cd5-2

TP ON BU CHNH VIN THNG VIT NAM HC VIN CNG NGH BU CHNH VIN THNG

VIN KHOA HC K THUT BU IN

BO CO CHUYN 5.2

Thuc nhim v: 003-2006-T-VT

Tn chuyn :

CUNG CP, T KHM PH V BO HIU TRONG MNG L2VPN

yu cu chung v Protocol theo draft-ietf-l2vpn-signaling-08

Nhng ngi thc hin chnh: Hong Vn Bnh CV Ban Vin thng

H ni 2007

MC LC

1.1. GII THIU CHUNG ............................................................................ 3 1.2. Cu trc khung giao thc bo hiu ......................................................... 4 1.2.1. Nhn in im cui ............................................................................... 4 1.2.2. Thit lp mt ng dy o hai hng n gin .................................... 5 1.2.3. Nhn din ghp ni v chuyn tip......................................................... 6 1.3. Cc ng dng .......................................................................................... 7 1.3.1. Cc ng dy o kt ni im im ring bit ..................................... 7 1.3.1.1. M hnh cung cp ............................................................................. 7 1.3.1.1.1. Cung cp hai hng ...................................................................... 7 1.3.1.1.2. Cung cp n hng kt hp vi khai ph ................................... 8 1.3.1.2. Bo hiu ............................................................................................ 8 1.3.2. Dch v mng LAN o ............................................................................ 9 1.3.2.1. Cung cp ........................................................................................... 9 1.3.2.2. T khai ph ..................................................................................... 10 1.3.2.2.1. T khai ph trn c s BGP........................................................ 10 1.3.2.3. Bo hiu .......................................................................................... 11 1.3.2.4. ng dy o nh mch ghp ni VPLS....................................... 12 1.3.3. Mng mesh y cc kt ni ng dy o im im..................... 12 1.3.3.1. Cung cp ......................................................................................... 12 1.3.3.2. T khai ph ..................................................................................... 13 1.3.3.2.1. T khai ph trn c s BGP........................................................ 13 1.3.3.3. Bo hiu .......................................................................................... 14 1.3.4. Mng mesh mt phn ............................................................................ 15 1.3.5. Phn b VPLS ....................................................................................... 16 1.3.5.1. Bo hiu .......................................................................................... 17 1.3.5.2. Cung cp v khai ph...................................................................... 18 1.3.5.3. Khng phn b VPLS nh mt trng hp ring .......................... 19 1.3.5.4. Ghp ni PW v mt phng d liu................................................ 19 1.4. Hot ng Inter-AS ............................................................................... 19 1.4.1. Phn b li nhiu on EBGP ca L2VPN NLRI ................................ 19 1.4.2. Phn b li EBGP ca L2VPN NLRI vi ng dy o nhiu phn on ............................................................................................................... 20 1.4.3. ng dng cung cp chung ca bo hiu VPLS phn b ...................... 21 1.4.4. Cc vn cn xem xt khai bo RT v RD ........................................ 22 1.5. Bo mt ................................................................................................. 23 1.6. IANA..................................................................................................... 23

TM TT

Nh cung cp dch v mng ring o lp 2 (Layer 2 Virtual Private Networks L2VPNs) c th c nhiu m hnh cung cp khc nhau (m hnh trong thng tin cn c nh dng theo cc phng thc no ). Mt khi c nh dng, cc thng tin dnh ring cho vic cung cp dch v c phn b thng qua qu trnh khm ph ti nguyn mng. Sau khi kt thc qu trnh khm ph, mt giao thc bo hiu c t ng kch hot thit lp cu hnh mesh ca cc ng dy o to thnh cu trc khung o ca L2VPN. Ti liu ny trnh by mt s m hnh cung cp L2VPN v mt s cu trc yu cu nhn din u cui ca mi m hnh. Ti liu ny cng a ra cc tho lun v phn b cc c tnh nhn din ny thng qua cc qu trnh khm ph ti nguyn, c bit khi qu trnh khm ph da trn giao thc cng bin gii (BGP-Border Gateway Protocol). Sau s quy nh cch thc cc u cui c nhn din c ti trn hai giao thc bo hiu c s dng thit lp cc ng dy o, giao thc phn b nhn (LDP-Label Distribution Protocol) v giao thc xuyn ngm lp 2 (L2TPv3-Layer 2 Tunneling Protocol).

1.1. GII THIU CHUNG

[I-D.ietf-l2vpn-l2-framwork] m t mt s phng thc khc nhau trong tp hp cc ng dy o c th c t hp li vi nhau thnh mng cung cp dch v mng ring o lp 2 (L2 PPVPN hay L2VPN), kt qu l c th to thnh nhiu loi L2VPN khc nhau vi nhiu m hnh cung cp khc nhau(m hnh trong thng tin cn c nh dng theo cc phng thc no ). Mt khi c nh dng, cc thng tin dnh ring cho vic cung cp dch v c phn b thng qua qu trnh khm ph ti nguyn mng. Sau khi kt thc qu trnh khm ph, mt giao thc bo hiu c t ng kch hot thit lp cc ng dy o cn thit. ngha ca cc nhn dng u cui c s dng trong cc giao thc bo hiu cho mt loi L2VPN c th no c quyt nh bi m hnh cung cp. iu ny c ngha l mi loi VPN khc nhau vi cc m hnh cung cp khc nhau yu cu kiu nhn dng u cui cng khc nhau. Ti liu ny xc nh s lng cc m hnh cung cp L2VPN v cu trc v mt ng ngha ca nhn din u cui c yu cu trong mi m hnh cung cp.

C hai loi giao thc LDP (quy nh trong RFC3036) vi phn m rng c quy nh trong I-D.ietf-pwe3-control-protocol v L2TP phin bn 3 (c quy nh trong RFC3931 vi phn m rng c quy nh trong I-D.ietf-l2tpext-l2vpn u c th c s dng nh l cc giao thc bo hiu thit lp v duy tr cc ng dy o (RFC3985). Giao thc no c dng thit lp cc kt ni phi cung cp phng thc cho mi im cui ca kt ni nhn din cc im kt ni cn li; mi giao thc bo hiu ng dy o do cng phi cung cp phng thc nhn din cc u cui ca ng dy o. Khi mi giao thc bo hiu cn phi h tr tt c cc loi L2VPN v cc m hnh cung cp th cc giao thc bo hiu phi c nhng phng thc c bn i din cho cc nhn din u cui, v cn thit phi xc nh cc lut l cho vic m

ha mi loi nhn din u cui ring bit vo cc trng tn hiu thch hp ca mi giao thc bo hiu. Ti liu ny trnh by cch thc m ha cc nhn din im cui ca mi m hnh vo trong cc giao thc bo hiu LDP v L2TPv3.

1.2. Cu trc khung giao thc bo hiu 1.2.1. Nhn in im cui

Theo [I-D.ietf-l2vpn-l2-framework], mt ng dy o c th c xem

nh mt mi lin h gia mt cp thit b chuyn tip (Forwarder). Trong cc trng hp VPWS n gin, mt thit b chuyn tip gn mt ng dy o vo mt thit b mch g lp n, bng cch ny cc khung d liu nhn c trn mt thit b c gi trn thit b kia v ngc li. Trong VPLS, mt thit b chuyn tip gn mt s ng dy o vo mt s mch g lp; khi mt khung d liu c nhn t mt thnh vin trong nhm th bng a ch MAC c s dng tham chiu xc nh thnh vin hoc cc thnh vin trong nhm truyn khung d liu ti. Trong cc trng hp phc tp hn, cc thit b chuyn tip c th gn cc ng dy o vi cc ng dy o, qua ni cc ng dy o vi nhau h tr cho vic phn b VPLS v mt s trng hp hot ng chung vi giao thc khc.

Trong VPWS n, thit b chuyn tip gn duy nht mt ng dy o vo mt mch g lp, th thit b chuyn tip c th c nhn din thng qua nhn din mch g lp gn vi n. Trong mt VPLS n gin, mt thit b chuyn tip c th c nhn din thng qua nhn din thit b PE ca n v VPN ca n.

thit lp mt ng dy o gia mt cp thit b chuyn tip, th tc bo hiu phi cho php thit b chuyn tip ti mt im cui nhn din c thit b chuyn tip pha bn kia. Trong [I-D.ietf-pwe3-control-protocol] thut ng "Attachment Identifier", hoc "AI" (tm dch l nhn din mch g lp) c s dng lm tham chiu nhn din mt thit b chuyn tip. Trong [I-D.ietf-l2tpext-l2vpn] thut ng "Forwarder Identifier" cng c dng vi cng mc ch. Trong ni dung ti liu ny, khi nim nhn din thit b chuyn tip v nhn din mch g lp c gi tr tng ng, c s dng thay th cho nhau.

