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


3.5 QoS-Related Technologies .............................................................................................8


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

2

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

3

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.

4

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.

5

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.

6

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.

7

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.


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

8

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

9


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



CIR/PIR

VLAN sub-interface2



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.

10

VLAN sub-interface2

Bandwidthof Physical

port

CIR/PIR

CIR/PIR

CIR/PIR

VLAN sub-interface1

VPN traffic AF4

Voice traffic AF1 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

11

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

12

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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