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Introduction MPLS

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Title: 1 Author: Lin, Jonson Last modified by: User Created Date: 3/7/2002 12:42:42 PM Document presentation format: Company – PowerPoint PPT presentation

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Title: Introduction MPLS


1
Introduction MPLS Technology Services

2
Agenda
  • Background and business case
  • Technology basics
  • What is MPLS? Where is it used?
  • Label Distribution in MPLS Networks
  • LDP, RSVP, BGP
  • Building MPLS based Services
  • IPATM Integration
  • VPNs
  • Traffic Engineering (FRR Protection)
  • Conclusions

3
Evolution of MPLS
  • From Tag Switching
  • Proposed in IETF Later combined with other
    proposals from IBM (ARIS), Toshiba (CSR)

MPLS Croup Formally Chartered by IETF
Traffic Engineering Deployed
Cisco Ships MPLS TE
Cisco Calls a BOF at IETF to Standardize Tag
Switching
Cisco Ships MPLS (Tag Switching)
MPLS VPN Deployed
Large Scale Deployment
1996
1997
1998
1999
2000
2001
Time
4
MPLS-Key Drivers

5
MPLS as a Foundation for Value Added Services
6
US VPN Spending
Infonetics VPN Spend Projections in (US
millions
Yankee Group Predictions for VPN Spending (US
millions)
7
New Applications for VPN
Source Infonetics April 2000
8
The Service Provider Challenge
  • Generate New services
  • Protect Existing Infrastructure ATM/FR
  • Combine Private Data Services with Internet
    Services
  • Move into rapid deployment

9
Technology Specifics

10
MPLS Concepts
  • MPLS Multi Protocol Label Switching
  • MPLS is a layer 2 switching
  • MPLS forwarding is done in the same way as in ATM
    switches
  • Packet forwarding is done based on Labels

11
LSRs and Labels
  • LSR Label Switch Router
  • Edge-LSR LSRs that do label imposition and
    disposition

12
LSRs and Labels
  • An IP routing protocol is used within the
    routing domain (e.g.OSPF, i-ISIS)
  • A label distribution protocol is used to
    distribute address/label mappings
    between adjacent neighbors
  • The ingress LSR receives IP packets, performs
    packet classification, assign a label, and
    forward the labelled packet into the MPLS network
  • Core LSRs switch packets/cells based on the label
    value
  • The egress LSR removes the label before
    forwarding the IP packet outside the MPLS network

13
LSRs and Labels
Label 20 bits Exp Experimental, 3 bits S
Bottom of stack, 1bit TTL Time to live, 8 bits
  • Uses new Ethertypes/PPP PIDs/SNAP values/etc
  • More than one Label is allowed -gt Label Stack
  • MPLS LSRs always forward packets based on the
    value of the label at the top of the stack

14
LSRs and Labels
PPP Header(Packet over SONET/SDH)
PPP Header
Layer 3 Header
Shim Header
Ethernet Hdr
Layer 3 Header
Shim Header
Ethernet
FR Hdr
Layer 3 Header
Shim Header
Frame Relay
HEC
DATA
CLP
PTI
VCI
GFC
VPI
ATM Cell Header
HEC
DATA
CLP
PTI
VCI
GFC
VPI
Subsequent cells
15
Label Assignment and Distribution
  • Labels have link-local significance
  • Each LSR binds his own label mappings
  • Each LSR assign labels to his FECs
  • Labels are assigned and exchanged between
    adjacent neighboring LSR
  • Applications may require non-adjacent
    neighbors

16
Label Assignment and Distribution
Upstream and Downstream LSRs
171.68.10/24
171.68.40/24
Rtr-B
Rtr-A
Rtr-C
  • Rtr-C is the downstream neighbor of Rtr-B for
    destination 171.68.10/24
  • Rtr-B is the downstream neighbor of Rtr-A for
    destination 171.68.10/24
  • LSRs know their downstream neighbors through the
    IP routing protocol
  • Next-hop address is the downstream neighbor

