PWE3 Protocol Layering PWE3 IETF-52 December 12, 2001 Stewart Bryant <stbryant@cisco.com> Lloyd Wood <lwood@cisco.com> 1
Layering issues • Current PWE3 approach is piecemeal with each payload design team proposing a point solution. • Example: Ethernet and Frame-relay, but not Packet (which could carry both and others besides) • Example: TDM services defining specific real-time support, requiring new packet services to define real- time (ie DVB TS) • Example: No definition of requirements for network layer carrying PWE3, leading to clash between IP and MPLS focused participants. 2 Bryant PWE3 Protocol layering
Present PWE3 layering approach Frame-relay Ethernet HDLC? ????? Sonet TDM ATM GRE/L2TPv3 Inner label IPv6 IPv4 MPLS MAC/Data-Link Physical 3 Bryant PWE3 Protocol layering
Protocol Layering Model +---------------------------+ | Payload | These should be defined +---------------------------+ only once with a minimum | Payload convergence layer | difference between payloads +---------------------------+ | Pseudo-wire common layer | +---------------------------+ | PSN convergence layer | This is an area of concern +---------------------------+ PWE3 area of interest | PSN header | +---------------------------+ | MAC/Data-link | These are givens +---------------------------+ | Physical | +---------------------------+ 4 Bryant PWE3 Protocol layering
PSN Header There is agreement that these are the lower layers PSN header IPv6 IPv4 MPLS MAC/Data-Link Physical 5 Bryant PWE3 Protocol layering
Payload Payload Payload (circuit/cell/packet) Use of generic payload types reduces number and scope of definitions and give guidance on how to support new types. Carrying payloads unchanged IPv6 IPv4 transparently is simpler MPLS and leads to greater flexibility. MAC/Data-Link Physical 6 Bryant PWE3 Protocol layering
Payload Framework Payload Payload (circuit/cell/packet) Bit-type Packet-type Cell-type Payload convergence specific specific specific Needed to carry “replay context” info. Area of maximum type difference. IPv6 IPv4 Goal is minimum MPLS number of sub-types. MAC/Data-Link Physical 7 Bryant PWE3 Protocol layering
Payload common support Payload Payload (circuit/cell/packet) Bit type Cell type Packet type Payload convergence specific specific specific PW common Optional timing /sequencing Needed for all generic payload types. IPv6 Requirements may IPv4 evolve with time as MPLS new payload and MAC/Data-Link PSN characteristics change. Physical 8 Bryant PWE3 Protocol layering
A proposed protocol layering Focus of PWE3 - above common multiplexing layer Payload Payload (circuit/cell/packet) Bit type Packet type Cell type Payload convergence specific specific specific Optional timing/sequencing (i.e. RTP) PW common Multiplexing (ie L2TPv3) Fragmentation PSN convergence Length IPv6 IPv4 & PSN header MPLS MAC/Data-Link Physical 9 Bryant PWE3 Protocol layering
Alternative layering model Focus of PWE3 - above a PSN specific multiplexing layer Payload (circuit/cell/packet) Bit type Packet type Cell type PWE3 Payload specific specific specific encapsulation definition Optional RTP/Sequencing PWE3 IP Fragmentation convergence L2TPv3 definition Length PWE3 MPLS convergence Inner Label IPv6 IPv4 Definition based MPLS on draft-martini MAC/Data-Link Physical 10 10 10 Bryant PWE3 Protocol layering
Recommendations • A layering model be incorporated in the PWE3 framework draft. • We move to generic, rather than individual, payload types. • Payloads sent transparently (as received), making translation for switch support a value-added service. • We define operation of PWE3 over IP and MPLS separately. 11 11 11 Bryant PWE3 Protocol layering
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