s.t rajan cjb0912010 ft12

M.S.Ramaiah School of Advanced Studies 1

Presentation

MPLS FOR TRAFFIC MANAGEMENT

S.T.RAJANCJB0912010, FT12

M. Sc. (Engg.) in Computer Science & Networking

Module Leader : Narasimha Murthy K.R


Session Topics

• Convention IP Datagram & ATM• MPLS by Definition• Traffic Management• Terminology & Components• Primary Protocols for Qos & Cos• Working Mechanism• Implementation• Deployment Strategy • Summary


Conventional IP Networks &ATMIP Routing Disadvantages:•It is based on connectionless so no QOS.• Each router has to make independent forwarding decisions based on the IP-

address.• Large IP Header - At least 20 bytes• Routing in Network Layer - Slower than Switching• Usually designed to obtain shortest path- Do not take into account additional

metrics .where it was not competent Overall it is Based on the Metric Optimisation .so the link constraints not taken

into consideration.ATM Principle :.• It overlays network solution.– fast packet switching with fixed length packets (cells)– integration of different traffic types (voice, data, video)Drawbacks Of ATM:• Not well integrated for engineering traffic flows• Wastage of bandwidth .• Complex & Expensive.


Evolution of MPLSIt stands for “Multi Protocol Label Switching”.

• Figures Represent protocol used in layer 2 & 3 in TCP/IP Stack

Control:

Longest-match Lookup

Forwarding:

ATM Forum Software

Control:

IP Router Software

Forwarding:

Label Swapping

Control:

IP Router Software

Forwarding:

Label Swapping


Need for MPLSMPLS Functions

•Uses Control-driven model.

•MPLS simplifies forwarding function by taking a totally different approach by introducing a connection oriented mechanism inside the connectionless IP networks•Initially Designed for Enhancing Look up Speed for Routers but essentially used for traffic engineering.• IETF creates MPLS working group to create unified standard (Frame Relay, PPP, SONET), not just ATM.MPLS Characteristics

– Mechanisms to manage traffic flows of various granularities (Flow Management) by using single forwarding algorithm .

– Is independent of Layer-2 and Layer-3 protocols – Maps IP-addresses to fixed length labels– Interfaces to existing routing protocols (RSVP, OSPF)&futuristic

M.S.Ramaiah School of Advanced Studies

MPLS-TE Example• Buses run with Route Number which is indication of route from

start point .

• Similarly in MPLS each LSR will label the packets with the route label or swaps label and sends to the end Router

• Traffic management is done by signaling protocol with dedicated path called Trunk Tunneling .

6

LSP

Trunk Tunneling

Router B Router B


Need For Traffic Management Traffic Management•The task of mapping traffic flows onto an existing physical topology to facilitate efficient and reliable network operations• traffic oriented e.g. minimization of packet loss •resource oriented - optimization of resource utilization e.g. efficient management of bandwidthPerformance Objective

Minimizing congestion is a major traffic and resource oriented performance objectiveCongestion manifest under two scenarios

-network resources are insufficient or inadequate can be solved by capacity expansion or classical congestion control techniques-traffic streams are inefficiently mapped onto available resources can be reduced by adopting load balancing policies


Advantages of TM & Working• Variously divisible traffic aggregation and disaggregation Maneuvering load distribution• Stand-by secondary paths and precomputed detouring paths Strongly unified measurement and control for each “traffic-

engineered path”Explanation :If network core runs conventional longest-match IP forwarding:

–Data from Host A and B follow path 1 since it is the shortest-path computed.–With MPLS, network administrator could split traffic:

•Host A traffic over path 1 & Host B traffic over path 2


Terminology • FEC (Forwarding Equivalence Class)-Group of packets sharing

the same type of transport.• LSR (Label Switched Router)-Swaps labels on packets in core of

network.• LER (Label Edge Router)-Attach Labels to packets based on a

FEC.• LSP (Label Switch Path)-Path through network based on a FEC

(simplex in nature). The “traffic-engineered path”• LIB (Label Information Base)- MPLS equivalent to IP routing

table, contains FEC-to-Label bindings• Traffic Trunk (TT)

