BaocaoMPLSTE

CHNG I - TNG QUAN V MPLS TE

1. K thut lu lng trong MPLS

1.1 Khi nim v k thut lu lng.

Khi i mt vi s pht trin v m rng mng, c hai vn k thut cn quan tm:

k thut mng ( network engineering) v k thut lu lng (traffic engineering).

- K thut mng l xy dng, t chc mng sao cho ph hp vi lu lng. Ban u

phi c s d on tt nht v lu lng trn mng s dng cc mch ( cc lin kt vt l)

v cc thit b mng ( router, switch,) thch hp. K thut mng phi m bo hiu qu v

sau ny v vic nng cp, lp t thm mi trong mng i hi nhiu thi gian cng nh l chi

ph kh ln.

- K thut lu lng l thao tc trn lu lng ph hp vi mng.

D c gng n u th lu lng mng cng khng bao gi c p ng hon ton

(100%) so vi d tnh. Gia thp nin 90 s tng trng lu lng vt qua mi s d tnh v

khng th nng cp kp thi c. i khi mt s kin ln xy ra ( s kin th thao, v b bi

chnh tr, mt trang web vi s lng truy cp qu ln) lm y lu lng trn mng, iu

ny khng th tnh ton c. Do , c th t mt ni nhu cu bng thng qu nhiu nhng

trong khi c cc ng lin kt (link) khc vn cha c s dng. K thut lu lng

thc hin mt cch mm do chuyn lu lng t cc lin kt b qu ti sang cc lin kt ri.

K thut lu lng c th c b sung: IP metric trn giao tip chy mt mt li ATM PVC

v xc nh li ng PVC da trn yu cu v lu lng i qua n. K thut lu lng trong

MPLS nhm t n k thut iu khin lu lng hng kt ni tt nht v kt hp vi nh

tuyn IP.

1.2. K thut lu lng trc MPLS TE

Ta xem xt cc k thut lu lng ca IP v ATM:

K thut lu lng IP ph bin nhng cht lng kh km. nh tuyn IP da vo chi ph (

cost), ng i no c cost thp nht s c chn v a vo bng nh tuyn, phc v

cho vic chuyn tip gi tin. Bn cnh , cc gi tin IP c chuyn tip ti mi node

(router) ch da trn a ch ch v n hon ton c lp vi cc gi tin c chuyn tip

trc cng nh sau . Do vy, mt router c th tip tc chuyn tip lu lng IP vo mt

lin kt, mc d lin kt b mt gi d liu do thiu bng thng. Kt qu l mt s lin

kt c th qu ti, gy nghn trong mng, trong khi cc lin kt khc c th khng c s

dng ng mc. gii quyt vn m khng cn phi nng cp mng tng thm

bng thng, ta c th thc hin cn bng ti (load balancing), bng cch thay i cost ca

cc lin kt c cc ng vi cost nh nhau; hoc c th s dng n c ch PBR ( Policy

Base Routing nh tuyn da trn chnh sch). Tuy nhin, bin php ny ch c th p dng

cho mng nh, v phi khai bo th cng v khi s dng cho mt mng ln th c th nh

hng n tuyn khc.

Ngc li, ATM thit lp cc PVC trn mng cho php lung traffic lu thng t mt

ngun n mt ch no , ngha l t c quyn iu khin cc lung lu lng tt hn.

Vi nh cung cp dch v (ISP) ln trn th gii s dng ATM qun l lu lng trn

mng ca h bng cch xy dng mng li y (full-mesh) cc ATM PVC gia cc

router, ti nh kch thc v v tr cc ATM PVC mt cch nh k da trn thng tin lu

lng do cc router cung cp. Bn cnh c th thit lp cc PVC t mt ngun no n

ch trnh nghn mng. Tuy nhin, mt vn xy ra i vi s full-mesh l flooding

O(N2) khi mt link down v O(N3) khi mt router ngng hot ng, gy trn ngp mng.

1.3. K thut lu lng vi MPLS.

MPLS TE kt hp kh nng iu khin lu lng ca ATM vi s mm do ca IP v

s phn bit cc lp dch v (CoS). MPLS cho php xy dng cc con ng chuyn mch

nhn ( LSP- Label Switch Path) trong mng gim lu lng chuyn tip. MPLS TE dng

mt ng hm TE iu khin lu lng t ngun xc nh n mt ch c th. Phng

php ny mm do hn k thut lu lng chuyn tip ch da trn a ch dch. MPLS TE

cng trnh c flooding O(N2) v O(N3) trong ATM. N s dng c ch gi l nh tuyn

ng (auto-route) xy dng bng nh tuyn bng MPLS TE LSP m khng cn mng li

y cc lng ging (neighbor). MPLS TE d tr bng thng khi xy dng LSP.

Tng quan v hot ng ca MPLS TE:

Hnh 1.1 M t hot ng ca MPLS TE.

MPLS TE l k thut nh tuyn, iu hng lu lng da trn cc rng buc v ti

nguyn, hay c s m bo v ti nguyn d tr ( Routing with Resource Reservation). Cc

rng buc y l bng thng ng truyn hoc mt s thng s khc ca kt ni ( TE

(link) attributions).

u tin, cc thuc tnh ca c cu hnh trn cc lin kt c s c cc LSR

qung b cho nhau thng qua giao thc trng thi ng link ( link state protocol). Cc giao

thc link state nh OSPF v IS-IS c m rng thc hin nhim v ny. Mt Head end

LSR ( LSR c thit lp TE tunnel vi a ch LSR ch n v cc rng buc c m

bo) da trn cc thng tin qung b trn xy dng mt c s d liu TE. T , n s

dng thut ton tnh ton ng PCALC hoc CSPF tm ra tuyn (LSP) ngn nht t

ngun xc dnh ( Head end LSR) n mt ch c th ( Tail end LSR) m vn tha mn cc

rng buc. Vic tnh ton ny c thc hin trn HE ( Head end LSR) v hon ton c lp

vi cc LSR khc.

Do hot ng trong mi trng nhn (MPLS) nn trn mi LSP ng vi Tunnel nht nh,

cc LSR chuyn tip ( Intermediate LSR) cn bit c nhn ti cng nh l nhn ra thc

hin vic hon i nhn. cc Intermediate LSR (INTER) c th hc c nhn th gia

chng v HE cn phi c mt giao thc bo hiu. Giao thc RSVP ( Resource Reservation

Protocol) c pht trin v m rng, cho php mang thng tin nhn MPLS v mt s thng

tin TE khc ( nh Explicit Route, Record Route object). RSVP thc hin bo hiu xuyn

sut trn LSP nhm ly thng tin v nhn cng nh l kim tra xem ti cc node cc ti

nguyn c cn p ng cho Tunnel hot ng c hay khng? (do s thay i thng tin TE

cc lin kt khng phi lc no cng c OSPF hoc IS-IS qung b kp thi), t m

HE c th ti u, chn li tuyn khc. Vic ny c thc hin thng qua gi cc bn tin

RSVP PATH message, RSVP RESV message hoc cc thng ip RSVP khc, s c trnh

by cc chng sau.

Khi nghin cu v k thut lu lng MPLS TE ta cn quan tm n 3 vn chnh:

(1) S phn phi thng tin ( Information distribution): Cch cc b nh tuyn nhn din ra

mng v cc ti nguyn no sn sng.

(2) Tnh ton v thit lp tuyn ( Path calculation and setup): Cch cc b nh tuyn quyt

nh to cc ng hm TE, cch xy dng v duy tr cc ng hm ny mt cch chnh

xc.

