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Technical White Paper for VLAN Sub-Interface Offloading
Technical White Paper for VLAN Sub-Interface Offloading
1 Background ...................................................................................................................1
2 Overview .......................................................................................................................2
3 Key Technologies ...........................................................................................................4
3.1 VLAN Sub-Interface .......................................................................................................4
3.2 VLAN Awareness ...........................................................................................................4
3.2.1 Technical Implementation ........................................................................................................................5
3.3 PE-PE Traffic Forwarding ................................................................................................6
3.4 Netstream .....................................................................................................................6
3.4.1 Technical Implementation ........................................................................................................................7
3.5 QoS-Related Technologies .............................................................................................8
3.5.1 Technical Implementation ........................................................................................................................9
3.6 GMPLS-UNI-Related Technologies ................................................................................10
4 Summary .....................................................................................................................11
5 Acronyms and Abbreviations ........................................................................................12
1
1 Background
As broadband services are growing, increasing bandwidth is required on
an IP backbone network. APPU, however, is increasing slowly. Increase in
bandwidth requires fast increase in CapEx. As increase in expenditure goes
faster than growth of revenue, profits of operators decline sharply. In this
situation, operators require a new mode of network construction to solve this
problem. Then, reducing network construction costs becomes the first choice
of operators.
According to Moore's Law, capacity expansion pressure on routers will
intensify as required bandwidth is increasing. In addition, traffic distribution
on a backbone network shows that transit traffic will take the majority on
P routers, exhausting switching capacity of P routers and thereby increasing
costs. To reduce costs of the entire backbone network, deploying a economic
optical layer to offload transit traffic on P routers is feasible and will be an
option for network construction.
Abstract
As broadband services are growing fast, increasing bandwidth is required
on an IP backbone network and thereby operators' CapEx is increasing.
Revenues of operators, however, grow slowly, leading a sharp decrease in
profits. This is a challenge for operators. To help operators overcome this
challenge, Huawei presents SingleBackbone Solution, and the idea is IP&OTN
synergy,which includes traffic synergy, protection synergy and OAM synergy,
and the VLAN sub-interface offloading solution is one realization method
of traffic synergy solution. VLAN sub-interface offloading means that traffic
is offloaded through VLAN sub-interfaces, significantly reducing CapEx and
OpEx for operators. This white paper focuses on the working principle and
key technologies of this solution.
Key Words
VLAN sub-interface, Netstream, GMPLS-UNI
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2 Overview
To conform to the current network trend, Huawei proposed the mainstream
SingleBackbone Solution, which includes traffic synergy, protection synergy
and OAM synergy. Among them, the main idea of traffic synergy solution
is to optimize network connection, and to improve the efficiency of the
network load, which can become true by physical interface offloading, VLAN
subinterface Interface offloading and cOTN interface offloading. This paper
just focuses on discussion of the principles and related key technologies of
the VLAN sub-interface offloading solution.
What is VLAN sub-interface offloading? When detecting such sharp increase
in PE-PE traffic that the traffic exceeds the preset threshhold, the relevant PEs
offload the traffic over to the paths at VLAN sub-interfaces, while affecting no
other traffic at all. This process is referred to as VLAN sub-interface offloading.
As illustrated by the blue line in Figure 2-1, on the IP backbone network, PE-PE
traffic is forwarded by P routers through physical interfaces in normal cases.
Packets at a physical interface on a router are untagged packets, because a
VLAN cannot be configured at such a physical interface. Therefore, the OTN/
WDM equipment has to identify these packets and effectively process them.
When detecting sharp increase in certain PE-PE traffic, a PE router creates
a VLAN sub-interface (VLAN 200, for example) and notifies the OTN/WDM
equipment directly connected to it to create an ODUk path for VLAN 200.
When the new VLAN sub-interface is created successfully, the PE router
offloads all or part of the traffic over to the ODUk path.
