IP Datagram Service MPLS. Virtual Call Call Request (CR) Agenda

Transcription

1 Datenkommunikation SS 29 Datenkommunikation SS 29 IP Datagram Service IP Host R IP Router R2 Destination Net Hop A R B R4 C.. R3.. R3 A2 B A2 B MPLS Multi-Protocol Label Switching User A.2 IP (structured Net-ID:Host-ID) Destination Net Hop A B R2 C R2.... IP Routing Table of R R4 Destination Net Hop A R2 B R C R2.... A2 B Destination Based Routing Destination Net Hop A R4 B C R4 R.... A2 B A2 B User B. 29, D.I. Lindner / D.I. Haas MPLS, v4. 3 Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods RFC s Virtual Call Call Request (CR) User A.2 Destination Net Hop A PS B PS4 PS P PS2 P C PS3 PS3.... P P2 P P2In OutP P: P3:2 A2 B CR 44 A2 B CR Destination Net Hop A B PS2 C PS2.... In Out P:44 P2: P P3 Routing Table of PS P A2 B CR 2 P2 Destination Net Hop A PS4 B C PS4.... In Out P:69 P2:9 P P2 Switching Table of PS Destination Net Hop A PS2 B PS C PS2.... In Out P:2 P2:69 PS4 A2 B CR 69 PS A2 B CR 9 User B. 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-29, D.I. Lindner / D.I. Haas Page App3-2

2 Datenkommunikation SS 29 Datenkommunikation SS 29 Virtual Call Call Accepted (CA) User A.2 44 CAA2 B PS P PS2 P P2In OutP PS3 P: P3:2 P P2 P In Out P:44 P2: CAA2 B P P3 P 2 CA A2 B P2 In Out P:69 P2:9 P P2 Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods RFC s In Out P:2 P2:69 PS4 69 CAA2 B PS 9 CAA2 B User B. 29, D.I. Lindner / D.I. Haas MPLS, v4. 29, D.I. Lindner / D.I. Haas MPLS, v4. 7 Virtual Call Data Transfer ATM as WAN Technology based on SDH PS P PS2 P P2In OutP PS3 P: P3:2 P P2 P 44 User A.2 In Out P:44 P2: Forwarding performed by switching tables P In Out P:2 P2:69 P3 P 2 PS4 P2 In Out P:69 P2:9 P P PS User B. POTS LE PABX STM- Mb/s E3 34Mb/s ISDN LE PRI / E 2Mb/s. SDH R R R SDH E3 up to hundreds of km s STM Mb/s E3 STM- Mb/s ISDN LE E3 34Mb/s PRI / E POTS LE PABX 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-3 29, D.I. Lindner / D.I. Haas Page App3-4

3 Datenkommunikation SS 29 Datenkommunikation SS 29 SDH Circuits (Timeslots of S-TDM) ATM as LAN/ MAN Technology based on Dark Fiber Dark Fiber SDH-Circuit 3 for Mb/s STM- Mb/s. SDH R R R SDH E3 STM--4 34Mb/s E3 622Mb/s E3 STM- Mb/s E3 34Mb/s up to some m s up to some km s up to some m s POTS LE ISDN LE SDH-Circuit 2 for 34Mb/s SDH-Circuit for 34Mb/s ISDN LE POTS LE PABX PRI / E 2Mb/s PRI / E PABX 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. ATM-VC s inside SDH-Circuit ATM Scenario -> VPI / VCI POTS LE PABX ATM-VC STM- Mb/s. SDH R R R SDH E3 STM--4 34Mb/s E3 622Mb/s E3 ISDN LE PRI / E 2Mb/s ATM as Intelligent Bandwidth Management System ATM-VC2 ATM-VC3 SDH-Circuit 3 for Mb/s SDH-Circuit 2 for 34Mb/s SDH-Circuit for 34Mb/s STM- Mb/s 29, D.I. Lindner / D.I. Haas MPLS, v4. ISDN LE E3 34Mb/s PRI / E POTS LE PABX VPI/VCI = / (A->B) A ATM-DTE ATM-DCE D VPI/VCI = /88 (D->C) ATM-DCE ATM-DTE VPI/VCI = /44 B 2 4 VPI/VCI = /99 3 C ATM-DTE ATM-DTE 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-29, D.I. Lindner / D.I. Haas Page App3-6

