7SC7,3

Adaptive transparent photonic network control techmiques based

on photonic-GMPLS-router network

Naoaki Yamanaka, Satoru Okamoto, Kohei Shiomoto, Elji Oki and WatanL Imajuku

NTT Network Innovation Laboratories

3-9-1 1 Midori-cho, Musashino-ski, Tokyo, 180-8585 Japan･

+8 1 -422-59-2047/+8 1 -422-59-6387

yamanaka. naoaki @lab ･ntt･ co.j p

Abstract: This paper describes multillayer traffic

englneenngand very cost-effective adaptlVe transparent

photonic network control teclmiques based on newsignaling teclmologleS　in　the photonic-GMPLS

(generalized multi-prot∝Ol label switcll)-rOuter netWOrk･

To realize multilayer traffic englneerlng, We Propose an

ospF extension that advertises boththe number of total

wavelengths and也e number of unreseⅣed waveleng血S･

According to the OSPF advertisement;the ingress edge

node canselect best link to establish a transparent optical

cut-tllrOughpath,anoptical direct pathwithout anywavelengthConversion･ ln addition,the paper describes the

RSVP-TE extension, which uses the least totalnumber of

wavelengthconversions. Compared tothe electrical MPLS

network, this approach yields cost reductions of the order

of80 %.

Keywords: Phiotonic, MPLS, GMPLS

I. IntroductioJl

nLe explosion of htemet traffic has led to a greater need

for a high-speed backbone network･ The growth in

lntemet-protocol (IP) traffic exceeds that of IP packet

processing capability･ Therefore,the next-generationbackbone networks should consist of lP routerswithIPI

packet switching capabilityand opticalcross-connects(OXC) with wavelength-path　Switching capability to

reduce the burden of heavy lP-packet switching loads･ In

addition, IP traffic nuctuates often over periods as short as

houm.

These needsare satisfied bythe photonic GMPLS router

developed by NTT l1]; it offers both IP packet switching

and waveleng血-pa血　switcbing capabilities 【2][3]･

Waveleng血　pa血S, called optical label switch pa血s

(OLSP)are set and released in a distributed manner based

on the functions offered bythe generalized multi-protocol

label switch (GMPLS). Sincethe photonic MPLS router

offers the functions of both switching and GMPLS, it

enables us to create the optlmum network configuration

dynamically by considering IP and photo山c netwo止

resources in a distributed manner.

An OSPF extension and a very sophisticated signaling

mechanism using RSVP-TE extension have been proposed

and now going to be implemented l4][5]･ The OSPF

extension is to advertise both the total number of

wavelengths andthe number of un陀Served wavelengths

for each link. TLis information lS PaSSedvia OSPF packets

toall ingress edge nodes so they are awaue of the GMPLS

link state. Ingress edge nodes ～ to establish new OLSPs

by applyingthe least-loadrule･ The least loaded OLSP has

the most vacant wavelengdlS. For OLSP setup, RSVP-TE

extension signaling protocol is used. The signaling packet

selectsthe proper wavelength that usesthe least number of

wavelength converters because wavelengthConversion is a

very expensive operation･ OLSP without wavelength

conversion is named the optical transparent cut-through

path (OTCP)･ OTCPs are realized by the passive networkcomponents and so are veJy Simple･ Establishing OTCP is

effectiveinterms of network cost reduction.

Combiming the OSPF extension routing PrOtOCOlwith the

RSVPITE signaling protocol allows the optimum level of

OLSP usage wi血1ess welength conversion to be

established adaptively. This can bring an approximately 80

%　Cost reduction compared to the electrical MPLS

network.

2. TrafTIC-driyeJl multilayer network

The pllOtOnic-GMPLS-router network is shownin若短ure

1. Some border IP router pal一s use a transit IP router to

carry their lP trafrlC.All electrical MPLS (EMPLS) paths

between border routers are monitored by the border lP

routerfunction and establish traffic exchanging matrix as

shownin源塗. 1.And when the traffic volume becomes

heavy, a cut-throughpathis set by using the GMPLSsignaling protocol of the RSVP-TE extension l6][7] as

shownin欝賂2. Notethat all ELSPand OLSP are

controlled and managed bythe same operation paradigm

based on GMPLS. This realizes very simple network

management as well as dynamic network control for multi-

layer operation. Dぬils or血e slgnaling and routlng

mechanism are described below.