[I-D.ietf-pwe3-control-protocol] quy nh hai thnh phn FEC c th c s dng khi thit lp cc ng dy o bao gm PWid FEC v ID FEC dng chung. PWid FEC ch mang mt nhn din thit b chuyn tip do ch c th c s dng khi cc b chuyn tip c chung nhn din, v m nhn din phi c m ha 32 bit. Id FEC dng chung mang hai nhn din thit b chuyn tip dng nhn din hai b chuyn tip kt ni vi nhau, mi m nhn din ny c xem nh nhn din mch g lp v mt bn tin bo hiu s mang c m nhn din mch ngun (SAI- Source Attachment Identifier) v m nhn din mch ch (TAI- Target Attachment Identifier).

ID FEC dng chung cn cung cp mt s cu trc thm ca m nhn din, gi thit rng trong mt s trng hp SAI v TAI c mt phn chung, c gi l nhn din nhm (Attachment Group Identifier-AGI), khi SAI v TAI c

th c hiu l s ghp ni ca AGI vi m nhn din ring (Attachment Individual Identifier-AII), do m nhn din c th c m ha theo ba trng: AGI, SAII v TAII. SAI l tp hp ca AGI v SAII, TAI l tp hp ca AGI v TAII.

Tng t nh vy, [I-D.ietf-l2tpext-l2vpn] cho php s dng mt hoc hai m nhn din thit lp cc ng dy o. Nu trong cc bn tin bo hiu L2TP ch s dng m nhn din ca b chuyn tip pha ch th iu c ngha l h thng ngm nh gi tr m nhn din ca c hai pha ngun v ch nh nhau. Nu cc m nhn din c mang trong bn tin bo hiu L2TP bao gm ca c b chuyn tip ngun v ch th mi b chuyn tip s dng mt gi tr nhn din c ngha ti a phng.

Nhn din b chuyn tip trong [I-D.ietf-l2ptext-l2vpn] c cng khi nim nh nhn din ghp ni trong [I-D.ietf-pwe3-control-protocol]. Mt nhn din chuyn tip cng c th bao gm mt nhm nhn din ghp ni v mt nhn din ghp ni ring l. Khng ging nh thnh phn ID FEC chung, AGI v AII c ti trn cc cp gi tr-thuc tnh L2TP ring bit. AGI c m ha trong AGI AVP cn SAII v TAII c m ha trong phn u cui a phng ID AVP v u cui pha xa ID AVP tng ng. Nhn din chuyn tip ngun l tp hp ca AGI v SAII trong khi nhn din chuyn tip ch l tp hp ca AGI v TAII.

Trong cc ng dng c tp hp cc nhm ca cc PW thnh cc mng ring o lp 2, AGI c hiu nh l nhn din mng ring o (VPN)

Cng cn lu trong khi cc chuyn tip khc nhau h tr cung cp ng dng khc nhau, nhng kiu ng dng khng cn thit phi c nhn ra t nhn din chuyn tip. B nh tuyn nhn c bn tin bo hiu vi mt TAI c th c th xc nh c b chuyn tip no ca n c xc nh bi TAI , v c th xc nh c ng dng c cung cp trn chuyn tip . Nhng cc nt khc khng th xc nh c ng dng thng qua kim tra cc bn tin bo hiu n gin.

Trong ti liu ny, mt s cu trc thm ca AGI v AII c xut cho cc ng dng L2VPN c th. [I-D.ietf- pwe3-control-protocol] xut cu trc TLV cho AGI v AII. Do ngi iu hnh mng chn cu trc AII y c th s dng kiu AGI hoc AII khc nu h mun s dng cu trc khc cho cc nhn din ny i vi ng dng khc. Th d kiu tin t di ca [I-D.metz-aii-aggregate] c th c s dng cho php trao i thng tin qun l, c th kt hp vi thng tin nhn c thng qua qu trnh khm ph mng.

1.2.2. Thit lp mt ng dy o hai hng n gin

Trong bt c khun dng no ca bo hiu LDP trn c s BGP, mi im cui ng dy o phi khi to mt LSP n hng. Mt ng dy o l mt cp LSP nh vy. Trong hu ht cc m hnh cung cp L2VPN, hai im cui ca mt ng dy o c th ng thi thit lp bo hiu cho n. Sau chng phi thc hin mt th tc no xc nh khi mt cp LSP d kin kt hp li vi nhau to thnh mt ng dy o.

Cch thc cc LSP kt hp vi nhau trong cc trng hp khng hon ton ging nhau, ph thuc vo cc dch v L2VPN v cc m hnh cung cp. Chi tit s c trnh by cc phn sau.

Bo hiu L2TP vn thit lp mt phin lm vic hai hng mang ng dy o gia hai im cui ca ng dy o. Hai im cui cng c th ng thi khi to bo hiu cho ng dy o. Do c kh nng hai ng dy o c th c thit lp i vi mt cp b chuyn tip.

trnh trng hp thit lp trng ng dy o gia hai b chuyn tip, mi PE phi c kh nng nhn bit c lp nh l mt mi ghp ng dy o. Th tc nhn bit mt mi ghp ng dy o c trnh by trong [I-D.ietf-l2tpext-l2vpn].

1.2.3. Nhn din ghp ni v chuyn tip

Tt c cc b chuyn tip trong mt PE phi c lin kt vi mt nhn din kt ni (AI), c th thng qua mt cu hnh hoc thng qua mt s thut ton. Nhn din kt ni phi c tnh n nht trong phm vi ca b nh tuyn PE m cc chuyn tip nm trong . T hp ca gi tr phi c tnh n nht trong ton b h thng.

Theo [I-D.ietf-pwe3-control-protocol], nhn din ghp ni c th bao gm mt nhm nhn din ghp ni (AGI) cng vi mt nhn din ghp ni ring bit (AII). Trong phm vi ca ti liu ny, AGI c th c hiu l VPN-ID, hoc mt s thng s c chia s bi cc mch ghp ni cho php kt ni ti n.

Trong mt s trng hp c th c ch khi xem xt mt s mch ghp ni ti mt PE nh l mt b chung. Th d mt s lng mch ghp ni s dng kt ni mt CE vi mt PE cho trc c th xem nh l mt b. Vic s dng cc b c trnh by chi tit mc 3.3

Chi tit vic xy dng cc trng AGI v AII nhn din cc im cui ng dy o trong cc m hnh c th c tho lun phn sau ca ti liu ny.

Chng ta xem xt mt LSP cho mt hng ca mt ng dy o c xc nh bi:

V mt LSP theo hng ngc li ca ng dy o c xc nh nh sau: Mt ng dy o l mt cp hai LSP kiu nh th ny, trong trng hp s dng bo hiu L2TP, cc dng LSP c tham chiu n mc L2TP hai hng.

Khi bn tin bo hiu c gi t PE1 n PE2, v PE1 cn tham chiu n mt nhn din ghp ni c thit lp trn mt trong s cc mch ghp ni ca n (hoc b), nhn din ghp ni ny c c gi l nhn din ghp ni ngun. Nu PE1 cn tham chiu n mt nhn din ghp ni c to ra bi mt trong s cc mch ghp ni ca PE2 (hoc b), nhn din ghp ni c gi l nhn din ghp ni ch. Do SAI ti mt im cui l TAI ti im pha xa v ngc li.

Trong dao thc bo hiu, cc phng thc m ha c xc lp cho ba trng: Nhn din ghp ni nhm (AGI) Nhn din ghp ni ring pha ngun (SAII) Nhn din ghp ni ring pha ch (TAII)

Nu AGI khng trng, th SAI bao gm AGI v SAII, cn TAI bao gm TAII v AGI. Nu AGI rng, th SAII v TAII tng ng l SAI v TAI.

Vi d nh PE no nhn c bn tin bo hiu ghp nhn LDP hoc bn tin yu cu cuc gi n L2TP (ICRQ) cha TAi s c kh nng ghp TAI mt cch n nht n mt trong s cc mch ghp ni ca n (hoc b). Cch thc trong PE ghp mt TAI vo mch ghp ni (hoc b) nn l mt vic c tin hnh ti cc b (bao gm vic la chn s dng mt hay nhiu byte trong TAI cho vic ghp knh). Do nh c cp trong cc th tc bo hiu, TAI thc t ch l mt dy cc byte k t, mt cookie.

