MPLS cisco QOS VPN full 01 mpls arch overview

MPLS Architecture Overview Jay Kumarasamy jayk@cisco.com Adopted from Stefano Previdi’s presentation â 2001, Cisco Systems Agenda MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Day in the Life of a Packet 2001 Cisco Systems, Inc www.cisco.com MPLS Concepts • MPLS: Multi Protocol Label Switching • MPLS is a layer 2+ switching • Developed to integrate IP and ATM • MPLS forwarding is done in the same way as in ATM switches • Packet forwarding is done based on Labels 2001 Cisco Systems, Inc www.cisco.com MPLS Concepts • Unlike IP, classification/label can be based on: Destination Unicast address Traffic Engineering VPN QoS • FEC: Forwarding Equivalence Class 2001 Cisco Systems, Inc www.cisco.com Agenda • MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Summary 2001 Cisco Systems, Inc www.cisco.com LSRs and Labels • LSR: Label Switch Router • Edge-LSR: LSRs that label imposition and disposition • ATM-LSR: An ATM switch with Label Switch Controller 2001 Cisco Systems, Inc www.cisco.com LSRs and Labels IGP domain with a label distribution protocol • An IP routing protocol is used within the routing domain (e.g.:OSPF, i-ISIS) • A label distribution protocol is used to distribute address/label mappings between adjacent neighbors • The ingress LSR receives IP packets, performs packet classification, assign a label, and forward the labelled packet into the MPLS network • Core LSRs switch packets/cells based on the label value • The egress LSR removes the label before forwarding the IP packet outside the MPLS network 2001 Cisco Systems, Inc www.cisco.com LSRs and Labels 01234567890123456789012345678901 Label | Exp|S| TTL Label = 20 bits Exp = Experimental, bits S = Bottom of stack, 1bit TTL = Time to live, bits • Uses new Ethertypes/PPP PIDs/SNAP values/etc • More than one Label is allowed -> Label Stack • MPLS LSRs always forward packets based on the value of the label at the top of the stack 2001 Cisco Systems, Inc www.cisco.com LSRs and Labels PPP Header(Packet over SONET/SDH) Ethernet Frame Relay ATM Cell Header GFC PPP Header Shim Header Layer Header Ethernet Hdr Shim Header Layer Header FR Hdr Shim Header Layer Header VPI VCI PTI CLP HEC DATA VCI PTI CLP HEC DATA Label Subsequent cells GFC VPI Label 2001 Cisco Systems, Inc www.cisco.com Agenda 2001 Cisco Systems, Inc • MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Day in the Life of a Packet www.cisco.com 10 Loops and TTL • LSRs using ATM not have TTL capability • Some suggested options: - hop-count object in LDP - Path Vector object in LDP 2001 Cisco Systems, Inc www.cisco.com 28 Loops and TTL LSR-1 LSR-3 LSR-2 IP packet TTL = 10 Label = 25 IP packet TTL = Label = 39 IP packet TTL = LSR-6 LSR-6 > 25 Hops=4 IGP domain with a label distribution protocol Label = 21 IP packet TTL = LSR-4 IP packet TTL = LSR-5 Egress • TTL is decremented prior to enter the non-TTL capable LSP If TTL is the packet is discarded at the ingress point • TTL is examined at the LSP exit 2001 Cisco Systems, Inc www.cisco.com 29 Agenda 2001 Cisco Systems, Inc • MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Day in the Life of a Packet www.cisco.com 30 LDP Concepts • Label Distribution Protocol • Labels map to FECs for Unicast Destination Prefix • LDP works between adjacent/non-adjacent peers • LDP sessions are established between peers 2001 Cisco Systems, Inc www.cisco.com 31 LDP Messages • Discovery messages • Used to discover and maintain the presence of new peers • Hello packets (UDP) sent to all-routers multicast address • Once neighbor is discovered, the LDP session is established over TCP 2001 Cisco Systems, Inc www.cisco.com 32 LDP Messages • Session messages • Establish, maintain and terminate LDP sessions • Advertisement messages • Create, modify, delete label mappings • Notification messages • Error signalling 2001 Cisco Systems, Inc www.cisco.com 33 Agenda • MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Day in the Life of a Packet 2001 Cisco Systems, Inc www.cisco.com 34 Day in the life of a Packet In I/F In Lab - Address Prefix 171.68/16 Out Out I/F Lab Next-Hop In I/F In Lab Address Prefix 171.68/16 Out Out I/F Lab Next-Hop In I/F In Lab P1 PE P 0 Use label for FEC 171.68/16 Out I/F Next-Hop Out Lab pop Address Next-Hop Prefix and mask Interface 171.68.10/24 171.68.9.1 Serial1 171.68.44/24 171.68.12.1 Serial2 171.68/16 Null 0 PE Use label “implicit-null” for FEC 171.68/16 Use label for FEC 171.68/16 Summary route for 171.68/16 CE Address Prefix 171.68/16 Summary route for 171.68/16 171.68.44/24 171.68.10/24 Summary route is propagate through the IGP and label is assigned by each LSR Egress LSR summarises more specific routes and advertises a label for the new FEC Egress LSR needs to an IP lookup for finding more specific route 2001 Cisco Systems, Inc www.cisco.com 35 Day in the life of a Packet Basic Layout C o n t r o l P la n e I P R o u t in g P r o t o c o ls R o u tin g E x c h