Figure 2-1 VLAN sub-interface offloading
1. PE-PEtrafficmonitor
3. PE-PEtrafficbypass
2. PE-PEVLAN-OTNtunnel setup
Router-P1
Router-PE1 OTN/WDM1
BBNS network
OTN/WDM2
Untagged
VLAN200
Untagged
VLAN200
Router-PE2
Untagged
VLAN200
Untagged
VLAN200
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According to network deployment and the pace of technological
development, the VLAN sub-interface offloading solution is divided into three
stages.the first stage known as the manual synergy can be supported by the
current device, but all the planning is done manually, so the effect depends
on the engineer's planning experience, and workload is large;the second
stage known as semi-automatic, the traffic matrix detection element and
offline multi-layer network planning tool are added to help operators to make
better decisions, to reduce manual labor and improve efficiency and accuracy;
The third stage is to meet the needs of dynamic development of the network,
to implement intelligent synergy, so the multi-layer PCE and the optimal path
of dynamic multi-domain/multi-layer calculation will be introduced, which rely
on standards evolution. Currently, the VLAN sub-interface offloading solution
is in semi-automatic stage.
In deployment of an IP backbone network, the VLAN sub-interface offloading
solution is valuable. The values are as follows:
Lowering CapEx •
A PE router offloads traffic through a VLAN sub-interface instead of a
physical interface, and equipment at the transport layer offloads transit
traffic of the P router. So it can significantly lowers CapEx of operators.
Saving bandwidth of interfaces on P routers and thereby increasing •
bandwidth utilization
When PE-PE traffic increases sharply, a PE router offloads the traffic
through a VLAN sub-interface. That is, PE routers are interconnected
through transmission equipment. In this manner, bandwidth of interfaces
on the intermediate P routers is saved, significantly increasing bandwidth
utilization.
Maintaining the current overlay network structure, enabling easy •
deployment of a network, and reducing OpEx
This solution helps maintain the current overlay network structure and
thereby has little impact on IP/MPLS routers. In addition, this solution is
compatible with the equipment on the live network and thus is easy to
deploy. That is, this solution helps considerably reduce OpEx for operators.
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3 Key Technologies
The VLAN sub-interface offloading solution involves technologies such as
VLAN sub-interface, VLAN awareness, traffic policing, QoS, and GMPLS-UNI.
This chapter elaborates these key technologies.
3.1 VLAN Sub-Interface
A VLAN sub-interface mentioned in this document refers to a Layer 3 logical
sub-interface. Such a sub-interface, when configured with an IP address,
routing protocol, and MPLS, can enable Layer 3 communication. A physical
interface can be divided into VLAN sub-interfaces to ensure isolation of
services at the same physical interface. The VLAN sub-interfaces at one
physical interface share bandwidth.
On an IP backbone network, the VLAN sub-interface offloading solution is
applicable to the following interfaces;
10GE interfaces and others •
PE routers are interconnected through 10GE interfaces and others. When
traffic at a PE router increases sharply and exceeds the threshhold, the PE
router can offload the traffic through a Layer 3 VLAN sub-interface.
Ethernet trunk interfaces •
An Ethernet trunk interface refers to a logical interface combining multiple
Ethernet interfaces. Such an interface improves service reliability while
multiplying bandwidth. PE routers are interconnected through Ethernet
trunk interfaces. When traffic at a PE router increases sharply and exceeds
the threshhold, the PE router can offload the traffic through a Layer 3
VLAN sub-interface at an Ethernet trunk interface.
3.2 VLAN Awareness
As aforementioned, when PE-PE traffic increases sharply and exceeds the
threshhold, the traffic is offloaded. That is, the router creates a VLAN sub-
interface and notifies the interconnected OTN/WDM equipment to create a
VLAN-based ODUk path. When the path is successfully created, the router
offloads the traffic over to the ODUk path. When successfully creating a
VLAN sub-interface, the OTN/WDM equipment notifies the PE router. Then,
the relevant PE routers offload the traffic to the new path, as shown in
Figure 3-1.