4 Datenkommunikation SS 29 Datenkommunikation SS 29 ATM Switching Tables Cell Forwarding / Label Swapping 2 ATM-DTE ATM-DCE ATM-DTE A B A B I 2 I: / : /77 D I I: /77 O2: /99 I4: /77 : 4/88 I I4 O2 3 I: /88 O2: /77 I4: /99 O2: /44 29, D.I. Lindner / D.I. Haas MPLS, v4. 3 O2 I4 I 4 I: 4/88 : 2/99 O2 Switching Table of ATM Switch 2 C I I: /77 O2: /99 I4: /77 : 4/88 2 I: / : /77 77 I I4 77 O2 I D I: /88 O2: / , D.I. Lindner / D.I. Haas MPLS, v4. 4 O2 O2 I4 I4: /99 O2: /44 I I: 4/88 : 2/99 C Cell Forwarding / Label Swapping Cell Forwarding / Label Swapping 3 Cell Header ( Byte) Payload (48 byte) A B A B I VPI / VCI I: / : /77 I: /77 O2: /99 I4: /77 : 4/88 I I4 O2 I4 O2 I4: /99 O2: /44 I I: /77 O2: /99 I4: /77 : 4/88 2 O2 I4 I 99 I4: /99 O2: /44 I: / : /77 I4 O2 O2 I 88 I D I: /88 O2: /77 C I: 4/88 : 2/99 29, D.I. Lindner / D.I. Haas MPLS, v4. 4 I D I: /88 O2: /77 O I 3 29, D.I. Lindner / D.I. Haas MPLS, v I: 4/88 : 2/99 C 29, D.I. Lindner / D.I. Haas Page App3-7 29, D.I. Lindner / D.I. Haas Page App3-8

5 Datenkommunikation SS 29 Datenkommunikation SS 29 Cell Forwarding / Label Swapping 4 A I I: /77 O2: /99 I4: /77 : 4/88 2 D I: /88 O2: /77 3 B 44 O2 O2 I4 I I4: /99 O2: /44 I: / : /77 I4 I O2 I , D.I. Lindner / D.I. Haas MPLS, v I: 4/88 : 2/99 C ATM Routing in Private ATM Networks PNNI is based on Link-State technique like OSPF Topology database Every switch maintains a database representing the states of the links and the switches Etension to link state routing!!! Announce status of node (!) as well as status of links Contains dynamic parameters like delay, available cell rate, etc. versus static-only parameters of OSPF (link up/down, node up/down, nominal bandwidth of link) Path determination based on metrics Much more comple than with standard routing protocols because of ATM-inherent QoS support 29, D.I. Lindner / D.I. Haas MPLS, v4. 9 Segmentation Principle Cells are much smaller than data packets Segmentation and Reassembly is necessary in ATM DTE s (!!!) ATM DCE s (ATM switches) are not involved in that Datagram H SDU T BOM COM COM COM COM EOM PAD H 44 Octet T H 44 Octet T 48 H Payload H Payload H Payload Bitstream 29, D.I. Lindner / D.I. Haas MPLS, v4. 8 PNNI Routing Generic Connection Admission Control (GCAC) Used by the source switch to select a path through the network Calculates the epected CAC (Connection Admission Control) behavior of another node. Support this QoS ly? CAC UNI/NNI 2. Yes/No GCAC 3.) Is it likely that path will deliver epected QoS? 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-9 29, D.I. Lindner / D.I. Haas Page App3 -

6 Datenkommunikation SS 29 Datenkommunikation SS 29 PNNI Routing (Simple QoS -> ACR only) Operation of the GCAC CR Cell Rate ACR Available Cell Rate D Distance like OSPF costs PNNI Routing Operation of the GCAC 2) Net, shortest path(s) to the destination is (are) calculated Metric component -> Distance value used ATM-DCE ATM-DTE S2 ACR = 2 S6 S2 ACR = 2 S6 Requested CR = 3 Requested CR = 3 ATM-DTE S ATM-DCE ACR = ACR =, ACR = S3 ACR = 4 ACR = D = ACR = S4 S ACR = 4 S ACR = ACR =, ACR = S3 ACR = 4 ACR = D = ACR = S4 S ACR = 4 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 23 PNNI Routing Operation of the GCAC ) Links not supporting requested CR are eliminated -> Metric component -> ACR value used PNNI Routing Operation of the GCAC 3) One path is chosen and source node S constructs a Designated Transit List (DTL) -> source routing --> Describes the complete route to the destination Requested CR = 3 S2 ACR = 2 S6 Requested CR = 3 S2 ACR = 2 S6 S ACR = ACR =, ACR = S3 ACR = 4 ACR = D = ACR = S4 29, D.I. Lindner / D.I. Haas MPLS, v4. 22 S ACR = 4 S ACR = ACR =, ACR = S3 ACR = 4 ACR = D = ACR = S4 29, D.I. Lindner / D.I. Haas MPLS, v4. 24 S ACR = 4 requested ACR = 3 29, D.I. Lindner / D.I. Haas Page App3-29, D.I. Lindner / D.I. Haas Page App3-2

