Service Providers Networks & Benefits of Multi Protocol ...ee.istanbul.edu.tr/data/uydu(15.03.2010).pdf · Benefits of Multi Protocol Label Switching (MPLS) 20/11/2009 Local Team

Service Providers Networks &

Benefits of Multi Protocol Label Benefits of Multi Protocol Label

Switching (MPLS)

20/11/2009

Local Team

Service Provider Networks & Carrier Networks

� A telephone company (or telco) provides telecommunication services such as

telephony and data communications. Telcos are also known as common carriers.

� A service provider is an entity that provides services to consumers.

� Most telcos now also function as internet service provider (ISPs), and the

distinction between telco and ISP may disappear completely over time, as the

current trend for supplier convergence in the industry continues.

– Primary Line – telephony

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– Primary Line – telephony– POTS and other telephony related service

– Leased Lines – Point-to-Point service

– Internet – WEB1.1 based(today), WEB2.0 (very near future)

– VPN– Customer Virtual Private Networks

� Today most of the services are delivered in different networks much rely on

different physical infrastructure.

� WHAT IS CONVERGENCE?

Service Provider Networks –TDM Networks

� TDM – Time Division Multiplexing

� Circuit switch structure

� Each circuit is assigned to a timeslot in time domain

� A circuit should be pre-configured and remain provisioned for connectivity even when

there is no data flow

� Waste of resources

– A popular example of TDM is GSM base station bachauling.


– A popular example of TDM is GSM base station bachauling.

– 100% resources should be dedicated for a 5% overall usage (Todays GSM)

– Possible over-subscribing(10 channels for 20 users) may lead out of Service time

– Very reliable and secure since no users share same medium

– High cost per BW

� In the early 1990s, most networks were private line (or point-to-point), meaning a

physical circuit ( combination of timeslots) had to be provisioned between locations.

If a headquarters location needed to communicate with 10 other locations, the location

needed 10 separate private lines.

Service Provider Networks – ATM & FR

� ATM is a packet oriented transfer method that uses asynchronous (TDM)

technique.

� No need to assign a dedicated physical channel to each information flow

� Virtual channels are introduced

� 53-Byte fixed length cell switching

� Sharing of physical resources between multiples of virtual channels (Overbooking)

� QoS is introduced via CAC


� QoS is introduced via CAC

– Up to now there was no need for any prioritization and policing of traffic since no sharing exist

� With frame relay and ATM, the big difference was a “logical” connection for

direct communications between locations.

� This greatly reduced costs.

� When organizations switched from private line to frame relay or ATM networks,

the primary driver was reducing transport cost – sometimes by more than 50%.

Service Provider Networks – ATM & FR


What happened to Internet ?

� The world's largest network of computer networks got its original name from the

U.S. military arm that funded it: Arpanet was for the Advanced Research

Projects Agency.

� Routers are the building blocks of Internet

� using IP at the control plane

� A hop by hop based architecture

� Routing protocols to discover paths


� When networks get too large, discovering and selecting routes becomes slow,

ineffective. For this reason, by the late 1990s, most large ISPs had created two-

tier architectures, with an outer ring of intelligent routers communicating

across a switched (typically ATM) core, implementing traffic engineering at the

core.

IP - over - everything

� This approach worked well until new customer needs come on surface

� More types of services with more BW

� Immidiate access to any service, anytime and anywhere

� There are three problems with this approach to newly surfaced consumer needs

� First is the well known "cell tax," the bandwidth overhead resulting from segmenting

large IP packets into 53-byte ATM cells.

– Increasing utilization of links with non-profit BW (increased CAPEX)


– Increasing utilization of links with non-profit BW (increased CAPEX)

� In addition, service providers must manage and administer multiple networks of devices

(optical transmission, ATM switching and IP routing),

– Increased OPEX.

� Inadaquate service differentiation capabilities

– ATM has only 3 types of flow classifier extended to 5 types of services in which IP has 64 Classes of service for end customer

– Current core networks almost use 8 classes of service

– With upcoming LTE 9 CoS will be required

– More the CoS is more consumer flexibility (Service Provider Perspective)

Raise of MPLS - 1

1. MPLS embraced IP

In the early 1990s, the telecom industry was pinning all of its hopes on ATM as the network

backbone technology of the future.

But in 1995, the Internet exploded, and carriers had to quickly refocus their efforts in a

different direction.

By 1996, IETF researchers were looking for ways to make circuit-oriented ATM technology

run over IP.

ATM proponents jumped aboard the MPLS bandwagon in 1997, when the IETF formed its MPLS

Working Group and MPLS team was wise to embrace—rather than fight—IP.


Working Group and MPLS team was wise to embrace—rather than fight—IP.

Raise of MPLS -2

2. MPLS is protocol neutral

MPLS was designed to work in a multiple protocol environment.

That allowed MPLS to work with ATM, Frame Relay, Sonet or Ethernet at the core..

MPLS also played a key role in supporting both legacy network technologies and

the latest IP-based technology.