Monitor ELSP tra丘ic

OLSP establish　- -

Bsvp-T司-　　　　.rL GMPLS Signaling

Figure 2 0ptiCalcut-throtlgh path technique

OLSP paths are very llighperfomance and cost-effectivecompared to the ELSP･ Becausethe OLSP pathSare

switched as waveleng血paths, no layer 3 protocol Ilandling

is needed. According to our estimation, in the future,the

photonic cut-throughteclmiquewill reduce the volume ofOCl1 92C forwarding by about 1/3.摂蛤ure 1 also shows the

results of our detailed study on the cost effectiveness

achieved by using the proposed photonic multi-layer

GMPLS router. the calculation is based on lP traffic

demandinthe year2005 and state-of-the-art electrical

routers as well as photonic teclmology. The Cluster ratio isthe crtlss traffic between routers, and so does not offer

effective lP forwarding between users. the Cluster ratio is

generally 2/3 in today's lntemet infrastructure traffic.

According to our calculation, we can expect a cost

reduction ofmorethan 60% by using the photonic GMPLS

multi-layer router. Given today's backbone network trafTlC

pattem, we expect　that photonic cut-throughwill be

applicable 60 to 70% of the time. In addition, multi-layer

operation can reduce today's duplicative network

management to one universal GMPLS operation. This

simpliflCation will dramatically reduce network cost.

OLSP (Cut-through)

3･ GMPLS-based photonic multilayer router

architecture

The basic logical structure of the photonic GMPLS multi-

layer router is shownin Fi釦re 3. It consists of an IP

router, wavelengthrouter, and photonic-GMPLS-router

manager･

The router is based on a photonic universal platformwith

the addition of　3R (Retiming, Reshaping　and

Regeneration)functions, wavelength conversion function,

and layer13functions･ These functions are used adaptively･

ln other words, if the transmission slgnal is degraded by

fiber loss as well as nonlinear effects such as PMD

bolarization mode dispersion) or ASE (Amplifiedspontaneous emission), die 3Rfunction is activated. In

addition, waveleng血　Conversion is also used when

slgnaling is blocked by wavelengthoverbooking･ Of

course, layer 3 (L3) packet forwarding is adaptively used

when L3 packet forwarding is necessarily.

Notethat the photonicIGMPLS router can transfer 3types

of signal as shownin難･ 3･ Type-A is transparent transfer

or bit-rate restrictionfree･ Thistype of path is very cost

S o舟ware structtue

LRU=WDM+Optical SW+Ll･Trunk

Ⅰ諾eg紹EcraP3PRaCok,eiZovTea;dgi.nhgLnve,si.n pa.h, EEwT=EsoLwqsbtddiangREuntiTngeunit

Type-C (Optical transparent path, Bit-rate restriction free)九一conv : Lambda converter

NE : Network Ekment

Figure 3 LogiCalStructure of photonic MPLS routerwith multi-layer trafGc engineering based on GMPLS management function

effective, because it needs only passive elementswithout

any electrical digital　function. Type-B is　九　relay

connectionsthat need wavelengthConversion. Today's

wavelength conversion needs O侶and costly electricaland

tunable laser devices. This isthe weakness of Type-B

connectionsI Type-B connections are also supported by

adaptive use of the 3Rfunction. Finally,type-C involves

layer 3 switching functions for operations such as MPLS

pa血aggregationand L3 packet level forwarding. The

photonicIGMPLS JIOuter Can　SuPpOrt all transfer

capabilities. To improve the networkrs cost effectiveness,

the proposed GMPLS manager tries to establish Type-A

transparent photonic cuHhrough　paths. Details are

described in session 4.

In the photonicIMPLS-router manager, die GMPLS

controller distributes ownlP and photonic link states, and

collects the link states of odler Photonic MPLS routers. lP

traffic is always monitored, andthe captured data is passed

tothe GMPLS controller througha lowIPaSS fllter l6]. Amultillayer topology design algoritlm　processes the

collected IP and pl10bI止c liI止states and the collected

trafrlC data.

(a) L3 forwarding

4･ Adaptive transpareJlt PhotoJlic cut-throughpathbased on exteJISioJI Of GMPLS

Optical wavelength conversion is very costly and needs a

lot of hardware today･ In other words, the transparent bit-

rate restriction free network is very attractive from the

viewpoints of low cost and highflexibility･ Accordingly,

Our OSPF extension and RSVPITE extension canprovide

effective route selection as well as the least number of

wavelengthconversions.

me optlCal transparent cut-through path is shownin葦軸. 4.