7 Datenkommunikation SS 29 Datenkommunikation SS 29 PNNI Routing - Source Routing Operation of the GCAC 4) DTL is inserted into signaling request and moved on to net switch ) After receipt net switch perform CAC a) ok -> pass PNNI signaling message on to net switch of DTL 6a) finally signaling request will reach destination ATM-DTE -> VC ok PNNI Signaling with DTL list S ACR = ACR =, ACR = S2 S3 ACR = 2 ACR = 4 ACR = D = ACR = S4 29, D.I. Lindner / D.I. Haas MPLS, v4. 2 S S6 ACR = 4 requested ACR = 3 PNNI Routing - New Trial Operation after Crankbank 7b) The other possible path is chosen - source node constructs again a new Designated Transit List (DTL) Requested CR = 3 S ACR = ACR =, ACR = S2 S3 ACR = 2 ACR = 4 ACR = D = ACR = S4 29, D.I. Lindner / D.I. Haas MPLS, v4. 27 S S6 ACR = 4 requested ACR = 3 PNNI Routing - Crankbank Operation of the GCAC ) After receipt net switch (S2) perform CAC b) nok -> return PNNI signaling message to originator of DTL 6b) S will construct alternate source route PNNI Signaling with DTL list S2 cannot fulfill requirements on trunk to S S2 ACR = 2 S6 PNNI Routing - Source Routing Operation of the GCAC 8b) DTL is inserted into signaling request 9b) After receipt net switch perform CAC ok -> pass PNNI signaling message on to net switch of DTL b) finally signaling request will reach destination ATM-DTE -> VC ok PNNI Signaling with DTL list S2 ACR = 2 S6 S ACR = ACR = S3 ACR = 4 ACR =, ACR = D = ACR = Crankbank to S S4 S ACR = 4 requested ACR = 3 S ACR = ACR =, ACR = S3 ACR = 4 ACR = D = ACR = S4 S ACR = 4 requested ACR = 3 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-3 29, D.I. Lindner / D.I. Haas Page App3-4

8 Datenkommunikation SS 29 Datenkommunikation SS 29 Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods RFC s A Simple Physical Network Physical wiring 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 3 IP Overlay Model - Scalability Base problem Nr. IP routing separated from ATM routing because of the normal IP overlay model no echange of routing information between IP and ATM world leads to scalability and performance problems many peers, configuration overhead, duplicate broadcasts note: IP system requests virtual circuits from the ATM network ATM virtual circuits are established according to PNNI routing virtual circuits are treated by IP as normal point-to-point links IP routing messages are transported via this point-to-point links to discover IP neighbors and IP network topology IP Data Link View (Non-NBMA) Every virtual circuit has its own IP Net-ID (subinterface technique) 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-29, D.I. Lindner / D.I. Haas Page App3-6

9 Datenkommunikation SS 29 Datenkommunikation SS 29 A Single Network Failure Eample - Physical Topology net A net B net A-A net B-B Ra Rb net D-D Sa Sb net C-C net D Rd Sd Sc Rc net C 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 3 Causes Loss of Multiple IP Router Peers!!! IP Connectivity through Full-mesh VC s net A net B net A-A net B-B Ra Rb net D-D net C-C net D Rd Rc net C 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-7 29, D.I. Lindner / D.I. Haas Page App3-8

10 Datenkommunikation SS 29 Datenkommunikation SS 29 Static Routing/No Routing Broadcasts net D net D-D Rd net A-A net A Ra Configuration Router Rd net B-B net C-C static routing resolution PVC resolution SVC net A via net hopra Ra map VPI/VCI Rd Ra Ra map ATM addr. Ra net B via net hoprb Rb map VPI/VCI Rd Rb Rb map ATM addr. Rb net C via net hoprc Rc map VPI/VCI Rd Rc Rc map ATM addr. Rc every network listed here! 29, D.I. Lindner / D.I. Haas MPLS, v4. 37 Rb net B Rc net C Observations This clearly does not scale Switch/router interaction needed peering model Without MPLS Only outside routers are layer 3 neighbors one ATM link failure causes multiple peer failures routing traffic does not scale (number of peers) With MPLS Inside MPLS switch is the layer 3 routing peer of an outside router one ATM link failure causes one peer failure highly improved routing traffic scalability 29, D.I. Lindner / D.I. Haas MPLS, v4. 39 Dynamic Routing/Routing Broadcasts A Simple Physical Network net A-A net A net B net B-B Physical wiring and NBMA behavior Ra Rb net D-D net C-C Rd Configuration Router Rd Rc net D dynamic routing on PVC resolution PVC net C VPI/VCI Rd Ra broadcast Ra map VPI/VCI Rd Ra VPI/VCI Rd Rb broadcast Rb map VPI/VCI Rd Rb VPI/VCI Rd Rc broadcast Rc map VPI/VCI Rd Rc note: SVCs may be possible Cisco neighbor command is specied for Cisco routing process because no automatic neighbor discovery is possible in this case 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-9 29, D.I. Lindner / D.I. Haas Page App3-2

