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OFC/NFOEC Technical Digest © 2013 OSA
DT’s Standardization Activities to achieve interoperability
on 100G for Metro Applications
Ruediger Kunze, et al.
Deutsche Telekom AG, Group Technology, Winterfeldtstraße 21, 10781 Berlin, GERMANY
1. Introduction
Complexity reduction of the network infrastructure including a common OSS is one of the key issues that incumbent
operators have to deal with today. This trend has been leveraged by the predominance of IP traffic. Traffic growth in
Deutsche Telekom’s networks is mainly driven by IP traffic of private customers and households. The
transformation towards an All-IP operator accelerates this process and leads to the need for a simpler and more
efficient interworking between IP and optical infrastructure by reducing the number of layers and network
equipment as shown in figure 1.
Infrastructure Cloud
(TV, IMS, CDN, OTT, …)
Infrastructure Cloud
(TV, IMS, CDN, OTT, …)
L2 Switch
L2 Agg
Node B
L2 Agg
Fig. 1. TeraStream Architecture of Deutsche Telekom
One important option to achieve this goal of complexity reduction is the so called “Black Link approach”. The Black
Link [1] allows supporting an optical transmitter/receiver pair of one vendor to inject a DWDM channel and run it
over an optical network composed of amplifiers, filters, add-drop multiplexers from a different vendor. As specified
for up to 10G in the current version of ITU-T G.698.2, it enables an optimized interconnection of client nodes and
the optical transport network, enabling Data Plane interoperability, which is a key aspect for carrier network
deployments. DT is pushing the community for an interoperable extension of the standard towards 100G at ITU-T.
For carrier network deployments, interoperability is a key requirement. Today it is state-of-the-art to interconnect IP
Routers from different vendors and WDM transport systems using short-reach, grey interfaces. Applying the Black
Link (BL) concept, routers now get directly connected to each via transport interfaces which must be interoperable
to each other. Additional to that point there must be a management solution that supports this improved interworking
between IP and transport.
This paper illustrates Deutsche Telekom’s main standardization activities at ITU-T and IETF and points out the next
important steps to achieve interoperability on 100G coherent optics and integrated, colored interfaces.
978-1-55752-962-6/13/$31.00 ©2013 Optical Society of America
OFC/NFOEC Technical Digest © 2013 OSA
Standardization Activities
To ensure that a solution becomes carrier-grade, it has to fulfill the following criteria’s:
Interoperability and
DT is pushing the topic at ITU-T for the interoperable data plane definition and at IETF to achieve the required
control & management interoperability, as well as with a complementing industry initiative at the Broadband Forum,
profiling service-provider requirements and solutions.
The extension of G.698.2 for 100G is one of the most important points DT is driving at ITU-T and first steps have
been made there. DT is trying to achieve a new an improved G.698.2 standard that fulfills the requirements focusing
on a metro-reach application for 100G and for distances up to 1000 km. This includes the requirement of a
standardized enhanced FEC for this kind of application. A common FEC will be the greatest achievement in
addition to list of the transmission parameters that are being specified. DT, together with a lot of equipment vendors,
initialized the discussion for 100G at ITU-T SG15Q6. As a first step, the parameter list (for ingress, egress and the
optical network) was agreed, to focus on detailed characteristics to be specified in detail by the community.
Among the parameter settings for 100G the current BL approach must be generalized and leveraged from a friendly
wavelength application towards an integral part of a future transport system. Today ITU-T G.698.2 specifies a
preconfigured and pre-defined single wavelength channel on an optical transport system as a black link. It must be
ensured for example that wavelengths can be used on all optical channels of the transport system. An interworking
with legacy equipment should be supported as well.
Optically transparent network:
Black Link (vendor A)
Terminal #1
(vendor B1)
Optical path
Rx Tx
(incl. e.g. OAs,
Terminal #2
(vendor B2)
Rx Tx
Fig. 2. Network Management scenario for integrated colored interfaces using the G.698.2 standard
An efficient, integrated management solution for IP and transport equipment is the second important issue that DT is
addressing within the standardization community. As first step a MIB [2] to manage the interfaces was introduced at
IETF CCAMP and OPSA. The MIB allows the exchange of parameters towards a management system. This MIB
module can be used as a base for a further information exchange between the node that hosts the colored interface
OFC/NFOEC Technical Digest © 2013 OSA
and the first optical node as shown in Figure 2 supporting all the information needed on both sides. In addition the
module can be used as blueprint for a “Netconf” adoption, if required.
Furthermore a solution for the exchange of link capabilities was introduced at IETF CCAMP. The data model of the
MIB has been used here as well. This approach ensures to have a more coordinated information exchange between
optical network and the router. The LMP Model from RFC4902 [3] is extended to provide link property correlation
between a client and an OLS (Optical Line Systems) device. By using LMP, the capabilities of either end of this link
are exchanged where the term ’link’ refers to the attachment link between OXC and OLS. By performing link
property correlation, both ends of the link can agree on a common parameter window that can be supported and
supervised by each device. The actual selection of a specific parameter value within the parameter window is
outside the scope of LMP. In GMPLS the parameter selection (e.g. wavelength) is performed by RSVP-TE and
Wavelength routing by IGP.
A further result of DTs considerations is that the existing GMPLS overlay model (RFC 4208) is not sufficient to
support a multi layer network architecture composed of IP and DWDM infrastructure. A strict separation of two
different network layers, from the routing point of view, limits a better optimization of both topologies.
This paper reports about the simplification of network infrastructure by reducing the number of interconnected
layers, integration of IP and Optics and the related standardization activities to ensure interoperability and
manageability of optical interfaces specified by G.698.2
The objective of Deutsche Telekom is, while aiming for a better operational efficiency and capex savings, to achieve
the same applicability and performance as in state-of-the-art transport networks, where IP Routers from different
vendors and optical transport systems are connected using short-reach, grey interfaces. An architecture using the
Black Link approach must support a multi-vendor environment, allowing the direct interconnection of WDM
interfaces of different vendors. This feature is significant for network operators in order to ensure interoperability of
equipment manufactured by different vendors in order to guarantee a seamless transport network.
[1] ITU-T G.698.2: “Amplified multichannel dense wavelength division multiplexing applications with single channel optical interfaces”,
November 2009
[2] IETF draft-galikunze-ccamp-g-698-2-snmp-mib-01: “An SNMP MIB extension to RFC3591 to manage optical interface parameters of
DWDM applications”
[3] IETF draft-dharinigert-ccamp-g-698-2-lmp-01: “Extension to the Link Management Protocol (LMP/DWDM -rfc4209) for Dense
Wavelength Division Multiplexing (DWDM) Optical Line Systems to manage black-link optical interface parameters of DWDM application
[4] IETF draft-kunze-g-698-2-management-control-framework-02: “ A framework for Management and Control of G.698.2 optical interface
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