1.3. Cc ng dng

Phn ny s lm r cch thc bo hiu ng dy o s dng cc du hiu ca b chuyn tip ngun v ch p dng vo cc ng dng khc nhau. i vi mt s ng dng c th c trinh by chi tit trong cc m hnh cung cp khc nhau, tuy nhin y khng phi l danh sch cui cng cc dch v cng nh m hnh dch v cung cp c p dng ln dch v, cc dch v v m hnh cung cp ca n cn ang c pht trin.

1.3.1. Cc ng dy o kt ni im im ring bit

Phng thc bo hiu c m t trong ti liu ny c th c s dng thit lp cung cp cc ng dy o kt ni im ni im ring bit. Trong ng dng ny, mi b chuyn tip ghp mt ng dy o n n mt mch ghp ni n. Mi PE phi c cung cp vi s lng mch ghp ni cn thit, v sau cc thng s nht nh phi c cung cp cho mi mch ghp ni.

1.3.1.1. M hnh cung cp 1.3.1.1.1. Cung cp hai hng

Trong m hnh ny, mch ghp ni phi c cung cp mt tn a

phng, mt a ch ca PE u xa, v mt tn u xa. Trong sut qu trnh bo hiu, tn a phng c s dng nh l SAII, tn u xa c s dng nh l TAII, cn AGI rng. Nu hai mch ghp ni c kt ni bi mt ng dy o, tn a phng ca ci ny phi l tn u xa ca ci kia.

Lu rng nu tn a phng v tn u xa ging nhau th nguyn t PWid FEC c th c s dng thay th cho PWid FEC tng qut trong vic bo hiu trn c s LDP.

Vi bo hiu L2TP, tn a phng c gi trong im cui a phng ID AVP, tn u xa c gi trong im cui u xa ID AVP. Vic s dng ID AVP c tnh la chn, nu s dng tnh nng ny, n cha c trng AGI c gi

tr di bng 0. Nu tn a phng v tn u xa ging nhau, im cui a phng ID AVP c th c loi b khi bn tin bo hiu L2TP.

1.3.1.1.2. Cung cp n hng kt hp vi khai ph

Trong m hnh ny, mi mch ghp ni phi c cung cp mt tn a phng. Tn a phng ny bao gm mt VPN-id (bo hiu nh l AGI) v mt nhn din mch ghp ni ring c quan h trc giao vi AGI. Nu hai mch ghp ni c kt ni vi nhau bi mt ng dy o, ch mt trong s chng cn c cung cp tn u xa (ng nhin l tn a phng ca mch ghp ni cn li). C hai mch ghp ni khng cn c cung cp a ch ca PE pha u xa, nhng phi c chung VPN-id.

Nh l mt phn ca th tc t khai ph, mi PE qung b cc cp gi tr ca n. Mi PE so snh cp gi tr ca n vi cp c qung b bi cc PE khc. Nu cc cp gi tr ny ging nhau, th hai PE cn c kt ni vi nhau. Khi bo hiu, VPN-id c s dng nh l AGI cn AII cho c phn remote v local c s dng nh l TAII. Tn a phng ca mch ghp ni pha local c gi i nh l SAII.

Li ch c bn ca m hnh cung cp ny khi so snh vi m hnh cung cp theo hai hng l n cho php chuyn mt mch ghp ni t PE ny sang PE khc m khng cn phi cu hnh li im cui u xa. Tuy nhin so snh vi hng tip cn c trnh by trong mc 3.3 di y, m hnh ny p t mt gnh nng ln c ch khai ph v tn ca mi mch ghp ni phi c gi i qung b ring bit (khng c nhm cc AC trong cu trc n gin ny)

1.3.1.2. Bo hiu

Bo hiu trn c s LDP tun theo cc th tc c ch ra trong [I-D.ietf-pw3-control-protocol], khi mt PE (PE2) nhn c mt bn tin ghp nhn t PE1 gi ti thit lp mt LSP theo mt hng. Nu bn tin c x l thnh cng, v cha c LSP no cho hng ngc li (PE1 n PE2), khi PE2 gi bn tin ghp nhn n PE1.

Thm vo th tc trong [I-D.ietf-pw3-control-protocol], khi mt PE nhn bn tin ghp nh v TAI nhn din mt mch ghp ni c th c cu hnh ghp vo mt ng dy o im ni im, th cc bc kim tra sau y c thc hin.

Nu mch ghp ni c ghp vi mt ng dy o (bao gm c trng hp khi ch c mt trong hai LSP tn ti), v im cui u xa khng phi l PE1 th PE2 gi bn tin gii phng nhn n PE1 vi m trng thi c ngha mch ghp ni ghp vi PE khc, qu trnh x l bn tin yu cu ghp ni kt thc. Nu mch ghp ni c ghp vi mt ng dy o (bao gm c trng hp khi mt trong hai LSP tn ti), nhng AI ti PE1 khc vi AI c ch nh trong trng AGI/SAII ca bn tin yu cu ghp ni th PE2 gi bn tin gii

phng nhn n PE1, vi m trng thi c ngha mch ghp ni ghp vi mch ghp ni u xa khc, qu trnh x l bn tin yu cu ghp ni kt thc.

Tng t vi cch thc bo hiu trn c s L2TP, khi mt PE nhn c mt bn tin ICRQ, v TAI nhn din c mt mch ghp ni c th c cu hnh ghp ni vi mt ng dy o im ni im, n tin hnh cc bc kim tra sau.

Nu mch ghp ni c ghp ni vi mt ng dy o v im cui pha u xa khng phi l PE1, th PE2 gi bn tin lu ngt cuc gi (CDN) n PE1, vi m trng thi c ngha mch kt ni ghp vi PE khc, qu trnh x l bn tin ICRQ kt thc.

Nu mch kt ni c gn vi mt ng dy o, nhng ng dy o c ghp vo mt b chuyn tip trn PE1 vi AI khc vi yu cu trong trng SAI ca bn tin ICRQ, th PE2 gi mt bn tin CDN n PE1, vi m trng thi c ngha mch kt ni ni vi mt mch kt ni u xa khc, qu trnh x l bn tin ICRQ kt thc.

Cc li trn cng xut hin trong trng hp cu hnh sai.

1.3.2. Dch v mng LAN o

Trong ng dng VPLS [I-D.ietf-l2vpn-vpls-ldp], cc mch kt ni c th c xem nh cc dao din mng LAN kt ni vi mt chuyn mch mng LAN o hoc trong thut ng c nh ngha trong [I-D.ietf-l2vpn-l2-framework] c gi l cc phin chuyn mch o (VSI). Mi b chuyn tip l mt VSI kt ni ti mt s lng cc PW v mt s lng cc mch kt ni. Dch v VPLS yu cu mt ng dy o n c thit lp gia mi hai cp hai VSI trong cng mt VPLS. Mi thit b PE c th c nhiu VSI, trong mi VSI thuc v mt VPLS khc nhau.

1.3.2.1. Cung cp

Mi VPLS phi c mt thuc tnh nhn din mang tnh n nht trn ton b mng, thuc tnh ny tham chiu theo [I-D.ietf-l2vpn-l2-framework] c bit n nh l m nhn din VPLS (VPLS-id). Mi VSI phi c thit lp vi VPLS-id ca VPLS m n nm trong .

Mi VSI cng phi c mt m nhn din duy nht, c gi l VSI-ID. M nhn din ny c th c t ng nh dng thng qua kt hp VPLS-id ca n vi mt a ch IP ca b nh tuyn PE ca n. (lu trong trng hp ny a ch PE ch c s dng nh l dng ca mt thuc tnh nh dng n nht; mt nh cung cp dch v c th chn s dng vi cu trc s khc nu mun, min sao m bo mi VSI c gn mt m nhn din c tnh n nht trong mt phin VPLS. Mc 4.4 s tho lun thm v vic gn cc nhn din trong trng hp nhiu nh cung cp dch v.

1.3.2.2. T khai ph 1.3.2.2.1. T khai ph trn c s BGP

Trong mc ny xc nh cch thc s dng BGP khai ph cc thng tin cn thit thit lp mt phin VPLS. Khi qu trnh t khai ph trn c s BGP c s dng thit lp VPLS, AFI/SAFI s c dng:

AFI c nh dng bi IANA cho L2VPN (c s dng nh nhau i vi mi cu trc L2VPN)

SAFI c quy nh bi IANA dnh ring cho mt dch v L2VPN trong cc ng dy o c thit lp s dng cc th tc c trnh by trong ti liu ny.

