The GMPLS control manager architecture presents the Interface Switching Capability (ISC) concept (RFC4202). A switching type related to a ISC describes the ability of a node to forward data of an specific type of data plane technology and identifies a network region. The ISC types and regions are: PSC (Packet Switching Capable) , L2SC (Layer 2 Switching Capable), TDM (Time Division Multiplexing) capable, LSC (Lambda Switching Capable), and FSC (Fiber switching Capable).
An end of a data link is an interface that connects a data link to a node. In a GMPLS network each end of a data-link is associated with an ISC. An Interface Switching Capability Descriptor (ISCD) attribute advertises the ISC value of TE-link end (RFC4202). The ISCD also contains information on encoding type, bandwidth granularity and unreserved bandwidth of each of the LSP's 8 priorities types. One TE-link advertisement may contain more than one ISCDs, as some TE-links are multi switching capable and are therfore present in more than one layer.
A single-switching-type-capable node advertises the same ISC in their ISCD as the termination capability of each of its interfaces (RFC4202). Multi-switching-type-capable LSRs (Label Switched Routers) can be “Simplex” or “Hybrid”.
A “Simplex” node would have separate interfaces for each switching capability connection. Therefore, it will advertise several TE-links each of which with one ISCD containing a single ISC value (RFC4206).
A “Hybrid” node offers the same interface for the different switching capabilities connections. Therefore it advertises only one TE-link with one ISCD containing several ISC values. In this case the node would interconnect external data-links via internal connections.
Figure 1 shows an example of an hybrid node: it has two switching elements supporting each one a different switching capability as for instance PCS and TDMC in link 1 and link 2 respectively. The two switching elements are internally interconnected so that via communication with interface b its possible to provide adjustments for PSC traffic.
Shiomoto, et al. (2008), "Requirements for GMPLS-Based Multi-Region and Multi-Layer Networks (MRN/MLN)", Technical report, RFC 5212, June 2008.
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