17
Label Assignment and Distribution
Unsolicited Downstream Distribution
171.68.40/24
171.68.10/24
Rtr-A
Rtr-B
Rtr-C
IGP derived routes
  • LSRs distribute labels to the upstream neighbors

18
Label Assignment and Distribution
On-Demand Downstream Distribution
171.68.10/24
171.68.40/24
Rtr-A
Rtr-B
Rtr-C
  • Upstream LSRs request labels to downstream
    neighbors
  • Downstream LSRs distribute labels upon request

19
Label Assignment and Distribution
Label Retention Modes
  • Liberal retention mode
  • LSR retains labels from all neighbors
  • Improve convergence time, when next-hop is again
    available after IP convergence
  • Require more memory and label space
  • Conservative retention mode
  • LSR retains labels only from next-hops neighbors
  • LSR discards all labels for FECs without next-hop
  • Free memory and label space

20
Label Assignment and Distribution
Label Distribution Modes
  • Independent LSP control
  • LSR binds a Label to a FEC independently, whether
    or not the LSR has received a Label the next-hop
    for the FEC
  • The LSR then advertises the Label to its neighbor
  • Ordered LSP control
  • LSR only binds and advertise a label for a
    particular FEC if
  • it is the egress LSR for that FEC or
  • it has already received a label binding from its
    next-hop

21
Label Assignment and Distribution
  • Several protocols for label exchange
  • LDP
  • Maps unicast IP destinations into labels
  • RSVP, CR-LDP
  • Used in traffic engineering
  • BGP
  • External labels (VPN)
  • PIM
  • For multicast states label mapping

22
Label Switch Path (LSP)
IGP domain with a label distribution protocol
IGP domain with a label distribution protocol
LSP follows IGP shortest path
LSP diverges from IGP shortest path
  • LSPs are derived from IGP routing information
  • LSPs may diverge from IGP shortest path
  • LSP tunnels (explicit routing) with TE
  • LSPs are unidirectional
  • Return traffic takes another LSP

23
Label Switch Path (LSP) Penultimate Hop Popping
  • The label at the top of the stack is removed
    (popped) by the upstream neighbor of the egress
    LSR
  • The egress LSR requests the popping through the
    label distribution protocol
  • Egress LSR advertises implicit-null label
  • The egress LSR will not have to do a lookup and
    remove itself the label
  • One lookup is saved in the egress LSR

24
Label Switch Path (LSP) Penultimate Hop Popping
  • Summary route for 171.68/16
  • Summary route for 171.68/16

0
0
1
1
171.68.44/24
  • Use label 4 for FEC 171.68/16
  • Use label implicit-null for FEC 171.68/16

171.68.10/24
Egress LSR summarises more specific routes and
advertises a label for the new FEC
Summary route is propagate through the IGP and
label is assigned by each LSR
Egress LSR needs to do an IP lookup for finding
more specific route Egress LSR need NOT receive a
labelled packet
25
Loops and TTL
  • In IP networks TTL is used to prevent packets to
    travel indefinitely in the network
  • MPLS may use same mechanism as IP, but not on all
    encapsulations
  • TTL is present in the label header for PPP and
    LAN headers (shim headers)
  • ATM cell header does not have TTL

26
Loops and TTL
  • LSRs using ATM do not have TTL capability
  • Some suggested options
  • - hop-count object in LDP
  • - Path Vector object in LDP

27
Loops and TTL
LSR-1
LSR-3
LSR-2
IP packet TTL 10
LSR-6
LSR-6 --gt 25 Hops4
IP packet TTL 6
IGP domain with a label distribution protocol
Egress
LSR-5
LSR-4
  • TTL is decremented prior to enter the non-TTL
    capable LSP
  • If TTL is 0 the packet is discarded at the
    ingress point
  • TTL is examined at the LSP exit

