VFEgypt- morning session 3-3-09

Tellabs Internal and Confidential

VFE meeting 3-3-09

Tellabs Internal and Confidential2 May 1, 2023

Data Forwarding & Routing

Two fundamental Network Paradigms in the industry> Connectionless

– IP, Ethernet, …> Connection Oriented

– Frame Relay, ATM, Circuit-Switched Voice,…– and MPLS

Industry has lived with these 2 models for >20 years> Traditionally dealt with in an “overlay” fashion


The Hyper aggregation Problem

C3

C1

C2

Path for C1 <> C3

Path for C2 <> C3

"Longer" paths become under-

utilized

How do we make traffic flow along the “belly of the fish”?


Carriers Moving to MPLS

>MPLS (Multi-Protocol Label Switching) has emerged as the preferred technology for building Multi-service IP-based networks

> Internet Engineering Task Force (IETF), ITU-T, and MPLS & Frame Relay Alliance (MFA) all cooperating on standards to enable MPLS-based convergence

>MPLS has the ability to support converged services> MPLS provides an circuit-like architecture > Majority of the operators are in the process or planning to upgrade

their IP network to an IP/MPLS backbone> Hundreds (perhaps thousands) of network operators have MPLS

running in the core of their network


Advantages of MPLS >Faster & Simple Packet Forwarding Paradigm

> Hierarchical label swapping/switching using one or more 32-bit labels prepended to packets

> Decreased packet processing complexity compared to traditional IP routing>Traffic Engineering and QoS Capabilities

> Explicit route specifications, as opposed to IP’s hop by hop routing> Fast Reroute during link failures; < 50 ms convergence> LSPs (Label Switched Paths) with circuit-like characteristics

>Virtual Private Networks > IP VPNs (IETF BGP/MPLS VPNs)> VPLS VPNs (Multi-point layer 2 Ethernet VPNs)


Multi Protocol Label Switching

Label based classification and forwarding capable of transporting protocols other than IP> Components:

> Signaling protocols: Label Distribution> MPLS enabled routers

> Ingress PE (LER): classification map to LSP> Transit P (LSR): Label Swapping> Egress PE (LER): Forward native packet

> IGP: Distribution of reachability information > Evolution not revolution

> MPLS control plane relies on underlying IP network


MPLS Functions of MPLS Switches

ATM

Frame Relay

Ethernet

CE CE

ATM

Frame Relay

Ethernet

LER (or PE) Assigns MPLS Labels for packets moving

toward core Removes MPLS labels for packets moving

away from core Provides Adaptation Header (e.g. PW Label)

for E/ATM/FR LSR (or P) Forwards packets based on Label Swaps labels Does not understand the contents

of the labeled packet

C D

E

F

G

B

LER (PE)

LSR LSRLSR

A

LER (PE)LSR LSR

Customer NetworkCustomer Network

MPLS Core


MPLS Functions of MPLS Switches

ATM

Frame Relay

Ethernet

CE CE

ATM

Frame Relay

Ethernet

CE devices Customer Edge equipment Could be a router, ethernet switch,

ATM or Frame Relay device Does NOT speak MPLS to the PE

C D

E

F

G

B

LER (PE)

LSR LSRLSR

A

LER (PE)LSR LSR


Label Switching vs. Routing

Routing> Packets contain an explicit destination address> Routers forward packets toward the destination> Each packet is forwarded as a separate event. The same process must

occur for each packet on each node.> No setup process needed, just a routing protocol to build the routing table> The lookup in the routing table is based on the best-match – there could be

multiple matches


Label Switching vs. Routing

Label switching> Incorporates a locally significant identifier called a “label”> Each hop inspects the label and makes a forwarding decision

based on its value> Label values are “swapped” as the packet is switched> Labels must be exchanged between nodes prior to data flow (there

must be a setup process)> The lookup in the forwarding table is based on exact match – there

is only one “right” answer


MPLS Routing (Determine Topology)

MPLS uses existing IP routing protocols> OSPF, IS-IS

IP routing protocols identify a “shortest path” onto which all packets will be forwarded

Traffic engineering requires “constraint-based” routing – finding a path that meets a set of specified constraints

Routing protocols have been extended to support TE> OSPF-TE, ISIS-TE


MPLS Signaling (Establish Path) Manual configuration (no signaling)

> As per ATM / FR PVCs LDP = Label Distribution Protocol

> Simple signaling protocol> Good for basic connectivity and soft QoS services

RSVP-TE = Resource reSerVation Protocol with Traffic Engineering extensions> Sophisticated signaling protocol> Enables resource allocation in each switch an LSP traverses

BGP = Border Gateway Protocol> Extended to carry label information – eg RFC 2547 VPNs (4364), VPLS-BGP