Xem mc 1.6 thm cc thng tin v gn cc AFI/SAFI. s dng t khai ph trn c s BGP, phi c t nht mt thng s nhn

din duy nht trn ton h thng lin quan n VPLS, v mi thng s nhn din ny phi c kh nng m ha nh mt RD 8 byte. Bt k phng php gn mt hoc nhiu thng s nhn din n nht vo mt VPLS v m ha tng thng s nh mt RD c th thc hin (s dng k thut m ha trong [RFC4364]).

Mi VSI cn c mt thng s nhn din c th c m ha nh l mt BGP NLRI. N c nh dng bng cch ghp RD vi mt a ch IP ca PE cha VSI. Vic ghp vi a ch IP ny n gin l xc nh mt thng s nhn din duy nht i vi cc VSI trong VPN; n khng cn thit phi l mt bng nh tuyn trn ton b h thng, nhng n phi c tnh n nht trong mt phin VPLS. Mt cu trc khc c th thay th l gn cc thng s nhn din n nht cho mi VSI trong mi phin VPLS c th c xem xt.

Khi s dng cc th tc c m t trong ti liu ny, iu cn thit l gn mt gi tr VPLS-id n nht trn ton h thng cho mi phin VPLS [I-D.ietf-l2vpn-vpls-ldp]. VPLS-id phi c kh nng m ha c nh l mt BGP EC [RFC4306]. Nh c m t trong mc 6, hai kiu EC ph c nh ngha trong bn d tho xut.

Kiu EC ph u tin l mt AC hai octet quy nh EC, kiu EC ph th hai l mt a ch IPv4 quy nh EC. M ha cc EC ny c quy nh trong [RFC4360]. Cc m ha ny m bo mt nh cung cp dch v c th inh v c mt VPLS-id trnh xung t vi nh cung cp dch v khc. Tuy nhin, cn lu rng s kt hp cc VPLS-id gia cc nh cung cp dch v l cn thit cho vic kt ni lin thng cc VPN ca cc nh cung cp dch v, nh c m t trong ma 4.4.

Mi VSI cng cn c kt hp vi mt hoc nhiu phn m rng chung nh tuyn ch (RT). Cc thng s ny iu khin phn b ca NLRI v do iu khin nh dng cu trc xp chng ca cc ng dy o cu thnh mt VPLS.

Cc qu trnh t ng khai ph bng cch nhn thng tin phn b PE, thng qua BGP, NLRI i vi mi VSI ca n, thng tin v bn thn n nh l mt BGP ca chng tip theo, v vi cc RT thch hp ca mi NLRI. Thng thng, mi PE c th l mt client ca mt nhm nh cc b phn x tuyn BGP, c chc nng phn b li thng tin n cc client khc.

Nu mt PE khng nhn c thng tin cp nht BGP t bt c phn t no c m t bn trn th vic cp nht thng tin b b qua.

Nu mt PE c mt VSI vi mt RT c th, n c th sau nhp tt c cc NLRI c cng RT , v t cc thuc tnh ca cc NLRI BGP chng k tip n c th hc cc a ch IP ca cc b nh tuyn PE c cc VSI c cng RT. Cc im cn xem xt p dng vo b phn x tuyn c quy nh trong [RFC4364] mc 4.3.3.

Nu mt VPLS xc nh mun tr thnh mt mng LAN kt ni y , tt c cc VSI ca n s c cng RT, trong trng hp ny RT c th l (mc d khng nht thit phi nh vy) mt m ha ca VPN-id. Mt VSI c th c t trong nhiu VPLS bng cch gn cho n nhiu RT.

Lu mt s phn cp VPLS c th c thit lp thng qua gn nhiu RT vo mt v VSI. C ch RT cho php mi mt c kh nng iu khin hon thin trn xp chng ng dy o cu thnh cu trc VPLS.

Nu phn b VPLS (miu t trong mc 3.5) c thit lp, ch cc N-PE tham gia trong qu trnh t khai ph trn c s BGP. iu ny c ngha l mt N-PE c th cn thit qung b kh nng vi ti n mi mt VSI n h tr, bao gm cc VSI nh v trong cc U-PE n kt ni n. thit lp mt thng s nhn din duy nht cho mi VSI ny, mt a ch IP ca mi U-PE kt hp vi RD ca phin VPLS c th c s dng. Tm li, bn tin qung co cho mt VSI c th ti mt PE c th bao gm:

Mt NLRI ca AFI=L2VPN, SAFI=TBA, m ha nh RD:PE_addr Mt BGP chng k tip tng ng a ch quay vng ca PE Mt thng s m rng chung cha VPLS-id Mt thng s m rng chung cha mt hoc nhiu RT.

Xem mc 6 v chi tit cc thng s AFI v SAFI. Cch thc qung b ny tng t nh nh dng NLRI trnh by trong [I-

D.ietf-l2vpn-vpls-bgp], im khc bit quan trng nht l [I-D.ietf-l2vpn-vpls-bgp] cn bao gm mt khi nhn trong NLRI. Hot ng lin thng gia cu trc VPLS a ra y v trong [I-D.ietf-l2vpn-vpls-bgp] nm ngoi phm vi ca ti liu ny.

1.3.2.3. Bo hiu

iu cn thit l phi to ra cc thng s nhn din ghp ni nhn din cc VSI. Trong cc phn trc, mt VSI-ID c m ha nh l RD:PE_addr, v VPLS-id c ti trn phn m rng chung BGP. i vi mc ch bo hiu, cc thng tin ny c m ha nh sau: m ha VPLS-id trong trng AGI, v t PE_addr (hay c bit hn l VSI-ID c cha trong NLRI trong BGP tr RD) trong trng TAII. Kt hp ca AGI v TAII xc nh VSI no c chn ng dy o kt ni vi n, trong c hai mi trng AS n v AS lin thng. SAII phi c t n a ch PE-addr ca PE gi i (hay c bit hn l VSI-ID, khng bao gm RD, ca VSI kt hp vi chnh VPLS trong PE gi i), kch hot bo hiu ca na ngc li ca ng dy o nu cn thit.

Cu trc ca cc trng AGI v AII cho ID FEC tng qut trong LDP c nh ngha trong [I-D.ietf-pwe3-control-protocol]. Trng AGI trong trng hp ny bao gm mt kiu thuc 1, mt trng di ca gi tr 8, v 8 byte ca VPLS-id. Trng AII bao gm mt kiu thuc 1, mt trng di ca gi tr 4, tip n 4 byte a ch PE (hoc 4 byte nhn din). Mc 6 trnh by v thit lp kiu AGI v AII.

M ha AGI v AII trong L2TP c quy nh trong [I-D.ietf-l2tpext-l2vpn]. Lu khng th dng k thut ny thit lp nhiu ng dy o trn mt cp hai VSI.

1.3.2.4. ng dy o nh mch ghp ni VPLS

K thut trn cng c th c s dng thit lp ng dy o ghp ni vi mt u cui ti mt VSI, nhng u cui bn kia ch kt ni vi mt mch ghp ni. C th c nhiu hn mt ng dy o kt thc ti VSI ny, cc ng dy o phi c phn bit theo mt cch no . Do mi ng dy o phi c mt SAII c lin h n nht vi VSI-ID.

1.3.3. Mng mesh y cc kt ni ng dy o im im

M hnh b mu ca nh iu hnh cung cp dch v mng l phng thc t ng cp pht ng dy ring o (VPWS). Trong m hnh ny, mi PE c th cha vi b gm cc mch kt ni, mi b kt hp vi mt VPN c th. Mt PE c th cha nhiu b trn VPN, v mi b c th tng ng vi mt thit b CE c th. C th xem xt thit lp mt ng dy o gia mi cp b c cng VPN, kt qu c th l mt cu hnh mesh u cc kt ni VC gia cc CE-CE i vi mi VPN.

1.3.3.1. Cung cp Mi b c thit lp cu hnh v lin kt vi:

Mt tp hp cc mch kt ni (AC) Mt mu, c th hiu l mt VPN-id hoc tng t nh vy Mt thng s nhn din lin quan n b, c lin h n nht vi mu.

Ph thuc vo cng ngh s dng cho mch kt ni m c th cn thit hoc khng cn thit cp pht cc mch kt ni ny. Th d nu cc AC l mch Frame Relay, c mt s h thng ring bit thit lp cc mch ny. Cp pht mt AC c th n gin l vic thc hin nh v mt VLAN ID cha s dng trn mt dao din v truyn thng s la chn n khch hng. Phng thc ny khng lin quan g n cc th tc c trnh by trong ti liu ny.