(3) Chuyn tip lu lng vo mt ng hm (Forwarding traffic down a tunnel): Sauk hi

ng hm c xy dng th s dng chng nh th no?

CHNG II PHN PHI THNG TIN TRONG MPLS TE

2. Phn phi thng tin trong k thut lu lng (TE):

Cc giao thc nh tuyn link state l cn thit cho vic thng tin nhng thuc tnh ca cc

lin kt trong mng n tt c cc router ang trin khai k thut lu lng.

2.1. Nhng yu cu i vi IGP trong MPLS TE:

IGP c kh nng gi thng tin topo mng cng nh thuc tnh ca cc lin n tt c cc

router khc trong mt vng, nh vy mi router trong vng c th tnh ton c nhng tuyn

i kh thi.

Trong IGP, ch giao thc link state c th thc hin nhim v ny khi c trin khai k

thut lu lng, v n gi trn trng thi tt c cc lin kt ca mt router n ton b cc

router khc trong mt vng. Do , mi router trong vng bit c tt c cc ng c th i

n ch.

Giao thc nh tuyn distance vector khng th dng khi trin khai k thut lu lng .

V n c thit k ch gi thng tin nhng tuyn m n cho l tt nht, do thng tin v

nhng tuyn kh thi khc b b st.

Cc giao thc nh tuyn dng Link-State (OSPF v IS-IS) c m rng cho MPLS-

TE khng ch qung b cc thng tin v lin kt thng thng m n cn mang thm thng

tin rng buc ca cc lin kt trong min MPLS nh l:

TE Metric: l mt thng s s dng cho vic xy dng topo TE, do ngiqun tr t

v mc nh TE metric bng vi IGP metric.

Maximum Bandwidth: l tng bng thng c dng cho lin kt trn mt hng

truyn. Trong Cisco tham s ny l gi tr vt l hoc l gi tr c thit lp lin kt.

Maximum Reservable Bandwidth: Bng thng dnh ring ti a trn lin kt,thng

gi tr mc nh nn l gi tr Maximum Bandwidth, n v l byte/s. C th ci t

thng s ny bng lnh ip rsvp bandwidth

Unreserved Bandwidth: phn bng thng kh dng cn li trn lin kt.

Administrative Group: l mt vng 32 bit khng c cu trc c th. Ngi iu khin

c th ci t ring r tng bit trong vng ny mang mt ngha do ngi t

chn.

2.2. Phn m rng ca OSPF cho TE:

OSPF m rng cho php mang thm thng tin thuc tnh ca lin kt c cu hnh trn

mt router. Cc thng tin c cung cp bi phn m rng c th c s dng xy dng

mt c s d liu trng thi lin kt m rng, ging nh c s d liu trng thi lin kt

S khc bit l c s d liu trng thi lin kt c m rng (cn c gi l c s d

liu k thut lu lng) c thm cc thuc tnh lin kt. Ngi ta c th s dng c s d liu

k thut lu lng :

Gim st cc thuc tnh lin kt.

nh tuyn ngun da vo cc rng buc.

Phn m rng ny gm 3 dng bn tin Opaque LSA l loi 9, loi 10 v loi 11, chng

khc nhau phm vi lan truyn:

Loi 9: ch qung b trong phm vi ni b (link-local).

Loi 10: qung b trong phm vi mng din rng v dng li cc router bin.

Loi 11: qung b khp min OSPF.

Hnh 2.1: Cu trc chung ca mt Opaque LSA

LSA ID ca 1 opaque LSA c nh ngha gm c 8 bit m t kiu d diu (Opaque

type) v 24 bit m t d liu c th (Opaque ID). Trong k thut lu lng LSA c

opaque type l 1. Cn li 24 bit l trng i tng, l mt gi tr ty dng duy

tr nhiu LSA TE. Gi tr ln nht ca LSAs TE la 16777216.

Trong trng Option c thm mt bit mi l O-bit, bit ny ch ra mt router c kh

nng truyn v nhn cc Opaque LSA hay khng.

* O DC EA N/P MC E *

Hnh 2.2: Cu trc TLV Header (Type length values)

Gm Router Address TLV v Link TLV

Router Address TLV: Ch ra mt a ch IP n nh ca router qung b m lun c

th kt ni nu c bt k mt kt ni no ti n v thng dng mt a ch loopback.

Trong cc giao thc khc, Router Address c xem nh mt Router ID.

Link TLV: Link TLV m t mt lin kt n, c xc nh bi mt tp cc sub-TLV,

cc sub-TLV ny mi thc s mang thng tin thuc tnh ca lin kt. Ch c mt link

TLV c mang trong mt LSA.

STT Tn Sub-TLV di (Octet)

1 Link Type 1

2 Link ID 4

3 Local Interface IP Address 4

4 Remote Interface IP Address 4

5 Traffic Engineering Metric 4

6 Maximum Bandwidth 4

7 Maximum Reservable Bandwidth 4

8 Unreserved Bandwidth 32

9 Administrative Group 4

Hnh 2.3: Cc sub-TLV ca link TLV

- Link Type: Ch ra lin kt ny l lin kt im-im hay lin kt im-a im

- Link ID: Xc nh u cui ca lin kt (router ID): vi lin kt im-im th l

router ID ca neighbor, vi lin kt a im th l a ch interface ca router c

ch nh.

- Local Interface IP Address: a ch interface tng ng ca lin kt ti router.

- Remote Interface IP Address: a ch IP ca interface neighbor tng ng trn lin kt

- Unreserved Bandwidth: Phn bng thng kh dng cn li cha c s dng ti mi

cp trong 8 cp u tin

- Gi tr ng ca bng thng c thit lp theo 8 cp u tin t cao ti thp theo

th t t 0-7, TE-LSP c u tin cao hn c th chim gi bng thng ca u

tin thp hn.Gi tr ca n nh hn hoc bng gi tr ca Maximum Reservable

Bandwidth , ban u c thit lp bng gi tr ca Maximum Reservable Bandwidth.

2.3. M rng giao thc IS-IS cho TE

IS-IS c cc trng Type-lengh-value mi nh km trong cc thng ip PDU link-

state ca n.Phn m rng cho php IS-IS mang cc thng tin thuc tnh lin kt ca MPLS-

TE. Gi tr metric ln nht c m rng thnh 224-1.

C ba loi TLV mi:

u tin l m rng IS Reachability TLV hoc TLV type 22: N l c xy dng t

TLV type 2 (IS Reachability TLV), m t nhng IS-IS neighbor ca n, mang theo

cc sub-TLV cn thit cho MPLS TE.

STT Tn Sub di (octet)

0-2 Unassigned -

3 Administrative group 4

4-5 Unassigned -

6 IPv4 interface address 4

7 Unassigned -

8 IPv4 neighbor address 4

9 Maximum Link Bandwidth 4

10

Reservable Link

Bandwidth 4

11 Unreserved Bandwidth 32

12-17 Unassigned -

18 TE metric 3

19-254 Unassigned -

255 Reserved -

Hnh 2.4: Cc Sub TLV ca TLV loi 22

Unreserved Bandwidth dnh 32 octet trong khi cc tham s bng thng khc ch c 4

octet. Trn thc t th Unreserved Bandwidth biu th mi cp u tin trn 4 octet. C 8

cp u tin t 0 n 7.

TLV mi th hai l m rng IP Reachability TLV (TLV type 135): N l s k tha

t TLV type 128 v 130.

TLV 134 - TE Router ID TLV: TLV ny miu t MPLS router ID vi 4 octet.

