NEXT GENERATION NETWORK (NGN)

AVAILABILITY & RESILIENCE RESEARCH

Progress Report No. 1

The University of Canterbury Team 28 November 2005

Progress Report

Canterbury Team has been working on the NGN resiliency research project and would

like to present our primary achievements and proposed solutions according to the

promised outputs in the proposal.

Output1 Watching Brief

See Appendix 1, which list the selected papers and reports related to NGN resiliency

research with Canterbury team’s brief comments. We strongly suggest that those

papers can be modified and applied to NGN project, even for the future NGN

projects.

Output 2 Simulator Review

We propose to develop a NGN simulator by using a network simulation tool with a

possibility of gradual adding NGN elements and functionality. The purpose of the

simulator is to make possible an analysis of requirements for modelling and

evaluating resiliency schemes and service availability in NGN.

The problem complexity requires a higher level abstraction approach without the

actual implementation of detailed elements and protocols. Only simplified protocols

are used in the simulation network, and only the functionalities needed for simulating

the NGN resiliency are implemented. We proposed that a simplified network model

should include a PSTN emulator, a SIP emulator, a Softswitch and the appropriate

Gateways (e.g., Media Gateway, Signaling Gateway) between the PSTN network and

IP backbone network; MPLS enabled core network with RSVP-TE signaling protocol;

VoIP Protocols Stacks such as SIP, SIGTRAN, H323, H.248/MEGACO, MGCP,

NCS, RTP/RTCP will to be added gradually to the NGN simulation.

We are doing and will continue our simulation work in the following steps,

Step 1 Simulator Selection

For the proper NGN simulator, we are doing a survey on the most popular simulators

(e.g., Opnet, NS2, OMNet++, Jsim, Qualnet ) at this moment, our purpose is to

identify their strengths, weakness and also explore their programming potentials to

further develop resiliency modelling and VoIP in NGN scenarios.

So far, Canterbury team are doing a simple simulation, which is dedicated to scenarios

with failure/recovery conditions. The analysis is performed in terms of MPLS means

in Opnet. It is worth to observe behaviors of the traffic in failure conditions with

different scenarios i.e. with and without protective features applies. In addition, we

already found that the performance of recovery mechanism is connected with

topology (e.g., length of shortest and 2nd shortest paths, number of disjoint paths etc.)

as well as MPLS configuration (signaling timers, static and dynamic LSPs, location of

switching point reacted to the failure path, node and link).

Here we show a glimpse of Opnet functionality and abilities, which are suited to NGN

resiliency project.

1. Genetic topology with MPLS enabled IP routers setup

The basic scenario involves configuration of simple core network with attached end

nodes, the core nodes is enabled with MPLS, i.e., the IP routers support MPLS

functionality. To indicate MPLS core, the routers are marked with icons relevant for

LERs (node_0, node_1) and LSRs (node_2, node_3, node_4) as Figure 1.

Figure 1 MPLS setup with dynamic LSPs configured

2. MPLS parameters

Several general MPLS parameters need to be configured within MPLS configuration

object. Fundamentally, they involve definitions of FECs and traffic trunk profiles in Figure

2.

Figure 2 MPLS configuration object attributes

3. Action upon failure conditions

Network failure situations cause special conditions for the network to cope with.

The failure and recovery side effects become very dangerous for traffic streams

when there is no other mechanism than simple routing to handle them. Therefore,

MPLS feature of resiliency engineering is exposed here, as it provides great

advantage and promise for proper traffic handling upon failure.

In order to investigate network performance in failure conditions, the

Failure/Recovery config object in Opnet is used to introduce link breakdown. In

order to show effects of failure, voice application performance will be analyzed. We

proposed that there will be two scenarios compared i.e. with OSPF routing, another

with voice traffic pushed to flow explicit way and with MPLS recovery by backup

paths employment.

For example , Link node_1 node_2 fails at 480 s of simulation time. (The

configuration is shown in Figure 3

Figure 3. Failure/Recovery configuration for simple MPLS model scenario

The failing link is contained within the one of the shortest path chosen by

OSPF. However it is not predictable which flows go through each of the two shortest

paths. Thus it is relevant to make MPLS forward traffic of interest on the same

path initially. This practice provides the same initial conditions. When failure occurs

OSPF uses routing to redirect traffic. The second scenario uses established LSP to

forward voice and when the link on the path fails, the LSP uses backup LSP

configured to take over the traffic.

Within the MPLS core there are two static LSPs setup – one is to ensure that the

traffic is directed through the failing shortest path links (node_0 node_2 node_1).

Setup is shown in Figure 4.

a) b)

Figure 4 Failure recovery scenario setup:

a) LSPs direct traffic through the failing shortest path links,

b) MPLS recovery setup acting upon failures by means of backup LSPs,

Additionally, Opnet also provide function on. Fast Reroute Status within its Recovery

Parameters (Figure 5, 6).