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3.2.1 Technical Implementation
A VLAN-aware board on the OTN/WDM equipment generates a table of
mapping relationships between VLAN IDs and ODUk paths. When receiving
a VLAN ID from a PE router, the OTN/WDM equipment searches the table for
the VLAN ID and then creates an ODUk path for the VLAN ID. When finishing
creating the ODUk path, the OTN/WDM equipment notifies PE router. When
receiving packets with the VLAN ID, the OTN/WDM equipment sends the
packets over to the ODUk path in mapping with the VLAN ID.
Figure 3-2 Mapping of VLAN packets at a VLAN-aware board
VLAN sub-interface
Client
Fabric
Untagged
VLAN 1
VLAN #
ODU2
ODUFlex 1
ODUFlex #
Line
VLAN sub-interface
Physical interface
10GE 10GE
P
PE1 PE2
Figure 3-1 VLAN awareness
10GInterface
PE - Router PE - RouterWDM/OTN
WDM WDM WDM
OTN OTN OTN
WDM/OTN WDM/OTN
ODUk PIPE1
ODUk PIPE2ODUk PIPE3Classifier
OUT Board
IP/MPLS
VLAN VLAN
L2 L2
PHY PHY
VLAN
L2
PHY
IP/MPLS
VLAN
L2
PHY
As shown in Figure 3-2, one physical interface at a PE router can send both
untagged packets (packets carried over the main interface) and tagged packets
(packets carried over VLAN sub-interfaces). A VLAN-aware board on the OTN/
WDM equipment must identify the packets and map them to ODUk paths
accordingly. In addition, VLAN IDs point to different ODUk paths. Therefore, a
PE router must ensure that the VLAN IDs allocated by it are unique.
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Similarly, in the receive direction, when receiving packets over an ODUk path,
a PE router sticks VLAN tags onto the packets according to interface-VLAN
relationships and then sends the tagged packets through interfaces.
3.3 PE-PE Traffic Forwarding
On an IP backbone network, how traffic is forwarded depends on how it is accessed.
Traffic access through VPN •
When traffic is accessed through VPN to an IP backbone network, it is
forwarded over MPLS LDP LSP by default, regardless of the traffic types.
To forward VPN traffic over RSVP-TE tunnel, options are as follows:
- Tunnel policy: To forward certain PE-PE VPN traffic over specified TE
tunnels, configure a tunnel policy and apply it to relevant VPNs.
- IGP shortcut: To forward traffic with the same destination over a TE
tunnel, enable IGP shortcut at interfaces along the TE tunnel.
- FA (similar to IGP shortcut)
- Static route: To forward all traffic with the same destination PE router
over a TE tunnel, configure a static route with a protocol priority higher
than that of IGP.
Direct traffic access •
If traffic is accessed directly to a backbone network, the traffic can be
forwarded in two ways:
- Native forwarding
On an IP backbone network, traffic is forwarded only as IP traffic.
Internet traffic is commonly forwarded in this way. Generally, non-VPN
traffic is forwarded as IP traffic on a public network with precedence.
- MPLS one-label forwarding
When traffic is directly accessed to an IP backbone network, the
traffic is forwarded in MPLS one-label forwarding mode. The label
instructs forwarding on the public network. That is, the label instructs
forwarding to a specified PE router. On an IP backbone network, PE-PE
traffic is forwarded over RSVP-TE tunnels. The traffic with the same PE
destination can be forwarded over the same RSVP-TE tunnel.
Generally, non-VPN traffic also can be forwarded over RSVP-TE tunnels
(one-label forwarding) on a public network by means of IGP shortcut,
FA or static route.
3.4 Netstream
To improve bandwidth utilization of a network, a network must be optimized.
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To optimize a network, traffic on the network must be policed. That is, accurate
information about traffic must be obtained through statistical analysis over traffic.
In the VLAN sub-interface offloading solution, when certain PE-PE traffic
increases sharply and exceeds the preset threshhold, the traffic is offloaded.
How to preset the traffic threshold? When is traffic offloading triggered and
how? Netstream is the answer.