a n g e I P R o u t in g T a b le L a b e l D is t r ib u t io n P r o t o c o l L a b e l B in d in g E x c h a n g e L ab el R em oved L lo o k u p O u tg o in g IP P a c k e ts In c o m in g IP P a c k e ts F o r w a r d I n f o r m a tio n B lo c k ( F IB ) In c o m in g L a b e lle d P a c k e t s L a b e l F o r w a r d In f o r m a tio n B lo c k (L F IB ) O u t g o in g L a b e lle d P a c k e t s F o r w a r d in g P la n e 2001 Cisco Systems, Inc www.cisco.com 36 Day in the life of a Packet Database Layout IS IS O SPF R o u tin g T a b le BG P LDP T IB F IB in c o m in g -ta g ta g _ re w r ite [ ] ta g _ h a s h fa s t-a d ja c e n c y fa s tta g -re w rite ta g _ in fo D e s t IP a d d r e s s ta g _ re w rite o u u t-if encaps in c o m in g -ta g o u tg o in g -ta g ID B v e c to r s T F IB tfib _ e n try ta g _ r e w rite lo a d in fo ta g _ in fo tfib _ e n try tfib _ e n try tfib _ e n try ip _ tu rb o _ fs ta g _ o p tim u m _ fs ip _ ta g _ o p tim u m _ fs In c o m i n g t a g 2001 Cisco Systems, Inc www.cisco.com 37 Day in the life of a Packet In -b o u n d in t e r f a c e d r iv e r checks encaps, in v o k e s h a n d le r th r u ID B v e c to r s - b g p - b a s e d p o lic y m a p p in g (Q P P B ) a n d s e t q o s - g r o u p ID - a u th e n t ic a t io n p r o x y - c h e c k f o r in p u t A C L s - c h e c k fo r c ry p to - c h e c k f o r s e t t in g in p u t Q o S m a r k in g - In p u t p o lic e / r a t e - in p u t - c h e c k f o r N A T ( o u ts id e -> in s id e - c h e c k p o lic y r o u t in g - c h e c k fo r W E B c a c h e r e d ir e c t io n check e a r ly fe a tu re s - c h e c k f o r N A T ( in s id e - > o u ts id e ) - p e r f o r m Q o S c la s s if ic a t io n - c h e c k fo r c ry p to - o u u t A C L c h e c k - c h e c k fo r s e t t in g o u t p u t Q o S m a r k in g - Q oS - W FQ - o u t p u t p o lic e / r a t e - lim it in g po st lo o k u p fe a tu r e s IP F IB lo o k u p a d ja -c e n c y lo o k u p IP fr a g m e n t ? s e n d IP packet M P L S IP IP M P L S la b e l im p o s itio n M P L S p ro c e ss la b e lle d packet 2001 Cisco Systems, Inc www.cisco.com - c o m p u te le n g th o f ta g (s ) t o b e c o p ie d & c h e c k if f r a g is r e q u ir e d - c o p y t o s f ie ld - s e t ttl - c o p y t h e la b e l( s ) - if ( f e a t u r e s ) { - p e rfo rm o u u t Q o S c la s s if ic a t io n - c h e c k f o r s e t t in g o u t p u t Q o S m a r k in g - d o o u t p u t r a t e - lim it in g - c h e c k f o r m u lti- v c } - fr a g m e n t , if n e c e s s a r y - s e n d la b e lle d p a c k e t 38 Day in the life of a Packet In -b o u n d in te r fa c e d r iv e r c h e c k s e n c a p s , in v o k e s h a n d le r th r u ID B v e c to rs check e a r ly fe a tu re s IP no r e w r ite in fo , d o L a y e r-3 lo o k u p M PLS p ro c e s s c h e c k la b e lle d e a r ly p a c k e t fe a tu r e s - O u u t Q o S C la s s ific a tio n - S e ttin g o u u t Q o S m a r k in g - D o o u u t r a te -lim it/p o lic in g ta g s w itc h in lin e ta g fo rw a rd in lin e - g e t la b e l h e a d e r - In p u t Q o S C la s s ific a tio n - S e ttin g in p u t Q o S m a r k in g - fr o m tfib g e t th e ta g e n tr y - D o in p u t r a te -lim it/p o lic in g - g e t r e w r ite in fo fr o m th e ta g e n try - u p d a te T T L v a lu e - u p d a te E X P v a lu e - S W A P /P O P la b e l, p r o c e s s in n e r la b e l - h a n d le m u lti-v c C o S - P la tfo r m s p e c ific W R E D d o n e in th e fin a l tr a n s m it p a th 2001 Cisco Systems, Inc www.cisco.com check post fe a tu r e s tr a n s m it packet 39 Summary • LSRs forward packet based on label information • IP header and forwarding decision have been de-coupled for better flexibility • Label information can derive from different sources IP routing protocols (destination based unicast routing) Multicast Traffic Engineering QoS VPN 2001 Cisco Systems, Inc www.cisco.com 40 Summary • MPLS allows flexible packet classification and network resources optimisation • Labels are distributed by different protocols •LDP, RSVP, BGP, PIM • Different distribution protocols may coexist in the same LSR • Label have local (LSR) significance No need for global (domain) wide label allocation/numbering 2001 Cisco Systems, Inc www.cisco.com 41 Thank You! 2001 Cisco Systems, Inc www.cisco.com 42 ... based on Labels 2001 Cisco Systems, Inc www .cisco. com MPLS Concepts • Unlike IP, classification/label can be based on: Destination Unicast address Traffic Engineering VPN QoS • FEC: Forwarding... engineering • BGP External labels (VPN) • PIM For multicast states label mapping 2001 Cisco Systems, Inc www .cisco. com 17 Agenda 2001 Cisco Systems, Inc • MPLS Concepts • LSRs and labels • Label... 2001 Cisco Systems, Inc www .cisco. com Agenda • MPLS Concepts • LSRs and labels • Label assignment and distribution • Label Switch Paths • ATM LSRs • Loops and TTL • LDP overview • Summary 2001 Cisco