High-Performance Hybrid-Switching Optical
Router for IP over WDM Integration
Wei Wei*, Qingji Zeng, Yong Ouyang, and David Lomone
State Laboratory on Local Fiber-optic Communication
Networks and Advanced Optical Communication Systems, Shanghai Jiaotong University, Shanghai 200030P.R. China
Received January 27, 2004; Revised September 08, 2004; Accepted September 13, 2004
Abstract. Because pure electrical routers with their bandwidth limitations can hardly keep up with the tremendous traﬃc growth in the
Internet, optical routers based on various optical switching techniques including optical wavelength switching (OWS), optical burst
switching (OBS), and optical packet switching (OPS) have been suggested to cope with this problem. However, because OBS and OPS
are both in their early experimental phase and OWS only provides coarse granularity switching, a hybrid-switching optical router with
combined OWS and electrical packet switching is a necessity in order to accommodate the entire multi-granularity traﬃc with multi-
service requirements in a cost-eﬀective manner. Its coordination capability of optical circuit switching and electrical packet switching
enables eﬃcient/intelligent usage of network resources. In this paper, we ﬁrst review research and developments of such IP routers
employing optical switching/interconnection techniques and examine how these techniques can be used inside routers to scale node
capacity and to improve optical Internet performance. We also present and study the performance of a terabit optical router with an
optical-electrical hybrid-switching fabric. The node architecture is based on the idea of IP over WDM integration with Generalized
Multi-Protocol Label Switching (GMPLS). The network-level performance evaluations show that the proposed hybrid-switching
optical router is a cost-eﬀective solution for building the next generation GMPLS-based multi-granularity optical Internet.
Keywords: optical Internet, hybrid-switching, optical router, Generalized Multi-Protocol Label Switching (GMPLS)
The explosive growth of Internet users, the
increased demand for bandwidth, and the declin-
ing cost of technology have all resulted in the
emergence of high-performance, multi-service IP
over WDM network architectures, which has been
proposed as a standard in an optical Internet [1,2].
Convergence solutions including the overlay, peer,
and integrated model have been separately pro-
posed [1,2,3]. Generally, we can categorize
research and developments of the optical Internet
architectures into ﬁve stages shown in Fig. 1.
1st-stage (IP over WDM and IP over OTN),
static model: wavelength paths are statically or
semi-statically conﬁgured between IP routers.
2nd-stage (IP over ASON), overlay model:
wavelength paths are dynamically assigned
among IP routers on demand (usually a
3rd-stage (IP over MGS), peer model/inte-
grated model: wavelength paths (optical label
switched paths -OLSP) combined with elec-
trical label switched paths (ELSP) are dynam-
ically routed/provisioned in an integrated
manner among edge IP routers.
4th-stage (IP over OBS/OFS), integrated
model: this architecture attempts to minimize
the need for processing and buﬀering by
aggregating ﬂows of IP packets into optical
5th-stage (IP over OPS), integrated model:
IP packets can be switched in the optical
domain. The integration of IP and opti-
cal technology will reach maturity and optical
processing/optical buﬀer will become possible
in this stage.
Photonic Network Communications, 9:2, 139–155, 2005
2005 Springer ScienceþBusiness Media, Inc. Manufactured in The Netherlands.