. Route Policy Enforcement . . . . . . . . . . . . . . . . . . 5
4.1. Route Policy Description . . . . . . . . . . . . . . . . 5
4.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 6
5. Service Tunnel Implementation . . . . . . . . . . . . . . . . 7
5.1. Service Tunnel Description . . . . . . . . . . . . . . . 7
5.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 8
6. Protection Mechanism . . . . . . . . . . . . . . . . . . . . 8
6.1. Protection Mechanism Description . . . . . . . . . . . . 8
6.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 9
7. Network Monitoring . . . . . . . . . . . . . . . . . . . . . 9
7.1. Network Monitoring Description . . . . . . . . . . . . . 9
7.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative Reference . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
In mobile backhaul network, traditional configuration and diagnoses
mechanisms based on device-level management tools and manual
processing are ill-suited to meet the requirements of today's
scalable, flexible, and complex network. The mobile backhaul network
now needs to serve various radio access modes and applications across
2G/3G / LTE/5G, build various network architectures based on the
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number of network devices or the integration of different Areas or
Autonomous System Numbers (ASNs), and support various network
protocols that can be adopted to meet different network requirements.
These needs make the mobile backhaul network configuration more and
more arduous.
Interface to the Routing System's (I2RS) Programmatic interfaces, as
defined in [I-D.ietf-i2rs-architecture], provides an alternative way
to control the configuration and diagnose the operational results.
The use cases described in this document cover the critical elements
of mobile backhaul networks, such as: application configuration,
route policy enforcement, service tunnel implementation, protection
mechanisms and network monitoring. The goal is to increase the
community's understanding of the mobile backhaul requirements for
I2RS in a the context of an entire network solution.
2. Definitions
I2RS: Interface to the Routing System
IGP: Interior Gateway Protocol
BGP: Border Gateway Protocol
MPLS: Multi-Protocol Label Switching
LDP: Label Distribution Protocol
RSVP-TE: Resource Reservation Protocol Traffic Engineering
PWE3: Pseudo Wire Emulation Edge-to-Edge
VPN: Virtual Private Network
L2VPN: L2 Virtual Private Network
L3VPN: L3 Virtual Private Network
SS-PW: Singe Segment PW
MS-PW: Multi-Segment PW
HVPN: Hierarchical VPN
EPC: Pseudo Wire Emulation Edge-to-Edge
LTE: Long Term Evolution
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FRR: Fast Reroute
ECMP: Equal Cost Multi-path
3. Application Configuration
3.1. Application Configuration
The mobile backhaul network has evolved into an IP-based network,
which faces three main challenges in network construction:
1. various radio access modes:
To protect existing investment and end user resource, TDM/ATM-
based access modes belonging to 2G and 3G will coexist with
Ethernet-based access mode belonging to 3G, LTE, and 5G for an
extended time into the future. The radio architecture
evolution will bring out new radio interfaces, such as the X2
interface in LTE which will not work in hub-spoke
communication mode and needs much more shorter latency. A
mobile backhaul network must be built to have the ability to
adapt to all the mobile access modes, providing PWE3 service
for TDM /ATM-based access mode and Native IP/Ethernet, PWE3/
VPLS or L3VPN service for IP-based access mode.
2. various radio applications:
A variety of radio applications (such as OM, signaling, data,
video, etc. ) which have different quality of services (QoS),
should be delivered in specific service channels in mobile
backhaul networks, meaning there will be more than one PW or
L3VPN instances binding with specific interfaces and service
tunnels.
3. various network architectures:
The mobile backhaul network maybe consist of hundreds of nodes
in a small county or thousands of nodes in a populous region.
It will be an integration of different ASNs rather than a
single AS, when EPC is deployed in the Core network with LTE.
The network devices on different points of the network (e.g.
access\aggregation\core) have different routing and protocol
processing capabilities, resulting in an integration of
different IGP routing areas rather than a single large IGP
routing area. Within various network architectures, different
service modes should be provided, such as SS- PW or MS-PW, E2E
L3VPN or HVPN, Seamless MPLS, and the integration of them.
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3.2. Requirements for I2RS
The challenges in mobile backhaul network construction show the
flexibility and complexity requirements of network configuration and
modification, such as:
o where the T-LDP should be configured,
o where a BGP peer should be established,
o where the VPN instance should be deployed, and
o where the BGP-based LSP should be set up.
Faced with flat or reduced budgets, network operators are trying to
squeeze the most from their network using device-level management
tools and manual processing. In contrast to management of entire
network devices, I2RS' programmatic interface would allow network
operators to distribute such configurations from a central location
where global mobile backhaul network solution provisioning
information could be stored Use of I2RS clients to distribute time-
critical changes in configuration to I2RS agents associated with each
node would simplify and automate configuration and monitoring of a
mobile backhaul network to allow it to readily adapt to changing
network sizes (and scales) and radio applications.