Figure 5 Router with MPLS interface configuration for local bypass LSP

Figure 6. Primary LSP configuration for fast reroute protection

The main results related to resiliency need to be measured is the recovery time in

failure condition, it can be divided two factors, i.e., LSP recovery time and LSP

Traffic reroute time.

• LSP recovery time (sec) - the time taken to recover the LSP through a

new route. It expresses the difference between time when LSP failed and the

time when the ingress node was able to reroute the LSP through a different

route. This scenario takes place in cases where there is no alternative local

tunnel to take over the traffic and the conditions allow the LSP to recover.

• Traffic reroute time (sec) - the time taken to switch traffic away from

failed LSP. It is the difference between time when LSP failed and time when the

ingress node or the Point of Local Recovery (PLR), switches the traffic away

from failed LSP. This scenario occurs when there is ingress backup or local

tunnel LSPs established or when the main LSP cannot be recovered.

So far, we found that resiliency is a crucial issue providing reliability in failure

conditions and MPLS provides means for protecting not only single nodes or links but

also full paths. All these scenarios can be implemented in OPNET modeller.

Step 2: Topology Investigation

After step1, we will use the selected simulator to perform specific work on Telecom

NGN case. In this step, based on the given Telecom topology (e.g., 9 tier one nodes,

29 tier two nodes, existing and possible new links), different topologies will be

generated and studied and their outcomes will be analyzed and evaluated according to

the following suggested measure metrics:

• Average node degree, it is a well-known and common factor used when

evaluating topologies, which characterizes how densely a topology is

connected and also provides information regarding equipment complexity and

cost.

• Number of shortest paths, which is used for MPLS routing computation

• Number of 2nd shortest paths, which plays a key role for protection

mechanisms and recovery/failure conditions in MPLS.

• Length of 2nd shortest path, which influences the capabilities for MPLS

traffic engineering and alternative route selection.

• Number of node- and link-disjoint paths, which can provide estimates for

protection mechanism planning.

Based on the above metrics, we will compare different possible topologies and

develop a new solution approach to find the optimal topology for the Telecom NGN,

considering different node and link failure scenarios (single and multiple failures).

Step 3: Traffic Configuration and Behavior Study

Service availability behavior analysis needs examination of current and future traffic

patterns. The base scenario involves two traffic patterns that exhibit different behavior

such as VoIP and HTTP (or an application suggested by Telecom/Alcatel). The

additional background traffic of best effort type can be added in further scenarios. The

simulation will be carried out with realistic traffic matrix and distribution gathered

through existing network measurements, if available.

In addition, the traffic start delay provides time for convergence of routing and

forwarding tables at routers. It should be noted that the convergence time depends on

the routing algorithm and traffic distribution. Therefore we will study VoIP end-to-end

delay, packet loss and jitter behaviors for varying different traffic distributions and

routing algorithms such as OSPF.

Step 4: MPLS-TE Recovery Mechanisms and Signaling Protocols

We will use OPNET to set up MPLS elements (LER, LSR, LSP), parameters (FECs)

and related attributes like traffic engineering in the core network based on Telecom

case. MPLS-TE is armed with traffic engineering and multiple protection and

restoration schemes such as protection switching at ingress, local rerouting and

dynamic LSP recovery, which provide reliability in failure conditions and its repair

coverage may comprise nodes and links as well as full paths.

The performance of the recovery mechanism is related to topology-related factors

such as the length of shortest and 2nd shortest paths, number of disjoint paths etc. The

main objective is to model and investigate MPLS fast restoration potential and

performance from the following two perspectives:

• MPLS recovery mechanisms, which are crucial internal components of VoIP

service availability practices. Service resilience will take into account the

existing routing protocols such as OSPF/ IS-IS. Furthermore we will study

their extension to enhance routing performance in the MPLS enabled network.

• MPLS signaling protocol. A simplified version of Constrained-based Routing

over Label Distribution Protocol (CR-LDP) and the RSVP protocol could be

researched in failure/recovery conditions with different factors accounted for

such as topology and traffic distribution.

With the above considerations in mind, service availability can be evaluated in term

of recovery time, which is the time taken to recover the LSP through a new route. The

expected simulation outcome would be a sensitivity analysis of recovery time and its

relation to factors such as topology and traffic distribution in the following scenarios:

• LSP with no protection, where LSPs do not have any pre-defined backups

and traffic needs to be rerouted by standard routing protocols e.g., OSPF. The

recovery time would include signaling delay, reroute convergence delay etc.