-Traffic Trunk - aggregation of traffic flows of the same class which are placed inside a Label Switched Path-forwarded through a common path with common TE requirements characterized by its ingress and egress

M.S.Ramaiah School of Advanced Studies

Positions In MPLS

10

Pune Secunderbad Vijayawada Bhuvaneshwar

Kolkata Mumbai

LER (Label Edge Router ) or Penultimate Router LSR (Label Switch Router) or Transit Router LSP:Label Switch PathMumbai is Ingress Router & Kolkata is Egress Router


MPLS provides two options to set up an LSP• Hop-by-hop routing

-Each LSR independently selects the next hop for a given FEC. LSRs support any available routing protocols (OSPF, ATM …).

• Explicit routing-Is similar to source routing. The ingress LSR specifies the list of nodes through which the packet traverses.

The LSP setup for an FEC is unidirectional. The return traffic must take another LSP!.Two types Static or dynamic.Induced MPLS Graph •analogous to a virtual topology in an overlay model•logically mapped onto the physical network through the selections o LSPs for traffic trunk•comprises a set of LSRs which act as nodes of the graph and a set of LSPs which provide logical point to point connectivity between LSRs and thus act as edges of the graph

LSP & Graphs


• Packet Forwarding ComponentMPLS, label switching itself

• Information Distribution ComponentIGP (OSPF/IS-IS) extension

• Path Selection ComponentConstrained Shortest Path First (CSPF) algorithm or BGP

• Signaling ComponentLDP, CR-LDP, and RSVP-TE-In MPLS, traffic engineering is inherently provided using explicitly routed paths.

• The LSPs are created independently, specifying different paths that are based on user-defined policies. However, this may require extensive operator intervention.

• RSVP-TE and LDP are two possible approaches to supply dynamic traffic engineering and QoS in MPLS.

Components MPLS-TE


Dynamic LSP using RSVP• Dynamic LSP Created without user intervention• User control used by two protocol RSVP or LDPRSVP (Resource Reservation Protocol)• Signaling Protocol designed by IETF• Application to request & reserves resources hop by hop• Request bandwidth and traffic conditions on a defined path. • Using “Path” message from source to destination • Reply message “Resv” From destination to source by updating “softstate”which is

database for reservation .• Establishes the LSP.• LSP is operation as long as soft state• QOS and COS • The generic protocol is extension of MPLS implementation

Pop

22

R2

R6

R4

R7R1

R5

R3

R8

Setup: Path (R2->R6->R7->R4)Setup: Path (R2->R6->R7->R4)

Labels Established on Resv Labels Established on Resv messagemessage


LDP

Four message classes

1. Discovery-Announce and maintain presence of an LSR.

2. Session-establish, maintain, terminate sessions b/w LDP peers.

3. Advertisement-create, change, delete label mappings.

4. Notification-advisory and error info. •Discovery: Runs over UDP

•All others run over TCP

Label Distribution Protocol designed specifically for MPLS

Multicast’s “Hello” message is by LSR


CBR-LDP• Enables a demand driven, resource reservation aware, routing

paradigm to co-exist with current topology driven protocols uses the following inputs

traffic trunk attributesresource attributesother topology state information

• Basic featuresprune the resources that do not meet the requirements of the traffic trunk attributerun a shortest path algorithm on the residual graph

Advantages of traffic trunks•No. of trunks dependent only on the topology •Forwarding table does not grow with the traffic •Rerouting RSVP, CR-LDP, or IGP


