Technical White Paper

Transcription

IP&OTN Synergy Solution
Issue
01
Date
2011-04-12
HUAWEI TECHNOLOGIES CO., LTD.
Copyright © Huawei Technologies Co., Ltd. 2011. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior
written consent of Huawei Technologies Co., Ltd.
Trademarks and Permissions
and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective
holders.
Notice
The purchased products, services and features are stipulated by the contract made between Huawei and
the customer. All or part of the products, services and features described in this document may not be
within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements,
information, and recommendations in this document are provided "AS IS" without warranties, guarantees or
representations of any kind, either express or implied.
The information in this document is subject to change without notice. Every effort has been made in the
preparation of this document to ensure accuracy of the contents, but all statements, information, and
recommendations in this document do not constitute a warranty of any kind, express or implied.
Huawei Technologies Co., Ltd.
Address:
Huawei Industrial Base
Bantian, Longgang
Shenzhen 518129
People's Republic of China
Website:
http://www.huawei.com
Email:
[email protected]
Issue 01 (2011-04-12)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd
i
Contents
Contents
1 Executive Summary ...................................................................................................................... 1
2 Introduction.................................................................................................................................... 2
3 Solution ........................................................................................................................................... 4
3.1 Overview .......................................................................................................................................................... 4
3.2 Optical Layer Protection .................................................................................................................................. 5
3.2.1 Optical Line Protection ........................................................................................................................... 5
3.2.2 Optical Channel Protection ..................................................................................................................... 6
3.2.3 Subnetwork Connection Protection......................................................................................................... 8
3.2.4 ASON Protection .................................................................................................................................... 9
3.3 IP/MPLS Layer Protection ............................................................................................................................. 15
3.3.1 Fault Detection Techniques ................................................................................................................... 15
3.3.2 Network Protection Techniques ............................................................................................................ 16
3.4 IP&OTN Protection Synergy ......................................................................................................................... 18
3.4.1 Multi-Layer Network Planning Tool ..................................................................................................... 18
3.4.2 SRLG .................................................................................................................................................... 19
3.4.3 Control Plane Intelligent Synergy ......................................................................................................... 20
3.4.4 Layered Protection Synergy .................................................................................................................. 21
3.5 IP&OTN OAM Synergy ................................................................................................................................ 21
3.5.1 Unified Network Management .............................................................................................................. 22
3.5.2 Visualized OAM ................................................................................................................................... 23
4 Experience..................................................................................................................................... 25
4.1 IP&OTN Synergy Solution Test ..................................................................................................................... 25
4.2 Global Application ......................................................................................................................................... 25
4.3 Success Stories ............................................................................................................................................... 26
5 Conclusion .................................................................................................................................... 27
6 Acronyms and Abbreviations ................................................................................................... 28
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Figures
Figures
Figure 3-1 IP&OTN synergy solution network ..................................................................................................... 5
Figure 3-2 Optical line protection ......................................................................................................................... 6
Figure 3-3 Client 1+1 protection ........................................................................................................................... 7
Figure 3-4 Intra-board 1+1 protection ................................................................................................................... 7
Figure 3-5 ODUk SNCP protection ....................................................................................................................... 9
Figure 3-6 Service protection and restoration using the mesh networking.......................................................... 10
Figure 3-7 Rerouting diagram ............................................................................................................................. 11
Figure 3-8 Resource sharing on working and protection paths ........................................................................... 12
Figure 3-9 Service association............................................................................................................................. 13
Figure 3-10 Diamond service .............................................................................................................................. 14
Figure 3-11 Silver service.................................................................................................................................... 15
Figure 3-12 Dynamic SRLG ............................................................................................................................... 20
Figure 3-13 IP&OTN alarm correlation and root cause analysis ........................................................................ 23
Figure 4-1 IP&OTN synergy solution test performed by EANTC ...................................................................... 25
Figure 4-2 Application of Huawei GMPLS/ASON in WDM/OTN fields........................................................... 26
Figure 4-3 IP&OTN synergy solution in Netherlands education network .......................................................... 26
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Tables
Tables
Table 3-1 Service levels ...................................................................................................................................... 13
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1 Executive Summary
1
Executive Summary
As enterprise branches are located in different regions and a lot of information needs to be
processed, the enterprises rely on WAN and backbone networks to implement department and
service collaboration. Therefore, the WAN and backbone networks must be reliable and easy
to maintain. A fault on the WAN or backbone network may interrupt enterprises' services or
even cause a disaster to the enterprises.
The WAN and backbone network involve the Internet protocol (IP) layer and optical transport
layer. Network maintenance is difficult and fault location is inefficient.
IP&OTN synergy is an important part of the Huawei "Integration, Easy, Clouding" solution. It
uses the intelligent optical transport network (OTN) and IP/MPLS technology to provide
protection synergy and operation, administration, and management (OAM) synergy. IP&OTN
synergy is a valuable solution for enterprises to implement communication and
informatization.
Huawei IP&OTN synergy solution has the following features:

High availability
Improves network reliability and service security by planning multi-layer networks and
using protection and fault recovery measures.

Easy to use
Manages network resources by using a unified network management system,
automatically discovers the topology of two layers, and creates end-to-end services
easily.

Easy to manage
Displays the topology of two layers on a screen, analyzes fault causes, deletes
unnecessary traps, helping to locate faults quickly.

