presented by: dmitri perelman nadav chachmon. agenda overview mpls evolution to gmpls switching...

Presented byPresented by::Dmitri PerelmanDmitri Perelman

Nadav ChachmonNadav Chachmon

Agenda

• Overview • MPLS evolution to GMPLS• Switching issues

– GMPLS label and its distribution– LSP creation– Suggestion of the label– Control plane vs. Data plane

• Scalability issues– Forwarding Adjacency LSP– Hierarchical LSP– Link Bundling

• Reliability• Summary• Questions and Answers

GMPLS overview

• The premise of multi protocol label switching is (MPLS):– speed up packet forwarding: MPLS device uses labels rather than

address matching to determine the next hop– provide traffic engineering in IP networks: tables and the labels

represent different levels of QoS for the end-to-end path

• Connectionless operation of IP networks becomes more like a connection-oriented network – the path between source and destination is precalculated based on user specifics.

• Generalized MPLS provides control plane (signaling and routing) for devices that switch in any of following domains: packet, time, wavelength and fiber.

MPLS background – reminder

• At the ingress of an MPLS network, incoming IP packets are examined and assigned a label by a label edge router (LER).

• The labeled packets are forwarded through label switched path (LSP), where each label switched router (LSR) makes a switching decision based on the packet’s label field.

An example…

Unlabeled Packet arrives

IP

Egress routerremoves label

IP

IP 20

Label switching & packet forwarding

Ingressrouter addslabel to packet

IP 10

Autonomoussystem boundary

LER

LER

LSR

Label Switched Path (LSP)

Label switched path

Evolution from MPLS to GMPLS

• MPLS suite of protocols is extended to include devices that switch in time (e.g. DCS), wavelength (e.g. DWDM) and space (e.g. OXC).

• Currently, in development by the International Engineering Task Force (IETF)

• The motivation to do it is the diversity and complexity in managing network devices (such as : ADM, DWDM, OXC , PXC, multiservice switching platforms)

• This extension allows GMPLS-based networks to provide an optimal path, based on user traffic requirements for a flow that may start on an IP network, and then pass dissimilar network types (SONET, optical and so on).

Evolution from MPLS to GMPLS - example

GMPLS control plane promises to simplify network operation and management by automating end-to-end provisioning

Of connections, managing network resources and providing the level of Qos that is expected by the user

Agenda

• Overview • MPLS evolution to GMPLS

• Switching issues– GMPLS label and its distribution– LSP creation– Suggestion of the label– Control plane vs. Data plane



GMPLS Label

• Need to be able to support devices that switch in different domains

• GMPLS introduces new label format – generalized label, that contains information to allow the receiving device to program its switch regardless of its construction (packet, TDM, lambda, etc.)

• Information embedded in generalized label should include LSP encoding type that indicates what type of label is being carried

• Label distribution starts from the upstream LSR requesting a label from downstream LSR (GMPLS allows suggesting the label by upstream LSR – see later).

LSP creation

• Consider a following example: the goal is to establish LSP between LSR1 and LSR4

LSP creation – cont.

• To establish LSP pc between LSR1 and LSR4 other LSPs in the other networks must be established to tunnel the LSPs in the lower hierarchy.

• This is done by sending a PATH/Label Request message downstream to the destination that will carry the lower hierarchy LSP.

• Only when the LSP in the higher hierarchy is established, initiator can establish an LSP with its peer per network domain.

Step 1 : LSP is established between 0XC1 and 0XC2 (LSP1)


Step 2: LSP is established between DCSi and DCSe



Step 3 : LSP is established between DCS-1 and DCS-2



Step 3 : LSP is established between DCS-1 and DCS-2

Step 4 : LSP is established between LSR2 and LSR3



Step 3 : LSP is established between DCS-1 and DCS-2Step 4 : LSP is established between LSR2 and LSR3

Step 5 : LSPpc is established between LSR1 and LSR4

Suggested label

• Upstream node can optionally suggest a label to its downstream node (although the downstream node may refuse and propose its own value).

• This operation is important for the systems that require time consuming processes to configure their switch fabric (DCS with high thousands of ports).

• A suggested label allows the DCS to configure itself with the proposed label instead of waiting to receive a label from the downstream node.

Control plane vs. Data plane

• The label-swapping paradigm logically separates the data and control planes.

• GMPLS extends this paradigm to those devices that are not designed to examine the content of the data fed into them. In this case GMPLS allows the data and control plane to be physically (or logically) separate.

• GMPLS doesn’t mandate how the control information is to be transported between two nodes.

