MPLS Intro. Cosmin Dumitru March 14, University of Amsterdam System and Network Engineering Research Group ...

Transcription

1 MPLS Intro Cosmin Dumitru University of Amsterdam System and Network Engineering Research Group March 14, 2011

2 Disclaimer Information presented in these slides may be slightly biased towards certain vendors. This presentation is not a guide on configuring routers MPLS is a huge topic itself. 20 slides can t cover it all

3 IP Forwarding Forwarding IP packets Traditionally done by destination IP address Routing protocols used to distribute Layer3 information Hop-by-hop decisions - connectionless Some shortcomings Often routing tables become large - search is O(log2 n) Limited traffic engineering options (follow the shortest path) L2 and L3 information is disconnected

4 ATM ATM - Asynchronous Transfer Mode Uses small fixed size bytes - cells to fragment and transport data Virtual Circuits between endpoints using labels - switching lookup O(1) QoS promise - low jitter

5 MPLS Combine the best of both worlds Packet forwarding Circuit switching Multi Protocol agnostic to the protocol used at layer 2 Label Switching Uses labels instead of IP Routing at the speed of switching Hybrid - Layer shim protocol Route at the edges, switch at the core Defined in RFC 3031

6 MPLS Operation MPLS Network

7 MPLS Label Label Exp S TTL label 20 bits - has local relevance experimental 3 bits - used for Class of Service stack 1 bit - indicates if bottom-of-stack TTL 8 bits - Time to Live - for IP the initial TTL

8 LER LER - Label Edge Router or Edge Label Switch Router positioned at the edge of the MPLS network assigns and removes labels for incoming traffic

9 LSR & LSP LSR - Label Switching Router positioned in the core of the network swaps labels and forwards packets LSP - Label Switched Path path from source to destination inside the MPLS network created in 2 ways hop-by-hop explicit routing (ER)

10 FEC FEC - Forward Equivalence Class Packets which are forwarded in the same manner a path is associated with a FEC

11 LIB LIB - Label Information Base(implementation dependent) Mapping between FEC and labels Each router has it s own LIB Input Port Incoming Port Label Output Port Outgoing Port Label 1 green 3 blue 2 red 1 orange

12 MPLS Operation(2) 1 3 MPLS Network Classify into FEC green 2. Push ( label green) 3. Swap (label green, label red) Swap (label red, label blue) 5. Pop (label blue) 6. Forward to destination

13 MPLS Architecture Control Plane Exchange L3 information and label information Data Plane switch/forward packets based on labels

14 Label Distribution LDP - Label Distribution Protocol UDP discovery, TCP session with peers Directly connected LSRs inform each other on the label bindings IGP protocol is configured on all LSRs New label bindings are pushed to neighbors whenever a new route is learned Labels can be withdrawn when IGP routes are no longer valid Hard-state - expected to work until explicitly torn

15 Label Distribution(2) RSVP-TE - Resource Reservation Protocol - Traffic Engineering Extension of RSVP unreliable delivery Soft-state - information needs to be periodically refreshed a LSP is created by propagating a RSVP message to the endpoint Paths are terminated if not refreshed on time

16 BGP Signaling MP-BGP - Multi Protocol Border Gateway Protocol Extension of BGP BGP route can also include the MPLS label for that route Used to distribute VPN routes extra label to allow route overlapping between different VPNs (stacked labels)

17 Advanced Services Traffic Engineering - With the help of RSPV-TE and OSPF-TE/IS-IS-TE Traffic steering across network in order to fully utilize resources Full network view (OSPF, IS-IS) and extra information about link state RSPV-TE creates LSPs on demand Quality of Service (QoS) Different types of service across the network Enforcing drop probability, bandwidth and delay (queueing) CoS bits or a FEC class (destination + class of service)

18 Advanced Services(2) Virtual Private Networks Private connections over shared networks can be offered as a service to businesses Stacked labels: egress router and VPN LDP or BGP used to transport label information Any Transport over MPLS(AToM) Transports L2 frames over a MPLS Network ATM, Frame-Relay, PPP, Ethernet 2 labels: egress router, egress router interface

19 VPNs CE - Customer Edge PE - Provider Edge Holds a different routing table for each customer Virtual Routing and Forwarding (VRF) - one FEC per VRF CE MPLS Network CE Customer A Customer A Customer B PE PE Customer B Customer C Customer C

20 Demo DEMO

21 Questions?