Thng s nhn din b, v thng s mu c gp li vi nhau to thnh mt thng s nhn din b n nht trn ton h thng. Do nu c n b cng mt mu, thng s nhn din cc b ny c th (mc d khng nht thit) bng cc con s t 1 n n.

H thng hot ng theo phng thc thit lp mt ng dy o gia mi cp b cha c cng mu, trong mi ng dy o s c gn n mt AC t mi b cha.

Nu mi b cha l mt tp hp ca cc AC dn n mt thit b CE n, th cch thc kt ni lp 2 gia cc CE c iu khin thng qua cc mu c ch nh cho cc b cha. thit lp mesh y , mu s phi l mt VPN-id.

Mt chc nng c tnh chn la thm l mt AC c th c th c thit lp vi thng s b cha lin quan ca mt b cha pha xa. Sau AC c th c gn ti mt ng dy o c th ch khi im cui u xa ca ng dy o l b cha vi thng s nhn din b cha lin quan. Vi chc nng ny, cng mt cp AC lun c ghp li thng qua cc ng dy o.

1.3.3.2. T khai ph 1.3.3.2.1. T khai ph trn c s BGP

Trong phn ny s trnh by cch thc s dng BGP khai ph thng tin cn thit thit lp cc phin VPWS Khi th tc t ng khai ph c s dng cho VPWS, cc thng s AFI/SAFI s c dng:

AFI c quy nh bi IANA cho L2VPN (c chung nh dng cho tt c cc cu trc L2VPN)

SAFI c quy nh bi IANA c bit cho mt dch v L2VPN trong cc ng dy o c thit lp s dng cc th tc c m t trong ti liu ny

Mc 6 s trnh by cc tho lun v ch nh AFI/SAFI. s dng t ng khai ph trn c s BGP, phi c mt hoc nhiu

thng s nhn din lin quan n mt phin VPWS c th. Mi thng s nhn din phi c m ha nh mt RD. Thng s nhn din c tnh n nht trn ton h thng ca b cha phi c m ha nh NLRI; thng s nhn din b cha c xc nh c s lng 4 byte c gn thm vo RD to NLRI.

Khi s dng cc th tc c m t trong ti liu ny, cn thit phi n nh mt thng s nhn din n nht ton cc cho mi phin VPWS. Thng s nhn din ny phi c m ha nh mt BGP m rng chung [RFC4360]. Nh c m t trong phn 6, hai kiu ph m rng chung c nh ngha trong bn d tho ny dnh cho mc ch .

Kiu ph m rng chung th nht l mt AC hai octet quy nh m rng chung, kiu ph m rng chung th hai l mt a ch IPv4 quy nh m rng chung. M ha ca cc thng s ny c quy nh trong [RFC4360]. Cc phng thc m ha ny m bo cho mt nh cung cp dch v c th nh v mt thng s nhn din VPWS trnh khi nguy c xung t vi nh cung cp dch v khc. Tuy nhin s hot ng chung ca thng s nhn din VPWS gia cc nh cung cp dch v cn thit cho vic cung cp L2VPN lin thng gia cc nh cung cp dch v c m t trong mc 1.4.4

Mi b cha cng phi c kt hp vi mt RT, cng c th l mt m ha ca mt mu. Nu yu cu cu trc mng phi l mesh y ca cc

ng dy o, tt c cc b cha c th c chung RT, xem mc 1.3.4 trnh by v cc cu trc khc.

Qu trnh t ng khai ph nhn thng tin phn b cc PE, thng tin BGP, NLRI ca mi b cha ca mi PE, xc nh BGP chng tip theo, nhn thng tin RT c m ha thng s mu ca b cha. Nu PE c mt b c mu (RT) xc nh, n phi nhn thng qua BGP tt c NLRI vi cng mu (RT). Thng thng mi PE s l mt trm khch ca mt tp hp nh ca cc phn t phn x tuyn BGP, s phn b li cc thng tin trn n cc trm khch khc.

Nu mt PE nhn mt bn tin cp nht BGP t bt c phn t no m t bn trn b thiu, vic cp nht nn c b qua.

Nu mt PE c mt b cha vi mu xc nh, n c th nhn c tt c cc NLRI c cng mu , v t BGP chng k tip cc thng s ca NLRI ny s nhn a ch IP ca cc b nh tuyn PE khc c cc b c cng mu. N c th cng nhn thng s nhn din ca cc b u xa c m ha nh NLRI. Thng s nhn din b cha u xa c tch khi NLRI v c s dng bo hiu, nh trnh by di y. Tm li, bn tin qung b BGP cho mt b cha c th ca cc AC ti mt PE cho trc s cha cc thng tin:

Mt NLRI c AFI=L2VPN, SAFI=TBA, m ha RD:pool_num BGP chng k tip tng ng a ch lp vng ca PE Mt thng s m rng chung cha thng tin nhn din VPWS Mt thng s m rng chung cha mt hay nhiu RT Cc gi tr ca AFI v SAFI c trnh by trong mc 1.6

1.3.3.3. Bo hiu

Bo hiu trn c s LDP tun theo cc th tc c trnh by trong [I-

D.ietf-pwe3-control-protocol]. Phng thc tin hnh c th c m t nh sau: mt PE (PE1) gi mt bn tin ghp nhn cho mt PE khc (PE2) thit lp mt LSP mt hng. a ch ca PE2 l a ch nhn c thng qua BGP c trnh by phn trn. Nu bn tin c x l thnh cng v cha c mt LSP cho ng dy o theo hng ngc li (PE1PE2), th PE2 gi bn tin ghp nhn ti PE1. Tng t nh vy, bo hiu trn c s L2TPv3 tun theo cc th tc trong [I-D.ietf-l2tpext-l2vpn]. Cc thng tin thm ca vic s dng cc dao thc bo hiu ny c trnh by di y.

Khi mt PE gi mt bn tin ghp nhn hoc mt bn tin ICRQ thit lp mt ng dy o gia hai b cha, n m ha m nhn din VPWS (nh phn b trong phn m rng chung ca BGP) nh l AGI, cc thng tin nhn din lin quan n b cha a phng c m ha nh l SAII, cc thng tin nhn din lin quan n b cha u xa c m ha nh l TAII.

Cu trc ca cc trng AGI v AII cho ID FEC chung trong LDP c xc nh trong [I-D.ietf-pwe3-control-protocol]. Trng AGI trong trng hp ny bao gm mt kiu thuc 1, mt trng di thuc gi tr 8, v 8 byte m thng tin nhn din VPWS. TAII bao gm mt kiu thuc 1, mt trng di

thuc gi tr 4, tip sau bi 4 byte mang s ca b cha u xa. SAII bao gm mt kiu thuc 1, mt trng di thuc gi tr 4, tip sau bi 4 byte mang s ca b cha a phng. Phn 1.6 s trnh by cc th tc ch nh kiu AGI v AII, cc th tc c trnh by trong ti liu ny cho VPLS v VPWS c th s dng cng mt kiu AGI (1) v cng mt kiu AII (1).

M ha cho AGI v AII trong L2TP c trnh by trong [I-D.ietf-l2tpext-l2vpn].

Khi PE2 nhn c mt bn tin ghp nhn hoc mt bn tin ICRQ t PE1 v TAI nhn din mt b cha, nhng c mt ng dy o kt ni mt AC trong b cha n mt AC ti PE1, v AI ti PE1 ca ng dy o ging nh SAI ca bn tin ghp nhn hoc bn tin ICRQ, th PE2 gi mt bn tin gii phng nhn hoc CDN n PE1, vi m trng thi c ngha AC c gn ti AC u xa. iu ny nhm trnh vic thit lp nhiu ng dy o gia mt cp hai b cha cho trc.

Lu rng bn thn vic bo hiu ch nhn din b cha u xa m ng dy o hng ti ch khng phi l AC c gn vi ng dy o . Tuy nhin PE u xa c th kim tra trng SAII xc nh AC no c gn vi ng dy o.

1.3.4. Mng mesh mt phn

Th tc thit lp mesh mt phn ca cc ng dy o gia mt tp hp cc b cha c gn m mu v cn bn ging nh cc th tc thit lp mesh y , vi mt s im khc bit sau:

Mi b cha c cu hnh c la chn vi mt s cc RT nhp v RT xut

Trong qu trnh t ng khai ph trn c s BGP, mu ca b cha vn c m ha trong RD, nhng nu b cha c cu hnh vi mt tp hp ca RT xut, th cc RT xut ny s c m ha trong cc RT ca bn tin cp nht BGP thay th cho mu.