• LSP with recovery feature, where there are pre-defined back-up explicitly-

routed LSPs, best suited to the traffic pattern. The recovery time here indicates

how much time should pass before the signaling protocol attempts to establish

a new LSP and switch the traffic.

Additionally, if time permits, some work will be devoted to GMPLS, which has been

developed by the IETF to extend the classical IP MPLS standard to address the

provisioning of paths at the fiber, wavelength, and SONET/SDH levels of the core

network. LSPs at each level of this hierarchy can therefore potentially benefit from

path protection approaches. It is suggested that GMPLS will be the future in NGN.

Therefore, we will explore MPLS/GMPLS with its label stacking capability to

implement an integrated two-layer restoration scheme. In addition, MPLS signaling

protocols need to be applied across the IP layer and the optical layer in a coordinated

manner.

Output 3 is cancelled and Outcome 4 and 5 will be partly considered

in other parts

Output 6 Service Availability Model Definition

Some papers already give us some good ideas of how to define and calculate network

and service availability in PSTN and IP network. We strongly suggest that the

recovery time regarding to different failure scenarios will be the most critical part in

the service availability modelling. In the paper and our further simulation work, we

will predict and measure the recovery time and try to find the efficient methods to

decrease recovery time, in other words, to improve the service resiliency in NGN. In

addition, we want to highlight that the recovery time also can be somehow translated

to packet loss, delay and jitter, which are also need to be considered in service

availability definition.

Output 7, 8 Network Component Selection and Prototype

Development

So far, we are still wondering what is the ‘network component selection’ means from

the Telecom and Alcatel point of view. Are they the new elements will be involved in

the future NGN network?

Also we suggest that output7 and 8 will be strongly combined and performed parallel

with output 2.

In addition, some new ideas are also can be applied to this project, for example, using

escalation strategies to propose multilayer resilience schemes in NZ NGN, which

includes

• DWDW layer -- protection schemes

• IP/MPLS layer -- restoration schemes

• Application and Middleware layers - Grid resilience schemes- checkpointing,

service migration and replication

• Treat all these schemes with a system point of view, and explore how to

coordinate them, i.e., which layer solutions are used for which type of failures

and how to trigger them

• Resiliency management and signaling model- 'GMPLS concept' - peer to peer

and overlay model

References

[1] Marek Małowidzki " Network Simulators : A Developer’s Perspective. Website

searching"

[2] G. Flores-Lucio, M. Paredes-Farrera, E. Jammeh, M. Fleury, and M. Reed,

"OPNET-Modeler and NS-2: Comparing the Accuracy of Network Simulators for

Packet-Level Analysis using a Network Testbed" 3rd WEAS Int. Conf. on Simulation,

Modelling and Optimization (ICOSMO 2003), Crete, vol. 2, pp. 700-707, 2003.

NOTE: An addendum to this paper is also available, clarifying some points made in

the paper with regards to OPNET Modeler.

[3] S. Wu, M. Riyadh, and M. Mannan, “OPNET Implementation of Megaco/H.248”

Doverspike, R. and J. Yates (2001). "Challenges for MPLS in optical network

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[5] Christophe Diot and Gianluca Iannaccone and Athina Markopoulou and Chen-

Nee Chuah and Supratik Bhattacharyya (2003). "Service Availability in IP Networks.

".Sprint ATL Research Report Nr. RR03-ATL-071888. Sprint ATL. July 2003.

[6] Kellerer, B. and Neises, J. (2002) "Modelling of Service Availability" Euromicro

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[7] Ruoshan Kone; Huaibei Zhou; "End-to-end availability analysis of physical

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International Conference on 14-16 Sept. 2004 Page(s):668 – 673

[8] Alcatel 5020 Softswitch Open Call Control Engine for your Next Generation Service Offering. Alcatel website [9] Alcatel 7510 MG Media Gateway, Release 2.1. Alcatel website

[10] Paul Drew, MetaSwitch; Chris Gallon, Next-Generation VoIP Network

Architecture, Fujitsu Date: March 2003

[11] Chris Gallon, Quality of Service for Next Generation Voice Over IP Networks ,

Fujitsu Date: February 2003

[12] Georgios Ellinas, et al. (2002) "Restoration in Layered Architectures with a

WDM Mesh Optical Layer"

[13] P. Demeester, et al. "Resilience in a Multi-Layer Network "

[14] Oki, E., N. Matsuura, et al. (2002). "A disjoint path selection scheme with shared

risk link groups in GMPLS networks." Communications Letters, IEEE 6(9): 406-408

[15] Schollmeier, G. and C. Winkler (2004). "Providing sustainable QoS in next-

generation networks." Communications Magazine, IEEE 42(6): 102-107

[16] Elwalid, A., D. Mitra, et al. (2003). "Routing and protection in GMPLS

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