Cb) showsthe optical.ローrelay network, which needs

wavelengthconversion for each node･ Today, wavelength

conversion is very costly, especially if based on tunable

lasers･ The network should use as many transparent paths,

shownin(C), as possible･ Transparent cut-through leaves

the wavelengthunchanged. The switch function transfers

the same wavelengdl Signal tothe output port･ This is very

simple and cost effective.

OptiCal　tr禦SParent Cut-through path con減Buration is

shownin蜜重苦･ 5･ A氏erthe cut-through block, onlyan

optical amplifier is needed inthe path･ ln other words,this

transparent pathCanestablish a direct optical path between

[麺]巨]弓

(b)九-relay

Figure 4 Cut-throughtecknique for GMPLS network

(a) Opticaltransparent path

Ingress edge router to egress edge router. All components

inthe path are passive devices. Of course, transmission

effects such as loss and cross-talk limit the hop number of

the transparent cut-throughpaths

First, for route advertisement, the OSPF extension is used

as shown　in寮豆･ 6･ Each photonic GMPLS router

advertises its total　number of used and unreserved

wavelengthS･ According to this advertisement, edge nodes

can discem GMPLS link state and canselect the least

expensive path. In addition, We have already proposed to

extendthe sub-TLV of IETF specification l4]. The

extensionsinclude 3R resourceinformation and statistical

information such as utilization of each wavelength, and 3R

and wavelengthconversion resources. Thisinformation

Will be used for source routing based on a combination of

shortest path flrStand loadinfomation.

The GMPLS link state is calculatedand detemined at theIngress edge node･ For the example in捌輩. 6, Route-A has

small hop number but large load. On the other hand Route-

B has larger hop number but the least load. We employ the

least load policy as the optical routing POlicy. Route-B

may be expected to allow more cut-throughpaths to be setbetween Ingress and Egress router.

For the signaling　function, we offer　the RSVP-TE

extension showninFi欝･ 71Link-by-link routing lS used

based on source routing･ the flrSt Photomic GMPLS router

sets the unused wavelength information in RSVP signaling

uslng the bit map format･ Each transit photonic GMPLS

I

l

I

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:入1

r-(_-_ -_ ヽ

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l｣____

r-(_-_ =tl　　　1

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r-I_こ._ ヽ●　:

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I----l　入l IH-HI　九l rM1人1---i-iq---･トぶ｣

L___l I LM王r L__;I il I llJ______I

F:　　　　Thnsmission Seg-t　　　　　弓

Figure 5 Optical transparent cut-throughpathcon丘gtmtion

NW: Number of wave,engths

NUW: Number of unreseⅣed wavelengths

WC: Wavelength Converter

Figure 6 0SPF routlng extension for advertising wavelength resource utilization

router over-wdtes this information by placing "And"

between amvlng Signaling unused wavelengthbitmap and

its own　unused wavelengths. lfthere is no　unused

wavelength, wavelength conversion is used. A routerthat

offers wavelength conversion creates a new unused

wavelength bitmap and sends it to the next router.

This signaling and routing teChniqueminimizesthe need

for wavelength conversion in the network and so can

provide very cost-effective photonic networks.若塗ure 8

shows the cost reduction effect possible by introducing

optical transparent cut-through paths. Because optical

transparent pa血s need no costly electrical components,血e

dramatic cost reduction of approximately 80 % can be

achieved.

5. Conclusions

This paper presented multi-layer traffic englneenng,

slgnalingand routing technologies in photonic-GMPLS-

router networks to realize cost effective optical transparent

cut-throughpathS. The photonic-GMPLS-router networkarchitecture is based on OSPF and RSVP-TE extensions.

Ⅵle rOutlng and signaling teclmique proposed herein yields

RSVP-TE extension

Link A Link B

Vacant Wavelengthblt map T

llOOIOll 00111000

the least nulI血er or waveleng血conversions and so

achieves very cost-effective photonic networks. By

monitonng IP traffic loads, photonic MPLS routers can

dynamically change the network configuration; network

resourcesare utilized efficiently in a distributed manner.

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慧Ity圏に妄まC璽▼ Vacant Waveleng血bit map

(LinkB) 10100001 1 1000110

匹司11001011 00111000　-･ifnounusedwavelengths matchthen

(Link A and B) iOOOOOOI 00000000 use wavelengthConversion (au"0")＼＼/

Select血ese waveleng血S

Figure 7 RSVPITE signaling extension for adaptive wavelength selection for optical tr弧Sparent Cut-throughpath

100%

Transparent path ratio

(Transparen廿′Wavelength connection path)

Figure 8 Cost reduction achieved by optical transparent cut-through paths

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