28
Label Distribution Protocol
  • Defined in RFC 3035 and 3036
  • Used to distribute Labels in a MPLS network
  • Forwarding Equivalence Class
  • How packets are mapped to LSPs (Label Switched
    Paths)
  • Advertise Labels per FEC
  • Reach destination a.b.c.d with label x
  • Neighbor discovery
  • Basic and Extended Discovery

29
LDP Concepts
  • Label Distribution Protocol
  • Labels map to FECs for Unicast Destination
    Prefix
  • LDP works between adjacent/non-adjacent peers
  • LDP sessions are established between peers

30
LDP Messages
  • Discovery messages
  • Used to discover and maintain the presence of
    new peers
  • Hello packets (UDP) sent to all-routers
    multicast address
  • Once neighbor is discovered, the LDP session is
    established over TCP

31
LDP Messages
  • Session messages
  • Establish, maintain and terminate LDP sessions
  • Advertisement messages
  • Create, modify, delete label mappings
  • Notification messages
  • Error signalling

32
Label Distribution Protocol
  • Label Merge
  • Done by default for packet networks unique
    label advertised per FEC
  • Requires VC merge for ATM networks

33
TDP LDP
  • Tag Distribution Protocol
  • Pre-cursor to LDP
  • Used for Cisco Tag Switching
  • TDP and LDP supported on the same box
  • Per neighbor/link basis
  • Per target basis

34
RSVP Label Distribution
  • Used in MPLS Traffic Engineering
  • Additions to RSVP signaling protocol
  • Leverage the admission control mechanism of RSVP
  • Label requests are sent in PATH messages and
    binding is done with RESV messages
  • EXPLICT-ROUTE object defines the path over which
    setup messages should be routed
  • Using RSVP has several advantages
  • Traffic Engineering, Shared Explicit, FRR

35
MPLS Example Forwarding Packets
In label
Address Prefix
Out Iface
Out label
In label
Address Prefix
Out Iface
Out label
In label
Address Prefix
Out Iface
Out label
-
128.89
1
4
4
128.89
0
9
9
128.89
0
-
-
171.69
1
5
5
171.69
1
7
...
...
...
...
...
...
...
...
...
...
...
...
128.89
0
0
128.89.25.4
Data
1
128.89.25.4
Data
9
1
128.89.25.4
Data
4
128.89.25.4
Data
Label Switch forwards based on label
171.69
36
Label Stacking
  • IGP Labels Used for routing packets
  • BGP Labels Used for assigning end
    users/communities
  • RSVP Labels Used for TE tunnels
  • If more than one service is used
  • Then multiple labels are required TE and FRR
  • In some cases a single service requires the use
    of multiple labels - VPNs

37
Label Stacking how?
  • Arrange Labels in a stack
  • Inner labels can be used to designate
    services/FECs etc
  • E.g VPNs, Fast Re-route
  • Outer label used to route/switch the MPLS packets
    in the network
  • Allows building services such as
  • MPLS VPNs Basic Advanced - CSC
  • Traffic Engineering and Fast Re-route
  • VPNs over Traffic Engineered core
  • Any Transport over MPLS

Outer Label
TE Label
IGP Label
VPN Label
IP Header
Inner Label
38
Day in the life of a Packet
P
P
1
PE
2
1
0
PE
0
0
  • Use label implicit-null for FEC 171.68/16
  • Use label 4 for FEC 171.68/16
  • Use label 7 for FEC 171.68/16

0
171.68.44/24
  • Summary route for 171.68/16
  • Summary route for 171.68/16

CE
171.68.10/24
Summary route is propagate through the IGP and
label is assigned by each LSR
Egress LSR summarises more specific routes and
advertises a label for the new FEC
Egress LSR needs to do an IP lookup for finding
more specific route
39
Day in the life of a Packet - Basic Layout
40
Day in the life of a Packet - Database Layout
41
Day in the life of a Packet
42
Day in the life of a Packet
43
MPLS based services