11 Datenkommunikation SS 29 Datenkommunikation SS 29 IP Data Link View (NBMA) Routers assume a LAN behavior because all interfaces have the same IP Net-ID but LAN broadcasting to reach all others is not possible RFC 222 Operation (Classical IP over ATM) ARP server for every LIS multiple hops for communication between Logical IP Subnets ARP Server Subnet LIS Logical IP Subnet ATM Network LIS LIS2 ARP Server Subnet 2 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 43 Some Solutions for the NBMA Problem MARS Architecture ARP (Address Resolution Protocol) Server keeps configuration overhead for resolution small but does not solve the routing issue (neighbor discovery and duplicate routing broadcasts on a single wire) MARS/MCS (Multicast Address Resolution Server / Multicast Server) additional keeps configuration overhead for routing small but does not solve the duplicate broadcast problem LANE (LAN Emulation = ATM VLAN s) simulates LAN behavior where resolution and routing broadcasts are not a problem All of them require a lot of control virtual circuits (p-t-p and p-t-m) and SVC support of the underlying ATM network CLIENT Control VC Cluster Control VC CLIENT CLIENT (SVC -> VC on Demand point-to-multipoint data VC CLIENT MARS 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-2 29, D.I. Lindner / D.I. Haas Page App3-22

12 Datenkommunikation SS 29 Datenkommunikation SS 29 MARS plus MCS Architecture LANE Connections MARS MCS Server Control VC MCS Control Direct LES Data Direct (SVC -> VC on Demand) Control Direct Control Distribute Multicast Forward Configure Direct Multicast Send CLIENT CLIENT Cluster Control VC 29, D.I. Lindner / D.I. Haas MPLS, v4. 4 LECS 29, D.I. Lindner / D.I. Haas MPLS, v4. 47 BUS MARS/MCS Architecture CLIENT Control VC Cluster Control VC CLIENT CLIENT point-to-multipoint data VC CLIENT MARS Server Control VC CLIENT MCS MCS CLIENT 29, D.I. Lindner / D.I. Haas MPLS, v4. 46 Scalability Aspects Number of IP peers determines number of data virtual circuits number of control virtual circuits number of duplicate broadcasts on a single wire Method to solve the duplicate broadcast problem split the network in several LIS (logical IP subnets) connect LIS s by normal IP router (ATM-DCE) which is of course outside the ATM network But then another problem arise traffic between to two systems which both are attached to the ATM network but belong to dferent LIS s must leave the ATM network and enter it again at the connecting IP router (-> SAR delay) 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-24

13 Datenkommunikation SS 29 Datenkommunikation SS 29 IP Multiple LIS s in case of ROLC (Routing over Large Clouds) IP router A connects LIS and LIS2 Router A Wish for Optimized Connectivity Logical Network LIS2 LIS LIS 2 Source Logical Network LIS ATM Network Logical Network LIS4 Logical Network LIS3 29, D.I. Lindner / D.I. Haas MPLS, v4. 49 Classical Path Optimized Path Destination 29, D.I. Lindner / D.I. Haas MPLS, v4. Some Solutions for the ROLC Problem NHRP (Net Hop Resolution Protocol) creates an ATM shortcut between two systems of dferent LIS s MPOA (Multi Protocol Over ATM) LANE + NHRP combined creates an ATM shortcut between two systems of dferent LIS s In both methods the ATM shortcut is created traffic between the two systems eceeds a certain threshold -> data-flow driven a lot of control virtual circuits (p-t-p and p-t-m) is required 29, D.I. Lindner / D.I. Haas MPLS, v4. Net Hop Resolution Protocol (RFC 2332) Net Hop Server NHS NHS2 NHS3 ATM Network LIS LIS2 LIS3 LIS4 Direct Connection NHS4 NH-Request NH-Reply Net hop requests are passed between net hop servers Net hop servers do not forward data NHS that knows about the destination sends back a NH-reply Allows direct connection between logical IP subnets across the ATM cloud Separates data forwarding path from reachability information 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-2 29, D.I. Lindner / D.I. Haas Page App3-26

