PWE3 Protocol Layering PWE3 IETF-53 March 21, 2002 Stewart Bryant - PowerPoint PPT Presentation

PWE3 Protocol Layering PWE3 IETF-53 March 21, 2002 Stewart Bryant <stbryant@cisco.com> Danny McPherson <danny@tcb.net> Mark Townsley <mark@townsley.net> Lloyd Wood <lwood@cisco.com> 1

Issues • Differing IP and MPLS approaches. • Is a PW a wire or is it a more complex network function? • Native Service Processing • Principle of Minimum Intervention • Details 2 Bryant PWE3 Protocol layering

Protocol Layering +---------------------------+ | Payload | +---------------------------+ Encapsulation Layer | Payload Convergence | +---------------------------+ | Timing | (Order change from draft) +---------------------------+ | Sequencing | +---------------------------+ | PW Identification | (PSN Tunnel) +---------------------------+ | PSN Convergence | ----------------------------+ | PSN | +---------------------------+ | MAC/Data-link | +---------------------------+ | Physical | +---------------------------+ Goals: • Identify the “necessary and sufficient” functionality of a PW (faithfulness). • Isolate PW from the PSN differences. • Partition native services and wire function. 3 Bryant PWE3 Protocol layering

PW over IP • IP ethos places a great importance on generality and re-use. • Employ existing IETF protocols where possible. 4 Bryant PWE3 Protocol layering

IP and the PLD +---------------------------+ +---------------------------+ | Payload | | Raw payload when possible | +---------------------------+ +---------------------------+ | Payload Convergence | | As Needed | +---------------------------+ +---------------------------+ | Timing | | RTP | +---------------------------+ +-------------+ | | Sequencing | | | | +---------------------------+ | +-------------+ | PW Identification | | L2TP, GRE, IPSec, MPLS etc| +---------------------------+ +---------------------------+ | PSN Convergence | | Not needed | ----------------------------+ ----------------------------+ | PSN | | IP | +---------------------------+ +---------------------------+ | MAC/Data-link | | MAC/Data-link | +---------------------------+ +---------------------------+ | Physical | | Physical | +---------------------------+ +---------------------------+ 5 Bryant PWE3 Protocol layering

draft-Martini and the PLD • MPLS ethos places a great importance on wire efficiency. • Martini approach has all the components of the PLD but compressed for maximum wire efficiency. 6 Bryant PWE3 Protocol layering

MPLS (Martini) and the PLD +---------------------------+ | Payload | +---------------------------+ | Payload Convergence | +---------------------------+ | Timing | +---------------------------+ | Sequencing | +---------------------------+ | PW Identification | +---------------------------+ | PSN Convergence | ----------------------------+ | PSN | +---------------------------+ | MAC/Data-link | +---------------------------+ +---------------------------------------------+ | Physical | +---------------------------+ | Rsvd | Flags |0 0| Length | Sequence Number | +---------------------------------------------+ | Inner Label | +---------------------------------------------+ | Outer Label | +---------------------------------------------+ 7 Bryant PWE3 Protocol layering

Where does the PW stop? PW End Service | |<------- Pseudo Wire ------>| | | | |<-- PSN Tunnel -->| | V V V V PW +-----+----+ +----+ End Service +-----+ |NSP1 | PE1|==================| PE2| | +-----+ | | | |............PW1.............|----------| | | CE1 |----| | | | | | | CE2 | | | ^ | |............PW2.............|----------| | +-----+ | | | |==================| | | ^ +-----+ | +-----+----+ +----+ | | | ^ | | | | | | | |<------- Emulated Service ------->| | | | | | Virtual physical | | termination | | ^ | CE1 native | CE2 native service | service | CE2 native NSP model reduces scope service of PW. 8 Bryant PWE3 Protocol layering

Native Service Processing Model +-----------------------------------+ | Native Service Processing | +---------------------+ +--------------+---+----------------+ | Payload | | | | Emulated | +---------------------+ | Service | | Service | | Payload Convergence | | Interface | | (TDM, ATM, | +---------------------+ | (TDM, ATM, | | Ethernet, |<=== Emulated == | Timing | | Ethernet, | | frame relay, | Service +---------------------+ | frame relay, | | etc.) | | Sequencing | | etc.) | +----------------+ +---------------------+ | | | Payload | | PW Identification | | | | Encapsulation |<==== Pseudo ==== +---------------------+ | | +----------------+ Wire | PSN Convergence | | | | PW Ident., | ----------------------+ | | | PSN & Physical |<==== PSN ======= | PSN | | | | Headers | Tunnel +---------------------+ | | +----------------+ | MAC/Data-link | | | | Physical | +---------------------+ +-------+------+ +-------+--------+ | Physical | | | +---------------------+ | | | | | | | | v v To CE To PSN 9 Bryant PWE3 Protocol layering

Principle of Minimum Intervention +---------------------------+ Is the Principle of | Payload | Minimum Intervention +---------------------------+ | Payload Convergence | the right approach? +---------------------------+ | Timing | +---------------------------+ Does it depend on the | Sequencing | +---------------------------+ PSN? | PW Identification | +---------------------------+ | PSN Convergence | RFC 1925 & RFC 1958 ----------------------------+ | PSN | +---------------------------+ | MAC/Data-link | +---------------------------+ | Physical | +---------------------------+ 10 10 10 Bryant PWE3 Protocol layering

Principle of Minimum Intervention • Non-Intervention • Decouples payload development from PW development. • Fewer translations at NSP for same to same. • Intervention • Can be more wire efficient • Fewer translations at NSP for any to any • Introduces new framing type 11 11 11 Bryant PWE3 Protocol layering

More Common Services? Pseudo-wire encapsulation layer +---------------------------+ | Payload | +---------------------------+ | Payload Convergence | +---------------------------+ Are there any other | Timing | common components +---------------------------+ | Sequencing | within PWE3 Encapsulation? +---------------------------+ | PW Identification | +---------------------------+ | PSN Convergence | ----------------------------+ | PSN | +---------------------------+ | MAC/Data-link | +---------------------------+ | Physical | +---------------------------+ Note that reference clock can be in-band or out-band 12 12 12 Bryant PWE3 Protocol layering

Segmentation and Reassembly +-------------------------------------------+ | Native Service Processing | +---------------+---------------------------+ Is fragmentation/SAR | Payload | needed? +---------------------------+ | Payload Convergence | +---------------------------+ Where does it belong? | Timing | +---------------------------+ | Sequencing | Is it needed at more +---------------------------+ | PSN Tunnel | than one layer? +---------------------------+ | PSN Convergence | +---------------------------+ | PSN | +---------------------------+ | MAC/Data-link | +---------------------------+ | Physical | +---------------------------+ 13 13 13 Bryant PWE3 Protocol layering