Transcript Document

An introduction to MPLS and GMPLS (and briefly T-MPLS)
Anne-Grethe Kåråsen, Telenor R&I
Modified by Steinar Bjørnstad NTNU
Two slides on T-MPLS added by Norvald Stol NTNU 2007
Why was MultiProtocol Label Switching
(MPLS) designed?
• To enhance the performance of the traffic forwarding
mechanisms (compared to traditional IP forwarding)
• To provide a traffic engineering (TE) capability in IP
networks
What is Traffic Engineering (TE)?
•
TE is concerned with performance optimization of
operational networks.
•
Traffic performance: A major goal of Internet TE is to
facilitate efficient and reliable network operations while
simultaneously optimizing network resource utilization and
traffic performance.
•
QoS: Traffic oriented performance objectives include the
aspects that enhance the QoS of traffic streams.
•
Resource utilization: Resource oriented performance
objectives include the aspects pertaining to the optimization
of resource utilization.
The resource problem to solve:
• Conventional IGP path computation is selected based
upon a simple additive metric.
– Bandwidth availability is not taken into account
• Some links may be underutilized while others are
congested.
A solution to the resource problem
Path for R1 to R3 traffic
Path for R2 to R3 traffic
MPLS - some main concepts
• Uses label switching to forward data
– A label is a short fixed length physically contiguous
identifier which is used to identify a FEC, usually of
local significance.
• MPLS path = Label Switched Path (LSP)
• Forwarding Equivalence Class (FEC)
– A group of IP packets that are forwarded in the same
manner
– FEC – label mapping in ingress MPLS node
– Criteria for assigning packets to FECs are configurable
• Next Hop Label Forwarding Entry (NHLFE)
– Packets next hop + label operation (swap, push, pop)
The MPLS shim header
•
The EXP Field is "Experimental" though it is proposed use
is to indicate Per Hop Behavior of labeled packets
traversing Label Switching Routers. (QoS)
•
The Stack (S) Field indicates the presence of a label
stack.
•
The Time to Live Field is decremented at each LSR hop
and is used to throw away looping packets.
LSP route determination
• An LSP must be set up and labels assigned at
each hop before traffic forwarding can take
place.
• There are two kinds of LSPs, based on the
method used for determining the route:
– control-driven LSPs (hop-by-hop LSPs)
– explicitly routed LSPs (ER-LSPs)
• A control-driven LSP follows the path that a
packet using default IP routing would have
used.
• An ER-LSP may be specified and controlled
so that the network traffic follows a path
independent of what is computed by IP routing.
Constraint-based routing
• Types of constraints:
– Resource related (e.g. bandwidth)
– Administrative (e.g. include/exclude certain links)
• Resource related and policy related attributes are
associated with links.
• Link attributes are flooded by the routing protocols
along with topology information.
• A constraint-based path computation process uses this
information when finding paths that satisfy given
constraints.
• Most used algorithm is Constraint Shortest Path First
(CSPF):
– Excludes all links that fail to meet constraint
– Chooses shortest path that meets constraint
– Convenient for online path selection, one LSP at a time
ER-LSPs
• Explicit LSP: route is determined at the originating
node. When we explicitly route an LSP, we call it an
LSP tunnel or a traffic-engineering tunnel.
• Explicit route information is carried only at the time
of LSP setup, not with each packet forwarded on the
LSP.
• LSP tunnels are uni-directional.
• Can be set up manually or by the use of a signaling
protocol.
ER-LSP setup example using RSVP-TE
LSR9
LSR8
LSR3
LSR4
LSR2
ERO=( 5)
ERO=(2, 6, 7, 4, 5)
ERO=(6, 7, 4, 5)
L=5
ERO=(4, 5)
ERO=(7, 4, 5)
L=14
LSR1
LSR5
L=21
L=10
LSR7
LSR6
L=21
RSVP Path message carried Explicit Route Object (ERO)
RSVP Resv message carries Label information (L)
MPLS Label Forwarding Example
Label-Switched Path
(LSP)
IP
Packet
LER
IP Forwarding
Label 1
IP
Packet
Label 2
LSR
IP
Packet
Label 3
LSR
LABEL SWITCHING
IP
Packet
LER
IP
Packet
IP Forwarding
Label stacking
Protocols for MPLS routing and signaling
Routing:
• Open Shortest Path First (OSPF) & Intermediate System –
Intermediate System (IS-IS) with TE extensions
Signaling:
• Label Distribution Protocol (LDP) [RFC 3036]
• Constraint based LDP (CR-LDP) [RFC 3212]
• Extensions to Resource Reservation Protocol (RSVP) for
LSP tunnels [RFC 3209]
• Border Gateway Protocol (BGP) [RFC 3107]
MPLS references
•
Multiprotocol Label Switching Architecture, RFC 3031, Jan
2001
•
Requirements for traffic engineering over MPLS, RFC 2702,
Sept 1999
•
Traffic engineering extensions to OSPF version 2, RFC 3630,
September 2003
•
Traffic Engineering Extensions to OSPF version 3, Internet
Draft <draft-ietf-ospf-ospfv3-traffic-07>, April 2006
•
IS-IS extensions for traffic engineering, RFC 3784, June 2004
•
LDP specification, RFC 3036, Jan 2001
•
Constraint-based LSP setup using LDP, RFC 3212, Jan 2002
•
RSVP-TE: Extensions to RSVP for LSP tunnels, RFC 3209, Dec
2001
•
Carrying label information in BGP-4, RFC 3107, May 2001
Generalized MultiProtocol Label
Switching (GMPLS)
• GMPLS is an enhanced version of the MPLS-concept.