I2RS Clients-Agent communication needs to pass information on:
o T-LDP configurations and status;
o BGP peer configurations, peer topologies and status;
o BGP-based LSP topologies and status;
o Reset VPN topologies, and per node configurations;
While a beginning exists in the I2RS RIB Information Model
[[I-D.ietf-i2rs-rib-info-model]] which includes in the route
interfaces with MPLS LSP ro VPN technology, additional features need
to be added to support mobile backhaul networks.
4. Route Policy Enforcement
4.1. Route Policy Description
The route policy in mobile backhaul networks mainly refers to BGP
policy when L3VPN is used to serve the radio applications. The
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complexity of today's network architecture and radio interfaces make
it very difficult to apply a network-wide route policy, for:
o avoiding route advertisement across entire network
When a mobile backhaul network contains more than 500 nodes,
utilizing a multi-segments service like HVPN is recommended to
reduce the routing and protocol processing overhead of network
devices. BGP policy should be configured with prefix filters
to advertise only the default or aggregate route to the access
nodes which have limited capability, while advertising to the
whole network routes to the core nodes which must have
capability to store large number of routes.
o supporting best route selection for VPN FRR or ECMP
The mobile backhaul network is recommended to be built with a
multi-homed network architecture for node failure protection,
where VPN FRR or ECMP should be configured. The best route
selection relies on BGP Policy using Local Preference, MED or
other path attributes defined in [RFC4760]. When a BGP RR is
adopted to simplify the BGP peer architecture from full-mesh
mode, the policy would become more complex, in some cases may
make be per-peer or per-route worse.
o allowing On-demand route advertisement
The advent of X2 interfaces in LTE, which need specific route
information between any two access nodes, makes the network
route advertisement more dynamic and unpredictable. The BGP
policy should be adjusted dynamically to meet this route
advertisement need across the entire network.
4.2. Requirements for I2RS
Route policy enforcement in mobile backhaul networks needs to be much
more dynamic and flexible. The I2RS interface provides a
programmatic way to configure (both policy and device) and monitor
thousands of devices individually whose configuration is based on the
devices role (such as ASRSs in one AS, ASBRs between ASs and other
service-touch nodes). Current methods take hours (or even days) to
configure route policy across a network.
In contrast, I2RS clients could contact I2RS agents on nodes to query
role-based information from the network status. After collecting the
status, the I2RS client could develop the BGP policies based on role
information and push the BGP policies to the I2RS agents that would
load the alternate policies into the network device. The I2RS Agents
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loading the alternate policies could then send status back to the
I2RS Client.
5. Service Tunnel Implementation
5.1. Service Tunnel Description
In mobile backhaul network, more than one kind of Service Tunnel can
be used according to network ability or other consideration in
different scenarios. The Tunnel deployment use case in mobile
backhaul includes:
o MPLS LDP LSP
MPLS LDP LSP is set up through LDP protocol. Both Label
Advertisement Mode of Downstream Unsolicited (DU) and
Downstream on Demand (DOD) defined in [RFC3036] can be used
individually or integrated across access networks and aggregate
/core networks. If needed, the longest length match defined in
[RFC5283] for LDP LSP should be supported. MPLS LDP LSP has
excellent scalability with flexible policy to control the label
advertisement of route, especially in DU mode, to decrease
needless LSPs to reduce the LSP capability requirement of
network devices.
o MPLS-TE LSP
MPLS-TE LSP is set up through RSVP-TE protocol, which has
multiple path control attributes (such as explicit-path, path
affinity property , path bandwidth assurance , path hop
limitation, e.g.) and multiple protection modes (such as hot-
standby, Fast Re-Route, protection group, e.g.). MPLS-TE LSP
should be designed using the attributes and protection modes
according to the requirements of the service delivery as
integrated across access network and aggregate/cores network.
o MPLS-TP LSP
MPLS-TP includes unidirectional LSP, bidirectional co-routed
LSP, and bidirectional associated LSP, which can be calculated
and set up manually or using dynamic network protocols such as
GMPLS. In mobile backhaul networks, the LSP selection depends
on the service need, and the creation of MPLS-TP LSP is always
assumed to be decoupled with the protocol control plane running
on separate network devices. Ideally, the static MPLS-TP LSP
should be designed and configured on the centralized control
plane.
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5.2. Requirements for I2RS
The mobile backhaul network is divided into an access network and an
aggregation/core network where service tunnel implementation is not
constant and unique. Therefore, it may be necessary to deploy
different kind of LSPs separately (such as LDP LSP or MPLS-TE LSP in
both access network and aggregate/core networks) or simultaneously
(such as MPLS-TP static LSP in access network while LDP LSP or MPLS-
TE LSP in aggregate/core network). Network operators need to know
the ability of all of the network devices and the service
requirements to make the most appropriate tunnel implementation.
I2RS clients can provide centralized control of many network devices
via the I2RS Client-Agent communication. The I2RS programmatic
interface can automate the collection and analysis of each device's
capability so that the centralized I2RS client could calculate the
optimal LSP path and distribute the configuration to individual
devices. While the I2RS RIB Information Model
[[I-D.ietf-i2rs-rib-info-model]] provides for routes with tunnels or
MPLS LSP, the features defined in this model are not sufficient to
configure both types of LSPs needed for the VPN technology in mobile
backhaul networks. Additional I2RS Informational models need to be
created to support these features.