2.4. Lan truyn thng tin trong IGP

Giao thc IGP s lan truyn thng tin v TE trong cc trng hp sau:

Thay i trng thi lin kt.

Thay i cu hnh kt ni.

Lan truyn theo chu k: c s dng vi chu k lan truyn mc nh l 3 pht. v khi

lin kt c s thay i nh v bng thng dnh ring th n s khng lan truyn ngay

s thay i ny ra ton mng.

S thay i ca bng thng dnh ring: Khi c s thay i th router s khng lan

truyn ngay thng tin thay i ny ngay nu nh s thay i v bng thng cha

vt ngng thit lp. C 2 ngng thay i l:

- Ngng xung l khi bng thng dnh ring gim: 100, 99, 98, 97, 96, 95, 80,

75, 60, 45, 30, 15.

- Ngng ln khi bng thng dnh ring tng ln mc nh l 15, 30, 45, 60, 75,

80, 85, 90, 95, 97, 98, 99 v 100

Khi thit lp tht bi mt ng hm: Khi Headend-LSR c gng thit lp mt tuyn

LSP m n tnh ton bng bn tin RSVP, nhng vic thit lp ny c th tht bi nu c

mt ng TE-LSP khc chim bng thng ca lin kt m tuyn TE ban u i qua nn s

khng bng thng cn thit cho n. M s thay i bng thng ny khng c thng bo

do cha vt ngng, v vy khi vic thit lp tht bi router trung gian s lan truyn

thng tin mi v Headend-LSR s cp nht d liu v tnh ton mt ng i khc nh CSPF.

2.5. nh tuyn v chi ph ca TE-LSP

2.5.1 Thuc tnh lin kt trong MPLS TE

Mi lin kt trong mng MLS c trin khai k thut lu lng c nhng c tnh c

lan truyn ra cc router, cc router ny khi tnh ton mt tuyn LSP xem xt liu c

th s dng c mt lin kt no cho TE-LSP hay khng. Cc lin kt c nhng cu

hnh c tnh nh sau:

Bng thng dnh ring ln nht (Maximum reservable bandwidth): l bng thng

dnh ring ln nht trong phn dng chung, phn m cc ng TE thng thng

c th s dng.

C thuc tnh (Affinity flag): ch ra lp ti nguyn, kh nng hay chnh sch qun

tr ca lin kt. C thuc tnh Affinity gm 32 bit, mi bit c th c thit lp

theo mc ch ca ngi qun tr. V d bt ny c th ch lin kt ny c tr

nh hn 100ms, cn bit khc ch lin kt c tc cao,

TE metric: hay cn gi l trng s qun tr (Administrative Weight).MPLS TE s

dng TE metric ca lin kt nh tuyn TE-LSP v mc nh TE metric bng

IGP metric. C th thay i TE metric khc vi IGP metric c chnh sch chn

ng tt hn. V d: IGP metric dng phn nh nhng tuyn ng i c bng

thng ln ph hp vi lu lng d liu, cn TE metric phn nh nhng tuyn

ng c tr thp ph vi vi lu lng voice.

Nhm lin kt chia s nguy c: ch nh nhng lin kt c dng chung ng

truyn vt l (v d cp quang). Nu ng truyn ny b t th s nhng lit kt

ny b nh hng cng thi im. SRLG c s dng cho trng hp d phng

FRR

Bng thng sub-pool dnh ring ln nht: l bng thng dnh ring cho nhng

dch v phn bit (DiffServ-aware). N l mt phanh mnh ca bng thng dng

chung.

2.5.2. Thuc tnh ca trung k MPLS TE

Bao gm:

a ch ch ca TE-LSP: l MPLS TE router ID ca tailend-LSR, im ch ca

LSP nh tuyn ti.

Bng thng mong mun: l bng thng yu cu ca TE-LSP

Affinity bit: thuc tnh ny iu khin TE-LSP s dng cc lin kt, cho php

p t cc chnh sch chn ng bng vic bao gm hay loi tr mt s lin kt

no . Thuc tnh Affinity c dng chui bit nh sau: Affinity (32bits), Mask (32

bits). Mask ch nh cc bit no trong lp ti nguyn cn c kim tra. Lin kt

c php s dng nu chui Affinity bit ca TE-LSP trng vi Affinity Flag ca

lin kt sau khi cng thc hin php AND vi Mask. Gi tr mc nh ca Mask l

0x0000FFFF.

u tin thit lp v cm gi (Setup and hold Priority): lc ch u tin cho mt s

ng hm lm vic trc nhng ng hm khc. Mi ng hm c mt u

tin, cc ng hm t quan trng hn b y ra khi ng i v ti nguyn ca

n nhng li cho ng hm quan trng hn. V d: Khi c mt TE-LSP khc

n cnh tranh bng thng trn lin kt vi TE-LSP ban u th Setup Priority ca

TE-LSP mi c so snh vi Hold Priority ca TE-LSP c, nu c u tin cao

hn (ch s nh hn) th TE-LSP mi s c u tin thit lp v TE-LSP c phi

nhng li ti nguyn.

Ti ti u ha (Reoptimization): c trng ca mng l bin ng theo thi gian,

v d c thm cc ti nguyn mi kch hot, nhng lin kt b s c c phc hi,

cc ti nguyn dnh ring trc thu hi v vy khi cc ti nguyn thay i trng

thi th cc LSP thit lp trc khng cn l ti u nht na nn lun duy tr

trng thi ti u nht ca LSP th cn thc hin ti u ti ha li. C th thc hin

theo ba c ch sau:

1) Ti ti u theo chu k: chu k ti ti u c th thay i t 0 n 168 gi, mc

nh l 1 gi. Chu k bng 0 tc l khng s dng chc nng ny.

2) Ti ti u theo s kin: khi mt lin kt c khc phc s c v quay tr li

trng thi up.

3) Ti ti u th cng: ti ti u li ngay khi c yu cu .Ty chn thit lp

ng (Path setup option): ta c th thit lp mt tuyn TE-LSP theohai cch

l: tuyn tng minh v tuyn ng.

CHNG III C CH THIT LP V TNH TON NG I

TRONG MPLS TE

3. Tnh ton v thit lp tuyn

3.1 Tnh ton ng i - Thut ton PCALC (CSPF).

PCALC l mt gii thut SPF c bit c s dng trong MPLS TE. PCALC c th tnh ton v tm ra tuyn khng ch da vo ng ngn nht m cn da vo ti nguyn ca

tuyn , nn c th gi n l mt gii thut CSPF (Constrain Shortest Path First). V c bn,

c hai im khc bit ng quan tm gia SPF do giao thc Link-state vector( c th l OSPF

v IS-IS) thc hin v CSPF ca MPLS TE. Th nht, tin trnh thit lp tuyn khng c

thc hin xy dng bng nh tuyn m ch mt tuyn n cui ng hm (tunnel

endpoint). Th hai, thay v ch quan tm n mt loi chi ph ( cost) trn kt ni gia 2 lng

ging cn phi quan tm n:

Bng thng (Bandwidth).

Cc thuc tnh kt ni (link attributes).

Trng s qun tr ( Administrative weigh hay TE cost)

Bn thuc tnh c th hin trong danh sch PATH/TENT: {link, cost, next hop,

available bandwidth}.

Cc bc thc hin ca thut ton CSPF:

Bc 1: Mt nt t a ra thng tin ca chnh mnh vo danh sch PATH vi cost =

0, next hop l chnh n v thit lp bng thng = N/A.

