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Appendix A. Example Deployment Scenarios

This section does not provide additional specification and is only here to provide examples of how this flexible approach for Diff-Serv support over MPLS may be deployed. Pros and cons of various deployment options for particular environments are beyond the scope of this document.

A.1. Scenario 1: 8 (or fewer) BAs, no Traffic Engineering, no MPLS Protection​

A Service Provider running 8 (or fewer) BAs over MPLS, not performing Traffic engineering, not using MPLS protection and using MPLS Shim Header encapsulation in his/her network, may elect to run Diff-Serv over MPLS using a single E-LSP per FEC established via LDP. Furthermore the Service Provider may elect to use the preconfigured `EXP<-->PHB mapping'.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR, the bi-directional mapping between each PHB and a value of the EXP field (e.g., 000<-->AF11, 001<-->AF12, 010<-->AF13)

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC (e.g., bandwidth allocated to AF1) and the dropping behavior for each PHB (e.g., drop profile for AF11, AF12, AF13)

  • LSRs signal establishment of a single E-LSP per FEC using LDP in accordance with the specification above (i.e., no Diff-Serv TLV in LDP Label Request/Label Mapping messages to implicitly indicate that the LSP is an E-LSP and that it uses the preconfigured mapping)

A.2. Scenario 2: More than 8 BAs, no Traffic Engineering, no MPLS Protection​

A Service Provider running more than 8 BAs over MPLS, not performing Traffic Engineering, not using MPLS protection and using MPLS Shim encapsulation in his/her network may elect to run Diff-Serv over MPLS using for each FEC:

  • one E-LSP established via LDP and using the preconfigured mapping to support a set of 8 (or less) BAs, AND

  • one L-LSP per <FEC,OA> established via LDP for support of the other BAs.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR the bi-directional mapping between each PHB and a value of the EXP field for the BAs transported over the E-LSP

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC supported over the E-LSP and the dropping behavior for each corresponding PHB

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC supported over the L-LSPs and the dropping behavior for each corresponding PHB

  • LSRs signal establishment of a single E-LSP per FEC for the set of E-LSP transported BAs using LDP as specified above (i.e., no Diff-Serv TLV in LDP Label Request/Label Mapping messages to implicitly indicate that the LSP is an E-LSP and that it uses the preconfigured mapping)

  • LSRs signal establishment of one L-LSP per <FEC,OA> for the other BAs using LDP as specified above (i.e., Diff-Serv TLV in LDP Label Request/Label Mapping messages to indicate the L-LSP's PSC).

A.3. Scenario 3: 8 (or fewer) BAs, Aggregate Traffic Engineering, Aggregate MPLS Protection​

A Service Provider running 8 (or fewer) BAs over MPLS, performing aggregate Traffic Engineering (i.e., performing a single common path selection for all BAs), using aggregate MPLS protection (i.e., restoring service to all PSCs jointly) and using MPLS Shim Header encapsulation in his/her network, may elect to run Diff-Serv over MPLS using a single E-LSP per FEC established via RSVP [RSVP_MPLS_TE] or CR-LDP [CR-LDP_MPLS_TE] and using the preconfigured mapping.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR the bi-directional mapping between each PHB and a value of the EXP field (e.g., 000<-->AF11, 001<-->AF12, 010<-->AF13)

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC (e.g., bandwidth allocated to AF1) and the dropping behavior for each PHB (eg drop profile for AF11, AF12, AF13)

  • LSRs signal establishment of a single E-LSP per FEC which will use the preconfigured mapping:

    • using the RSVP protocol as specified above (i.e., no DIFFSERV RSVP Object in the PATH message containing the LABEL_REQUEST Object), OR

    • using the CR-LDP protocol as specified above (i.e., no Diff-Serv TLV in LDP Label Request/Label Mapping messages).

  • protection is activated on all the E-LSPs in order to achieve MPLS protection via mechanisms outside the scope of this document.

A.4. Scenario 4: per-OA Traffic Engineering/MPLS Protection​

A Service Provider running any number of BAs over MPLS, performing per-OA Traffic Engineering (i.e., performing a separate path selection for each OA) and performing per-OA MPLS protection (i.e., performing protection with potentially different levels of protection for the different OAs) in his/her network, may elect to run Diff-Serv over MPLS using one L-LSP per <FEC,OA> pair established via RSVP or CR-LDP.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC (e.g., bandwidth allocated to AF1) and the dropping behavior for each PHB (e.g., drop profile for AF11, AF12, AF13)

  • LSRs signal establishment of one L-LSP per <FEC,OA>:

    • using the RSVP as specified above to signal the L-LSP's PSC (i.e., DIFFSERV RSVP Object in the PATH message containing the LABEL_REQUEST), OR

    • using the CR-LDP protocol as specified above to signal the L-LSP PSC (i.e., Diff-Serv TLV in LDP Label Request/Label Mapping messages).