44
Provider Provisioned VPNs

45
Categories
  • BGP MPLS VPNs RFC 2547
  • Supported by Cisco
  • Virtual Routers
  • Alternative proposal relies on logical
    partitioning of the physical box
  • Requires the use of Multicast/broadcast for
    better convergence

46
MPLS Based IP-VPN Architecture
  • Scalable VPNs
  • IP QoS and traffic engineering
  • Easy to manage and No VC provisioning required
  • Provides a level of Security equivalent to
    Frame-relay and ATM
  • Supports the deployment of new value-added
    applications
  • Customer IP address freedom

VPN Membership- Based on Logical Port
VPN A Site 2
MPLS Network
Corp B Site 2
MPLS VPN Renault
MPLS VPN Bankcorp
Corp B Site 1
Traffic Separation at Layer 3 Each VPN has Unique
RD
47
Using Labels to Build an IP VPN
  • The network distributes labels to each VPN
  • only labels for other VPN members are distributed
  • each VPN is provisioned automatically by IP
    routing
  • Privacy and QoS of ATM without tunnels or
    encryption
  • each network is as secure as a Frame Relay
    connection
  • One mechanism (labels) for QoS and VPNs - no
    tradeoffs

48
Service Provider Benefits of MPLS-based VPNs
Multicast
VPN A
VPN B
VPN C
VPN C
VPN B
Hosting
Intranet
VPN A
VoIP
Extranet
VPN A
VPN B
VPN C
VPN C
VPN A
VPN B
  • MPLS-based VPNs
  • enables content hosting inside the network
  • flat cost curve
  • transport independent
  • easy grouping of users and services
  • enables QoS inside the VPNs
  • Overlay VPN
  • pushes content outside the network
  • costs scale exponentially
  • transport dependent
  • groups endpoints, not groups
  • complex overlay with QoS, tunnels, IP

49
Validating Cisco MPLS Based IP-VPN as a Secure
Network
Miercom independent testing confirmed Cisco MPLS
VPN is secure
  • Customers network topology is not revealed to the
    outside world
  • Customers can maintain own addressing plans and
    the freedom to use either public or private
    address space
  • Attackers cannot gain access into VPNs or Service
    Providers network
  • Impossible for attacker to insert spoofed label
    into a Cisco MPLS network and thus gain access to
    a VPN or the MPLS core

Test Network Topology
50
BGP/MPLS VPN - Summary
  • Supports large scale VPN service
  • Increases value add by the VPN Service Provider
  • Decreases Service Provider cost of providing VPN
    services
  • Mechanisms are general enough to enable VPN
    Service Provider to support a wide range of VPN
    customers

51
MPLS Traffic Engineering

52
Why Traffic Engineering?
  • Congestion in the network due to changing traffic
    patterns
  • Election news, online trading, major sports
    events
  • Better utilization of available bandwidth
  • Route on the non-shortest path
  • Route around failed links/nodes
  • Fast rerouting around failures, transparently to
    users
  • Like SONET APS (Automatic Protection Switching)
  • Build New Services - Virtual leased line services
  • VoIP Toll-Bypass applications, point-to-point
    bandwidth guarantees
  • Capacity planning
  • TE improves aggregate availability of the network

53
IP Routing and The Fish
R8
R3
R4
R5
R2
R1
R6
R7
IP (Mostly) Uses Destination-Based Least-Cost
Routing Flows from R8 and R1 Merge at R2 and
Become Indistinguishable From R2, Traffic to R3,
R4, R5 Use Upper Route
Alternate Path Under-Utilized
54
Applications of MPLS TE
LINK NODE PROTECTION
R9
R8
R3
R4
R2
R1
R5
R7
R6
Mimic SONET APS Re-route in 50ms or less
  • Multiple hops can be by-passed. R2 swaps the
    label which R4 expects before pushing the label
    for R6
  • R2 locally patches traffic onto the link with R6