Support for various new services
Provides differentiated Service Level Agreements (SLAs) according to service priorities.
In legacy network solutions, the IP layer and optical layer are separated from each other and
each layer uses individual protection and maintenance plans. The IP&OTN synergy solution
provides collaborative and efficient protection and maintenance for different layers.
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2 Introduction
2
Introduction
Networks play an important role during informatization development of enterprises. The
networks must use new solutions to adapt to changes. Many problems occurring on network
products have been solved by new network technologies.
Technology Development at the Optical Transport Layer
OTNs use the GMPLS/ASON technology to improve reliability, flexibility, bandwidth usage,
maintainability, and manageability. In addition, GMPLS/ASON supports many service levels
and speeds up service provisioning. OTNs improve their operability using the techniques of
GMPLS, such as automatic resource discovery, traffic engineering, dynamic bandwidth
adjustment, and interconnection.
Technology Development at the IP/MPLS Layer
The IP/MPLS layer has used the reliability technologies such as BFD for Anything and MPLS
OAM, which fix the problems such as forwarding engine faults and unidirectional link faults.
These technologies use the fault detection, fault report, active/standby switchover, and fast
detection packet sending methods to trigger the IP/LDP/TE FRR protection switching when
faults occur.
Challenges
Although the technologies on the OTNs and routers develop, legacy networks are facing the
following problems:

Hard to live: The IP layer plan does not consider the paths at the optical layer. Faults at
the optical layer may cause failures in the protection paths at the IP layer may cause
faults at the optical layer. As a result, the protection measures will fail to function and
networks face breakdown.

High costs on logical links: If the IP layer and optical layer are designed separately, the
costs on the optical layer will not be considered in the IP layer design. Therefore, the
optimal paths at the IP layer may cause a high cost at the optical layer.

Failed cooperation between protection mechanisms When a fiber is faulty, both the
optical layer and IP layer enable their protection mechanisms, causing frequently service
flapping. Faults may occur.

Hard to locate faults: When a fiber is faulty, both the optical layer and IP layer will
generate a lot of traps. Fault location is difficult and inefficient because there is a lack of
trap association and cause analysis mechanisms.
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2 Introduction
To solve the preceding problems, routers at the IP layer must collaborate with OTN devices to
provide multi-layer network plan, collaborative protection, and collaborative maintenance.
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3 Solution
3
Solution
3.1 Overview
The Huawei IP&OTN synergy solution is applied to enterprises' backbone networks. In this
solution, the optical transport network uses the ASON technique to dynamically adjust
bandwidth according to Ethernet traffic volume and support long distance transmission. The
routers at the IP layer provide differentiated quality according to the IP precedence or MPLS
EXP priorities in service packets. The optical layer and IP layer collaborate with each other to
provide high quality, high reliability, and easy operation and maintenance.
The IP layer and optical layer collaborate in two modes:

Manual mode
The network planning engineers manually plan the IP layer and optical layer with their
professional knowledge and experience. Protection is implemented by static Shared Risk
Link Group (SRLG) and uniform protection switchover parameters. Huawei network
management system U2000 manages the topology of the two layers and locates faults.

Dynamic mode
In this mode, network plan is implemented by the intelligent multi-layer network
planning tool and protection is implemented by the GMPLS-UNI-based dynamic SRLG
and multi-layer path computation elements (PCEs).
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Figure 3-1 IP&OTN synergy solution network
Unified Control Plane
A
B
BFD for XX
& YY FRR
Multi-Layer NMS
Multi-Layer PCE
GMPLS-UNI
PCECP
ASON
Multi-Layer Network
Planning Tool
The IP&OTN synergy solution provides the following functions for the enterprise's WAN and
backbone networks:

Optical layer protection

IP/MPLS layer protection

IP&OTN protection synergy

IP&OTN OAM synergy
3.2 Optical Layer Protection
The optical layer is a low-layer physical network of the service and data networks. If the
optical layer is unreliable, the service and data networks cannot operate properly. Therefore,
the optical layer uses various protection measures to ensure high reliability.
Protection measures at the optical layer include equipment-level protection measures and
network-level protection measures. Equipment-level protection includes SCC 1+1 protection,
cross-connect board 1+1 protection, DC input protection, centralized power protection, fan
redundancy protection, and subrack communication protection. The equipment-level
protection measures are not described in this document.
Network-level protection refers to the protection on all devices and links on the entire
network, including:

Optical line protection

Optical channel protection

Subnet connection protection

ASON protection
3.2.1 Optical Line Protection
Optical line protection uses the dual fed and selective receiving function of OLP boards and
diverse routes to protect the fibers between adjacent stations.
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Each optical line uses two pairs of fibers. One pair functions as the working path to transmit
service signals. The other pair functions as the protection path to transmit service signals
when a fiber break occurs on the working path or signal attenuation is too large. Figure 3-2
shows the diagram of optical line protection.
Figure 3-2 Optical line protection
Working signals
Protection signals
3.2.2 Optical Channel Protection
Optical channel protection includes client 1+1 protection and intra-board 1+1 protection.
Client 1+1 Protection
Client 1+1 protection uses the dual fed and selective receiving function of OLP/DCP boards
or the dual fed and dual receiving function of SCS boards to protect OTUs and OCh fibers. A
working wavelength and a protection wavelength are transmitted in two different routes to
protect OTUs.
When the SCS board is used on a device, the device opens the client-side laser of the working
OTU and closes the client-side laser of the backup OUT. When the working OTU detects an
SFor SD alarm, it reports the SF or SD alarm to the SCC board. The SCC board then closes
the client-side laser of the working OTU and opens the client-side laser of the backup OTU. A
switchover is completed.
When the OLP or DCP board is used on a device, the device opens the client-side laser of
both the working OTU and backup OTU. When the working OTU detects an SF or SD alarm,
it sends SF (or SD) event to the SCC board. The SCC board then closes the client-side laser of
the working OTU. So the R_LOS alarm occurs on the OLP and the OLP performs switching.
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Figure 3-3 Client 1+1 protection
Working signals
Protection signals
Intra-Board 1+1 Protection
Intra-board 1+1 protection uses the dual fed and selective receiving function of OTU, OLP, or
DCP boards and diverse routes to protect services. This protection measure is applicable to
chain networks and ring networks and uses the single-ended switching mode.
On a chain network, intra-board 1+1 protection provides diverse routes between adjacent
stations the same way as optical line protection. On a ring network, intra-board 1+1 protection
uses the diverse routes to protect services. Services are transmitted in the clockwise or
counter-clockwise direction on the ring, and finally reach the destination node.
Intra-board 1+1 protection is implemented in the following ways:

Uses the OTU with the dual fed and selective receiving function to protect services, as
shown in Figure 3-4.

Uses the OLP or DCP board with the dual fed and selective receiving function to protect
services. The network diagram is the same as Figure 3-4.
Figure 3-4 Intra-board 1+1 protection
Working signals
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3.2.3 Subnetwork Connection Protection
Subnetwork connection protection (SNCP) means that a dedicated protection route is preset
for a subnet. If a fault occurs on the subnet, the protection route replaces the subnet to
transmit traffic.
SNCP protects channels without using the APS protocol. It sets up a two-fiber path protection
ring on a ring network. SNCP is applicable to various complex network topologies and
provides fast service switching.
SNCP includes sub-wavelength (SW) SNCP, ODUk SNCP, VLAN SNCP, tributary SNCP,
and master slave (MS) SNCP. This document uses ODUk SNMP as an example. For the other
types of SNCP, see the OptiX OSN 6800 documents.
ODUk SNCP protection uses the dual fed and selective receiving function of the
cross-connections at the electrical layer to protect line boards and OCh fibers. It protects
inter-subnet services without using any protocol. ODUk SNCP is applicable to various
networks. Figure 3-5 shows the working process of ODUk SNCP.

In the transmit direction, services to be protected are input through the tributary board.
They are transmitted to the working line board and backup line board by using working
signals and protection signals. The working signals and protection signals are
respectively transmitted in the working channel and the protection channel.

In the receive direction, only the cross connection corresponding to the working line board is
valid and the cross connection corresponding to the backup line board is disconnected. When
the working channel is faulty, the line board reports an alarm to trigger an SF or SD
event. After detecting the SF or SD event, the main control board disconnects the cross
connection corresponding to the working line board and enables the cross connection
corresponding to the backup line board. Service signals are transmitted over the
protection channel.

After the working channel is recovered, service signals are switched back to the cross
connection corresponding to the specified line board.
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Figure 3-5 ODUk SNCP protection
Working signals
Protection signals
3.2.4 ASON Protection
On legacy networks, wavelength division multiplexing (WDM) devices were the replacement
for fibers. In recent years, they have been used to transmit user's services. The devices must
be easy to operate and manage. The legacy networks have the following problems:

Service configuration procedures are complex, and it takes a long time to expand
capacity or launch services.

Bandwidth use is inefficient because about 50% bandwidth must be reserved on the ring
network.

Only a few protection measures are provided, so network self-healing capability is poor.
Automatically Switched Optical Network (ASON), also called intelligent optical transport
network, is introduced to solve the preceding problems. ASON uses GMPLS-UNIs and a
control plane on transport networks to enhance the network connection management and fault
recovery capabilities of optical transport devices. It supports end-to-end service configuration
and multiple service restoration methods.
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Compared with WDM, ASON has the following advantages:

Computes routes using optical parameters and discards the routes that do not match the
optical parameters.

Adjusts wavelength during rerouting, eliminating wavelength conflicts.

Allocates wavelength for new services.

Supports automatic configurations for end-to-end services.

Discovers topology automatically.

Protects the mesh network to enhance network availability.

Assigns protection priorities to services according to the priorities of the client-layer
signals.

Uses traffic engineering to dynamically adjust network topology according to customers'
service requirements. This implements optimal network resource allocation.
The following sections describe the transport layer protection mechanisms based on ASON.
Mesh Networking
Mesh networking is a widely used networking type of ASON, and is flexible and easy to
extend. Compared with WDM networking, mesh networking supports more recovery paths,
which improve network security and reduce network resource waste.
In addition to the traditional protection measures (such as 1+1 protection) and shared
protection measures, the mesh networking can also use the rerouting mechanism to protect
services. Using all the preceding measures, the mesh networking is capable of restoring
services in any situations.
As shown in Figure 3-6, if the link between device C and device G is interrupted, a route from
device D to device H is generated. Services are restored through a newly generated LSP.
Figure 3-6 Service protection and restoration using the mesh networking
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Dynamic Rerouting
Rerouting recovers services when network faults occur. In non-revertive mode, the first node
on an interrupted LSP calculates the optimal path, and then sets up a new LSP using signaling
messages. Services are transmitted over the new LSP. The interrupted LSP is deleted after the
new LSP takes effect.
Rerouting, as a key technology of GMPLS/ASON, protects services without a waste of
resources. It is also a revolutionary improvement for traditional protection measures.
Rerouting protects services even if fibers are interrupted frequently.
As shown in Figure 3-7, an LSP passes devices A, D, G, and K. When the link between
devices D and G is interrupted, the rerouting process is as follows:

The FIU (for optical layer) or OUT (for electrical layer) of device D detects an alarm,
and then reports the alarm to the GMPLS module.