14 Datenkommunikation SS 29 Datenkommunikation SS 29 IP Performance Base problem Nr.2 IP forwarding is slow compared to ATM cell forwarding IP routing paradigm hop-by-hop routing with (recursive) IP routing table lookup, IP TTL decrement and IP checksum computing destination based routing (large tables in the core of the Internet) Load balancing in a stable network all IP datagram's will follow the same path (least cost routing versus ATM s QoS routing) QoS (Quality of Service) IP is connectionless packet switching (best-effort delivery versus ATM s guarantees) VPN (Virtual Private Networks) ATM VC s have a natural closed user group (=VPN) behavior MPLS Several similar technologies were invented in the mid-99s IP Switching (Ipsilon) Cell Switching Router (CSR, Toshiba) Tag Switching (Cisco) Aggregated Route-Based IP Switching (ARIS, IBM) IETF merges these technologies MPLS (Multi Protocol Label Switching) note: multiprotocol means that IP is just one possible protocol to be transported by a MPLS switched network RFC 33 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. Basic Ideas to Solve the Problems Make ATM topology visible to IP routing to solve the scalability problems an ATM switch gets IP router functionality Divide IP routing from IP forwarding to solve the performance problems IP forwarding based on ATM s swapping paradigm (connection-oriented packet switching) Combine best of both forwarding based on ATM swapping paradigm routing done by traditional IP routing protocols 29, D.I. Lindner / D.I. Haas MPLS, v4. 4 MPLS Building Blocks MPLS Transport You always need this! MPLS Transport solves most of the mentioned problems (scalability / performance) MPLS VPN (Virtual Private Network) MPLS Multicast MPLS ATOM (Any Transport over MPLS) MPLS TE (Traffic Engineering) MPLS QoS (Quality of Service) If you need "Advanced Features like VPN or Multicast support you optionally may choose from these building blocks riding on top of a MPLS Transport network 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-28

15 Datenkommunikation SS 29 Datenkommunikation SS 29 Agenda MPLS Network Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods RFC s MPLS Edge Router or LER (Label Edge Router) MPLS Network MPLS Switch or LSR (Label Switching Router) Router Component + Control Component Forwarding Component 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 9 MPLS Approach Traditional IP uses the same information for path determination (routing) packet forwarding (switching) MPLS separates the tasks L3 es used for path determination s used for switching MPLS Network consists of MPLS Edge Routers and MPLS Switches Edge Routers and Switches echange routing information about L3 IP networks echange forwarding information about the actual usage of s 29, D.I. Lindner / D.I. Haas MPLS, v4. 8 MPLS LSR Internal Components Routing Component still accomplished by using standard IP routing protocols creating routing table Control Component maintains correct distribution among a group of switches Label Distribution Protocol for communication between MPLS Switches between MPLS Switch and MPLS Edge Router Forwarding Component uses s carried by packets plus information maintained by a switch (switching table) to perform packet forwarding -> swapping 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-3

16 Datenkommunikation SS 29 Datenkommunikation SS 29 MPLS Control Communication MPLS Basic Operations Label Distribution Protocol a. Routing protocol (e.g. OSPF) establishes reachability to destination networks b. Label Distribution Protocol establishes MPLS paths (VC) along switching tables 4. Egress MPLS router at egress removes and delivers packet Routing Protocol 2. Ingress MPLS router receives packet, s it and by sends it along a particular MPLS path (VC) 3. MPLS switches ed packets using switching table 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 63 Generic Overview of MPLS LSR Internal Processes and Communication Routing Protocol Label Distribution Protocol control packets in for routing and distribution ed data packets in Routing Table (RT) Routing Component Control Component Label Mgt. Process Routing Process Label Information Base (LIB) Forwarding Component Forwarding Process Label Switching Table Routing Protocol Label Distribution Protocol control packets out for routing and distribution ed data packets out 29, D.I. Lindner / D.I. Haas MPLS, v4. 62 MPLS Header: Frame Mode Layer 2 (Ethernet, PPP) Layer 2 One 4 Byte MPLS header Label Ep S TTL IP 2 Bit 3 8 Label Stack MPLS Header 3 MPLS Header 2 MPLS Header "Layer 2. can be used over Ethernet, 82.3 or PPP links note: 2. means 32 bit 2-bit MPLS (Label) 3-bit eperimental field (Ep) could be copy of IP Precedence -> MPLS QoS like IP QoS with DfServ Model based on DSCP -bit bottom-of-stack indicator (S) Labels could be stacked (Push & Pop) MPLS switching performed always on the first of the stack 8-bit time-to-live field (TTL) 29, D.I. Lindner / D.I. Haas MPLS, v4. 64 IP 29, D.I. Lindner / D.I. Haas Page App3-3 29, D.I. Lindner / D.I. Haas Page App3-32

