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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
Tellabs Internal and Confidential3 May 1, 2023
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”?
Tellabs Internal and Confidential4 May 1, 2023
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
Tellabs Internal and Confidential5 May 1, 2023
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)
Tellabs Internal and Confidential6 May 1, 2023
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
Tellabs Internal and Confidential7 May 1, 2023
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
Tellabs Internal and Confidential8 May 1, 2023
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
Tellabs Internal and Confidential9 May 1, 2023
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
Tellabs Internal and Confidential10 May 1, 2023
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
Tellabs Internal and Confidential11 May 1, 2023
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
Tellabs Internal and Confidential12 May 1, 2023
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
Tellabs Internal and Confidential13 May 1, 2023
Label Switched Paths
PE
IP/MPLS Core
New York
IP IP
PE
London
Label Exchange
Direction of Data FlowUpstream Downstream
P PIP/MPLS
Tellabs Internal and Confidential14 May 1, 2023
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
Tellabs Internal and Confidential15 May 1, 2023
> 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
Tellabs Internal and Confidential16 May 1, 2023
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
Tellabs Internal and Confidential17 May 1, 2023
Label Switched Paths
31
48
PE PE
IP/MPLS Core
LondonNew York
P
P
P
P
LSP
57
P
P
IP
IP
IP
IP
IP
P
Tellabs Internal and Confidential18 May 1, 2023
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
Tellabs Internal and Confidential19 May 1, 2023
Label Switched Paths
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
Tellabs Internal and Confidential21 May 1, 2023
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
Tellabs Internal and Confidential22 May 1, 2023
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
Tellabs Internal and Confidential23 May 1, 2023
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
Tellabs Internal and Confidential24 May 1, 2023
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
1036 CW VLAN 21/Ethernet
1038 CW VLAN 31/Ethernet
PWE3 Encapsulation
MPLS Labels
11
21
31
110
210
31
VLAN
Tunnel = 150VC = 1034, 1036, 1038
MPLS
Tellabs Internal and Confidential25 May 1, 2023
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
Tellabs Internal and Confidential26 May 1, 2023
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
Tellabs Internal and Confidential27 May 1, 2023
MPLS Protection Methods:> ITU Y.1720 OAM 1+1 protection groups.> IETF pre-signalled secondary path protection. (Hello msg, BFD)
Tellabs Internal and Confidential28 May 1, 2023
Scheduling
Egressport
#N
CS7
WFQ
EFAF1AF2AF3AF4BE
SP
Network ControlReal Time
Premium Data
Services
Best Effort
Strict Priority queuing (SP) and Weighted Fair Queuing (WFQ)
Tellabs Internal and Confidential29 May 1, 2023
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