55
MPLS Traffic Engineering for a QoS-Optimized
Backbone
DiffServ-aware TE QoS!
MPLS Backbone
DiffServ over IP on Access Links
DiffServ over IP on Access Links
PE
PE
DiffServ aware TE
CE
CE
DS-TE QoS GB-TE
DiffServ o IP
DiffServ o IP
Constrained
Constrained
Optimized
56
DiffServ Aware TE Virtual Leased line
Class 5 legacy switches
PSTN Traditional TDM Network
Central Office
Central Office
Traditional Telephony
Traditional Telephony
MPLS Network
VoIP Gateway
VoIP Gateway
Toll Bypass
Voice Trunking
PE
GB Tunnel
PE
PE
PE
Regular TE Tunnel
CE
CE
Enterprise LAN
Enterprise LAN
PE
PE
VPN Service
Legend
GB-TE Tunnel
Internet Access Router
Internet Access Router
Enterprise LAN
Enterprise LAN
Regular TE Tunnel
Internet Service
Physical Link
57
MPLS TE Summary
  • Useful for re-routing traffic in congested
    environments
  • Build innovative services like Virtual Leased
    line
  • Build protection solutions using MPLS FRR

58
Any Transport over MPLS

59
Any Transport over MPLS
  • Trunking Layer 2 over an MPLS Network
  • Ethernet
  • Frame Relay
  • ATM AAL5, Cell Mode
  • PPP
  • Cisco HDLC
  • SONET

60
Ethernet over MPLS
ISP C
MPLS Network
ISP A
Enterprise LAN
ISP B
PE
PE
ISP 2
PE
PE
ISP 1
PE
PE
Enterprise LAN
ISP 3
61
Frame Relay over MPLS
Any Transport over MPLS (AToM) Tunnel
MPLS Backbone
PE
PE
DS-TE Tunnel
Virtual Leased Line (DS-TE QoS)
Frame Relay
Frame Relay
Frame Relay DLCI
CPE Router, FRAD
CPE Router, FRAD
62
ATM over MPLS
Any Transport over MPLS (AToM) Tunnel
MPLS Backbone
PE
PE
DS-TE Tunnel
Virtual Leased Line (DS-TE QoS)
ATM
ATM
ATM Virtual Circuits
CPE Router
CPE Router
63
PPP, Cisco HDLC over MPLS
64
Pseudo Wire Reference Model
draft-ietf-pwe3-requirements
Customer Site
Customer Site
PSN Tunnel
PE
PE
Pseudo Wires
PWES
PWES
PWES
PWES
Customer Site
Customer Site
Emulated Service
A pseudo-wire (PW) is a connection between two
provider edge (PE) devices which connects two
pseudo-wire end-services (PWESs) of the same type
65
Pseudo Wire Reference Model
PSN Tunnel
Customer Site
Customer Site
PW PDUs
PE
PE
PDU
Pseudo Wires
PDU
PDU
PDU
Customer Site
Customer Site
  • PDUs are encapsulated at the ingress PE router
    and forwarded between PEs as PW PDUs
  • The Pseudo wire PDU contains ALL data control
    information (control word) necessary to provide
    Layer-2 service
  • although some information may be stored as state
    at PW set-up

66
Layer-2 Transport across MPLS
  • Two relevant drafts by Luca Martini
  • draft-martini-l2circuit-trans-mpls
  • describes label distribution mechanisms for VC
    labels
  • draft-martini-l2circuit-encap-mpls
  • describes emulated VC encapsulation mechanisms
  • Relevant for the transport of FR, ATM AAL5, ATM
    cell, Ethernet (Port Trunking), Ethernet 802.1q
    (VLAN), POS, TDM, Cisco HDLC PPP protocol data
    units
  • across either an MPLS or an IP backbone