Nu mt b cha c mt RT nhp c th c mu gi tr X, n s to mt PW n mi b cha khc nu c X l gi tr ca mt trong s cc RT xut. Bn tin bo hiu v cc th tc gia chng nh trong 3.3.3

Th d n gin nht trong trng hp ny l xy dng mt cu trc dng hub-and-spoke vi mt hub. Mt b cha ng vai tr l hub, c cu hnh vi mt RT xut ca RT_hub v mt RT nhp ca RT_spoke. Tt c cc b cha khc (ng vai tr l spoke) c thit lp cu hnh vi mt RT xut ca RT_spoke v mt RT nhp ca RT_hub. Theo cu hnh ny Hub s kt ni vi tt c cc spoke v ngc li nhng cc b cha spoke khng kt ni trc tip vi nhau. Cc th d phc tp hn c trnh by trong mc 4.2.2 ca [I-D.ietf-l3vpn-bgpvpn-auto].

1.3.5. Phn b VPLS

Trong phn b VPLS ([I-D.ietf-l2vpn-l2-framework]), cc chc nng VPLS ca mt b nh tuyn PE c chia theo hai h thng: mt U-PE v N-PE. U-PE nm gia ngi s dng v N-PE. Chc nng VSI (nh nhn a ch MAC v cu ni) c thit lp trn U-PE. Mt s lng cc U-PE kt ni n mt N-PE. i vi mi VPLS c cung cp bi mt U-PE, U-PE duy tr mt ng dy o n mi U-PE khc trong cng mt VPLS. Tuy nhin, cc U-PE khng duy tr iu khin bo hiu kt ni vi nhau. Hn th na, mi U-PE ch c mt ng bo hiu n n cc N-PE ca n. Nh vy mi kt ni ng dy o U-PE n U-PE bao gm ba on dy o tch bit: mt t U-PE n N-PE, mt t N-PE n N-PE v mt t N-PE n U-PE. Trong ni dung ca [I-D.ietf-pwe3-ms-pw-arch], cc N-PE thc hin chc nng chuyn mch ng dy o thit lp cc ng dy o nhiu phn on t U-PE n U-PE.

Xem xt v d v cu trc sau: U-PE A-----| |----U-PE C | | | | N-PE E--------N-PE F | | | | U-PE B-----| |-----U-PE D

C 4 U-PE u trong mt VPLS chung, cch thc cc ng dy o c ghp ni trong cu hnh trn thit lp cc ng dy o cn thit t U-PE A n cc U-PE khc c tin hnh nh sau:

C ba ng dy o t A n E c t tn l A-E/1, A-E/2 v A-E/3. kt ni A n cc U-PE khc, phi c hai ng dy o t E n F (E-F/1 v E-F/2), mt ng dy o t E n B (E-B/1), mt t F n C (F-C/1) v mt t F n D (F-D/1).

Cc N-PE phi ghp ni cc ng dy o ny vi nhau c mt s tng ng cho php c ch bo hiu khng phn b VPLS c th cung cp:

PW t A n B: A-E/1 ghp ni vi E-B/1 PW t A n C: A-E/2 ghp ni vi E-F/1 ghp ni vi F-C/1 PW t A n D: A-E/3 ghp ni vi E-F/2 ghp ni vi F-D/1 Vic la chn cc PW no ghp ni vi nhau khng quan trng, ch

cn kt qu l c PW t A n cc im B,C,D. Tng t nh vy, c cc PW thm phi c ghp ni vi nhau m

bo kt ni lin thng U-PE B vi U-PE C v D cng nh kt ni gia U-PE C vi U-PE D.

Hnh v sau biu th cc PW t A n C v t B n D, d theo di, 4 PW khc khng c trnh by trong hnh.

Cc im ghp ni | | V V A-C PW U-PE A-----| |----U-PE C | | | | N-PE E--------N-PE F | | | | U-PE B-----| |-----U-PE D B-D PW ^ ^ | | Cc im ghp ni

C th thy rng phn b VPLS khng lm gim s lng cc PW trn mi U-PE, nhng n lm gim cc kt ni iu khin trn U-PE

1.3.5.1. Bo hiu

Bo hiu cung cp VPLS phn b c th c thc hin vi cc c ch c m t trong ti liu ny. Tuy nhin, cc th tc dnh cho VPLS (mc 3.2.3) cn c mt s c ch b sung m bo s lng cc PW tng ng c thit lp gia nhiu N-PE v U-PE, v gia cc N-PE.

Ti mt N-PE, cc U-Pe kt ni trc tip vo mt VPLS xc nh c th c nh s t 1 n n. Thng s nhn din U-PE ny c lin quan n mt VPN-id c th v mt N-PE c th.

Sau khi kt thc phn t cu hnh v khai ph, mi U-PE phi nhn c mt danh sch cc cp . Mi phn t trong danh sch ny cho bit U-PE thit lp J PW n a ch IP c xc nh. Khi U-PE bo hiu n N-PE, n thit lp AGI l VPN-id thch hp v thit lp SAII bng s PW, TAII trng.

Trong v d trn, U-PE A c th nhn c , c ngha n phi thit lp 3 PW n E. Khi bo hiu, A c th thit lp AGI l VPN thch hp, SAII bng 1, 2, 3 ph thuc vo PW no ang c bo hiu.

Sau khi kt thc phn t cu hnh v khai ph, mi N-PE phi nhn c danh sch cc thng tin sau cho mi VPLS:

Mt danh sch a phng: {}, trong mi phn t bo cho N-PE bit thit lp J PW n U-PE kt ni a phng n a ch c xc nh. Con s cc phn t trong danh sch c th l n l s U-PE kt ni a phng trong VPLS ny. Trong v d c trnh by bn trn, danh sch a phng s l {,} cho bit thit lp 3 PW n A v 3 PW n B.

Mt s a phng, lin quan n VPLS v N-PE c th ca U-PE ca n, trong v d trn E c th c bo U-PE A l 1 v U-PE B l 2.

Mt danh sch pha u xa: {} cho bit thit lp k PW cho mi U-PE n a ch c xc nh, v k quy nh s ca cc U-PE trong VPLS ti N-PE. Trong v d c trnh by bn trn, E nhn c danh sch u xa {} khi N-PE E c hai U-PE n cho bit thit lp 4 PW n N-PE F, mi U-PE ca E s dng hai ci. Bo hiu ca mt PW t N-PE n U-PE da trn danh sch a phng

v s lng a phng ca cc U-PE. Khi bo hiu mt PW c th t mt N-PE n mt U-PE, AGI c t bng VPN-id tng ng v SAII trng, TAII t bng s PW (lin quan n VPLS c th v U-PE). Trong v d trn khi E bo hiu n A, n t TAII l 1, 2, 3 tng ng vi PW c thit lp n A, n c th bo hiu tng t nh vy n B.

Bo hiu LSP t U-PE n N-PE c kt hp vi mt LSP t N-PE n U-PE theo cch thng thng, mt PW gia mt U-PE v mt N-PE c gi l U-PW.

Bo hiu ca mt s PW tng ng t N-PE n N-PE da trn danh sch u xa. Cc PW gia cc N-PE c th c xem nh tng ng. Khi s lng tng cc PW c xc nh, cc N-PE c th ghp cc PW ny n cc U-PW thch hp. Bo hiu s chnh xc ca cc PW t N-PE n N-PE da trn danh sch u xa, danh sch u xa quy nh s cc PW thit lp, cho tng U-PE n mt N-PE u xa c th.

Khi bo hiu mt PW c th t mt N-PE n mt N-PE, AGI c t bng VPN-id tng ng, TAII xc nh N-PE u xa nh trong trng hp khng phn b. Nu c n PW nh vy, chng c phn bit bng cch thit lp SAII. c th thit lp nhiu gi tr SAII khc nhau trong mt VPLS, N-PE bn gi cn c s lng VSI-ID bng U-PE. Nh ch thch trong mc 3.2.2, iu ny c th t c bng cch s dng mt a ch IP cho mi U-PE ghp vo. PW gia hai N-PE c gi l N-PW.

Mi U-PW phi c ghp ti mt N-PW, iu ny c thc hin thng qua danh sch pha u xa. Nu danh sch pha u xa cha cc thng s , th i U-PW t mi U-PE a phng phi c ghp n i N-PW t N-PE u xa. Vic la chn U-PW no ghp vi N-PW no khng cn phi ch n.