6. Protection Mechanism
6.1. Protection Mechanism Description
The SLA for radio services is strict, which requires interworking
among multiple protection mechanisms. Two critical aspects should be
taken into account for inter-working, hierarchical protection
architectures and multiple OAM protocol interactions.
1. tunnel protection:
The protection mechanisms of different the tunnel protocols,
mentioned above, are different from each other. To enhance
the reliability, LDP LSP should configure LDP FRR, which is
calculated depending on the protect route algorithm, and be
Loop-Free Algorithm (LFA), Remote-LFA, or Maximally Redundant
Trees (MRT) used together with LDP MT as described in
[I-D.ietf-mpls-ldp-multi-topology]. MPLS-TE LSP should apply
TE Fast Reroute or TE hot-standby. When MPLS-TP LSP is used,
the LSP protection group should be configured with 1:1 or 1+1
mode for MPLS-TP line protection, as well as wrapping or
steering modes fault processing for MPLS-TP ring protection.
2. service protection:
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Service protection is recommended to be configured for node
failure handover in mobile backhaul network, where PW
redundancy defined in [RFC6718] or BGP VPN FRR or ECMP
realization should be deployed exactly.
6.2. Requirements for I2RS
The hierarchical protection architecture in mobile backhaul network
offer high network reliability and more flexibility to meet the
various needs of the tunnels and services. The I2RS interface in
this use case is needed to automate the configuration and monitoring
so that tunnel protection and service protection interwork in a
flexible and reliable manner.
7. Network Monitoring
7.1. Network Monitoring Description
The mobile backhaul network operators are asked to give an accurate
cause when a link or node failure occurs, and get the real reason for
service quality reduction. They need to apply different network
monitor tools for different service mode, like Network Quality
Analysis (NQA), MPLS-TP OAM, and IP Flow Performance Monitor (IPFPM).
Determining the exact traffic path is really significant when using
IPFPM for point-to-point detection.
Multiple monitor tools require network operators to distinguish
granular traffic flow to apply the appropriate one. At the same
time, getting the traffic path with traditional device-level
management tools is difficult, which may enhancing the existing
protocols or designing a new specific protocol to do the job. Both
will increase the burden of mobile backhaul network.
7.2. Requirements for I2RS
The I2RS architecture (client-agent) should solve the two problems
mentioned above naturally by enabling the use of centralized
controllers, which control and manage the entire network's devices
and store the whole routing and service information directly.
Meanwhile, the outages and traffic congestion or discards can be
detected real-time with I2RS Client(s) connected to the I2RS agents
in each node which provide real-time status via notification service.
An I2RS client with this ability will allow the I2RS clients to keep
optimal state dynamically all the time.
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8. Security Considerations
The mobile backhaul network use cases described in this document
assumes use of I2RS's programmatic interfaces described in the I2RS
framework mentioned in[I-D.ietf-i2rs-architecture]. This document
does not change the underlying security issues inherent in the
existing [I-D.ietf-i2rs-architecture].
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative Reference
[I-D.ietf-i2rs-architecture]
Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
Nadeau, "An Architecture for the Interface to the Routing
System", draft-ietf-i2rs-architecture-01 (work in
progress), February 2014.
[I-D.ietf-i2rs-problem-statement]
Atlas, A., Nadeau, T., and D. Ward, "Interface to the
Routing System Problem Statement", draft-ietf-i2rs-
problem-statement-00 (work in progress), August 2013.
[I-D.ietf-i2rs-rib-info-model]
Bahadur, N., Folkes, R., Kini, S., and J. Medved, "Routing
Information Base Info Model", draft-ietf-i2rs-rib-info-
model-01 (work in progress), October 2013.
[I-D.ietf-mpls-ldp-multi-topology]
Zhao, Q., Fang, L., Zhou, C., Li, L., and K. Raza, "LDP
Extensions for Multi Topology Routing", draft-ietf-mpls-
ldp-multi-topology-09 (work in progress), October 2013.
[I-D.ietf-mpls-seamless-mpls]
Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
M., and D. Steinberg, "Seamless MPLS Architecture", draft-
ietf-mpls-seamless-mpls-05 (work in progress), January
2014.
[I-D.li-mpls-seamless-mpls-mbb]
Li, Z., Li, L., Morillo, M., and T. Yang, "Seamless MPLS
for Mobile Backhaul", draft-li-mpls-seamless-mpls-mbb-00
(work in progress), July 2013.
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[RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and
B. Thomas, "LDP Specification", RFC 3036, January 2001.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
[RFC5283] Decraene, B., Le Roux, JL., and I. Minei, "LDP Extension
for Inter-Area Label Switched Paths (LSPs)", RFC 5283,
July 2008.
[RFC6718] Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire
Redundancy", RFC 6718, August 2012.
Authors' Addresses
Li Zhang
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: monica.zhangli@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Dapeng Liu
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: liudapeng@chinamobile.com
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Susan Hares
Hickory Hill Consulting
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
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