## 1 Introduction  
Generalized multi-protocol label-switching (GMPLS) provides packet-switching with multiple speeds and quality-of-services (QoSs) over optical networks in the time, wavelength, and space domains [1; 2; 3]. The typical quality comes from adopting the packet process operated by an internet protocol. The superiority of GMPLS is due to a unified control plane that includes separate network layers, and transparent data transmissions can be supported in a continuously changing environment. If the edge nodes for a connection of a packet flow are in different networks, GMPLS can merge new and previous networks and automatically set up a link configuration. Such advantages have drawn attention to GMPLS and it has achieved a lot in optical packet-switching (OPS) networks [4; 5; 6].  
However, a packet stops switching in GMPLS if conflicts about the resources of channels or paths happen. When conflicts come into existence, resolution algorithms based on optical buffering take action. Buffering management at the core codes deals with packets that simultaneously compete to obtain the same resource [7; 8; 9; 10; 11; 12]. The goal of packet buffering is to reduce the packet loss to the lowest possible level. As the OPS network will experience less packet-dropping, GMPLS with conflict resolution can support the development of future OPS networks. Optical buffering schemes can be generally boiled down to three categories: fiber delay line [7; 8], wavelength conversion [9; 10], and code-switching [11; 12].  
As the components of optical codecs have reached a mature state, code-switching has been emphasized in all optical buffering designs. The multiplexing technique of optical coding provides users with a shared bandwidth to employ asynchronous packet transmission [13; 14; 15]. Presently, networks are known for their diverse multimedia applications, so enabling multi-service data transmissions has become necessary. Several optical coding schemes have been proposed to achieve differentiated services in access networks. In [16], the parameters of optical code-words, such as length and weight, were changed to offer new data rates. To change the QoS, frequency hopping was combined with multi-wavelength optical codes in a two-dimension coding system [17].  
In this paper, a family of codes known as composite maximal-length sequence (CMLS) codes [18; 19] is introduced into a buffering scheme where packets are queued in the optical domain. Although code-switching can be treated as a promising scheme in optical buffering, it only provides a single-level buffering service in most cases. The contribution of this paper is that we consider the multiple schemes of partitioning a CMLS code set, design the corresponding CMLS codec in the buffer architecture, and model the buffering processes to obtain the performance curves that show various levels of packet-dropping probabilities (PDPs).  
In the proposed scheme, a fixed number of CMLS codes is equally divided into several subsets. The partition scenario with a lower subset number but with a higher number of codes in an individual subset is used as an encoding method to achieve packet buffering for high-QoS users. To examine the buffering performance in detail, the QoS index of the PDP of different classes of users is studied. The PDP is applied to describe a scenario in which a buffer is full, and no more packets are allowed to enter it. In the buffering model that we use to derive the PDP, the packet traffic at the system inputs and outputs behaves as described in [PERSON]'s model [20; 21].