Label Switched Paths

PE

IP/MPLS Core

New York

IP IP

PE

London

Label Exchange

Direction of Data FlowUpstream Downstream

P PIP/MPLS


MPLS Label Switched Path (LSP) A Label Switched Path (LSP) is a uni-directional Virtual Circuit that

carries aggregated flows of traffic This path is identified by a label, which is swapped as the packet

traverses the network (similar to ATM VPI/VCI or Frame Relay DLCI) Since IP and Ethernet packets don’t have a field that can be used as

a label, a header must be added to these packets to include a label LSP’s can be engineered to take explicit routes and be allocated

specific resources


> Label> Fixed-length packet identifier> Link local significance

> Fields> Label (20bits) = Label Value (220 = 1,048,576)> EXP (3bits) = Experimental (usually CoS)> S (1bit) = Bottom of stack “1” or not “0”> TTL (8bits) = Time to live, analogous to IP TTL

TTLLabel (20-bits) EXP S

L2 or L3 Packet (Payload)L2 or L3 Packet (Payload)32-bits

MPLS Header

Packet Based MPLS Label“The Shim”

0x8847SADA


Other MPLS Header Formats

Frame-Relay> MPLS was defined to use the DLCI field in the frame relay header as

the MPLS label> RFC 3034

ATM> MPLS was defined to use VPI/VCI as a 2-label stack in the ATM header> RFC 3031

Optical> MPLS has been “generalized” to include a wavelength as a label in the

optical domain> Can also include a waveband, fiber, or set of timeslots> RFC3945



31

48

PE PE

IP/MPLS Core

LondonNew York

P

P

P

P

LSP

57

P

P

IP

IP

IP

IP

IP

P


Label Operations “Push” at ingress to MPLS network

> Ingress PE applies label to non-MPLS packet “Swap” at each switch point in the network

> P routers forward packets based on incoming label> P routers swap in label for out label (similar to ATM and FR)

“Pop” at the egress to the MPLS network> Egress PE strips off the MPLS label to deliver native packet to the

customer network



31

48

PE PE

IP/MPLS Core

LondonNew York

P

P

P

PPush

57

P

P

IP

IP

IP

IP

IP

P

48

Swap

57

31

Swap

Pop

Tellabs Internal and Confidential

MPLS Pseudowires


ATMTDM FR Ethernet

SDH (PoS) Ethernet

IP

2G (GSM)

MPLS Pseudowires

DSL

MPLS

3G (UMTS/HSPA)

Pseudowires decouple service from transport> Enables you to converge all services over one network> Use the cheapest available transport alternative

Enables decoupling of transport cost and capacity


Pseudowire (PWE3) Reference Model

Emulated service> Ethernet, ATM, FR, PPP,

HDLC, TDM Pseudowire (PW)

> Two MPLS label stack> Outer label identifies PE-PE

connection (tunnel)> Inner label identifies customer

Outer label (LSP) established with LDP or RSVP-TE

Inner label established with manual configuration or targeted LDP (or BGP)

PE PECE CE

Pseudowire

Emulated Service

MPLS Labels Payload

AttachmentCircuit


LDP in VC Label Signalling

VC labels established with manual configuration or with targeted LDP

LDP established between two directly connected PEs

Targeted LDP established between two non-adjacent PEs

Special TLV for signalling VC labels> VC Type: Ethernet, FR, ATM,…> PW ID (32 bits): unique identifier in element,

identifies the service PW consists of two unidirectional VC-LSPs

with same PW ID

LDP

LDP

Targeted LDP

Targeted LDP

IP/MPLS


Mapping Traffic to MPLS Tunnels

One tunnel carries several pseudowires

Payload may also be different per pseudowire (Ethernet, ATM, FR, TDM)

Multiple tunnels possible based on TE, QoS or protection requirements

LocalHeader

(e.g. Ethernet)

TunnelLabel150

1034 CW VLAN 11/Ethernet



PWE3 Encapsulation

MPLS Labels

11

21

31

110

210

31

VLAN

Tunnel = 150VC = 1034, 1036, 1038

MPLS


Tellabs 8600 Support for MPLS Pseudowires

MPLS LSPPseudowire

AttachmentCircuit PW Granularity

TDM E1, 64 kbps

PPP, HDLC Port

Frame Relay Port, DLCI

ATM VP, VC

Ethernet Port, VLAN

TDM

PPP/HDLC

ATM (IMA)

FR

Ethernet

Layer 1 or layer 2 traffic mapped to MPLS pseudowires

Transport for 2G and 3G mobile traffic Ethernet point-to-point services


VP

VP

ATM to Pseudowire to ATM

VP

VP

EF EF

BE BE

VP or VC mappingto PW

DiffServschedulingSP or WFQ

PW mapping toPSN tunnel

CBR CBR

UBR UBR

PSN tunnel and PW

termination

Mapping toATM PHY port

ATM VP/VCscheduling

PW

PW

EF EF

BE BE

VC

VC

DiffServschedulingSP or WFQ

CBR

UBR


MPLS Protection Methods:> ITU Y.1720 OAM 1+1 protection groups.> IETF pre-signalled secondary path protection. (Hello msg, BFD)


Scheduling

Egressport

#N

CS7

WFQ

EFAF1AF2AF3AF4BE

SP

Network ControlReal Time

Premium Data

Services

Best Effort

Strict Priority queuing (SP) and Weighted Fair Queuing (WFQ)


PWE3

In order to achieve a reasonable efficiency cell concatenation should be enabled

Traffic Management and QoS for Pseudowires )> N=1, N>1 use of VCG

VFEgypt- morning session 3-3-09

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