Internet Enhancements - Coexistence with ATM
by Magda Chatzaki and Stelios Sartzetakis
The IthACI project - Internet and the ATM: Experiments & Enhancements
for Convergence and Integration - aims at contributing to the
Multi-Protocol Layer Switching (MPLS) standardization efforts
by developing and demonstrating enhanced features in the areas
of multicast, QoS and resource management in IPSOFACTO and Tag-Switching,
and mobility in a multicast environment. The project is setting
up a testbed consisting of three distinct technology islands based
on ATM switching technologies of different vendors, which incorporate
different approaches for short-cutting IP traffic. NEC’s ‘IPSOFACTO’,
CISCO’s ‘Tag Switching’ and ALCATEL’s ‘Yalsa technologies’ are
in operation in the test networks in three different countries
in Europe, the enhanced features are under development on these
technology islands, and their interconnection is planned over
a Pan-European ATM wide area network.
Internet technology dominates communications today, with its TCP/IP
protocols suite mostly appreciated because of its simplicity and
flexibility. Traditional Internet supports only best effort service.
However it transforms quickly into a commercial environment demanding
support for Quality of Service (QoS). In order to provide means
to guarantee QoS in the Internet environment we might increase
its complexity by adding protocols for resource management, like
RSVP (Resource reSerVation Protocol), so loosing some of its original
simplicity. Coming from the Telecom Operators world, ATM has been
designed to support different QoS requirements providing simple
and clean solutions. IP switching seems to be a promising new
approach to combine the speed of ATM switching with the simplicity
and flexibility of IP internetworks. The basic idea of IP switching
is to use IP network control on top of an ATM switch. MPLS (MultiProtocol
Layer Switching) is the standard solution for IP switching proposed
by the Internet Engineering Task Force (IETF). The MPLS standard
is currently evolving to cover the areas of Quality of Service
and Resource Management, Multicast support and Mobility for IP
switching technologies.
QoS and Resource Management Enhancements in Tag Switching aim
at providing QoS and Resource Management functionality to the
Tag Switching technology and consequently to MPLS. The enhancements
to Tag Switching towards QoS and Resource Management are based
on the idea of establishing an overall QoS provisioning framework
from the viewpoint of a Service Provider. The QoS provisioning
framework should provide differentiation between the services
in terms of their transfer characteristics and above all differentiation
among customers in terms of the services they may request. The
framework is compatible with both IntServ and DiffServ approaches
for QoS provisioning emerging in the Internet. It entails two
aspects:
- definition of a set of discrete Service Classes (SCs) for requesting
QoS-based services
- definition of a suitable architecture and protocols required for
supporting the provisioning of the defined QoS-based services
in the network.
The basic idea underlying this QoS framework is to create and
dynamically manage a virtual topology induced to the physical
one for allowing segregation of network resources (ie bandwidth)
to the different SCs, cost-effectively and according to business
policies. We name this virtual topology soft-network. The soft-network
is used to configure and reserve the available network resources
according to the characteristics of the supported SCs. Our architecture
includes a mechanism that supports multiservice, multipath routing
in Tag Switching (MPLS) capable networks. It supports initial
allocation and dynamic reallocation of network resources whenever
necessary for multiple SCs. We consider a network that supports
a number of SCs with different QoS guarantees. In our approach,
network resources are initially allocated to the different SCs
according to the administrative policies of the network operator.
This means that appropriate virtual networks are created to accommodate
the traffic demands of the SCs according to their QoS characteristics.
ICS-FORTH is mainly involved in this task and together with Algosystems
S.A. develops the architecture shown in the figure in order to
support the QoS and Resource Management enhancements for Tag Switching.
QoS and Resource Management Enhancements in IPSOFACTO include
several tasks. The existing flow detection mechanisms in the IPSOFACTO
architecture are being enhanced further with an real time protocol
(RTP) flow detection mechanism. It should be noted here that RTP
applications are very important, as they are actually real-time
and therefore require a better service than traditional data applications.
Further flow differentiation among the RTP flows is done using
some clever assignment of flows with specific RTP profiles that
will be mapped to the appropriate ATM switch service classes treatment.
The Resource Management enhancements first task is the development
of a common prototype for the co-existence of a topology-driven
unicast-oriented IP switching technique (MPLS) and a flow-driven
IP switching technique (NECs IPSOFACTO). Interoperability and
resource management issues involved with their co-existence will
be studied. The second task is the design and implementation of
a Flow Management Information Base (Flow MIB) to be used with
NECs IPSOFACTO. The Flow MIB provides information on past and
present flows.
For the Multicast Service enhancements we apply MPLS-style shortcut
techniques to IP multicast in order to optimize the network without
modifying the end-user environment and the existing IP multicast
protocols. The shortcut point-to-multipoint ATM connections will
follow dynamically the tree topology changes that are the result
of IP hosts joining or leaving the group. Among various Multicast
Routing Protocols being implemented and standardised IthACI selected
the PIM-SM (Protocol Independent Multicast - Sparse Mode) because
of the scalability limitations of the others. PIM-SM is deployed
as the Multicast Routing Protocol in all three IthACI islands.
However, each island uses its own method to do the mapping of
multicast streams onto layer 2 connections. Besides correct interworking
of IP multicast and IP switching in the separate islands, the
goal is to demonstrate the interoperability between Alcatels,
NECs and Ciscos multicast solutions, either on layer 2 or layer
3.
The enhancements for mobility in a multicast environment follow
the approaches supported by the IETF standards. The realisations
in IthACI will conform to appropriate ‘Requests for Comments’
as long as they are available. Some ongoing work in IETF will
also be considered and related Internet drafts are examined and
applied accordingly. Two major schemes are possible to make the
multicast service available to a mobile node. While away from
home, a Mobile Node may be allowed to exercise its role either
as if it were a logical entity in the home network or a logical
entity in its current foreign network. In the first scheme, the
Home Agent acts as the logical point of service. In the second
scheme, the Mobile Node has to use a temporary co-located care-of-address
to fulfil its role in the multicast scenarios.
The demand for higher throughput IP networks is huge. IthACI focuses
on applying IP switching technologies to better satisfy this demand.
Most of the major switch/router manufacturers have already announced
MPLS support in their products, and will deliver by years end.
IthACI also examines MPLS extensions and applicability to IP over
DWDM (Dense Wave Division Multiplexing) layered networks.
IthACI project partly funded by ACTS started March 1998. The other
consortium members are AlgoSystems S.A., University of Surrey,
ABT, GMD-Fokus, CISCO Systems S.A., NEC Europe Ltd. and IMEC.
Further information can be found at: http://www.algo.com.gr/acts/ithaci/
Please contact:
Stelios Sartzetakis - ICS-FORTH
Tel: +30 81 39 1727
E-mail: stelios@ics.forth.gr
Magda Chatzaki - ICS-FORTH
Tel: +30 81 39 1723
E-mail: magda@ics.forth.gr