67
Layer-2 Transport across MPLS
  • Emulated Circuits use 3 layers of encapsulation
  • Tunnel Header
  • to get PDU from ingress to egress PE
  • could be an MPLS label, GRE tunnel, L2TP tunnel
  • Demultiplexer field
  • to identify individual circuits within a tunnel
  • could be an MPLS label or GRE key
  • Emulated VC encapsulation
  • information on enclosed Layer-2 PDU
  • implemented as a 32-bit control word

68
VC Information Exchange
  • VC labels are exchanged across a directed LDP
    session between PE routers
  • Carried in Generic Label TLV within LDP Label
    Mapping Message
  • New LDP FEC element defined to carry VC
    information
  • FEC element type 128 Virtual Circuit FEC
    Element
  • Carried within LDP Label Mapping Message
  • VC information exchanged using Downstream
    Unsolicited label distribution procedures
  • Described in draft-martini-l2circuit-trans-mpls

69
Virtual Circuit FEC Element
0 1
2
3 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
6 7 8 9 0 1
C
VC info length
VC-type
VC TLV (0x80)
Group ID
VC ID
Interface Parameters
C Control Word (1 bit) Control word present
if bit set VC-type (15 bits) - Type of VC e.g FR,
ATM, VLAN, Ethernet, PPP, HDLC VC info length (8
bits) Length of VCID field and interface
parameters Group ID (32 bits) Represents a
groups of VCs. Can be used for mass label
withdrawal VC ID (32
bits) Connection identifier used in conjunction
with the VC-type to
identify a particular VC Interface Parameters
(Variable) Edge facing interface parameters,
such as MTU
70
LDP Label Mapping Exchange
0 1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-------------------------
------- 0 Label Mapping (0x0400)
Message Length
-------------------------
------- Message
ID
-------------------------
------- 00 FEC (0x0100)
Length
-------------------------
------- VC tlv (0x80) C VC
Type VC info Length
-------------------------
------- Group
ID
-------------------------
------- VC
ID
-------------------------
-------
Interface parameters
"
------------------
-------------- 00 Generic
Label (0x0200) Length
---------------------
-----------
Label
-------------------------
------- Optional
Parameters
-------------------------
-------
LDP Label Mapping Message (Specified in RFC 3036)
FEC TLV Header (Specified in RFC 3036)
Virtual Circuit FEC Element
(Specified in draft-martini-l2circuit-trans-mpls)
Label TLV Header (Specified in RFC 3036)
71
Layer-2 Transport Control Word
0 1
2
3 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
6 7 8 9 0 1
0
Tunnel Label
EXP
TTL
Tunnel Label (LDP or RSVP)
VC Label
VC Label (VC)
EXP
1
TTL (set to 2)
Sequence number
Rsvd
Flags
Length
0
0
Control Word
Layer-2 PDU
  • When transporting layer-2 protocols over an IP or
    MPLS backbone
  • The sequence of the packets may need to be
    preserved
  • Small packets may need to be padded if the
    minimum MTU of the medium is larger than actual
    packet size
  • Control bits carried in header of Layer-2 frame
    may need to be transported

72
AToM Any Transport over MPLS
  • Cisco solution AToM Any Transport over MPLS
  • Tunnel Header is implemented as an MPLS label
  • Which is learned via LDP and is used to transport
    frames from ingress to egress PE routers
  • Demultiplexer Field is implemented as a VC label
  • Which is learnt across a directed LDP session
    between PE routers
  • Emulated VC encapsulation is implemented as a
    control word

73
AToM Label Distribution Usage
Customer Site
Customer Site
TUNNEL LSP
PE
PE
DIRECTED LDP
Customer Site
Customer Site
TUNNEL LSP
  • Tunnel LSPs between PE routers
  • to transport PW PDU from PE to PE using tunnel
    labels
  • Directed LDP session between PE routers
  • to exchange VC information, such as VC labels and
    control information