Nu mt N-PE c nhiu hn 1 U-PE a phng trong mt VPLS cho trc, n phi m bo mt U-PW t mi U-PE c ghp n mt U-PW t mi U-PE khc.

1.3.5.2. Cung cp v khai ph

Mi N-PE phi c cung cp vi mt s lng phin VPLS n h tr mt VPN-id cho mi phin v mt danh sch cc U-PE a phng cho mi VPLS . Nh mt phn ca th tc khai ph, N-PE qung b s lng cc U-PE cho mi VPLS. Xem mc 3.2.2 bit thm chi tit.

T ng khai ph c th c s dng khai ph tt c cc N-PE khc trong VPLS, v i vi mi N-PE , danh sch cc U-PE a phng cho mi VPLS cng c cp nht. T cc thng tin ny, c th tnh ton s lng tng

cng cc U-PE trong VPLS. Thng tin ny cho php ngi ta tnh ton danh sch a phng v danh sch u xa cho mi N-PE.

1.3.5.3. Khng phn b VPLS nh mt trng hp ring Mt PE m c cung cp VPLS khng phn b (PE hot ng c cc

chc nng ca U-PE v N-PE) c th hot ng lin thng vi cc cp N-PE/U-PE c cung cp VPLS phn b. PE khng phn b thc hin qung b thng qua th tc khai ph rng n c mt U-PE a phng trn mi VPLS, v ng nhin PE khng phn b khng thc hin chuyn mch PW.

Nu mi PE trong mt VPLS c cung cp VPLS khng phn b, v do mi PE qung b chnh n nh mt N-PE vi mt U-PE a phng, kt qu qu trnh bo hiu chnh xc nh m t trong mc 1.3.2.3 bn trn

1.3.5.4. Ghp ni PW v mt phng d liu

Ghp ni cc PW vi nhau c thc hin kh d dng trong mt phng d liu MPLS. Vic thc hin chuyn mt gi t mt PW trc tip n PW khc ch thng qua vic thay th nhn trong nhn PW. Khi mt PW bao gm hai hoc hn hai PW ghp vi nhau, gi s rng d liu s i n nt mng ti vic ghp ni c thc hin th ng i ca d liu s xuyn qua cc nt ph hp trong bo hiu PW.

Chi tit v ghp ni PW c tho lun trong [I-D.ietf-pwe3-segmented-pw]

1.4. Hot ng Inter-AS

Cc c ch phn b, t ng khai ph v bo hiu c trnh by bn trn c th c p dng hon ton trong mi trng hot ng Inter-AS. Nh c trnh by trong [RFC4364], c mt s la chn cho hot ng Inter-AS.

1.4.1. Phn b li nhiu on EBGP ca L2VPN NLRI

La chn ny tng t nh la chn (c) trong [RFC4364]. l ngi ta s dng phn b li nhiu on EBGP ca cc L2VPN NLRI gia cc AS ngun v ch, vi phn b li EBGP ca cc tuyn nhn IPv4 hoc IPv6 t AS n AS ln cn.

Mt ASBR phi duy tr c cc tuyn nhn IPv4/32 hoc IPv6/128 n cc b nh tuyn bn trong phm vi AS ca n. N s dng EBGP phn b li cc tuyn n cc AS khc, v thit lp bn thn n nh mt BGP chng tip theo cho cc tuyn ny. Cc ASBR trong bt k AS chuyn tip s cng phi s dng EBGP i qua cc tuyn /32 hoc /128. iu ny dn n s thit lp mt s ng dn chuyn mch nhn t tt c cc b nh tuyn PE li vo n tt c cc b nh tuyn PE li ra. Khi cc b nh tuyn PE trong cc AS khc nhau c th thit lp cc kt ni EBGP nhiu on vi nhau, v c th trao i cc L2VPN NLRI thng qua cc kt ni ny. Tip theo qu trnh trao i,

mt cp PE trong cc AS khc nhau c th thit lp mt phin LDP bo hiu cc PW bn trong vi nhau.

i vi VPLS, thng tin qung co BGP v bo hiu PW ging nh c trnh by trong mc 1.3.2. Kt qu ca vic thit lp phin EBGP nhiu chng gia AS ngun v AS ch l cc PE trong mt AS m c cc VSI ca mt VPLS xc nh s khm ph cc PE trong AS khc m c cc VSI cng VPLS vi n. Cc PE ny sau s cho php thit lp phin bo hiu PW thch hp v thit lp mesh y ca cc PW VSI-VSI xy dng VPLS nh trnh by trong mc 1.3.2.3.

i vi VPWS, thng tin qung co BGP v bo hiu PW ging nh c m t trong phn 1.3.3. Kt qu ca vic thit lp phin EBGP nhiu chng gia AS ngun v AS ch l cc PE trong mt AS c cc b cha ca mt mu xc nh (VPN) s khm ph cc PE trong AS khc m c cc b cha cng mu vi n. Cc PE ny sau s cho php thit lp bo hiu PW v thit lp mesh y PW nh c m t trong mc 1.3.2.3. Mt mesh mt phn cng c th c thit lp tng t nh vy s dng cc th tc trinhg by trong phn 1.3.4

Ging nh trong VPN lp 3, xy dng mt L2VPN c phm vi nm trn nhiu nh cung cp dch v yu cu nhiu s cng tc trong vic s dng cc RT v RD. Ni dung ny s c tho lun sau trong mc 1.4.4.

1.4.2. Phn b li EBGP ca L2VPN NLRI vi ng dy o nhiu phn on

Mt kh nng hn ch ca hng tip cn c trnh by trong mc trn

l n to ra cc phin bo hiu PW trong tt c cc PE ca L2VPN (VPLS hoc VPWS). iu ny c ngha l mt s lng ln cc phin LDP hoc L2TPv3 s xuyn qua bin gii AS v cc phin lm vic ny kt ni qu nhiu thit b trong mt AS. Trong trng hp cc AS thuc v nhiu nh cung cp dch v khc nhau, c th tng tng cc nh cung cp c th mong mun c t cc phin bo hiu vt qua bin AS hn v iu ny c ngha l gii hn cc phin ny lin quan n t thit b hn. Hn na, vic p cc phin bo hiu LDP hay L2TPv3 gii hn trong mt s lng nh cc ASBR, mt nh cung cp dch v c th s dng cc th tc thm nh tiu chun trn mt s lng nh cc phin lm vic lin thng nh cung cp. iu ny lin quan r vi hng tip cn c m t di y.

[I-D.ietf-pwe3-segmented-pw] m t mt hng tip cn chuyn mch cc gi t mt PW n PW khc to mt nt mng c th. Hng tip cn ny cho php mt PW u cui n u cui hay nhiu phn on c th c xy dng trn nhiu phn on khng cn phi duy tr mt kt ni iu khin u cui n u cui. Hng tip cn ny c th c s dng to ra gii php cho inter-AS gn ging la chn (b) trong [RFC4364] hn.

Trong m hnh ny, phn b li EBGP ca L2VPN NLRI c s dng t AS n AS ln cn. Trc tin, cc b nh tuyn PE s dng IBGP phn b li L2VPN NLRI cng nh n mt ASBR (Autonomous System Border Router), hoc n mt b phn x tuyn m ASBR l mt client ca n. ASBR

sau s dng EBGP phn b li cc L2VPN NLRI n mt ASBR trong AS khc, hoc c th n ASBR khc phn b li chng...

Trong trng hp ny, mt PE c th hc a ch ca mt ASBR thng qua nhng g n c th vi ti PE khc m n mun thit lp PW ti. iu ny c ngha l, mt PE a phng s nhn c mt qung co BGP cha L2VPN NLRI tng ng n mt phin L2VPN trong PE a phng c mt vi phn t kt ni n. BGP chng k tip cho L2VPN NLRI s l mt ASBR ca AS a phng. Sau , thay v xy dng mt kt ni iu khin trn tt c on ng n PE u xa, n ch xy dng mt n ASBR. Mt phn on PW c th c thit lp t PE n ASBR k tip. n phin ASBR c th thit lp mt PW n ASBR ca AS tip theo, v ghp ni PW n PW t PE nh c m t trong mc 1.3.5.4 v [I-D.ietf-pwe3-segmented-pw]. Qu trnh lp li ti mi ASBR dn n mt chui ca cc on PW, khi chng kt ni li vi nhau th s hnh thnh kt ni gia hai PE.