The GMPLS module on device D checks the affected intelligent services and sends a
Notify message to device A.

After receiving the Notify message, the GMPLS module of device A calculates an
end-to-end protection path and sends a PATH message along the new path. A reverse
cross-connected path destined for device K is set up.

After receiving the PATH message, the GMPLS module of device K returns a RESV
message along the new path to set up a cross-connected path destined for device A.

After receiving the RESV message, device A enables the alarm function and sends a
PATH message to request the downstream devices to enable the alarm function. The
downstream devices enable the alarm function for the new path.

After all devices on the LSP enable the alarm function, the old LSP is deleted if the
non-revertive mode is used. The rerouting process is complete.
Figure 3-7 Rerouting diagram
D
fy
Noti
A
G
PA
TH
K
F
C
PA
TH
B
H
PAT
E
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Preset Protection Path
Preset protection paths ensure high reliability for services. When a path fails, the GMPLS and
ASON networks restore services using the preset protection path. The service paths on the
networks are controllable. If services cannot be restored, a new route is calculated.
To ensure that routes are controllable after fibers are disconnected multiple times, the ASON
allows more than one preset protection path for an end-to-end route (at the optical layer or
electrical layer). An LSP can have two preset protection paths and the paths have their own
priorities.
Resource Sharing on Working/Protection Paths
Resource sharing on the working and protection paths provides restoration resources as many
as possible. Figure 3-8 shows a tangent ring network where resource sharing is used.
The blue and red real lines indicate the working and protection paths. When link 1 and link 2
are broken, the working and protection paths are invalid. If the working and protection paths
cannot share resources, services will not be restored. If the paths can share resources, some
links on the paths form a complete backup path. The green broken lines in the figure indicate
the backup path. If link 3 is broken, the path represented by purple lines is formed.
Figure 3-8 Resource sharing on working and protection paths
Service Association
Two LSPs are associated. When an LSP is performing rerouting or optimization, this LSP is
separated from the other one. The two LSPs do not overlap each other. Service association is
applicable to the services having two access points (dual homing).
As shown in Figure 3-9, the two LSPs D-E-I and A-B-G-H are associated. If the link between
devices B and G is broken, the LSP A-B-G-H performs rerouting and the LSP D-E-I is not
affected.
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Figure 3-9 Service association
SLA for Differentiated Services
WDM/OTN-based GMPLS and ASON provide protection services of different levels,
including Diamond, Silver, and Bronze. Customers pay different fees for different service
levels. Table 3-1 lists the service levels.
Table 3-1 Service levels
Service
Level
Protection
Recovery
Diamond
and
Implementation
Switchover
Time
Protection and recovery
Intra-board 1+1 protection,
ODUk SNCP, SW SNCP,
rerouting
Shorter than 50
ms
Silver
Recovery
Rerouting
-
Bronze
No
protection,
recovery
-
-
no
1. Diamond service
Diamond service has the best protection ability. When there are enough resources on the
network, diamond service provides permanent 1+1 protection for paths such as ODUk paths.
Diamond services are applicable to voice and data services, VIP private line, such as banking,
security, and aviation.
A diamond service provides 1+1 protection from the source node to the sink node. It is also
called a 1+1 service. There are two LSPs available between the source node and the sink node.
The two LSPs are separated. One is the working LSP and the other is the protection LSP. The
same service is transmitted to the working LSP and the protection LSP at the same time.
When the working LSP is normal, the sink node receives services from the working LSP;
otherwise, the working LSP receives services from the protection LSP.
Figure 3-10 shows the network diagram of diamond service.
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Figure 3-10 Diamond service
The diamond service uses the following rerouting policies:

Permanent 1+1 protection: triggers rerouting once an LSP fails.

Rerouting 1+1 protection: triggers rerouting only when the two LSPs fail.

No rerouting: does not trigger rerouting no matter whether LSPs fail.
2. Silver service
Silver services include WDM ASON OCh paths, ODUk paths and Client paths. The recovery
time is several seconds. The silver service is suitable for the delay-insensitive services such as
data service and residential Internet service.
Silver service provides connections from the source node to the sink node with the rerouting
protection. It is also called rerouting services. If an LSP fails, rerouting is repeatedly initiated
to restore services until rerouting is successful. The silver service computes protection paths
without a reservation of resources. Hence, the bandwidth utilization is high. However, if
network resources are insufficient, services may be interrupted.
As shown in Figure 3-11, the silver service is provided for the path A-B-G-H-I. If the link
between devices B and G is broken, device A initiates rerouting to create a new path.
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Figure 3-11 Silver service
3. Bronze service
The bronze services are seldom used. Generally, temporary services, such as the abrupt
services in holidays, use the bronze service. The paths of bronze service include OCh paths,
ODUk paths, and Client paths.
The bronze service means no protection. If an LSP fails, rerouting is not triggered and
services are interrupted.
3.3 IP/MPLS Layer Protection
Most IP/MPLS reliability techniques aim at shortening the fault detection time and improving
network protection.
3.3.1 Fault Detection Techniques
The traditional fault detection technique detects faults by monitoring the device interface
status. This detection technique can detect only physical faults and depends on Keepalive or
Hello packets sent by upper-layer routing protocols to detect faults such as forwarding engine
faults and unidirectional link faults.
Therefore, this fault detection mechanism requires a long time, uses a lot of resources, and is
not applicable to scenarios where different protocols are running.
To speed up fault detection and improve fault detection efficiency at the IP/MPLS layer, a
mechanism that can detect faults rapidly and support various protocols is required. MPLS
OAM and BFD are such mechanisms.
BFD
BFD is an interactive detection mechanism that rapidly detects communication faults between
systems and reports the detected faults to upper-layer applications.
BFD has the following functions:
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
Provides low-overhead, short-duration detection of faults in the path between adjacent
forwarding engines. These faults include interface faults, data link faults, and forwarding
engine faults. The BFD detection time is usually within 50 ms.