17 Datenkommunikation SS 29 Datenkommunikation SS 29 MPLS Header: Cell Mode Label Binding Layer 2 MPLS Header(s) ATM Convergence Sublayer (CS): Layer 2 IP Packet AAL Trailer ATM Switches can only switch VPI/VCI no MPLS s! Only the topmost is inserted in the VPI/VCI field (first cell) GFC VPI VCI PTI CLP HEC MPLS Header(s) IP Header Topmost Label MPLS Header(s) GFC VPI VCI PTI CLP HEC Topmost Label IP Packet ATM Segmentation and Reassembling Sublayer (SAR): (subsequent cells) DATA DATA Two neighboring LSR s R and R2 may agree that when R transmits a packet to R2, R will with packet with value L and only the packet is a member of a particular FEC F They agree on a so called "binding" between L and FEC F for packets moving from R to R2 As a result L becomes R s "outgoing " or representing FEC F L becomes R2 s "incoming " or representing FEC F 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 67 Labels and FEC A is used to identy a certain subset of packets which take the same MPLS path or which get the same forwarding treatment in the MPLS switched network The path is so called Label Switched Path (LSP) The MPLS Virtual Circuit Thus a represents a so called Forwarding Equivalence Class (FEC) The assignment of a packet to FEC is done just once by the MPLS Edge Router, as the packet enters the network most commonly is based on the network layer destination 29, D.I. Lindner / D.I. Haas MPLS, v4. 66 Creating and Destroying Label Binding Control Driven (favored by IETF-WG) creation or deconstruction of s is triggered by control information such as OSPF routing PIM Join/Prune messages in case of IP multicast routing IntSrv RSVP messages in case of IP QoS IntSrv Model DfSrv Traffic Engineering in case of IP QoS DfSrv Model hence we have a pre-assignment of s based on reachability information and optionally based on QoS needs also called Topology Driven 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-34

18 Datenkommunikation SS 29 Datenkommunikation SS 29 Creating and Destroying Label Binding 2 Data Driven creation or deconstruction of s is triggered by data packets but only a critical threshold number of packets for a specic communication relationship is reached may have a big performance impact hence we have dynamic assignment of s based on data flow detection also called Traffic Driven Label Distribution MPLS architecture allows an LSR to distribute bindings to LSR s that have not eplicitly requested them Unsolicited Downstream" distribution usually used by Frame-Mode MPLS MPLS architecture allows an LSR to eplicitly request, from its net hop for a particular FEC, a binding for that FEC Downstream-On-Demand" distribution must be used by Cell-Mode MPLS 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 7 Some FEC Eamples for Topology Driven FEC s could be for eample a set of unicast packets whose network layer destination matches a particular IP MPLS application: Destination Based (Unicast) Routing a set of multicast packets with the same source and destination network layer MPLS application: Multicast Routing a set of unicast packets whose network layer destination matches a particular IP and whose Type of Service (ToS) or DSCP bits are the same MPLS application: Quality of Service MPLS application: Traffic Engineering or Constraint Based Routing Label Binding The decision to bind a particular L to a particular FEC F is made by the LSR which is DOWNSTREAM with respect to that binding the downstream LSR then informs the upstream LSR of the binding thus s are "downstream-assigned thus bindings are distributed in the "downstream to upstream direction Discussion were about s should also be upstream-assigned not any longer part of current MPLS-RFC 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-3 29, D.I. Lindner / D.I. Haas Page App3-36

19 Datenkommunikation SS 29 Datenkommunikation SS 29 Label Retention Mode A LSR may receive a binding for a particular FEC from another LSR, which is not net hop based on the routing table for that FEC This LSR then has the choice of whether to keep track of such bindings, or whether to discard such bindings A LSR supports "Liberal Label Retention Mode" it maintains the bindings between a and a FEC which are received from LSR s which are not its net hop for that FEC Independent versus Ordered Control Independent Control: each LSR may make an independent decision to assign a a to a FEC and to advertise the assignment to its neighbors typically used in Frame-Mode MPLS for destination based routing loop prevention must be done by other means (-> MPLS TTL) but there is faster convergence Ordered Control: assignment proceeds in an orderly fashion from one end of a LSP to the other under ordered control, LSP setup may be initiated by the ingress (header) or egress (tail) MPLS Edge Router 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v4. 7 Label Retention Mode 2 A LSR supports "Conservative Label Retention mode " If it discards the bindings between a and a FEC which are received from LSR s which are not its net hop for that FEC Liberal Label Retention mode allows for quicker adaptation to routing changes LSR can switch over to net best LSP Conservative Label Retention mode requires an LSR to maintain fewer s LSR has to wait for new bindings in case of topology changes Ordered Control - Egress in case of egress method the only LSR which can initiate the process of assignment is the egress LSR a LSR knows that it is the egress for a given FEC its net hop for this FEC is not an LSR this LSR will sent a advertisement to all neighboring LSR s a neighboring LSR receiving such a advertisement from a interface which is the net hop to a given FEC will assign its own and advertise it to all other neighboring LSR s inherent loop prevention slower convergence 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-38