Agenda





Forwarding adjacency LSP• A FA-LSP is a GMPLS based LSP to carry other LSPs• An FA-LSP established between GMPLS nodes can be viewed as a virtual link.• LSP can be advertised as a point-to-point Traffic

Engineering (TE) link in the routing protocol; thus, an advertised TE link need no longer be between two OSPF direct neighbors.

• This can reduce the size of the database reduce the time spent in look-up operation.• The aggregation is accomplished by:

– the LSR creating a TE LSP– the LSR forming a forwarding adjacency out of that LSP

(advertising this LSP as a TE link into IS-IS/OSPF)

Forwarding Adjacency

ATMSwitch

ATMSwitch

SONET/SDHADM

Ingress Node(High Order LSP)

Egress Node(High Order LSP)

FA-LSPSONET/SDHADM

Hierarchical LSP

• End-to-end flow may pass over the networks with devices that are not designed to configure connections with flexible bandwidth level.

• It is better to aggregate low-speed flows into higher-speed ones. This brings the notion of hierarchical LSP.

• LSP interface hierarchy– Fiber Switch Capable (FSC) Highest– Lambda Switch Capable (LSC)– TDM Capable– Packet Switch Capable (PSC) Lowest

• This way, an LSP that starts and ends on a PSC interface can be nested (together with other LSPs) into an LSP that starts and ends on a TDM interface. In turn, this LSP can be nested (together with other LSPs) into an LSP that starts and ends on a LSC interface, which in turn can be nested (together with other LSPs) into an LSP that starts and ends on a FSC interface.

Hierarchical LSP – cont.

Hierarchical LSP – cont.

FA-LSC

FA-TDMFA-PSC

BundleFiber n

Fiber 1

FSC CloudLSCCloud

TDMCloud

PSCCloud

LSCCloud

TDMCloud

PSCCloud

ExplicitLabel LSPs

Time-slotLSPs Fiber LSPs LSPs

ExplicitLabel LSPs

Time-slotLSPs

(Multiplex Low-order LSPs) (Demultiplex Low-order LSPs)

LSPs

• Nesting LSPs enhances system scalability

• Optimal usage of network resources.

Link bundling

• Two adjacent LSRs in an optical network may be connected by several hundreds of parallel wavelengths.

• Advertising every wavelength separately (during OSPF, IS-IS) may create too large link database at the nodes.

• When a pair of LSR is connected by multiple links, it is possible to advertise several (or all) of these links as a single link into OSPF and/or IS-IS. This process is called link bundling.

• Restrictions for bundling the links that comprise the same bundled link are as follows:– All links must begin and end at the same pair of LSR– All links must have the same switching capability – All links must have the same traffic metric

• Bundling reduces link-state databases, but results in loss of granularity in network resources.

Bundled Link 1

Bundled Link 2

Link bundling

Agenda





Reliability

• GMPLS provides protection against failed channels between two adjacent nodes (span protection) and end-to-end protection (path protection).

• One possibility is to keep secondary back-up path

– For end-to-end path protection there is a mechanism for establishing back-up LSPs that do not have any links in common with the primary LSP (OSPF/IS-IS extension).

• Another option is restoration of a failed path, which means dynamic establishment of a back-up path.

– Line restoration: finds an alternate route at an intermediate node

– Path restoration: initiated at the source node to route around a failed path

• Restoration schemes take longer to switch to a back-up path, but they are more efficient in bandwidth usage, as they do not pre-allocate any resources.

Reliability – example

GMPLS Summary

• GMPLS provides a common control plane for multiple layers and multi-vendors

• Greater service intelligence and efficiency

• Scalable

• The efficacy of GMPLS may take years to prove

Examination

• Which of the following network types does the control plane specified for GMPLS support?

1. Packet

2. TDM/SONET

3. Optical

4. All of the above

Examination

• The control plane can be physically separate from the data plane in GMPLS network

1. True

2. False

• Forwarding adjacency allows an LSP to be reported and treated as any other link in an OSPF-TE link database

1. True

2. False

Examination

• Which GMPLS concept helps with addressing the latency in the switch fabric configuration of optical networks?

1. Hierarchical LSPs2. Link bundling3. Suggested label4. All of the above

• Which GMPLS concept helps to overcome the problem of connections with discrete bandwidth levels available?

1. Hierarchical LSPs2. Link bundling3. Suggested label4. All of the above

presented by: dmitri perelman nadav chachmon. agenda overview mpls evolution to gmpls switching...

Documents

label ip

issues gmpls label

label distribution

generalized label

path lsp label

type of label

gmpls label need

label control plane