C mt iu cn lu trong m hnh c m t bn trn l PE a phng c th khng nhn c a ch IP ca PE u xa, n nhn bn tin qung co L2VPN NLRI c gi bi PE u xa m bn tin ny khng nht thit phi cha a chi IP ca PE u xa, v n nhn a ch IP ca ASBR l BGP chng k tip ca NLRI .

Khi m hnh ny c s dng cho VPLS, hoc mesh y ca VPWS, n thit lp mt mesh y ca cc PW gia cc PE, ging nh phn trc nhng n khng i hi mt mesh y cc kt ni iu khin (phin LDP hoc L2TPv3). Thay th cho cc kt ni iu khin gia cc AS chy theo tt c cc PE ca AS v cc ASBR ca cc AS, mt ng iu khin gia cc ASBR ca cc AS lin k c th c s dng thc hin tuy nhin li cn nhiu phn on PW AS-to-AS thc hin iu ny.

Cc th tc c m t trn y s dn n cc im ghp ni (S-PE trong [I-D.ietf-pwe3-ms-pw-arch]) c xc nh chung bi cc ASBR. C th c nhiu kt ni ASBR-ASBR gia mt cp AS cho trc. trong trng hp ny mt PE c th chn theo cc ASBR c sn da trn mt khong tiu chun nh ma trn IGP, cu hnh ti u a phng... tng t vi vic la chn li ra ca mt tuyn IP thng thng. Vic s dng nhiu ASBR c th dn n s hi phc cao (ti thang thi gian hi t tuyn BGP) khi mt PE c th la chn mt ASBR mi trong trng hp kt ni hin ti b s c.

Nh trong cc L3VPN, xy dng mt L2VPN m rng cc mng ca nhiu nh khai thc yu cu mt s s thng nht chung trong vic s dng RT v RD. Phn ny c m t chi tit hn trong mc 1.4.4.

1.4.3. ng dng cung cp chung ca bo hiu VPLS phn b

Mt hng tip cn thay th cho VPLS chung gia cc nh cung cp dch v c th nhn c t m hnh phn b VPLS c m t pha trn, m hnh ca n c trnh by trong hnh sau:

PE A --- Network 1 ----- Border ----- Border ----- Network 2 --- PE B Router 12 Router 21 | | PE C

Trong A, B v C l cc PE trong cng mt VPLS, nhng mng 1 v 2

c nh cung cp dch v khc nhau, Border Router 12 l b nh tuyn bin ca mng 1 n mng 2 v Border Router 21 l b nh tuyn bin ca mng 2 n mng 1. Gi s cc PE khng c phn b v c cung cp cc chc nng N-Pe v U-PE.

Nh c trnh by trong m hnh, cn phi c hai PW xuyn gia hai nh cung cp A-B v A-C.

Nu cc nh cung cp quyt nh, cho d bt c l do no cng khng mun cc PE ca h c chung kt ni iu khin vi bt c PE no ca mng khc, do cc kt ni iu khin lin mng ch c th hot ng ti cc b nh tuyn bin.

iu ny c th c thc hin s dng k thut c trnh by trong mc 1.3.5, trong cc PE ng vai tr nh U-PE, v cc BR nh N-PE. Trong m hnh minh ha, PE A c th hnh x nh mt U-PE kt ni a phng n BR12, PE B v C ging nh U-PE kt ni vi BR21 v hai BR nh hai N-PE.

Kt qu l mt PW t A n B c th bao gm ba phn on: A-BR12, BR12-BR21 v BR21-B. Cc b nh tuyn bin c nhim v ghp cc on tng ng vi nhau.

iu ny yu cu cc PE trong mt VPLS phi c nh s th t 1 n n (lin quan n VPLS ) trong mt mng cho trc.

1.4.4. Cc vn cn xem xt v khai bo RT v RD

Cn lu rng, nhm mc ch bt c th tc no c m t trn y hot ng theo mong mun, hai AS phi s dng cc RT v RD tng ng, ging nh trong cc L3VPN [RFC4364]. Cu trc ca cc RT v RD m bo c khng xut hin cc nguy c ln v s c mng. iu quan trng l ngi iu hnh mng ca AS phi bit c RT v RD no c ch trong AS mng bn kia thit lp VPN lin gia hai AS. Nh trong cc L3VPN, c nhiu cch thc hin iu ny nhng tt c u yu cu s cng tc chung gia cc nh cung cp dch v. Th d nh cung cp dch v A c th tag tt c cc NLRI ca mt VPN cho trc vi mt RT (RT_A) v nh cung cp dch v B sau c th thit lp cu hnh cc PE kt ni ti cc im ca VPN nhp cc NLRI c cha RT . Hoc nh cung cp B c th chn mt RT khc (RT_B) tag tt c cc NLRI cho VPN vi RT , v sau nh cung cp dch v A c th nhp NLRI vi TR ti cc PE thch hp. iu ny i hi cc nh cung cp dch v c hai pha phi thng bo s la chn cc RT ca h i vi mi VPN, hoc c hai pha nh cung cp dch v nht tr s dng chung RT cho mt VPN xc nh. Trong bt c trng hp no vic thng bo cc RT gia cc nh cung cp dch v u cn thit. Nh trong L3VPN, cc nh cung cp dch v c th cu

hnh lc RT m bo ch cc gi tr RT ph hp c cho php i xuyn qua bin gii AS.

Mt m nhn din VPN (c mang trong phn m rng chung BGP) phi c thit lp cho mi phin VPLS hoc VPWS. Quy tc m ha ca cc m nhn din ny [RFC4360] m bo khng xut hin s xung t vi nh cung cp dch v khc. Tuy nhin i vi mt phin VPLS hoc VPWS c phm vi trn mng ca nhiu nh cung cp dch v th mt nh cung cp cn nh dng m nhn din ri chuyn s la chn ca mnh cho cc nh cung cp dch v khc thng nht gi tr s dng trong phin VPLS hoc VPWS.

1.5. Bo mt

Ti liu ny trnh by mt s m hnh cung cp dch v L2VPN khc nhau, v xc nh cc m nhn din im u cui phi c cung cp cho mi m hnh. Ti liu ny cng quy ch cch thc cc m nhn din u cui c ghp vo cc trng trong cc giao thc t ng khai ph v cc giao thc bo hiu.

Vn bo mt lin quan n cc giao thc bo hiu c tho lun trong cc ti liu lin quan n giao thc ([RFC3036] [I-D.ietf-pwe3-control-protocol] [RFC3931] [I-D.ietf-l2tpext-l2vpn]).

Vn bo mt lin quan n giao thc t ng khai ph trn c s BGP, bao gm c trng hp hot ng lin AS, c tho lun trong [RFC4264]. Cc L2VPN s dng t ng khai ph trn c s BGP c th t ng ci t cc c ch bo mt. Chi tit v cc c ch bo mt t ng nm ngoi phm vi ti liu ny v vn cn ang c nghin cu.

Vn bo mt lin quan n dch v L2VPN ang c cung cp c tho lun trong cc ti liu [I-D.ietf-l2vpn-l2-framework], [I-D.ietf-l2vpn-requirements], v [I-D.ietf-l2vpn-vpls-ldp].

Cch thc cc nhn din u cui c ghp vo cc trng giao thc bo hiu v khai ph khng to ra bt c nguy c v bo mt no thm vo.

1.6. IANA

Cc th tc trong ti liu ny tha nhn vic thit lp mt AFI v mt SAFI cho L2VPN NLRI, c AFI v SAFI nn c gi tr ging nh trong [I-D.ietf-l2vpn-vpls-bgp]: AFI bng 25 (L2VPN) v SAFI bng 65. Cc gi tr AFI v SAFI c s dng nh nhau trong th tc t ng khai ph cho c hai trng hp VPLS v VPWS.

Khuyn ngh [I-D.ietf-pwe3-iana-allocation] xut cc kiu cho AGI v AII, nh dng kiu 1 ca AGI v AII c s dng trong cc th tc c trnh by trong ti liu ny.

Cc th tc trnh by trong ti liu ny s dng hai m trng thi LDP mi, cc gi tr mi c th dng l:

0x0000002C "AC gn vi PE khc " 0x0000002D "AC gn vi AC u xa khc".

Cc th tc trnh by trong ti liu ny s dng hai m kt qu L2TP mi cho bn tin CDN, cc gi tr mi c th dng l:

RC-TBD1: AC gn vi PE khc RC-TBD2: AC gn vi AC u xa khc Cc gi tr xut cho m nhn din AS v a ch IPv4 VPN l 0x000A M nhn din Two-octet AS Layer 2 VPN 0x010A M nhn din a ch IPv4 Layer 2 VPN

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