Bc 2: Xem xt nt va vo danh sch PATH, v gi l nt PATH. Kim tra danh

sch cc nt lng ging ca n. Thm mi lng ging vo danh sch TENT vi mt next

hop ca nt PATH, tr khi nt lng ging c danh sch TENT hoc PATH c chi ph

thp hn. Khng thm ng i ny vo TENT tr khi n c cu hnh rang buc cho

ng hm bng thng (bandwidth) v quan h (affinity). Nu nt va c thm vo

danh sch TENT c trong danh sch, nhng vi mt chi ph cao hn hoc bng thng

thp hn bng thng ti thiu, thay th ng i c chi ph cao hn bng ng i hin

ti.

Bc 3: Tm lng ging trong danh sch TENT vi chi ph thp hn, thm lng ging

vo danh sch PATH, v lp li bc 2. Nu TENT rng hoc PATH cn li l nt

cui cng ng hm th dng.

Hnh 3.1 Minh ha thut ton CSPF.

Quan st hnh ta thy, Router A mun to mt ng hm TE n router D vi bng thng

60 Mbps. Mi kt ni lit k metric v bng thng sn c ca n. D thy, ng i tt nht

t router A n router D l A B C D, vi thng chi ph bng 12, nhng khng tha

bng thng yu cu 60 Mpbs. CSPF cn tnh li ng i ngn nht vi bng thng ti thiu

l 60 Mbps.

Bc 1: t chnh n vo PATH vi gi tr ng i = 0, next hop = self,

bandwidth = N/A.

PATH TENT {A,0,self,N/A} (empty)

Bc 2: t cc lng ging ca router A vo TENT.

PATH TENT {A,0,self,N/A} {B,5,B,100} {C,10,C,100}

Bc 3: Chuyn B t TENT sang PATH, v t lng ging ca B vo TENT.

PATH TENT {A,0,self,N/A} {C,10,C,100} {B,5,B,100} {D,13,B,90}

{C,8,B,50} khng c thm vo TENT do bng thng ca n nh hn so vi yu

cu.

Bc 4: t lng ging ca B vo TENT, v chuyn C t TENT sang PATH.

PATH TENT {A,0,self,N/A} {D,13,B,90} {B,5,B,100} {C,10,C,100}

{D,14,C,60} khng c thm vo TENT do chi ph (cost) n D thng qua B nh

hn so vi qua C.

Bc 5: Ly D ra khi TENT. Lc ny ng i tt nht n D nm trong PATH.

Trng hp ny TENT rng; D tr thnh nt cui ng c xem xt trong SPF. Nu

tm c ng tt nht n D m vn cn trong nt TENT, th vn dng thut ton

y.

PATH TENT {A,0,self,N/A} {B,5,B,100} {C,10,C,100} {D,13,B,90}

Trong thc t vic tnh ton phc tp hn nhiu. CSPF phi lu gi mi nt trn

ng i, khng ch nt k tip. Cng nh, khng ch quan tm n bng thng m

cn xem xt n cc thuc tnh kt ni v phng php quyt nh (tiebreakers).

Cc phng php quyt nh trong CSPF ( Tiebreaker in CSPF).

SPF thng thng ( dng trong OSPF, IS-IS) c th s dng nhiu ng i

n ch c cng chi ph. iu ny thnh thong c gi l ECMP Equal Cost

Multipath, v n rt hu dng trong giao thc IGP. Tuy nhin trong CSPF, khng tm

mi ng i tt nht c th c n mt ch, m n ch tm mt ng i n mt

ch. Trng hp t ra l khi t mt nt vo TENT v nt c trong TENT vi

cng chi ph th x l nh th no, cng nh l tm ra mt cch phn bit cc ng

i vi nhau ?

gii quyt vn trn, ta c cc phng php quyt nh ng i c cng chi ph:

Chn ng i c bng thng c sn ti thiu rng nht.

Nu cha c, chn ng i c hop count thp nht ( s lng router trong

ng i t nht )

Nu vn cha tha, chn ng ngu nhin.

3.2 C ch thit lp ng i

Sau khi mt ng i c tnh ton theo CSPF, ng i c bo hiu qua mng nhm:

Thit lp mt chui cc nhn theo tng chng i din cho ng i.

s dng bt k ti nguyn no c th dng c (bng thng) trn ng i.

Vic bo hiu c thc hin bng RSVP, cng vi RSVP m rng cho MPLS TE.

RSVP c xc nh trong RFC 2205, c mt s m rng trong RFC 2210. MPLS TE m

rng thm RSVP c xc nh trong RFC 3209.

3.2.1. Tng quan v RSVP.

RSVP l mt c ch bo hiu dng dnh ring ti nguyn trn mt mng. RSVP khng

phi l mt giao thc nh tuyn, vic quyt nh tuyn do IGP ( gm c cc m rng TE) v

CSPF.

Cng vic ca RSVP l bo hiu v duy tr ti nguyn dnh ring qua mt mng. Trong

MPLS TE, RSVP d tr bng thng ti mt phng iu khin (control-plane), khng c chnh

sch lu lng trn mt phng chuyn tip (forwarding-plane). Khi s dng cc mc ch

khc nhau ( nh VoIP hay DLSW+reservations), RSVP c th dng dnh ring khng gian

hang i cng bng c trng s (WFQ Weighted Fair Queing) hay xy dng cc ATM

SVC.

Ba chc nng c bn ca RSVP :

Thit lp v duy tr ng i ( Path setup and maintenance)

Hy ng i ( Path teardown).

Bo li ( Error signaling).

3.2.2. Cc thng ip v cc gi s dng trong RSVP.

Cc loi thng ip.

Loi thng ip M t

Path Dng thit lp v duy tr s dnh ring

Resv Gi hi p cho cc thng ip Path thit lp v suy tr s dnh ring

PathTear Tng t cc thng ip Path, nhng c dng hy s dnh ring ra khi mng

ResvTear Tng t cc thng ip Resv, nhng c dng hy s dnh ring ra khi mng

PathErr c gi bi pha nhn thng ip Path, bo rng pht hin ra mt li trong thng ip

.

ResvErr c gi t pha nhn thng ip Resv, bo rng pht hin ra mt li trog thng ip

.

ResvConf c gi t pha nhn thng ip Resv bo rng ti nguyn dnh ring a ra

c thit lp.

ResvTearConf Mt thng dip ring ca Cisco tng t nh ResvConf, bo rng s dnh ring b

hy khi mng

Hello Mt s m rng c xc nh trong RFC 3209 cho php kt ni cc b ( link-local)

c duy tr gia 2 lng ging RSVP kt ni trc tip.

Cc gi RSVP.

nh dng gi RSVP kh n gin. Mi thng ip RSVP gm c mt tiu chung

(common header), theo sau l mt hoc nhiu i tng. S lng i tng ph thuc vo

ty loi thng ip.

Hnh 3.2 a, Cu trc ca chung ca 1 header RSVP

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

Phin bn

(4 bit)

C

( 4 bit)

Loi thng ip

( 8 bit )

RSVP Checksum

( 16 bit )

TTL

( 8 bit)

Dnh ring

(8 bit )

di RSVP

( 16 bit )

b.Cc trng trong tiu chung RSVP

Trng M t

Version Phin bn ca giao thc RSVP

Flags Cha c c no c nh ngha

Message Type 1. Path message 2. Resv message 3. PathErr message 4. ResvErr message 5. PathTear message 6. ResvTear message 7. ResvConf message 10. ResvTearConf message

20. Hello message

RSVP Checksum Kim tra li trong thng ip RSVP

Send TTL Gi tr TTL trn gi IP

Reserved Khng s dng

RSVP Length Chiu di ca thng ip RSVP tnh bng byte bao gm c tiu chung, ti

thiu l 8 byte.