Provides a single mechanism for fault detection over any media and at any protocol layer
to implement BFD for Everything, such as BFD for IS-IS, OSPF, BGP, LSP, and TE.
With the preceding functions, BFD has been widely used to detect link faults and protocol
faults.
MPLS OAM
MPLS OAM is a rapid detection mechanism that checks MPLS LSP connectivity by allowing
nodes along an LSP to exchange OAM packets.
MPLS OAM provides the following functions, independent of upper-layer or lower-layer
protocols:

Detects, identifies, and locates MPLS user-plane faults efficiently.

Evaluates network usage and performance.

Performs protection switching in the event of a link defect or fault to provide services
according to the Service Level Agreements (SLAs).
For more information about MPLS OAM, see ITU-T Recommendation Y.1710 and Y.1711.
3.3.2 Network Protection Techniques
On IP/MPLS networks, various network protection techniques are used to rectify faults:

Redundancy backup of main control boards, hot swapping of boards, and GR, which
ensure device reliability.

Virtual Router Redundancy Protocol (VRRP) and Gateway Load Balancing Protocol
(GLBP), which improve node reliability

IGP fast route convergence and TE FRR, which ensure path availability

VPN FRR, which ensures PE reliability
The following are common network protection techniques.
IGP Fast Convergence
IGP fast convergence speeds up IGP route recalculation and convergence when a network
fault occurs. IGP fast convergence provides the following features:

Incremental SPF (I-SPF): calculates only the changed routes, not all routes each time.

Partial route calculation (PRC): calculates only the changed routes. It does not calculate
the shortest path but updates leaf routes based on the SPT calculated by I-SPF.

LSP fast flooding: When a router receives one or more new LSPs, it floods out the LSPs
with a number smaller than the specified number before calculating routes. This
accelerates LSDB synchronization and network convergence.

Intelligent timer: adjusts the delay based on the route change frequency. This ensures fast
route convergence, without affecting router performance. Intelligent timers include the
SPF intelligent timer and LSP generation intelligent timer.
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IP FRR
On legacy IP networks, it takes the routing system several seconds to complete route
convergence after a fault is detected. This convergence speed cannot meet requirements of the
services that are sensitive to packet delay and packet loss. For example, Voice over Internet
Protocol (VoIP) services are tolerant of millisecond-level interruption.
IP FRR allows the forwarding system to rapidly detect faults and take measures to restore
services as soon as possible. The IP FRR implementation principles are as follows:

When the primary link is available, you can configure IP FRR by using a routing policy
to provide the backup route information for the forwarding engine.

When the forwarding engine finds that the primary link fails, it uses the backup link to
forward traffic before the routes converge on the control plane.
IGP Auto FRR
In IP FRR, the backup next hop needs to be manually configured, which is complex and prone
to network loops if network planning is improper. IGP Auto FRR overcomes the preceding
problem.
IGP Auto FRR is a technique that allows routing protocols to generate the backup next hop
using routing algorithms according to the link status. This technique does not require manual
intervention, which reduces maintenance costs.
BGP FRR
IGP/LDP FRR can rapidly switch traffic to another link when a link fault occurs. However,
when a fault occurs on a BGP node, routes need to converge on the BGP control plane and
then be delivered to the forwarding table. The route convergence time may reach the second
level. The BGP indirect next hop technique speeds up route convergence on the control plane,
but it still cannot ensure carrier-class reliability.
In BGP FRR, the LDP label or BGP label of a sub-optimal route is installed into the
forwarding table as a backup routing entry. When a rapid fault detection mechanism such as
BFD detects that the optimal route becomes unavailable, services are switched to the backup
route. This implements fast service switchover.
LDP FRR
LDP FRR allows a device to install both the optimal route and sub-optimal route that
functions as the backup route into the forwarding table. When the next hop of the optimal
route fails, traffic is forwarded using the backup route or label.
LDP FRR can work with BFD to rapidly detect faults in the next hop of the optimal route and
implement route convergence within 50 ms.
There are some shortcomings in LDP FRR. For example, on a ring network, the next hop of
the sub-optimal route may send packets to the local node, causing a loop.
Compared with RSVP TE FRR, LDP FRR provides only single-point protection but not
end-to-end protection.
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3 Solution
MPLS TE FRR
MPLS TE FRR protects links and nodes in MPLS TE. When an LSP link or a node fails,
traffic can be forwarded along the tunnel of the protected link or protected node. This ensures
uninterrupted traffic forwarding. In addition, the ingress can continue re-establishing the
primary path without affecting data transmission.
In MPLS TE FRR, an LSP is established to protect one or more LSPs. This LSP is called the
FRR LSP and the protected LSP is called the primary LSP. When a link or node fails, MPLS
TE FRR uses the FRR LSP to transmit traffic; therefore, the primary LSP is protected. All the
nodes in the MPLS TE system need to participate in the establishment of the FRR LSP and
primary LSP.
MPLS TE FRR is implemented based on RSVP TE and complies with RFC 4090.
VPN FRR
MPLS TE FRR protects services in the case of a link or node failure between two PEs at both
ends of a TE tunnel; however, MPLS TE FRR cannot protect services in the case of a PE
failure.
Once a PE fails, services can only be restored by means of end-to-end route convergence and
LSP convergence. The service convergence time depends on the quantities of MPLS VPN
routes and hops on a bearer network. The convergence time is usually 5s on a typical network,
which is longer than 1s required for end-to-end service convergence.
VPN FRR solves the preceding problem. In VPN FRR, primary and backup forwarding
entries with the primary PE and backup PE as their respective destinations are preconfigured
on the remote PE. Rapid PE failure detection is also used so that the end-to-end service
convergence is within 1s on an MPLS VPN where a CE is dual homed to two PEs. The
recovery time is independent of the quantity of VPN routes.
3.4 IP&OTN Protection Synergy
A fault on the WAN or backbone network affects thousands of enterprises' services, which
lowers these enterprises' production efficiency and delays their response to market changes.
Therefore, reliability of the WAN and backbone network is important to enterprises' business
and competitiveness.
Although both the IP layer and transport layer have many protection mechanisms,
mechanisms may not collaborate well with each other. For example, some protection
mechanisms fail to function together or some protection mechanisms repeat each other,
resulting in a waste of resources and service quality degrade.
Protection synergy uses the protection mechanisms on both the IP layer and transport layer
according to requirements of the WAN and backbone network. The major protection features
include static SRLG, dynamic SRLG, intelligent control plane synergy, and layered protection
synergy.
3.4.1 Multi-Layer Network Planning Tool
Legacy WAN and backbone network are planned layer by layer, wasting network resources
and making QoS and reliability complex. When the network is large, concurrent designs are
very difficult.
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3 Solution
Unlike layer-by-layer network planning tools, a multi-layer network planning tool improves
resource utilization and network reliability by planning the IP layer and transport layer
together. This tool has the following advantages:

Allocates bandwidth for the two layers based on traffic volume so that traffic is loaded
evenly, improving utilization of network resources.

Isolates faults on the IP layer and transport layer to prevent a fault from triggering
repeated protection at the two layers. This ensures effective protection and improves
network reliability, laying a foundation for intelligent synergy between the IP layer and
transport layer of a backbone network.
3.4.2 SRLG
An SRLG is a group of links with the same reliability risks. For example, multiple links on a
router involve the same transport path. If the transport path fails, both the working and
protection links on the router will also fail. To prevent this problem, links in the same SRLG
are not assigned to a pair of working and protection paths during path computation. This
improves reliability on the IP layer because a link failure will not cause both the working and
protection paths to fail.
Static SRLG
Static SRLG requires the IP network administrators to manually configure SRLG information
on routers after confirming the information with the transport network administrators.
Static SRLG is easy to implement and does not require configuration of other parameters.
However, static SRLG has the following disadvantages:

The administrators of the IP network and transport network have to exchange and
configure a large amount of detailed information, which is labor-consuming and prone to
errors.

When links on the transport layer are re-planned or adjusted, the transport network
administrators must notify the IP network administrators, and the IP network
administrators modify configurations on the IP layer.

If the GMPLS ASON technology is used at the transport layer, the transport paths may
change automatically. The IP network administrators cannot be notified of the changes in
real time.
Dynamic SRLG
Huawei presents the dynamic SRLG solution to overcome problems of static SRLG.
Transport devices transfer SRLG information to routers through extended GMPLS-UNIs
between them. Dynamic SRLG has the following advantages:

The SRLG information is transmitted from the transport layer to the IP layer
automatically and no manual operation is required, reducing workload in maintenance
and preventing configuration errors.

Transport devices update SRLG information when transport links are adjusted, saving
network administrators' workload in modifying configurations.

When the GMPLS ASON re-computes routes, transport devices notify routers of SRLG
information update.
Transport devices send SRLG information to routers, including information specific to each
layer such as OTN layer, optical layer, and fiber layer. Each router calculates and updates
links on the working and protection paths according to the SRLG information received from
Issue 01 (2011-04-12)
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3 Solution
the transport layer to ensure that the working and protection paths do not contain links in the
same SRLG. Figure 3-12 shows dynamic SRLG implementation.
Figure 3-12 Dynamic SRLG
SRLG: O-S4, L-S4, FS1, F-S3, F-S4
IP/MPLS
GMPLS-UNI
extension
O-S2
O-S1
O-S6
OTN/sublambda
O-S4
L-S5
WDM/lambda
L-S4
O-S5
O-S3
O-S4
L-S2
L-S3
L-S1
L-S4
F-S2
F-S1
Fiber
F-S3
F-S1
F-S3
F-S4
F-S4
3.4.3 Control Plane Intelligent Synergy
The control plane is not involved in static synergy, but it plays an important role in static
synergy. The key technologies used on the control plane are GMPLS-UNI, and PCE.
GMPLS-UNI
The GMPLS-UNI technology defined by IETF is a key technology to enhance information
exchange between the IP layer and transport layer. Routers on the IP layer send messages to
request transport devices to set up or delete paths through GMPLS-UNIs.
After a router sets up a link, it sends GMPLS-UNI signaling messages to notify transport
devices of the source node, destination node, and attributes (such as bandwidth and protection
attributes) of the link. Transport devices then set up a transport path according to the link
information.
PCE
On a large network, constraint-based path computation is complex, and devices participating
in path computation must have high calculation capabilities. If distributed path computation is
performed on the network, each node must have high calculation capabilities, causing high
costs on network construction. If the network is divided into multiple domains, the topology
of each domain is hidden to other domains. Therefore, devices on the network must cooperate
to compute the optimal end-to-end path.
The PCE technology is introduced to solve the path computation problem. A PCE has high
path computation capabilities and is deployed on a network device or an external server. A
PCE is responsible for path computation in a domain. All path computation requests in a
domain are sent to the PCE in this domain. After completing path computation, the PCE sends
the computation result to the path computation clients (PCCs) that sent the path computation
requests. PCEs in multiple domains work together to compute the optimal path.
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3 Solution
3.4.4 Layered Protection Synergy
The IP&OTN synergy solution provides layered protection for each layer by using the
protection mechanisms on both the IP layer and transport layer. This solution provides the
following protection modes:

TE FRR&ASON diamond 1+1 protection

TE FRR&ASON silver reroute protection

TE hot standby&optical line 1+1 protection
TE FRR&ASON Diamond 1+1 Protection
This protection mode is applicable to networks that have sufficient optical lines and IP links
and require high reliability.
TE FRR is used at the IP/MPLS layer to protect key paths, and ASON diamond 1+1
protection is used at the transport layer. TE FRR&ASON diamond 1+1 protection prevents
service interruption caused by link and node failures at the IP layer and transport layer. In
addition, this protection mode protects services against multiple fiber break events.
TE FRR&ASON Silver Reroute Protection
This protection mode is applicable to networks that have sufficient optical lines and require
high reliability.
TE FRR is used at the IP/MPLS layer to protect key paths, and ASON silver 1+1 protection is
used at the transport layer. When WDM fibers at the transport layer fail, TE FRR triggers
protection switching at the IP/MPLS layer to switch traffic to the bypass tunnel. After a new
path is selected at the transport layer using silver reroute, traffic is switched back to the
primary tunnel. During the switching process, routers use the make-before-break technique to
prevent packet loss.
TE Hot Standby and Optical Line 1+1 Protection
This protection mode is applicable to networks that require medium reliability and do not
have sufficient optical lines or IP links. It only protects services against fiber faults between
sites but cannot protect services against failure of the entire transport board or site. In addition,
this protection mode can withstand only one fiber break event.
TE hot standby is used at the IP/MPLS layer to protect end-to-end paths, and optical line 1+1
protection is used at the transport layer. When a WDM fiber fails, optical line 1+1 protection
is triggered to switch traffic to the backup fiber.
3.5 IP&OTN OAM Synergy
On a legacy network, devices at the IP layer and transport layer are managed by different
NMSs and maintained by different departments, making quick service provisioning and fault
identification difficult. For example:

Issue 01 (2011-04-12)
When the IP network requires one more wavelength, it may take one or two months to
provide a wavelength on the transport network. This greatly delays service provisioning
and launch.
21
3 Solution

Over 80% traffic from the IP network is carried over wavelengths. When services on a
router are interrupted, it is difficult to quickly identify whether the fault occurred on the
IP network or on a WDM device, let alone to isolate the fault.

When a fault occurs on a transport device, the transport network administrators do not
know whether this fault affects IP links and which IP links are affected.

Device connections on the IP network are complex, making OAM on IP networks
difficult. Network administrators usually have to open many pages on the NMS to
configure a service.
The OAM synergy solution is introduced to reduce workload on network management and
make network OAM easy. It solves the preceding problems implementing unified
management on the IP network and OTN and visualized service maintenance.
3.5.1 Unified Network Management
The U2000 is a unified NMS that manages NEs on the IP network and transport network
uniformly and provides functions such as quick service provisioning, and quick fault
identification.
Unified NE Management
The U2000 manages transport devices, access devices, and IP devices uniformly. It manages
devices such as routers, switches, DSLAMs, and firewalls, and services such as MSTP, WDM,
OTN, microwave, PTN, MSAN, and FTTx.
Quick Service Provisioning
The U2000 implements quick end-to-end service provisioning by using the following
functions:

Service templates: The U2000 provides various service templates such as tunnel
templates, L2VPN/ L3VPN/VPLS/PWE3 service templates, and QoS policy templates.
These templates implement one-stop service parameter configuration, improving
configuration efficiency by 3 to 6 times.

Batch service delivery: improves configuration efficiency by 2 to 3 times.

Automatic calculation of static routes: The U2000 calculates static routes and allocates
MPLS labels, and no manual operation is required.

Inter-domain end-to-end service maintenance: helps to identify and locate faults
accurately.

One-key layer switching and layered service presentation: Administrators can switch
between the IP layer and optical layer easily to configure services. The relationship
between IP and WDM services is displayed clearly on the GUI.
Quick Fault Identification
The U2000 helps to analyze root causes of alarms on the IP network and clears 85% of
ineffective alarms to improve availability of alarms on the IP network. The U2000 also
provides IP and OTN alarm correlation analysis and displays IP links affected by OTN alarms.
Figure 3-13 shows alarm correlation and root analysis.
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3 Solution
Figure 3-13 IP&OTN alarm correlation and root cause analysis
23,000 Alarms/Day, KPN IP Backbone
• Abundant alarms database in both layers
• Customized alarm correlation analysis rules
U2000 NMS &
Alarm Center
P
P
E
P
P
E
Where is the fault?
Alarms caused by the root
alarms are shielded

Only need to maintain a unified alarm report
after Correlation Analysis and Suppression

Help to fast trouble shooting
6,000 alarms per day on KPN WDM Backbone
3.5.2 Visualized OAM
The legacy IP network is more difficult to manage and maintain than other types of networks
due to technical limitations:

Service routes on the IP network are invisible to administrators.

Fault identification on the IP network is difficult and time-consuming. Some transient
faults cannot be eliminated permanently.