• GMPLS related work is coordinated by the IETF
Common Control and Measurement Plane (ccamp)
working group.
• In data networks, MPLS covers both the control plane
(label binding, label distribution, etc.) and the data
plane (packet forwarding).
• In circuit switched networks there is no packet
forwarding.
• Only MPLS control plane components are applicable to
circuit switched networks.
• GMPLS assumes IP-based routing and signaling
protocols, and IP addresses. (IP-centric)
GMPLS (former MPlS) – mapping to OTN
Main features applicable to OTN (Optical Transport
Network)
• MPLS control plane is implemented in each OXC
• Constraint-based routing and signaling provide
control plane for OXCs
– to discover, distribute, and maintain relevant state
information associated with the OTN
– to establish and maintain OCh trails
• Each OXC is considered an equivalent of a Label
Switched Router (LSR)
• Lightpaths (OCh trails) are considered similar to
Label Switched Paths (LSPs)
• Lambdas and switch ports are considered similar to
labels
GMPLS – new set of LSP interfaces
• Packet Switch Capable (PSC) interfaces:
– Recognize packet boundaries and can forward data based on the
content of the packet header (IP header, MPLS shim header).
• Layer-2 Switch Capable (L2SC) interfaces:
– Recognize frame/cell boundaries and can forward data based on
the content of the frame/cell header (Ethernet MAC header, ATM
VPI/VCI).
• Time-Division Multiplex Capable (TDM) interfaces:
– Forward data based on the data’s time slot in a repeating cycle
(SDH/SONET, G.709 TDM, PDH).
• Lambda Switch Capable (LSC) interfaces:
– Forward data based on the wavelength on which the data is
received (wavelength, waveband).
• Fiber-Switch Capable (FSC) interfaces:
– Forward data based on a position of the data in the real world
physical spaces (port, fiber).
GMPLS control plane – functional
components
• Resource discovery and link management
– The transaction that establishes, verifies, updates and
maintains the LSR adjacencies and their port pair association
for their transport (data) plane.
– LSR level resource table: resource map that includes
attributes, neighbor identifiers, and real-time operation states.
• Routing
– Topology information dissemination
– Path selection
• Signaling
– LSP creation, modification, deletion, restoration, and exception
handling
GMPLS – LSR level resource
discovery and link management
• Self resource awareness/discovery
– As a result, the LSR resource table is populated with local
ID, physical attributes, and logical constraints parameters
• Neighbor discovery and port association
– The process of discovering the status of local links to all
neighbors by each LSR in the network, The up/down status
of each link, link parameters, and the identity of the remote
end of the link must be determined (periodical operation)
[LMP].
• Resource verification and monitoring
– Neighbor operation state detection and configuration
verification (continuous operation).
• Service negotiation/discovery
– Covers all aspects related to service rules/policy negotiation
between neighbors.
GMPLS - Routing
• Topology information dissemination
– Distribution of topology information through the
network to form a consistent network level resource
view among LSRs.
– What type of information is required?
– How is the information disseminated?
– Triggering mechanisms for information update?
• GMPLS assumes that an IP-based routing protocol is
used for topology information dissemination.
• GMPLS extensions have been defined for the TE
extended versions of OSPF and IS-IS.
GMPLS – Routing cont.
• Path selection
– Usually a constraint-based computation process,
resulting in an explicit route or source route.
– Hop-by-hop routing is also possible.
• Specific constraints on optical layer routing
– Re-configurable (but blocking) network elements
such as OADMs
– Transmission impairments
– Absence of wavelength conversion
– Path diversity
GMPLS - IGP Extensions
OSPF and IS-IS extensions to carry additional
information:
•
switching capabilities of link (PSC, L2SC, TDM, LSC, FSC)
•
link encoding (e.g. SONET, SDH, GbE, etc.)