Cc i tng c cha trong cc thng ip ca RSVP

Object Name Loi bn tin

RSVP M t

Adspec PATH Mang d liu qung b: tr, bng thng, thng

s iu khin t QoS

Detour PATH Used in one-to-one backup to identify detour

LSPs

Error

PATH Err

RESV Err

RESV Conf

Xc nh mt li trong bn tin PATH Err v

RESV Err hoc xc nhn trong bn tin RESV

Conf

Explicit Route PATH ng nh tuyn xc nh

Fast Reroute PATH c s dng to ng d phng cho LSP

chnh

Filter

RESV

RESV Tear

RESV Err

Xc nh ngun gc ca phin giao dch

Filter Spec RESV nh ngha mt nhm cc gi tin nhn c yu

cu v QoS

Flow Spec RESV nh ngha yu cu v QoS

Hello Hello C th l mt yu cu hay hi p

Hop

PATH

RESV

Mang a ch IP ca node gi bn tin ( node

c RSVP )v cng giao tip ng ra.

Integrity Tt c cc bn tin Mang d liu xc thc ngun gc v m bo

tnh ton vn ca bn tin RSVP

Label RESV Cha gi tr nhn

Label Request PATH Yu cu ng k nhn

Null C Class Number l 0, khng c C-type, ni

dung s c b qua ni nhn.

Policy data

PATH

RESV

PATH Err

RESV Err

Chnh sch vi d liu

Record Route

PATH

RESV

Danh sch cc a ch Ip m bn tin PATH i qua

RESV Conf

RESV

RESV Conf

Hi p v xc nhn mt yu cu t ch

Scope

RESV

RESV Err

Mang mt danh sch cc node gi vi thng

tin trong bn tin c chuyn tip

RESV Tear

Sender PATH a ch IP ca node gi v mt s thng tin

xc nh

Session Tt c cc bn tin Cha a ch IP ch, giao thc IP v s port, xc

nh mt phin lm vic c th

Session Attribute PATH Cha cc thng s v u tin, c, di tn

v tn phin.

Source Route PATH Cha cc a ch trong phn nh tuyn xc nh

( ERO)

Style RESV H tr thng tin v vic t ch

Time

PATH

RESV

Thi gian cho vic lm mi bn tin

Tspec PATH nh ngha tnh cht ca lung lu lng

3.2.3 Cc chc nng ca RSVP.

3.2.3.1 Thit lp v duy tr ng i.

phn ny, ta tp trung i phn tch cc bn tin PATH v RESV cng nh cc i

tng i km vi cc thng ip ny, nhm lm r qu trnh thit lp v duy tr ng i.

a,Bn tin PATH: Vi giao thc RSVP m rng, bn tin PATH c thm mt thnh phn mi:

ERO ( explicit route object). Sau y, chng ta tm hiu v ba thnh phn chnh ca bn tin

PATH:

Thnh phn yu cu nhn( Label request object)

Thnh phn nh tuyn xc nh( Explicit route object)

Thnh phn nh tuyn mnh tin ( Record route object)

Thnh phn yu cu nhn ( LQO) :

Igress LSR yu cu n nh nhn cho LSP cn x l, ngoi ra thnh phn cn mang

gi tr m nhn dng giao thc lp mng L3PID ( Layer 3 protocol identifier) xc nh giao

thc lp mng s dng. Nh ta bit, c 3 loi nhn c s dng:

Nu giao thc lp 2 khng c cu trc xc nh th nhn c dng l nhn chn thm

(shim label) nm gia tiu lp 2 v lp 3.

Nu giao thc lp 2 l ATM th gi tr nhn cha trong vng thng tin VCI v VPI

Nu giao thc lp 2 l Frame Relay th nhn c cha trong vng DLCI.

Khi nhn c bn tin PATH, cc LSR s gi li trong khi trng thi ng dn (

Path State Block) dnh cho LSP ny. Nu xch nh c loi nhn th s tin hnh qu trnh

n nh nhn.

Cc li c th xy ra:

LSR nhn c bn tin PATH nhng khng n nh c nhn th n s gi bn tin

PATH Error bo vi igress LSR bit xy ra li nh tuyn hoc li ca n nh gi

tr nhn.

Nu LSR nhn c khng h tr L3PID th s gi PATH Err cho igress LSR. Li

ny xy ra s kt thc qu trnh khi to LSP.

Nu nhn c bn tin ny m khng nhn ra c thnh phn yu cu nhn (Label

request object) th cng gi PATH Err v kt thc khi to LSP.

Thnh phn nh tuyn xc nh ( ERO):

Thng tin trong thnh phn ny l ng i ca bn tin PATH trong mng. Cc LSR

cn c vo thnh phn ny chuyn bn tin n ch nhn tip theo trong mng. ERO ch

s dng unicast v ch khi tt c cc b nh tuyn trn ton tuyn u h tr RSVP v ERO.

Cu trc ca ERO gm mt chui cc thnh phn ph ( subobject). Mi thnh phn ny xc

nh mt nhm cc nt mng hay ch l mt nt mng trn ng nh tuyn hoc ch ra mt

thao tc trn tuyn. Mi thnh phn ph nh th c gi l abstract node v nu ch c duy

nht mt nt mng th gi l Simple Abstract Node. Cc thnh phn ph trong mt ERO c

th l nhng ch s AS ( Autonomous System), trong mi AS c th c nhiu nt mng nhng

chng hon ton trong sut i vi igress LSR. Di y l nh dng ca mt thnh phn

ph trong ERO:

Bit L Loi

(Type)

di

(Length)

Ni dung thnh phn ph

( Subobject content)

Bit L =1: l mt ghp lng ( loose hop)

L =0: l mt ghp cht (strict hop) trn ng nh tuyn xc nh ( explicit route).

C 4 loi thnh phn ph (subobject) c nh ngha:

Ipv4: cc nt mng trong abstract node c a ch IP thuc phin bn 4. Mi a

ch c 32 bit.

Ipv6: a ch ca mi nt mng thuc phin bn 6, 128 bit.

Autonomous System Number: nhng nt mng nm trong abstract node cng nm

trong mt AS.

Thnh phn nh tuyn mnh tin ( RRO):

Vi thnh phn ny trong bn tin PATH, LSR s bit c tt c cc LSR nm trn

ng i ca bn tin PATH ( cng chnh l LSP) t igress LSR n egress LSR. Khi igress

LSR xy dng mt LSP, u tin, n s gi i bn tin PATH c cha thnh phn Label object

v c thnh phn RRO. Thng tin cha trong RRO lc ny ch c a ch IP ca igress LSR.

Khi mt LSR trung gian nhn c bn tin ny, LSR s sao li thnh phn RRO trong khi

trng thi ng dn ( Path state block) v thm a ch IP ca n vo trong thnh phn RRO.

Ring egress LSR khi nhn c bn tin PATH s hi p li bng bn tin RESV. Bn tin ny

s sao li thnh phn RRO ca bn tin PATH. Nh vy, sau qu trnh trao i bn tin PATH

v RESV, mi LSR s bit c ton b LSR thuc LSP ny. iu ny rt hu ch cho cng

vic qun tr mng.

b,Bn tin RESV:

Bn tin ny dc egress LSR gi i tr li bn tin PATH. Bn tin RESV mang thng

tin v gi tr nhn c n nh cng nh ti nguyn mng c dnh cho LSP ny. Trong

phn ny, chng ta ch xem xt thnh phn chnh nhn ( Label object).