20 Datenkommunikation SS 29 Datenkommunikation SS 29 Ordered Control - Ingress Routing Table Created by Routing Protocol in case of ingress method the LSR which initiates the process of assignment is the ingress LSR the ingress LSR constructs a source route and pass on requests for bindings to the net LSR this is done until LSR which is the end of the source route is reached from this LSR bindings will flow upstream to the ingress LSR used for MPLS Traffic Engineering (TE) FEC Label Binding: Control Driven Destination Based Routing i/f interface i/f interface LSR Routing Table interface LER LER i/f LER i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 77 interface , D.I. Lindner / D.I. Haas MPLS, v4. 79 Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods Unsolicited Downstream Downstream On Demand RFC s Labels Sent by LDP Label Distribution: Unsolicited Downstream i/f i/f i/f Switching Table (ST) Advertises binding <,28.89.> Advertises binding <7,7.69> Routing Table (RT) Label Binding i/f i/f Advertisings received from the IP net hop (RT) for those networks (FEC s) -> switching table , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-4

21 Datenkommunikation SS 29 Datenkommunikation SS 29 Labels Sent and Switching Table Entry Created by MPLS Switch Label Distribution: Unsolicited Downstream i/f i/f Advertises bindings <3,28.89.> <4,7.69> i/f Advertisings received from the IP net hop (RT) for those networks (FEC s) -> switching table Label Binding , D.I. Lindner / D.I. Haas MPLS, v4. 8 i/f i/f Routing Table Created by Routing Protocol i/f LER FEC Label Binding: Control Driven Destination Based Routing interface i/f interface , D.I. Lindner / D.I. Haas MPLS, v4. 83 LSR interface i/f i/f LER LER interface MPLS Switched Packets Labels Sent by LDP MPLS Path = LSP to FEC Label Swapping Label Distribution: Unsolicited Downstream i/f data data MPLS Edge Router does longest match, adds ( impose ) subsequent MPLS switch forwards on (based on ST), swaps , D.I. Lindner / D.I. Haas MPLS, v4. 82 MPLS Path = LSP to FEC data last MPLS router strip off the ( untag ) and routes packet based on RT data i/f Advertises binding <, 3.24.> Advertising received from the IP net hop (RT) for those networks (FEC s) -> switching table i/f , D.I. Lindner / D.I. Haas MPLS, v4. 84 i/f 29, D.I. Lindner / D.I. Haas Page App3-4 29, D.I. Lindner / D.I. Haas Page App3-42

22 Datenkommunikation SS 29 Datenkommunikation SS 29 Labels Sent and Switching Table Entry Created by MPLS Switch i/f Label Distribution: Unsolicited Downstream 7 i/f , D.I. Lindner / D.I. Haas MPLS, v4. 8 Advertises binding <7, 3.24.> i/f Advertisings received from the IP net hop (RT) for those networks (FEC s) -> switching table Advertises binding <7, 3.24.> i/f Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods Unsolicited Downstream Downstream On Demand RFC s 29, D.I. Lindner / D.I. Haas MPLS, v4. 87 Label Merging - LSP Merging Routing Table Created by Routing Protocol MPLS Path = LPS to FEC data data last MPLS router strip off the and routes packet subsequent data MPLS switch data forwards on, MPLS Edge Router swaps does longest match, adds ( imose ) 29, D.I. Lindner / D.I. Haas MPLS, v MPLS Path = LSP to FEC MPLS Path = LSP to FEC LER FEC Label Binding: Control Driven Destination Based Routing i/f interface i/f i/f interface , D.I. Lindner / D.I. Haas MPLS, v4. 88 LSR interface LER LER i/f i/f interface , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-44

23 Datenkommunikation SS 29 Datenkommunikation SS 29 Labels Requested by MPLS Edge Routers Labels Allocated by MPLS Edge Router Label Distribution: Downstream-On-Demand i/f Request binding <28.89.> Request binding <7.69> i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 89 Request binding are sent in direction of the IP net hop (RT) for these networks (FEC s) i/f i/f Label Distribution: Downstream-On-Demand i/f i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 9 Advertises binding <,28.89.> i/f i/f Advertise-Bindings caused by former requests will lead to entries in the switching table Advertises binding <7,7.69> 7.69 Labels Requested by MPLS Switch Labels Allocated and Switching Table Built by MPLS Switch Label Distribution: Downstream-On-Demand i/f i/f i/f Request binding <28.89.> Request binding <7.69> i/f i/f Request binding are passed on in direction of the IP net hop (RT) for these networks (FEC s) 7.69 Label Distribution: Downstream-On-Demand i/f Advertises bindings <3,28.89.> <4,7.69> i/f i/f i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 9 Advertise-Bindings caused by former requests will lead to entries in the switching table , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-4 29, D.I. Lindner / D.I. Haas Page App3-46