End users are unaware of services transmitted over the IP network, so QoS is difficult to
manage on the IP network.
Huawei provides a visualized service quality management (SQM) solution to improve
maintainability of IP networks. This solution is implemented by the U2520 (an IP SQM
system) and the U2000.
The SQM solution provides the following functions:

KPI monitoring
The SQM system effectively monitors key performance indicators (KPIs) on the IP
network, such as latency, jitter, and packet loss ratio. The user experience can be
measured and evaluated in various usage scenarios, and pre-warnings can be generated
for factors that degrade user experience.

End-to-end IP service management
The SQM system implements end-to-end monitoring and presentation of IP services such
as video, voice, and file transfer. It monitors service performance and detects faults in
real time, helping to locate faults quickly.

Real-time IP route display
The SQM system collects and displays IGP routes and LSPs on the entire network in real
time. Historical transient faults can be traced and eliminated.
Issue 01 (2011-04-12)
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
3 Solution
IP fault locating
The SQM system uses Huawei's IP fault locating techniques to locate faults on the IP
network. After the source IP address/port and destination IP address/port are entered, the
SQM system can locate the fault in 5 minutes.
Issue 01 (2011-04-12)
24
4 Experience
4
Experience
4.1 IP&OTN Synergy Solution Test
Huawei, leading in the IP&OTN synergy solution, launched the IP&OTN synergy solution
based on ASON intelligent optical network and IP/MPLS routers launched in the second half
of 2009. This solution gained an excellent result in the test carried out by European Advanced
Networking Test Center (EANTC) in 2010. Figure 4-1 shows the test networking diagram.
Figure 4-1 IP&OTN synergy solution test performed by EANTC
R2-VenderX
R1-Huawei
R3-Huawei
Control plane DCN
(GMPLS-UNI sinaling)
N3-VenderY
N1-Huawei
N4-VenderY
N2-Huawei
4.2 Global Application
As a leader in the ASON intelligent optical network market, Huawei has successfully
deployed more than 300 ASON networks for over 80 carriers around the word, and
accumulated rich experience in ASON project delivery and OAM.
Issue 01 (2011-04-12)
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4 Experience
Figure 4-2 Application of Huawei GMPLS/ASON in WDM/OTN fields
Turk
Telekom
Telefonica Greece
OTE
Azerbaijan
Spain
Azertelecom Bengal GP
Telecom
Italy
Vodafone
UK
China Telecom
Vodafone
Portugal
Morocco
Telecom
Egypt TE
Angola
Msteleco
m
China Mobile
UAE
Qatar DU
QTel Vodafone
India
Thailand
TT&T
Venezuela
CANTV
China Unicom
Philippines
PLDT
Vietnam
VNPT
Malaysia CTS
Malaysia
Celcom
SDH ASON
OTN/WDM ASON
Huawei provides cutting-edge routing techniques and is serving 36 of top-50 carriers in the
world. Huawei has deployed over 120 IP/MPLS networks and over 620 metro networks in
102 countries and regions, and provides services for the most users (1 billion) among all
telecommunications device vendors.
4.3 Success Stories
Huawei has rich experience in WAN and backbone network deployment. Huawei's optical
network and data communication products are widely used on the WAN and backbone
network in energy, government, transportation, education, and finance industries. These
applications help to popularize the IP&OTN synergy solution. Figure 4-2 shows the
application of the IP&OTN synergy solution (using NE40Es and OSN6800s) in Netherlands
education network.
Figure 4-3 IP&OTN synergy solution in Netherlands education network
Regional
POP
OSN1800
Regional
ring
Core POP
(NE40E+
OSN6800)
Site B
S5300
S5300
External
network
Site A
Gigabit
metro ring
DWDM core network
S5300
Core POP
Issue 01 (2011-04-12)
Core POP
(NE40E+
OSN6800)
S5300
Site C
26
5 Conclusion
5
Conclusion
The IP&OTN synergy solution enhances reliability and security of the GMPLS/ASON
intelligent and provides a multi-layer network planning tool to improve network planning
efficiency. It takes advantages of high flexibility and reliability of the IP/MPLS network and
uses the U2000 unified OAM platform to improve reliability and maintenance efficiency of
WAN and backbone network. This solution provides high-quality cloud networks to help
enterprise implement informatization and create value for customers.
Issue 01 (2011-04-12)
27
6 Acronyms and Abbreviations
6
Acronyms and Abbreviations
Abbreviation
Full Spelling
ASON
Automatically Switched Optical Network
BFD
Bi-directional Forwarding Detection
E-NNI
External Network-Network Interface
FRR
Fast Reroute
GMPLS
Generalized Multi-Protocol Label Switching
IETF
Internet engineering task force
IGP
Interior Gateway Protocol
I-NNI
Internal Network-Network Interface
ITU-T
International Telecommunication Union - Telecommunication
Standardization Sector
LMP
Link Management Protocol
LSP
Label Switch Path
NNI
Network Node Interface (Network-to-Network)
OIF
Optical Internetworking Forum
OTN
Optical Transport Network
OTU
Optical Transport Unit
PCE
Path Computation Element
RSVP-TE
Resource reservation protocol with traffic-engineering extension
SDH
Synchronous Digital Hierarchy
SLA
Service Level Agreement
SRLG
Shared Risk Link Group
TE
Traffic Engineering
Issue 01 (2011-04-12)
28
6 Acronyms and Abbreviations
Abbreviation
Full Spelling
UNI
User Network Interface
WDM
Dense Wavelength Division Multiplexing
Issue 01 (2011-04-12)
29

Technical White Paper

Transcription

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