Hnh 3.3 Thnh phn Label Object trong bn tin RESV

Khi nhn c mt bn tin RESV, LSR s kim tra xem bn tin ny tng ng vi

bn tin PATH no v LSR gi c phi l nt mng k tip thuc LSP hay khng. Khi tt c

u hp l th LSR s n nh gi tr nhn trong bn tin RESV cho vng nhn u ra

(outgoing label). ng thi LSR cng gi i bn tin RESV vi gi tr nhn s dng cho LSP

ny ti LSR ngc dng.

Nh vy khi igress LSR nhn c bn tin RESV, lung lu lng xc nh c LSP

dnh cho n. Qu trnh n nh nhn cho LSP c thc hin di hnh thc downstream on

demand.

c,Qu trnh xy dng LSP:

Hnh 3.4 M t qu trnh xy dng tuyn.

Qu trnh gi bn tin PATH:

Ti PE1-AS1 (LSR 1): LSR gi i bn tin PATH v ba thnh phn chnh trong bn

tin PATH:

Explicit route: m t ng i ca bn tin PATH trong mng xy dng LSP v

dnh sn ti nguyn mng trn LSP ny.

Label request: a ra yu cu v gi tr nhn dnh cho LSP.

Record route: thnh phn ny trong bn tin gip igress LSR c c thng tin

chnh xc v LSP nh a ch ca cc LSR thuc LSP. Thnh phn ny rt thit

thc trong vic khc phc hin tng lp vng.

Ti P1-AS1 (LSR 2):

Khi nhn c bn tin PATH, LSR 2 lu thnh phn Label request v Explicit

route trong khi trng thi ng dn ( Path state block). ng thi a ch IP ca

LSR gi LSR 1, session, tpec cng c lu li s dng cho vic nh tuyn bn

tin RESV tng ng vi LSR 1.

Cn c vo thnh phn Explicit route, LSR 2 chuyn bn tin PATH n LSR 3.

Trong trng hp khng th n nh nhn cho LSP, LSR 2 s gi bn tin PATH

Err bo li n LSR 1

Ti P2-AS1 (LSR 3): Qu trnh tng t nh LSR 2.

Ti PE2-AS1 (LSR 4): Nhn c bn tin PATH, LSR 4 bit c n chnh l egress

LSR v tin hnh gi bn tin RESV v LSR 1.

Qu trnh gi bn tin RESV:

Ti LSR 4:

LSR 4 n nh gi tr nhn implicit NULL cho LSP, a gi tr nhn ny vo

thnh phn Label ca bn tin RESV. L do LSR 4 s dng gi tr nhn ny l

bo cho LSR 3 ( LSR k cui) bit c n l egress LSR, khi LSR 3 nhn c

mt gi tin c gn nhn c a ch mng ch c hc t LSR 4, n s g

nhn v nh tuyn gi bng cc giao thc nh tuyn IP truyn thng ( theo c

ch PHP).

LSR 4 s dng thng tin Sender_Tpec ( Traffic Specification ) to ra thnh phn

Receiver_Tpec ( Request Specification). ng i ca bn tin RESV c xc

nh da vo thng tin lu li trong khi trng thi ng ( Path state block).

Ti LSR 3:

Nhn c bn tin RESV, LSR 3 c thng tin trong thnh phn Label.T vi

nhng gi d liu n LSR 4 trn LSP ny, LSR 3 s thc hin g nhn ( POP)

v chuyn tip gi tin IP n LSR 4.

LSR 3 s n nh mt nhn thch hp cho LSP ny. y, nhn ny bng 3, gn

gi tr ny vo bn tin RESV v gi n LSR 2.

Ti LSR 2: Qu trnh tng t nh LSR 3, v nhn c gn bng 2.

Ti LSR 1:

Khi nhn c bn tin RESV, qu trnh xy dng LSP kt thc. Vi nhng lung

lu lng thch hp, LSR 1 s gn nhn bng 2 cho cc gi d liu chuyn ti

LSR 2.

ng i ca gi d liu t igress LSR n egress LSR

Di y l qu trnh di chuyn trn LSP ca cc gi d liu sau khi kt thc qu trnh

n nh nhn.

LSR 1 l igress LSR, nhn cc gi d liu IP. Da vo thng tin trn tiu IP, LSR 1

nh dng li gi d liu ph hp vi k thut lp lin kt d liu, gn nhn bng 2 v

chuyn n LSR 2 trn Serial 0.

Nhn c d liu trn Serial 1 c nhn bng 2, LSR 2 da vo LIB xc nh c gi

tr nhn u ra. Trn hnh cho thy LSR 2 gi d liu c nhn bng 3 trn Serial 0 n

LSR 3.

Nhn c d liu trn Serial 1 c nhn bng 3, LSR 3 thc hin g nhn v chuyn

tip gi tin IP trn Serial0 n LSR 4.

Nhn c d liu, LSR 4 da vo bng nh tuyn thc hin chuyn tip gi tin IP

n ch.

d,Duy tr ng i.

Thot nhn, vic duy tr ng i cng ging nh thit lp ng i. Mi 30s u cui

ng hm gi mt thng ip Path n downstream LSR ca n. Nu mt LSR gi i mt

dy 4 thng ip Path m khng thy Resv, n ngh rng s dnh ring b mt v gi thng

ip ngc dng (Message upstream) bo rng s dnh ring b mt.

Cc thng ip Path v Resv c gi c lp v bt ng b gia cc lng ging vi

nhau. Mi 30s, LSR1 gi thng ip Path cho mt s dnh ring ca n ti LSR 2. V mi

30s, LSR 2 gi mt thng ip Resv n LSR 1 vi cng s dnh ring . Tuy nhin hai

thng diep865 ny khng lin h vi nhau. Thng ip Resv c dng lm ti (refresh)

mt s dnh ring ang tn ti ch khng phi tr li cho thng dip Path.

3.2.3.2 Hy ng di ( Path Teardown)

Nu mt nt ( thng l u ng hm) quyt nh mt s dnh ring khng cn cn

thit trong mng, n gi mt thng ip PathTear dc theo ng thng ip Path i v

mt ResvTear dc theo ng ca Resv.

Thng ip ResvTear c gi hi p cho PathTear bo hiu ui ng hm.

PathTear v ResvTear cng c gi tr li mt iu kin li trong ng hm.

Khng ging thng ip lm ti, PathTear khng cn i n ht downstream trc

khi nhn c kt qu. Trong hnh trn, nu LSR 1 gi PathTear n LSR 2, ngay lp tc

LSR 2 tr li bng mt ResvTear, sau gi PathTear xung dng ca n.

Ngoi 2 chc nng chnh trn, RSVP cn thc hin bo li bng cc thng ip

PathErr hay ResvErr.

Chng IV CHUYN TIP LU LNG VO MPLS TE

TUNNEL

Sau khi to ra mt TE Tunnel, vn tip theo l lm sao chc chn rng n s c

chuyn tip vo trong ng hm. C 6 cch chuyn tip lu lng vo trong cc TE

Tunnel, bao gm:

Static routing (nh tuyn tnh).

Policy-based routing (nh tuyn da trn nn cc chnh sch).

Autoroute annuonce (nh tuyn t ng da trn vic thng bo).

Forwarding adjacency (Ln cn chuyn tip).