24 Datenkommunikation SS 29 Datenkommunikation SS 29 MPLS Switched Packets data data MPLS Edge Router does longest match, adds subsequent MPLS switch forwards solely on, swaps , D.I. Lindner / D.I. Haas MPLS, v4. 93 MPLS Path = LSP to FEC MPLS Path = LSP to FEC data last MPLS router strip off the and routes packet data Labels Requested by MPLS Edge Routers i/f Label Distribution: Downstream-On-Demand in- 2 i/f i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 9 out- i/f requests binding < > request binding < > i/f Routing Table Created by Routing Protocol Labels Requested by MPLS Switch i/f interface LER FEC Label Binding: Control Driven Destination Based Routing i/f interface interface , D.I. Lindner / D.I. Haas MPLS, v4. 94 LSR i/f i/f LER LER interface i/f Label Distribution: Downstream-On-Demand in- 2 i/f requests binding < > request binding < > i/f i/f 2 29, D.I. Lindner / D.I. Haas MPLS, v4. 96 out- i/f i/f , D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3-48

25 Datenkommunikation SS 29 Datenkommunikation SS 29 Labels Allocated by MPLS Edge Router i/f Label Distribution: Downstream-On-Demand in- 2 advertise binding <, > advertise binding <7, > i/f i/f i/f 2 29, D.I. Lindner / D.I. Haas MPLS, v4. 97 out- i/f i/f Two Separate LSP s MPLS Path = LPS to FEC data data last MPLS router strip off the and routes packet in subsequent data MPLS switch data forwards solely MPLS Edge Router on, does longest match, swaps adds 29, D.I. Lindner / D.I. Haas MPLS, v4. 99 out- MPLS Path = LSP to FEC MPLS Path 2 = LSP 2 to FEC Labels Allocated and Switching Table Built by MPLS Switch i/f Label Distribution: Downstream-On-Demand in i/f i/f i/f , D.I. Lindner / D.I. Haas MPLS, v4. 98 out- advertise binding <3, > advertise binding <4, > i/f i/f Label Switching and ATM Can be easily deployed with ATM because ATM uses swapping VPI/VCI is used as a ATM switches needs to implement control component of switching ATM attached router peers with ATM switch ( switch) echange binding information Dferences how s are set up distribution -> downstream on demand allocation merging in order to scale, merging of multiple streams (s) into one stream () is required 29, D.I. Lindner / D.I. Haas MPLS, v4. 29, D.I. Lindner / D.I. Haas Page App , D.I. Lindner / D.I. Haas Page App3 -

26 Datenkommunikation SS 29 Datenkommunikation SS 29 Label Switching and ATM Label Distribution Solution for ATM IP Packet 3 y input i/f output i/f IP Packet ATM switch interleaves cells of dferent packets onto same. That is a problem in case of AAL encapsulation. No problem in case of AAL3/AAL4 encapsulation because of AAL3/AAL4 s inherent multipleing capability. 29, D.I. Lindner / D.I. Haas MPLS, v4. Downstream On Demand distribution is necessary multiple s per FEC may be assigned one per (ingress, egress) router pair Label space can be reduced with VC-merge technique 29, D.I. Lindner / D.I. Haas MPLS, v4. 3 Label Distribution Solution for ATM VC Merge Technique requests a for input i/f output i/f requests a for requests two s for returns a to each requester Downstream On Demand Label Distribution 29, D.I. Lindner / D.I. Haas MPLS, v4. 2 ATM switch avoids interleaving of frames VC Merge technique looking for AAL trailers and storing corresponding cells of a frame until AAL trailer is seen 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-29, D.I. Lindner / D.I. Haas Page App3-2

27 Datenkommunikation SS 29 Datenkommunikation SS 29 Agenda Review CL versus CO Packet Switching Review ATM IP over WAN Problems (Traditional Approach) MPLS Principles Label Distribution Methods RFC s RFC References RFC 33 Multiprotocol Label Switching Architecture RFC 332 MPLS Label Stack Encoding RFC 336 LDP Specication RFC 363 MPLS Loop Prevention Mechanism RFC 327 MPLS Support of Dferentiated Services 29, D.I. Lindner / D.I. Haas MPLS, v4. 29, D.I. Lindner / D.I. Haas MPLS, v4. 7 MPLS Applications and MPLS Control Plane RFC References 2 Unicast Fwd. Any IGP IP RT LDP/TDP Dferent Control Planes Multicast Fwd. MPLS TE MPLS QoS MPLS VPN OSPF/ISIS Any IGP Any IGP M-RT IP RT IP RT IP RT PIMv2 LDP RSVP LDP/TDP LDP BGP Label Switching Table RFC 3443 Time To Live (TTL) Processing in MPLS RFC 3469 Framework for Multi-Protocol Label Switching (MPLS)- based Recovery RFC 3478 Graceful Restart Mechanism for Label Distribution Protocol RFC 3479 Fault Tolerance for the Label Distribution Protocol (LDP) Data Plane (Forwarding Plane) 29, D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas MPLS, v , D.I. Lindner / D.I. Haas Page App3-3 29, D.I. Lindner / D.I. Haas Page App3-4