Today, MPLS is being used to support metro-Ethernet services, mobile


Today, MPLS is being used to support metro-Ethernet services, mobile

communications back-haul communications and video distribution.

Raise of MPLS - 3

3. MPLS scales

Successful Internet technologies need to be able to scale quickly, and MPLS was

able to do that.

Verizon uses MPLS for several global networks including its public and private IP

networks

Verizon’s Public IP network, for example, spans 410 points of presence on six


Verizon’s Public IP network, for example, spans 410 points of presence on six

continents and spans more than 150 countries.

These massive networks showed that "MPLS did work, and that it worked on a

significant scale."

Service Provider Networks - MPLS

� MPLS = Multiprotocol Label Switching

� Objectives of MPLS Working Group:

� Enhance performance and scalability of IP routing

� Facilitate explicit routing and traffic engineering

� Separate control (routing) from the forwarding mechanism so each can be modified

independently

� Develop a single forwarding algorithm to support a wide range of routing functionality


� Develop a single forwarding algorithm to support a wide range of routing functionality

Example : Forwarding in IP network

Access

Edge

• LPM lookup IP addr.• Forward to next hop

• LPM lookup IP addr.• Forward to next hop

• LPM lookup IP addr.• Forward to customer

IP router IP routerIP router

IP router

AA EEBBCC


Core

IP router IP routerIP router

IP router

IP routerDD

AA

IP network view:

BBCC

DDEE

Example : Forwarding in MPLS network

Access

• LPM lookup IP addr.• Insert label• Forward to next LSR

• Exact match lookup • Swap label• Forward to next LSR

• Remove label• LPM lookup IP addr.• Forward to customer

Label Edge Label EdgeLabel Switch

AAEE


Label EdgeRouter (LER)

Label EdgeRouter (LER)Label Switch

Routers (LSRs)

AA EE

IP network view:

MPLS network

MPLS Basic Components

• MPLS header MUST include : OSI layeringmodel

What is a label?

� a label is a short, fixed length, locally significant identifier that is carried by

the packet and used to identify a FEC

� the generic solution for assigning a label to a packet is by insertion of the label

between the network layer (IP packet) and the data link layer. This may look as

follows


• MPLS header MUST include : • label or label stack

• MPLS header MAY include :• TTL value• stack indicator• class of service

model

4

3

2½

2

payload

IP Header

MPLS header

Layer 2 header

MPLS header

IP Header

IP Header

payload

payload

payload

MPLS Basic Components - Labels

What does a label look like?

� This depends on L2/L1 protocol used

� For PPP data links and LAN data link (e.g. Ethernet):

32-bits

IP Payload L2 HeaderMPLS HeaderIP Header


� TTL value enables the following like in IP to• Avoid loops: TTL = 0 drops the packet• Limit the forwarding scope of the packet

• To reflect total number of hops, TTL value from IP packets is copied inside label and decreased at each LSR it passes through. At egress, LSP TTL may be copied back into IP TTL

TTLLabel (20-bits) EXP S

MPLS Terminology

Ingress LER/LSR Transit LSR Egress LER/LSR

Label PUSH Label SWAP Label POP


LSP: Label Switched Path

DownstreamUpstream

MPLS Forwarding Example

134.5.1.5

2 6

134.5.6.1MPLS Table

In Out

(2, 84) (6, 3)

Ingress Routing Table

Destination Next Hop

134.5/16

200.3.2/24

LSP3

LSP5

PUSHSWAP

POP


200.3.2.7

1 2 3 5

200.3.2.1

MPLS TableIn Out

(1, 99) (2, 56)

134.5.1.5 LSP3

LSP5

2

3

MPLS TableIn Out

(3, 56) (5, 3)

MPLS Table

Next Hop

LSP3

LSP5

(2, 84)

(3, 99)

Egress Routing Table

Destination Next Hop

134.5/16

200.3.2/24

134.5.6.1

200.3.2.1

Destination

MPLS Label Distribution Protocols

MPLS requires a signaling protocol to:

� Coordinate label distribution

� Explicitly route the LSP

� Bandwidth reservation (optional)

� Class of Service (DiffServ style)

� Resource re-assignment

� Pre-emption of existing LSPs

� Loop prevention


� Loop prevention

MPLS signaling protocols defined by IETF

� Label Distribution Protocol (LDP)

� Resource Reservation Protocol (RSVP)

Label Distribution Protocol - LDP

UpstreamLDP peer

DownstreamLDP peer

LSR

MPLS TableIn Out

(3, 29)

Net: 10.0.0.0 Label: 29

In OutMPLS Table

(1, 17) (4, 17)

Net: 10.0.0.0 Label: 17

Advertiseincominglabel

MPLS TableIn Out

(5, 52)

Receiveoutgoinglabel (2, 52)

Net: 10.0.0.0 Label: 52

IP Route

43 321 510.0.0.0


Distributes label binding informationRuns on LSRs in conjunction with IP routing protocols Labels are periodically refreshed