Netstream is a technology similar to Netflow, which is used to collect statistics
on and advertises network stream information. To be specific, Netstream
enables classification and statistics on traffic volume and resource usage on
a network, and thereby enables management and billing of various services
with different QoS.
3.4.1 Technical Implementation
To implement Netstream, a PE router must be able to collect stream
information and save the information in mode of V5, V8, or V9. The
Netstream server, according to a certain sampling ratio, performs statistical
analysis over the traffic data sent by a PE router, generates a traffic report by
certain traffic aggregation conditions, and then sends the report to the NMS.
Corresponding to three achieved stages of the VLAN sub-interface offloading,
traffic monitoring can be divided into manual monitoring, semi-automatic
monitoring, and automatic monitoring:
Figure 3-3 Traffic policing - Netstream
NMS/Operator
Netflow/NetstreamCollect & AnalyzeServer
Netflow/NetstreamV5/V8/V9
PE2 PE3P1
P2PE1 PE4
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Manual monitoring: Netstream Server report traffic over-threshold •
alarms by means of SNMP Trap, and the user manually trigger the traffic
switching through the NMS, such as adjustment of the route-policy,
configuration of DWDM channels, and so on.
Semi-automatic monitoring: based on manual monitoring, NMS launch GMPLS •
and UNI features for the network equipment such as routers and OTN/DWDM
equipment, and realize transmission of VLAN_IDs and bandwidth information
between IP/MPLS layer and Optical layer to achieve partial automation.
Automatic monitoring: In the semi-automatic basis, by setting interface •
between Netstream server, multi-layer PCE and multi-layer planning
tools and NMS, to realize the traffic over-threshold alarms reporting
automatically, multi-layer and multi-domain paths calculating automatically,
multi-layer and multi-domain interactive information transferring
automatically, and the traffic offloading auto triggering, through the above,
achieve the greatest degree of intelligence consequently.
3.5 QoS-Related Technologies
On an IP backbone network, QoS is commonly ensured as follows:
At the traffic incoming side, traffic is classified by an attribute such as IP DSP or •
MPLS EXP and CAR is executed for the traffic for the purpose of traffic policing.
At the intersecting area of an IP domain and an MPLS domain, traffic is mapped •
by IP DSCP or MPLS EXP according to certain rules and then is classified.
At the traffic outgoing side, streams are dispatched to queues, traffic •
is scheduled among queues, and traffic is shaped. To avoid network
congestion, congestion avoidance must be also conducted.
Figure 3-4 shows end-to-end deployment of QoS on an IP backbone VPN.
Figure 3-4 End-to-end deployment of QoS
E2E QoS Planning and Deployment
MPLS Network
CE CE
PE PE
PE PE
P1 P3
P2 P4
PE-CE802.1P-MPLS EXPIP DSCP-MPLS EXPCar & Mapping
Diff-ServScheduling congestionavoiding, shaping
Diff-ServScheduling congestionavoiding, shaping
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3.5.1 Technical Implementation
In the VLAN sub-interface offloading solution, one physical interface on a PE
router carries traffic on the main interface and traffic on one or multiple VLAN
sub-interfaces. That is, the main interface and VLAN sub-interfaces share
bandwidth. Then, QoS must be deployed on the PE router to ensure QoS as
good as before, after services are offloaded, and to reduce total OpEx on the
network and thereby to maximize profits for operators.
When PE-PE traffic is offloaded, maybe the total PE-PE traffic is offloaded
to the VLAN sub-interface; maybe only certain burst traffic, such as Internet
traffic, is offloaded to a VLAN sub-interface, and other traffic is still forwarded
by a P router.
When total traffic is offloaded, there are multiple types of services on the
VLAN sub-interface and thereby queue scheduling or CAR is required. For
more information, see Figure 3-5.