Working Mechanism -TESteps For TE Establishment• LSP Tunnels which are Signaled to RSVP which are unidirectional•Link State IGP for global flooding of resource Information & automatic routing of traffic .•MPLS traffic engineering module for path calculation which path to be used LSP tunnel.•Link Management Module link admission and book keeping of resource information to be flooded•Label Switching Forwarding based on Resource based Routing AlgorithmMapping into Tunnel •IGP uses Dijkstra's shortest path first (SPF) algorithm. Routing Tables are Derived from Shortest Path Tree.•Another Algorithm calculates explicit route from one or more nodes based on LSP and TE Tunnels


SFP ComputationDetermination of first Hop Information•When Path is found for new node it moves new node from tentative list to path lists •Based on TE Tunnel the tail end is First Hop Information updated•Without TE Tunnel the uses First Hop Information from adjacent of just connected node.•When both Cases fail ,it copies the information from parent node to new node.Advantages If there is more than one TE tunnel to different intermediate nodes on the path to destinationnode X, traffic flows over the TE tunnel whose tailend node is closest to node X.


TE-Tunneling Mesh Network

The diagram shows Mesh Topology with dedicated trunks

R-A

R-B

R-D R-E

R-C

Assume Tunneling present from A to D and Same cost Network. Then SFP implements to do load sharing


Protocol Routing Traffic engineering

LDP Implicit NO

BGP Implicit NO

IS-IS Implicit NO

CR-LPD Explicit YES

RSVP-TE Explicit YES

OSPF-TE Explicit YES

•Implicit routing- labels are set-up and torn-down (like telephone calls), also known as hard state.

•Explicit routing- allows for better traffic engineering, traffic tunnels are created based on overall view of topology. More dynamic.

Signaling Protocols


Management Interface

MPLSConstraint BasedRouting Process

ConventionalIGP Process

Resource AttributeAvailability Database

Link StateDatabase

Implementation Consideration


Deployment Strategy-1Congestion Free Network :

1) Configure your IGP, RSVP2) Configure TE tunnels around congested links

- one IGP tunnel, one or more explicit-path tunnels.3) Turn up tunnels one at a time via ‘autoroute announce’

4) Add BW requirements to tunnelsTunnel BW ratio is important.

Link Protection:Step1: link failure detection

O(depends on L2/L1)Step2: IGP reaction (ISIS case)

Either via Step1 or via IGP hello expiration (30s by default for ISIS) .5s (default) must occur by default before the generation of a new LSP

Step3: RSVP signalization


Step4: Either stepA or stepB alarms the head-endStep3\5: Re-optimization

dijkstra computation: O(0.5)ms per node (rule of thumb) RSVP signalisation time to install re-routed tunnel

convergence in the order of several seconds (at least).This includes fast switch over into secondary TE tunnel Path.

Deployment Strategy-2

R2

R6

R3

R7

R1 R5

R4

Backup Tunnel to the next-hop of the LSPs next-hop


MPLS is proposed as a standard TE solution by IETF, BUT• Vendor Interoperability problem• Limitation in online path calculation• Problems on Traffic Trunks• Measurement and Control Issues

MPLS-TE Deployment Issues


SummaryBased On MPLS•Improves packet-forwarding performance in the network •Supports QoS and CoS for service differentiation •Supports network scalability •Integrates IP and ATM in the network •Builds interoperable networks Based on MPLS TE:•MPLS supports tunneling, which breaks the transparency paradigm.•MPLS supports sessions, it breaks the datagram model.•TE Done by SFP based on different Protocols.•Higher return on network backbone infrastructure investment.•Reduction in operating costs•To increase the resource utilization

MPLS Traffic Engineering•To speed up convergence upon link or node failure

MPLS TE and Link/Node protection•To ease capacity planning -Aggregate Admission Control


References

• Sreekanth P V, Digital Transmission Hierarchies, Universities Press ,2010,p209-225.

• Ramaswami .R and Sivarajan. K. N. , Optical Networks: A Practical Perspective ,Morgan Kaufmann Publishers, 2nd .

• Cisco IOS Release 11.3 Network Protocols Configuration Guide, Part 1, “Multiple Label Switching Traffic” chapter.


Thank You

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