A network comprising a network path computer and at least one asymmetrical network switch adapted to auto-discover and advertise into a traffic engineering, TE, domain an asymmetrical network switch detailed connectivity matrix, SDCM, containing for each allowed switching combination of interfaces of said asymmetrical network switch at least one switch detailed connectivity matrix entry, SDCME, wherein each SDCME represents a potential connection internal to said asymmetrical network switch and interconnecting the interfaces of said interface switching combination, wherein said SDCME advertisement includes a switch detailed connectivity matrix entry cost vector, SDCME CV, which comprises a set of attributes describing cost penalties in terms of various service characteristics that a network service path or tree will incur should it include respective interfaces of said interface switching combination in accordance with the SDCME in question, wherein said asymmetrical network switch detailed connectivity matrix, SDCM, comprising one or more of said switch detailed connectivity matrix entries, SDCMEs, is advertised by said at least one asymmetrical network switch into the traffic engineering, TE, domain and, thus, made available to the network path computer which is adapted to: - calculate optimal network service paths or trees traversing at least one network switch, taking into account the cost vectors, SDCME CVs, advertised by that at least one asymmetrical network switch for one or more switch detailed connectivity matrix entries, SDCMEs; and - signal the calculated optimal network service paths or trees to that at least one asymmetrical network switch such that that at least one asymmetrical network switch is informed which of the potential connections internal to that at least one asymmetrical network switch are to be used. wherein each SDCME represents a potential connection internal to said asymmetrical network switch and interconnecting the interfaces of said interface switching combination, wherein said SDCME advertisement includes a switch detailed connectivity matrix entry cost vector, SDCME CV, which comprises a set of attributes describing cost penalties in terms of various service characteristics that a network service path or tree will incur should it include respective interfaces of said interface switching combination in accordance with the SDCME in question, wherein said asymmetrical network switch detailed connectivity matrix, SDCM, comprising one or more of said switch detailed connectivity matrix entries, SDCMEs, is advertised by said at least one asymmetrical network switch into the traffic engineering, TE, domain and, thus, made available to the network path computer which is adapted to: - calculate optimal network service paths or trees traversing at least one network switch, taking into account the cost vectors, SDCME CVs, advertised by that at least one asymmetrical network switch for one or more switch detailed connectivity matrix entries, SDCMEs; and - signal the calculated optimal network service paths or trees to that at least one asymmetrical network switch such that that at least one asymmetrical network switch is informed which of the potential connections internal to that at least one asymmetrical network switch are to be used. - calculate optimal network service paths or trees traversing at least one network switch, taking into account the cost vectors, SDCME CVs, advertised by that at least one asymmetrical network switch for one or more switch detailed connectivity matrix entries, SDCMEs; and - signal the calculated optimal network service paths or trees to that at least one asymmetrical network switch such that that at least one asymmetrical network switch is informed which of the potential connections internal to that at least one asymmetrical network switch are to be used.