  • the appropriate level of protection is activated on the different L-LSPs (potentially with a different level of protection for each PSC) via mechanisms outside the scope of this document.

A.5. Scenario 5: 8 (or fewer) BAs, per-OA Traffic Engineering/MPLS Protection​

A Service Provider running 8 (or fewer) BAs over MPLS, performing per-OA Traffic Engineering (i.e., performing a separate path selection for each OA) and performing per-OA MPLS protection (i.e., performing protection with potentially different levels of protection for the different OAs) in his/her network, may elect to run Diff-Serv over MPLS using one E-LSP per <FEC,OA> pair established via RSVP or CR-LDP. Furthermore, the Service Provider may elect to use the preconfigured mapping on all the E-LSPs.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR the bi-directional mapping between each PHB and a value of the EXP field (e.g., 000<-->AF11, 001<-->AF12, 010<-->AF13)

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC (e.g., bandwidth allocated to AF1) and the dropping behavior for each PHB (eg drop profile for AF11, AF12, AF13)

  • LSRs signal establishment of one E-LSP per <FEC,OA>:

    • using the RSVP protocol as specified above to signal that the LSP is an E-LSP which uses the preconfigured mapping (i.e., no DIFFSERV RSVP Object in the PATH message containing the LABEL_REQUEST), OR

    • using the CR-LDP protocol as specified above to signal that the LSP is an E-LSP which uses the preconfigured mapping (i.e., no Diff-Serv TLV in LDP Label Request/Label Mapping messages)

  • the Service Provider configures, for each E-LSP, at the head-end of that E-LSP, a filtering/forwarding criteria so that only the packets belonging to a given OA are forwarded on the E-LSP established for the corresponding FEC and corresponding OA.

  • the appropriate level of protection is activated on the different E-LSPs (potentially with a different level of protection depending on the PSC actually transported over each E-LSP) via mechanisms outside the scope of this document.

A.6. Scenario 6: no Traffic Engineering/MPLS Protection on 8 BAs, per-OA Traffic Engineering/MPLS Protection on other BAs.​

A Service Provider not performing Traffic Engineering/MPLS Protection on 8 (or fewer) BAs, performing per-OA Traffic Engineering/MPLS Protection on the other BAs (i.e., performing a separate path selection for each OA corresponding to the other BAs and performing MPLS Protection with a potentially different policy for each of these OA) and using the MPLS Shim encapsulation in his/her network may elect to run Diff-Serv over MPLS, using for each FEC:

  • one E-LSP using the preconfigured mapping established via LDP to support the set of 8 (or fewer) non-traffic-engineered/non-protected BAs, AND

  • one L-LSP per <FEC,OA> pair established via RSVP or CR-LDP for support of the other BAs.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR the bi-directional mapping between each PHB and a value of the EXP field for the BAs supported over the E-LSP

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC supported over the E-LSP and the dropping behavior for each corresponding PHB

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC supported over the L-LSPs and the dropping behavior for each corresponding PHB

  • LSRs signal establishment of a single E-LSP per FEC for the non-traffic engineered BAs using LDP as specified above (i.e., no Diff-Serv TLV in LDP Label Request/Label Mapping messages)

  • LSRs signal establishment of one L-LSP per <FEC,OA> for the other BAs:

    • using the RSVP protocol as specified above to signal the L-LSP PSC (i.e., DIFFSERV RSVP Object in the PATH message containing the LABEL_REQUEST Object), OR

    • using the CR-LDP protocol as specified above to signal the L-LSP PSC (i.e., Diff-Serv TLV in LDP Label Request/Label Mapping messages).

  • protection is not activated on the E-LSPs.

  • the appropriate level of protection is activated on the different L-LSPs (potentially with a different level of protection depending on the L-LSP's PSC) via mechanisms outside the scope of this document.

A.7. Scenario 7: More than 8 BAs, no Traffic Engineering, no MPLS Protection​

A Service Provider running more than 8 BAs over MPLS, not performing Traffic engineering, not performing MPLS protection and using MPLS Shim Header encapsulation in his/her network, may elect to run Diff-Serv over MPLS using two E-LSPs per FEC established via LDP and using signaled `EXP<-->PHB mapping'.

Operations can be summarized as follows:

  • the Service Provider configures at every LSR, and for every interface, the scheduling behavior for each PSC (e.g., bandwidth allocated to AF1) and the dropping behavior for each PHB (e.g., drop profile for AF11, AF12, AF13)

  • LSRs signal establishment of two E-LSPs per FEC using LDP in accordance with the specification above (i.e., Diff-Serv TLV in LDP Label Request/Label Mapping messages to explicitly indicate that the LSP is an E-LSP and its `EXP<-->PHB mapping'). The signaled mapping will indicate the subset of 8 (or less) BAs to be transported on each E-LSP and what EXP values are mapped to each BA on each E-LSP.