74
AToM Label Mapping Exchange
PE2 repeats steps 1-5 so that bi-directional
label/VCID mappings are established
CE
CE1
1. L2 transport route entered on ingress PE
4. PE1 sends label mapping message containing VC
FEC TLV VC label TLV
PE1
PE2
5. PE2 receives VC FEC TLV VC label TLV that
matches local VCID
3. PE1 allocates VC label for new interface
binds to configured VCID
2. PE1 starts LDP session with PE2 if one does
not already exist
Tunnel Label
VC Label
PDU
Bi-directional Label/VCID mapping exchange
75
VC Label Withdrawal Procedures
  • If a PE router detects a condition that affects
    normal service it MUST withdraw the corresponding
    VC label
  • Through the use of LDP signalling
  • A PE router may provide circuit status signalling
  • FR MUST through the use of LMI procedures ATM
    SHOULD through the use of ILMI procedures

LDP Label Withdraw VCID 320 VC Label 16
PE1 1.0.0.4
PE2 1.0.0.8
Circuit Status Signalling
Layer-2 Circuit
MPLS
76
AToM - MTU Considerations
Ingress PE checks Egress PE outbound interface
MTU AND egress interface into MPLS backbone
Customer Site
Customer Site
Egress MTU Signalled using LDP
PE1
PE2
PDU
NO mechanism to check backbone MTU
Incoming PDU dropped if MTU exceeded
Provider MUST dictate MTU or direct traffic away
from low MTU links
77
Transport of Ethernet over MPLS
  • Three main requirements for transport of Ethernet
    frames
  • 802.1q VLAN to 802.1q VLAN transport
  • 802.1q VLAN port to port transport
  • Ethernet port to port transport
  • Phase 1 of AToM supports 802.1q VLAN to VLAN
    transport ONLY
  • VC-type 0x0004 within draft-martini-l2circuit-tran
    s-mpls
  • 7600 will support VC-type 0x0005 port-to-port
    Ethernet trunking port-to-port VLAN trunking in
    Hubble release
  • GSR planned to support VC-type 0x0005 in
    12.0(23)ST
  • ISL encapsulation is NOT supported

78
Ethernet 802.1q VLAN Transport
Interface GigabitEthernet0/0.2 encapsulation
dot1q 41 mpls l2transport route 1.0.0.8 312
ltsequencinggt ! Interface GigabitEthernet1/0.2
encapsulation dot1q 56 mpls l2transport route
1.0.0.8 313 ltsequencinggt
VLAN 56
MPLS
Customer Site
PE1 1.0.0.8
PE1 1.0.0.4
VLAN 41
VLAN 41
VLAN 56
Customer Site
Customer Site
Customer Site
802.1q to 802.1q VLAN Transport
79
EoMPLS Encapsulation Details
  • Ethernet PDUs are transported without the
    preamble, SFD and FCS
  • but including all VLAN information such as VCID
  • The control word is optional
  • C bit is set by default in Cisco implementation
    (except 7600)
  • If the control word is used then the flags must
    be set to zero
  • The VLAN tag is transmitted unchanged but may be
    overwritten by the egress PE router

0 1
2
3 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
6 7 8 9 0 1
Rsvd
Optional
Sequence number
0
0
Length
0 0 0 0
Ethernet PDU
80
Ethernet Frame Formats
Ethernet II Encapsulation
lt7 octetsgt
lt1 octetgt
lt6 octetsgt
lt2 octetsgt
lt6 octetsgt
lt4 octetsgt
lt46-1500gt
Preamble
SFD
SA
Data
FCS
DA
Ethertype
802.1q Encapsulation
TPID
TCI
lt2 octetsgt
lt2 octetsgt
802.3/802.2/SNAP Encapsulation
lt7 octetsgt
lt1 octetgt
lt6 octetsgt
lt8 octetsgt
lt2 octetsgt
lt6 octetsgt
lt4 octetsgt
lt46-1492gt
Preamble
SFD
SA
LLC
Data
DA
Length
FCS
OUI 0x00-00-00
802.1q Encapsulation
TPID
TCI
Ethertype
AA-AA-03
lt2 octetsgt
lt2 octetsgt
lt3 octetsgt
lt2 octetsgt
lt3 octetsgt
Different Ethernet frame formats supported
81
EoMPLS Transport Formats
Ethernet II Encapsulation
lt4 octetsgt
lt7 octetsgt
lt6 octetsgt
lt46-1500gt
lt2 octetsgt
lt2 octetsgt
lt1 octetgt
lt2 octetsgt
lt6 octetsgt