Labels assigned by downstream peer

Limitations

� LSPs follow conventional IGP path

� Does not support explicit routing

Resource Reservation Protocol - RSVP

RSVP was originally designed for use in IP networks

� Enables end-to-end QoS reservation of resources for individual data flows

(IntServ)- Integrated Services

� Requires all routers to maintain state of each micro-flow from source to

destination

Scalability issues limited deployment of RSVP to a few private networks


Signaling component is now used for other applications

� Differentiated Services (DiffServ)

� MPLS Traffic Engineering

Resource Reservation Protocol - RSVP

RSVP already has the resource reservation component built-in

R1 R4 R8 R9

IngressLSR Egress

LSR

Explicit route = {R1, R4, R8, R9}

PATH

RESV


RSVP already has the resource reservation component built-in

� Makes it ideal to reserve resources for LSPs

� RSVP is structured, extensible protocol (TLV: Time, Length, Value)

� Proposed extensions are backward compatible with traditional RSVP

implementations

Comparing Label Distribution Protocols

LDP RSVP-TE

Hard state (TCP) Soft state - needs refresh

Slow failure detection (IGP) Fast failure detection (hello timeout)

Shortest path only Allows control of path


Shortest path only Allows control of path

No QoS or BW reservation Allows QoS, BW reservation

Automatic LSP setup Manual LSP setup (N-squared)

MPLS Path Protection – Fast Re-Route

Primary/Backup

� MPLS tunnel consists of Primary LSP and Secondary LSP (optional)

� Backup path calculation by constraint based routing algorithm or

external tool� No other routers in common with primary LSP

� Backup LSP can be cold standby or hot standby

� No traffic on backup LSP as long as primary LSP is up


ingress egress

Backup LSP

Primary LSP

Traffic Engineering - CSPF

Path calculation by constraint based routing algorithm or external tool

Constraint Based Routing Algorithm (CSPF)

� TE extensions to OSPF and IS-IS

� Traffic engineering database created through OSPF or IS-IS extensions

� Used to exchange available bandwidth and color of links

� Constraints


� Bandwidth

� Administrative color

– Include-color-group: All the links that are chosen must have at least one color found in the include color group

– Exclude-color-group: All the links that are chosen must not have a color listed in the exclude color group

� Max number of hops

� Include strict/loose hops

� Avoid node(s): e.g. secondary LSP should avoid nodes/interfaces used for primary

MPLS – DiffServ

The DiffServ model offers a scalable solution for IP QoS in backbones

MPLS has been enhanced in support of DiffServ:

� an IP packet’s DSCP can be mapped in the MPLS header information (EXP-

bits, or EXP-bits and label)

L-LSP� Separate LSP for each QoS class => support >8 QoS

classes

E-LSP� Up to 8 QoS classes in a single LSP� EXP field encodes DSCP� Advantages compared to L-LSPs


Access Accessedge edgeCore

classes� EXP field encodes drop precedence� Finer granularity for TE and LSP protection

� Advantages compared to L-LSPs• label space conservation• less signalling overhead• less consumption of forwarding state in

LSRs

TCP/IPhost

IPphone

Server

DiffServ aware MPLS

DiffServ-aware MPLS TE in a DiffServ

network

� LSRs advertise multiple available

bandwidths via IGP

� Aggregate admission control against a

MPLSPE

PP

DiffServ

PE

CE


particular bandwidth pool

� Packets should be routed based on

expected QoSPE PE

P

P

P

P

CE

DiffServ

Why we need MPLS?

ASIC design has improved tremendously in last decade

Today, 10Gbps IP forwarding can easily be done in hardware

Memory has become drastically cheaper in last decade

� No problem storing 1 Million destinations …


Today, MPLS does not offer faster forwarding than IP

Do we need QoS?

Actually, most backbone IP networks today do not use ATM or MPLS for QoS

Enforcing QoS is only important when there is congestion

Perfect QoS can be provided in IP, if there is no congestion

� “Just overprovision the network !”


Most IP networks keep bandwidth utilization at ~30-40%

Is this cheaper or more expensive?

� Depends on the operator…

Real reasons to deploy MPLS?

Traffic Engineering:

� Manage traffic load on different parts of the network

� Differeciate Service approach

Virtual Private Networks

� Offer point-to-multipoint services - IP VPNs and VPLS

� Replace traditional (point-to-point) FR/ATM services - VLLs


� Replace traditional (point-to-point) FR/ATM services - VLLs

� New services such as VoIP or Video

Introduction of New Service

� Tripple Play Service (Voice, Video and Data together)

� Differentiation between consumers within same service type

Rushmore Evolution Phase 2 HW & SW


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Documents

Service Providers Networks & Benefits of Multi Protocol ...ee.istanbul.edu.tr/data/uydu(15.03.2010).pdf · Benefits of Multi Protocol Label Switching (MPLS) 20/11/2009 Local Team