Figure 3-5 End-to-end deployment of QoS for total traffic offloading
Bandwidthof Physical
port
CIR/PIRVoice traffic AF1 PQ/WFQ/LPQ
Internet traffic AF3 PQ/WFQ/LPQ
VPN traffic AF4 PQ/WFQ/LPQ
CIR/PIR
VLAN sub-interface1
Voice traffic AF1 PQ/WFQ/LPQ
Internet traffic AF3 PQ/WFQ/LPQ
VPN traffic AF4 PQ/WFQ/LPQ
CIR/PIR
VLAN sub-interface2
Internet traffic AF3 PQ/WFQ/LPQ
VPN traffic AF4 PQ/WFQ/LPQ
VLAN sub-interface
Physicalport
Primaryinterface
Different traffic mappinginto different queue
As showed in Figure 3-6, when only certain burst traffic is offloaded, there
is only one type of service on the VLAN sub-interface and queue scheduling
is unnecessary. In this way, the key difference is that the only certain burst
traffic, such as Internet traffic is offloaded on VLAN sub-interfaces so we need
not configure queuing policy on VLAN sub-interfaces, only CAR is ok.
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VLAN sub-interface2
Bandwidthof Physical
port
CIR/PIR
CIR/PIR
CIR/PIR
VLAN sub-interface1
VPN traffic AF4
Voice traffic AF1 PQ/WFQ/LPQ
Internet traffic AF3 PQ/WFQ/LPQ
VPN traffic AF4 PQ/WFQ/LPQ
VPN traffic AF4
VLAN sub-interface
Physicalport
Primaryinterface
Different traffic mappinginto different queue
Figure 3-6 End-to-end deployment of QoS for only certain burst traffic offloading
3.6 GMPLS-UNI-Related Technologies
In the VLAN sub-interface offloading solution, when PE-PE traffic needs to be
offloaded, a PE router transfers VLAN IDs to the interconnected OTN/WDM
equipment. The transfer can be based on manual operations or the GMPLS-
UNI signaling. When the transfer is based on the GMPLS-UNI signaling,
VLAN IDs are transferred in GMPLS RSVP-TE signaling messages. For more
information, see the draft-ietf-ccamp-gmpls-mef-uni-02.txt and draft-ietf-
ccamp-gmpls-ether-svcs-03.txt.
For more information regarding GMPLS-UNI, see Technical White Paper for
the Unified Control Plane of the SingleBackbone Solution
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4 Summary
The VLAN sub-interface offloading solution is mainly applicable to a fixed-
line backbone network carrying Internet traffic or a mobile backbone network
with dominance of Internet traffic. In this solution, a PE router can offload
traffic through a VLAN sub-interface without a new physical interface and
a P router offloads transit traffic onto the low-cost transmission equipment,
reducing CapEx for operators to a great extent. This is the major advantage of
this solution. In addition, this solution maintains the current overlay network
structure and is easy to deploy, because it is compatible with equipment on
the live network. This considerably reduces OpEx for operators. The VLAN
sub-interface offloading solution, with these advantages, is acknowledged by
more and more operators, and will be widely deployed on live networks.
In summary, the VLAN sub-interface offloading is one traffic synergy
implement method of IP&OTN synergy of Huawei's SingleBackbone Solution.
More detailed information of SingleBackbone Solution, you can refer to the
Technical White Paper for the SingleBackbone Solution
http://www.huawei.com/broadband/iptime_backbone_solution.do
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5 Acronyms and Abbreviations
ARPU Average Revenue Per User
BFD Bidirectional Forwarding Detection
BGP Border Gateway Protocol
CAGR Compound Annual Growth Rate
CAR Committed Access Rate
DWDM Dense Wavelength Division Multiplexing
EBGP External BGP
FA Forwarding Adjacency
FRR Fast ReRoute
GMPLS General MultiProtocal Label Switching
HQoS Hierarchical QoS
IBGP Interior BGP
IGP Interior Gateway Protocol
IS-IS Intermediate System to Intermediate System
MP-BGP Multi-protocol Extensions for Border Gateway Protocol
OSPF Open Shortest Path First
QoS Quality of Service
UNI User-Network Interface
VPN Virtual Private Network
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Technical White Paper for VLAN Sub-Interface Offloading
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