Preamble
SFD
DA
SA
TPID
TCI
Ethertype
Data
FCS
Transported using AToM

OUI 0x00-00-00
Preamble
SFD
DA
SA
TPID
TCI
Length
AA-AA-03
Ethertype
Data
FCS
lt6 octetsgt
lt1 octetgt
lt2 octetsgt
lt7 octetsgt
lt4 octetsgt
lt2 octetsgt
lt6 octetsgt
lt2 octetsgt
lt46-1492gt
lt3 octetsgt
lt2 octetsgt
lt3 octetsgt
802.3/802.2/SNAP Encapsulation
82
MPLS QoS

83
MPLS Class of Service
  • Class of Service (CoS)
  • network implements distinct service classes
  • traffic flows are classified
  • based on Layer 3 application, destination, etc.
  • simpler and more efficient than mesh of VCs
  • Two methods to indicate service class
  • IP precedence copied to MPLS header (CoS field)
  • up to 8 classes can be defined (3 bits)
  • use separate labels for different service classes
  • no limit to number of labels

84
MPLS QoS Summary
  • Use the same underlying IP QoS mechanisms
  • Queuing LLQ, CBWFQ
  • Policing
  • WRED
  • Classification and marking done on EXP bits in
    the label header
  • Label header marking can be different from the IP
    header DSCP providing a transparency

85
Summary

86
What isnt MPLS?
  • MPLS is not just integration of IP and ATM, BUT
  • Integration of IP and ATM is just one of the
    applications of MPLS

87
What isnt MPLS?
  • MPLS is not a way to make routers (much) faster,
    BUT
  • MPLS forwarding algorithm is simpler than IP
    forwarding algorithm, AND it enables more
    functionality than could be provided with the IP
    forwarding algorithm

88
MPLS and the OSI Reference Model (OSIRM)
  • MPLS is not a Network Layer
  • doesnt have routing and addressing on its own -
    uses IP addressing IP routing (with extensions)
  • MPLS is not a Link Layer
  • because MPLS works over various Link Layer
    technologies (e.g., SONET, Ethernet, ATM, etc)
  • MPLS is not a Layer in the OSIRM sense
  • doesnt have a single format for transport of the
    data from the layer above
  • shim on SONET, VCI/VPI on ATM, lambda on OXC,
    etc...

MPLS does not fit into the OSI Reference Model
89
MPLS Key Benefits
  • New value added services
  • BGP MPLS VPNS RFC 2547
  • Traffic Engineering
  • L2 VPNS
  • Protection Solutions
  • Link and Node protection
  • Bandwidth Protection - Future

90
MPLS and its applications
  • Separate forwarding information (label) from the
    content of IP header
  • Single forwarding paradigm (label swapping) -
    multiple routing paradigms
  • Multiple link-specific realizations of the label
    swapping forwarding paradigm
  • Flexibility of forming FECs
  • Forwarding hierarchy via label stacking
  • Traffic Engineering
  • Fast re-route
  • Hard QoS support
  • Integration with Optical Cross Connects
  • Scalable VPN

91
End-to-End Solution
VPN HQ Back-up
5 Mbps
1 Mbps
HQ1
MPLS TE
MPLS VPN
VPN and Traffic Engineering Combined to Provide
End-to-End Services
92
Questions?
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