•
grouping of links that share same fate (SRLG)
•
protection capabilities of link
•
incoming and outgoing interface ID
•
CSPF extensions:
– take into account new constraints (e.g. link
encoding, multiplexing capabilities, etc.)
– compute diverse paths
– compute bi-directional paths
GMPLS - Signaling
• GMPLS inherits all signaling functions from MPLS-TE:
– LSP creation
– LSP deletion
– LSP modification
– LSP exception handling
• Additional GMPLS signaling protocol requirements:
– Creation of bi-directional LSPs
– Support of unnumbered links
– Rapid failure notification
– LSP fast restoration
GMPLS – signaling extensions
•
Generalized label request
– Supports communication of characteristics required to support the LSP
being requested, including LSP encoding, switching type, and LSP
payload
– LSP bandwidth encoding values, carried in a per protocol specific
manner (e.g. in the CR-LDP Traffic Parameters TLV)
•
Generalized label
– Extends the traditional label by allowing the representation of labels
that identify time-slots, wavelengths, or space division multiplexed
positions, or “anything that is sufficient to identify a traffic flow”.
– Non-hierarchical label.
•
Support of waveband switching
– A waveband represents a set of contiguous wavelengths that can be
switched together to a new waveband.
– Waveband label contains 3 fields: waveband ID, start label, end label.
•
Suggested label
– Is used to provide a downstream node with the upstream node's label
preference.
– May reduce latency of LSP setup
GMPLS – signaling extensions cont.
•
Label set
– Is used to limit the label choices of a downstream node to a set of
acceptable labels.
•
Explicit label control
– Ingress LSR may specify the label(s) to use on one, some or all of
the explicitly routed links for the forward and/or reverse path.
•
Bi-directional symmetric LSP
– A symmetric bi-directional LSP has the same traffic engineering
requirements including fate sharing, protection and restoration,
LSRs, and resource requirements in each direction.
– Downstream and upstream data paths are established using a single
set of signaling messages.
– New Upstream Label Object/TLV
•
Rapid notification of failure and events
– Acceptable Label Set for notification on label error
– Expedited notification (RSVP-TE only)
•
Link protection
– Protection Information Object/TLV indicates:
– The desired link protection for each link of an LSP
– Whether the LSP is a primary or secondary LSP
GMPLS – LSP Protection and restoration
• So far, only intra-area, intra-layer P&R mechanisms for
handling single failure scenarios are being discussed.
• Protection schemes:
– 1+1 link protection
– 1:N or M:N link protection
– Enhanced protection
– 1+1 LSP protection
• Restoration schemes:
– End-to-end LSP restoration with re-provisioning
– End-to-end LSP restoration with pre-signaled recovery
bandwidth reservation and no label pre-selection
– End-to-end LSP restoration with pre-signaled recovery
bandwidth reservation and label pre-selection
– Local LSP restoration
GMPLS extensions to the MPLS
control plane – a summary
• Support of devices that perform switching in the
time, wavelength and space domain.
• Use of label stacking and the resulting LSP
interface hierarchy
• The concept of link bundling
• The new Link Management Protocol (LMP) for
automatic link configuration and control
• Computation of physically disjoint paths by use
of Shared Risk Link Group (SRLG).
• The establishment of bi-directional symmetric
LSPs
GMPLS - LSP hierarchy
PSC
Cloud
TDM
Cloud
LSC
Cloud
LSC
Cloud
FSC Cloud
Fiber 1
Fiber n
TDM
Cloud
PSC
Cloud
Bundle
PSC
TDM
Explicit
Label LSPs
Time-slot
LSPs
LSC
l LSPs
l LSPs
Fiber LSPs
(multiplex low-order LSPs)
Time-slot
Explicit
LSPs
Label LSPs
(demultiplex low-order LSPs)
•
Nesting LSPs enhances system scalability
•
LSPs always start and terminate on similar interface types
•
LSP interface hierarchy
– Packet Switch Capable (PSC)
Lowest
– Layer 2 Switch Capable (L2SC)
– Time Division Multiplexing Capable (TDM)
– Lambda Switch Capable (LSC)
– Fiber Switch Capable (FSC)
Highest
GMPLS - Link Bundling
Bundled Link 1
Bundled Link 2
•
Allows multiple parallel links between nodes to be
advertised as a single link into the IGP
•
Enhances IGP and traffic engineering scalability
•
Component links must have the same:
– Link type
– Traffic engineering metric
– Set of resource classes (colors)
– Link multiplex capability (packet, TDM, λ, port)
•
(Max bandwidth request)  (bandwidth of a component
link)
•
Admission control is applied on a per-component link basis
GMPLS references
•
Optical Network Service Requirements, Internet Draft <draftietf-ipo-carrier-requirements-05>, December 2002
•
Generalized Multi-Protocol Label Switching (GMPLS)
Architecture, RFC 3945, October 2004
•
Generalized Multi-Protocol Label Switching (GMPLS) Signaling
Functional Description, RFC 3471, January 2003
•
Routing extensions in support of generalized MPLS, RFC 4202,
October 2005
•
LSP hierarchy with generalized MPLS TE, RFC 4206, October
2005
•
Requirements for Generalized MPLS (GMPLS) Signaling Usage
and Extensions for Automatically Switched Optical Network
(ASON), RFC 4139, July 2005
•
Requirements for Generalized MPLS (GMPLS) Routing for
Automatically Switched Optical Network (ASON), RFC 4258,
November 2005
GMPLS references cont.