Direct mapping of AToM trafc onto TE tunnels (Ghp trc tip lu lng ca AtoM trn cc TE Tunnel)

Class-based tunnel selection (la chn cc Class-based Tunnel)

4.1. Static routing (nh tuyn tnh) y l phng php n gin v d thc hin nht chuyn tip lu lng vo cc

TE Tunnel. N c cu hnh thit lp mt TE_LSP t u n cui ca tuyn LSP .

Ngi qun tr s ch nh c th cc tuyn LSP no c s dng chuyn tip lu lng

TE. Do , Static routing c u im l rt d thc hin nhng c nhc im l khng linh

hot khi trin khai trong mt mng li rng ln.

4.2. Policy-based routing (nh tuyn theo chnh sch) Policy based routing (PBR) s dng cc chnh sch thit lp trn cc giao tip

ng vo vn chuyn data sang cc hop k cn c xc nh trc. Cc TE LSP s

c xc nh d vo cc chnh sch v TE Tunnel s c thit lp da trn cc chnh sch

ny. Khi thc hin PBR c th nh tuyn lu lng n mt TE Tunnel c th bng cch

thit lp giao din m khng cn phi thay i bng nh tuyn.

4.3. Autoroute Announce (nh tuyn t ng bng cch thng bo) Tunnel MPLS TE Autoroute announce l qu trnh iu khin thit lp cc giao dn

ng hm trn cc MPLS TE tunnel u v cui cc router v vy LSR c th tm thy cc c ch IP ch, next hop v TE Tunnel nh l giao din ng ra trn bng nh tuyn. V c bn, Autoroute Announce lm thay i thut ton SPF v vy LSR c th tm thy cc a ch IP Prefix . Lc , headend-LSR c xem l c kt ni trc tip vi tailend-LSR qua mt TE-LSP, v vy lu lng i ti tailend-LSR v cc router pha sau tailend-LSR u s dng TE-LSP lm giao din ng ra.

4.4. Forwarding adjacency (Ln cn chuyn tip). Phng thc ny cho php cc headend-LSR qung b cc TE-LSP nh l lin kt ca

n. Nhng router trong vng c th xt thm nhng TE-LSP ny nh l lin kt trong qu

trnh tnh ton ng i. c th s dng phng thc ln cn chuyn tip th cn phi thit

lp 2 ng TE-LSP gia 2 LSR, mi ng tng ng mt hng v trn 2 LSR phi kch

hot chc nng ln cn chuyn tip. Mt u im ca phng php ny l mt cp TE-LSP

c xem nh l mt lin kt v c qung b trong min IGP, v mt router trong vng

khng chy MPLS TE cng c th thy lin kt ny v xem xt n trong qu trnh tnh ton ng. V d : Chuyn tip lu lng trn cc TE Tunnel

Vi c ch nh tuyn IP, lu lng chuyn tip T R1 sang R7 s chn tuyn ngn

nht l R1, R2, R3, R7. Nu thit lp mt ng TE-LSP gia R2-R3 v mt ng na gia

R4-R6 th lu lng vn ch i trn TE-LSP R2-R3 bt chp TE-LSP R4-R6 c tt hn. Bi

v lung lu lng ch c chuyn tip vo TE-LSP ti headend-LSR (R2 v R4) m cc

router khc trong vng khng bit c s tn ti ca 2 TE-LSP ny v n khng c qung

b. Nn khi lung lu lng i t R1 sang R7, R1 s chuyn tip lu lng ti R2 v n tnh

ton c rng tuyn i ti u nht l i qua R2, ti R2 s chuyn tip lu lng ln TE-LSP

R2-R3.

Khi s dng ln cn chuyn tip, cc TE-LSP R2-R3 v R4-R6 c qung b nh l

lin kt ca 4 router R2, R3, R4, R6. Lin kt ny c qung b thng qua OSPF hoc IS-IS

n router R1 v R7. R1 thm hai lin kt tng ng vi hai TE-LSP ny vo qu trnh

tnh ton ng CSPF.Lc ny TE-LSP no c chi ph thp nht s c R1 chn truyn

lu lng, nu chi ph bng nhau th R1 s thc hin cn bng ti trn cc TE-LSP ny.

4.5. Direct mapping of AToM trafc onto TE tunnels (Ghp trc tip lu lng

ca AtoM trn cc TE Tunnel):

y l mt ng dng nng cao ca MPLS TE, cho php ng gi cc gi tin IPv4/IPv6, cc giao thc lp lin kt lp d liu ATM. Frame Relay, PPP, HDLC, Ethernet, . Vo bn tin MPLS. N ch cho php truyn theo phng thc im im, c cu hnh ti Headend-LSR ch nh c th lu lng ca loi giao thc no s truyn trn TE-LSP no.

4.6. Class-based tunnel selection (la chn cc Class-based Tunnel) Cho php truyn lu lng ca cc lp dch v (CoS) khc nhau trn nhng TE-LSP

khc nhau ca cng mt cp Headend-LSR v Tailend-LSR. Router s kim tra gi tr IP-

Precedence trong trng ToS ca header IP hoc gi tr EXP trong MPLS. Da trn gi tr

ny, router s quyt nh TE-LSP ph hp cho lung lu lng. Ta c 3 bit EXP tng ng

vi 8 mc QoS, v vy ta c th nh x 8 mc Qos ny n 8 TE-LSP khc nhau gia 1 cp

LSRs.

M PHNG

1.M hnh thc hin v cch cu hnh trn GNS3:

M hnh thc hin :

- Router ID l cc a ch Loopback.

- Cc cng c nh a ch nh trong hnh.

- Cc kt ni u l kt ni T1, c bng thng l 1,544Mbps

- Bng thng dnh ring trn cc lin kt l 1000Kbps

- TE metric mc nh l bng vi IGP metric. Trn tt c cc lin kt u thit lp TE

metric = 1.

- Affinitity Flag ca tt c cc lin kt l 0x0.

- M hnh s dng giao thc bo hiu RSVP bo hiu thit lp v duy tr

ng i.

Mc ch m phng:

Kim tra v xem xt s nh hng ca:

- Bng thng.

- Affinity bit.

- TE metric.

Cc bc cu hnh:

Bc 1: Cu hnh a ch Loopback v a ch cc cng trn cc Router

Cu hnh a ch Loopback:

- Router#configure terminal

- Router(config)#interface Looback {number}

- Router(config-if)#ip address {ip-address}

Cu hnh a ch cng:

- Router#configure terminal

- Router(config)#interface {number interface}

- Router(config-if)#ip address {ip-address}

- Router(config)#no shutdown

Bc 2: Kch hot s dng MPLS TE trn Router v cc cng

Kch hot trn Router:

- Router(config)#mpls ip

- Router(config)#mpls trafic-eng tunnels

Kch hot trn cng:

- Router(config)#interface {type} {number interface}

- Router(config-if)#mpls ip

- Router(config-if)#mpls trafic-eng tunnels

Bc 3: Cu hnh bng thng dnh ring ca cc cng s dng MPLS TE bo hiu v

phc v tin trnh dnh ring ti nguyn cho ng hm (Tunnel).

Cu hnh bng thng dnh ring v lung lu lng ln nht c i qua:

- Router(config)#interface {type} {number interface}

- Router(config-if)#ip rsvp bandwidth {reservable bandwidth 1-1000000 kbps}

{maximum reservable bandwidth 1-1000000 kbps}

Cu hnh thng s Attribute Flag dng nh ngha lp ti nguyn:

- Router(config-if)#mpls traffic-eng attribute-flags {0x0-0xFFFFFFFF}

Cu hnh thng s TE metric:

- Router(config-if)#mpls traffic-eng administrative-weigh {weigh}

Bc 4: Cu hnh giao thc nh tuyn ni vng IGP s dng giao thc OSPF

Cu hnh OSPF

- Router(config)#router ospf {process-id}

- Router(config-router)#network {ip address} {wild-card mask} area {area-id}

- Router(config-router)#mpls traffic-eng area {area-id}

- Router(config-router)#mpls traffic-eng router-id {interface number}

Bc 5: Cu hnh thit lp ng hm TE-LSP: gm cc cng vic cu hnh cng

Loopback l TE Router ID ca Tunnel, a ch ch, ch hot ng , bng thng yu cu...

Sau , cn ch th tc thit lp tuyn: mt tuyn tng minh hoc router s t tnh ton ng

i bng thut ton CSPF. Mt ng hm c th cu hnh theo hai ty chn vi cc thng s ty

theo mc ch ca ngi qun tr.

Cu hnh cng cho ng hm:

- Router(config)#interface tunnel {number}

Cu hnh a ch cng ca ng hm l cng Loopback:

- Router(config-if)#ip unnumbered loopback {number}

Cu hnh a ch ch ca ng hm:

- Router(config-if)#tunnel destination {ip address}

Cu hnh ch hot ng ca ng hm:

- Router(config-if)#tunnel mode mpls traffic-eng

Cu hnh thng s bng thng cn thit cho ng hm

- Router(config-if)#tunnel mpls traffic-eng bandwidth {kbps}

Cu hnh c thuc tnh phn lp ti nguyn cho ng hm

- Router(config-if)#tunnel mpls traffic-eng affinity {0x0-0xFFFFFFFF} mask{0x0-

0xFFFFFFFF}

Cu hnh thng s u tin cho ng hm

- Router(config-if)#tunnel mpls traffic-eng priority {setup priority-value} {hold

priority-value}

Cu hnh ty chn thit lp ng hm (ng hoc tng minh)

- Router(config-if)#tunnel mpls traffic-eng path-option {priority} {dynamic| explicit

{name {LSP name} } }

- Bc 6: Nu ty chn thit lp ng hm l tng minh th ta phi ch r a ch IP ca

cc Router m ng hm s i qua.

- Router(config)#ip explicit-path name {LSP name} enable

- Router(cfg-ip-expl-path)#next-address {ip address}

- Router(cfg-ip-expl-path)#next-address {ip address}

Bc 7: Kch hot c ch chuyn tip lu lng ln ng hm

- Router(config)#interface tunnel {number}

- Router(config-if)#tunnel mpls traffic-eng autoroute announce

2.Thc hin m phng :

a. To ng hm TE tunnel :

Ta s tin hnh to mt ng hm Tunnel 0 t Router 1 n Router 6 nh sau:

- Router(config)#interface tunnel 0

- Router(config-if)#ip unnumbered loopback0

- Router(config-if)#tunnel destination 10.10.10.106


- Router(config-if)#tunnel mpls traffic-eng bandwidth 100

- Router(config-if)#tunnel mpls traffic-eng priority 1 1

- Router(config-if)#tunnel mpls traffic-eng path-option 1 dynamic


Kim tra kt qu :

- Router#show mpls traffic-eng tunnels tunnel 0

Do bn ng ti ch R6 c cng tnh cht, nhng c 1 ng c TE metric = 3 l R1-

R2-R3-R6 v R1-R4-R5-R6, 2 ng c TE metric = 2 l R1-R4-R6 v R1-R5-R6. V y l

dynamic nn tunnel s chn con ng no c ng i ngn nht nn Tunnel 0 chn ngu

nhin mt trong 2 ng ngn nht i ti ch, con ng i qua R1-R5-R6.

b. Kho st s nh hng ca cc thng s :

S nh hng ca TE metric :

thy c s nh hng ca TE metric, ta thay i gi tr TE metric trn cc lin kt R1-R5

l 2, trn lin kt R5-R6 l 2

.Kim tra ng hm tunnel 0:

Kt qu cho thy, ng hm tunnel 0 chn li tuyn ng thit lp ng i cho

n l R1-R4-R6 vi tng TE metric = 2, thp nht so vi bn ng cn li. Nh vy, TE metric

c th c s dng i din cho tr lin kt v cu hnh cc ng hm mang lu lng

thoi trong khi IGP metric c s dng trong cu hnh cc ng hm mang d liu.

S nh hng ca bng thng :

kho st s nh hng ca bng thng ta thit lp bng thng dnh ring trn lin kt

R1-R2, R1-R5, R2-R3, R3-R6, R4-R6 l 400kbps, cc lin kt cn li c bng thng l

1000 kbps nh hnh.

Sau , ta to ng hm Tunnel 1 c bng thng l 500 kbps i t R1 ti R6:









Kim tra ng hm Tunnel 1:

- Router#show mpls traffic-eng tunnels tunnel 1

Kt qu cho thy, Tunnel 1 chn con ng i qua R1-R4-R5-R6, l con ng c

bng thng dnh ring ln nht i qua. iu ny cng chnh xc nu ta thc hin tng t trn

cc lin kt cn li. Nh vy, chng t k thut lu lng MPLS c xu hng chn tuyn ng

c bng thng dnh ring cao nht vn chuyn lu lng ch khng ph thuc vo bng

thng mc nh ca cc lin kt.

Vn ln chim :

By gi, ta s to mt ng hm tunnel 2 c thuc tnh ging nh ng hm tunnel 1

nhng c thng s u tin l 4 so vi tunnel 1 l 7.









Kt qu thu c l c 2 ng hm up l tunnel 0 v tunnel 2 c th ti ch R6 t cng s1/1,

nhng lc ny tunnel 2 ln chim tunnel 1 v c u tin cao hn do tunnel 1 b mt

quyn chim dng bng thng (protocol down) trn ng R1-R4-R5-R6.

Ta thc hin lnh: Show mpls traffic-eng traffic tunnels kim tra vic truyn gi tin trn 2

tunnel 1 v tunnel 2

Tunnel 1

Tunnel 2

Ta tip tc thay i u tin ca tunnel 1 l 3 th tunnel 1 s chim ng (R1-R4-R5-R6) ca

tunnel 2 do u tin ca tunnel 1 l cao hn.

Ta thc hin lnh: Show mpls traffic-eng tunnels kim tra vic truyn gi tin trn tunnel 1

v tunnel 2

Tunnel 1

Tunnel 2

S nh hng ca Affinity bit

kho st s nh hng ca bng thng ta thit lp Affinity bit trn lin kt R1-R4, R1-R2,

R2-R3, R3-R6, R4-R6, R4-R5 l 0x1 v cc lin kt cn li c affinity bit l 0x0 nh hnh.

Lc u khi cha thit lp Affinity bit trn cc lin kt R1-R4, R1-R2, R2-R3, R3-R6, R4-

R6, R4-R5 l 0x1th tunnel 0 chn ng t R1-R4-R6 lm ng i ca n.

Sau khi thit lp Affinity bit trn lin kt R1-R4, R1-R2, R2-R3, R3-R6, R4-R6, R4-R5 l

0x1 th tunnel 0 chn ng t R1-R5-R6 lm ng i ca n.

Kt qu cho thy, Tunnel 0 chn con ng i qua R1-R5-R6, l con ng m xuyn

sut n, cc c thuc tnh phn lp ti nguyn cho ng hm u mang gi tr 0x0. iu ny

cho thy rng, c thuc tnh phn lp ti nguyn cho ng hm phi trng vi c thuc tnh

trn lin kt th lin kt mi c chn xy dng ng hm.

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