•
OSPF extensions in support of generalized MPLS, RFC 4203, October
2005
•
IS-IS extensions in support of generalized MPLS, RFC 4205, October
2005
•
Generalized Multi-Protocol Label Switching (GMPLS) signaling –
Constraint-based routed label distribution protocol (CR-LDP)
extensions, RFC 3472, January 2003
•
Generalized Multi-Protocol Label Switching (GMPLS) signaling
Resource ReserVation Protocol-Traffic Engineering (RSVP-TE)
extensions, RFC 3473, January 2003
•
Link management protocol (LMP), RFC 4204, October 2005
•
Impairments and other constraints on optical layer routing, RFC 4054,
May 2005
•
Shared risk link groups inference and processing, Internet Draft
<draft-papadimitriou-ccamp-srlg-processing-02>, June 2003
GMPLS technology specific references
•
Framework for GMPLS-based control of SDH/SONET networks,
RFC 4257, December 2005
•
Generalized Multi-Protocol Label Switching (GMPLS)
Extensions for Synchronous Optical Network (SONET) and
Synchronous Digital Hierarchy (SDH) Control, RFC 3946,
October 2004
•
Generalized MPLS (GMPLS) signaling extensions for G.709
optical transport networks control, RFC 4328, January 2006
•
Traffic engineering extensions to OSPF for Generalized MPLS
control of Sonet/SDH networks, Internet Draft <draft-mannieccamp-gmpls-sonet-sdh-ospf-01>, February 2003
•
Traffic engineering extensions to OSPF for Generalized MPLS
control of G.709 optical transport networks, Internet Draft
<draft-gasparini-ccamp-gmpls-g709-ospf-00>, November
2002
ITU-T Recommendations
•
G.8080 Architecture for the Automatic Switched Optical Network
(ASON) (06/2006)
•
G.7712 Architecture and Specification of Data Communication Network
(03/2003)
•
G.7713 Distributed Call and Connection Management (DCM) (05/2006)
– G.7713.1 Distributed call and connection management (DCM)
based on PNNI (03/2003)
– G.7713.2 Distributed Call and Connection Management: Signaling
mechanism using GMPLS RSVP-TE (03/2003)
– G.7713.3 Distributed Call and Connection Management: Signaling
mechanism using GMPLS CR-LDP (03/2003)
•
G.7714 Generalized automatic discovery for transport entities
(08/2005)
•
G.7715 Architecture and Requirements for Routing in the Automatic
Switched Optical Networks (06/2002)
– G.7715.1 ASON routing architecture and requirements for link
state protocols (02/2004)
Optical Internetworking Forum (OIF)
Implementation agreements
•
User Network Interface (UNI) 1.0 Signaling Specification,
October 2001
•
User Network Interface (UNI) 1.0 Signaling Specification,
Release 2: Common Part, February 2004
•
RSVP Extensions for User Network Interface (UNI) 1.0
Signaling, Release 2, February 2004
•
Intra-carrier E-NNI Signaling Specification, February 2004
Transport-MPLS (T-MPLS)
•
Standardized by ITU-T for application in transport part of
network only.
•
Simplified MPLS: all features not necessary for connectionoriented applications are removed, i.e. less complex operation
and more easily managed than MPLS.
•
Management principles are adopted from existing
standards/practice, e.g. from SONET/SDH.
•
Supports
- engineered point-to-point bi-directional LSPs,
- end-to-end LSP protection, and
- advanced OAM.
•
Goal is to provide reliable packet-based technology (MPLS) in a
form that is aligned with circuit-based transport networking.
T-MPLS (2)
Differences from MPLS:
• Use of bi-directional LSPs traversing the same links and
nodes.
• No LSP merging option. (Multipoint-to-point is allowed in
MPLS, as in IP). Not allowed in pure connection oriented
network.
• No Equal Cost Multiple Path (ECMP) option. Not needed in
connection-oriented network.
• No Penultimate Hop Popping (PHP) option. Label must be
present in last node.
• (See whitepaper by TPACK: ”Transport-MPLS A New
Route to Carrier Ethernet” for overview – or standards).