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IETF-52 PWE3 Workgroup TDM Circuit Emulation over Packet Switching Networks CESoPSN draft-vainshtein-cesopsn-01.txt

12/12/2001. CESoPSN. Encapsulation for emulation of low-rate TDM circuits over PSN:From fractional T1/E1 and unframed T1/E1circuits up to unframed E3 and DS3 circuitsWith minor modifications applicable to unstructured low-rate SONET/SDH circuits (STS-3c/STM-1)Example application - connection of

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IETF-52 PWE3 Workgroup TDM Circuit Emulation over Packet Switching Networks CESoPSN draft-vainshtein-cesopsn-01.txt

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    1. IETF-52 PWE3 Workgroup TDM Circuit Emulation over Packet Switching Networks (CESoPSN) draft-vainshtein-cesopsn-01.txt Sasha Vainshtein, Israel Sasson, Akiva Sadovski, Eduard Metz

    2. 12/12/2001 CESoPSN Encapsulation for emulation of low-rate TDM circuits over PSN: From fractional T1/E1 and unframed T1/E1circuits up to unframed E3 and DS3 circuits With minor modifications applicable to unstructured low-rate SONET/SDH circuits (STS-3c/STM-1) Example application - connection of Class 5 switches in the Carriers' Carrier deployment scenario Invariant to: PSN Type (IPv4 or MPLS) PW demuxing (UDP/IP, L2TPv3/IP, MPLS/MPLS) End Service connection to PE: Physical TDM line Payload of a virtual SONET/SDH tributary Virtual line in a channelized PDH link

    3. 12/12/2001 CESoPSN - Synchronization Minimal requirements to the PE synchronization scheme: Does not require central network clock Local PE oscillators should be 'just as good as required' for the services carried, i.e.: Stratum 4 for T1/E1 Stratum 3E for unstructured SONET/SDH Allows carrying of clock with data -- thus synchronizing otherwise isolated islands of customers' networks

    4. 12/12/2001 CESoPSN - Highlights Configurable fixed size payload: Limited by path MTU and packetization delay requirements Furnishes savings in both BW and PSN switching capacity in a trade-off with packetization delay Fixed for the PW life cycle – no padding problems Multiple of the size of the "natural delineation data chunk" (if allowed by path MTU) Provides SONET/SDH-compatible PM parameters Circuit payload is always octet-aligned (hence padding for unframed T1) Structures are always aligned with the packet payload boundary No need for structure pointers in the PW header For very big natural delineation chunks - packets carrying first octets of fragmented structures are marked

    5. 12/12/2001 CESoPSN - RTP Header RTP header used for: Carrying the clock of incoming ES from ingress to egress over PSN Jitter buffer size defined only by the PSN jitter Suitable for delay-sensitive applications Marking (packets carrying structures' first octets) Sequencing including: Detection of lost packets Limited reordering support Misconnection and mistype defects detection Compatible with RTP header compression techniques over slow or high-noise links

    6. 12/12/2001 CESoPSN - The Control Word CESoPSN Control word is used for: Dynamic BW allocation (save bandwidth in case of the end service outage) Signaling problems detected at egress back to ingress: Loss of packets - may be used as congestion indication Loss of synchronization Signaling of PW loopbacks (not loopbacks of the emulated service) Request PW loopback from the peer PE Signal loopback condition to peer PE

    7. 12/12/2001 CESoPSN - OAM Issues Defects Hierarchy of defects is considered Generic PW defects (misconnection, packet loss) Specific defects (loss of synchronization) Defects that are at higher levels of hierarchy override defects at lower levels E.g., misconnection packets will not affect sequencing Defects’ detection and handling rules explicitly specified PW Loopbacks Can be set/cleared locally or by a command from the remote peer Loopback traffic can be distinguished by a mark in the CW

    8. 12/12/2001 Issues For Further Study Usage of RTCP Fractional E1/T1 with CAS (if found to be of sufficient interest) Explicit specification of rules for detection of lost packets Effects of timestamp resolution upon quality of clock recovery PM issues (not mentioned in the draft, but G.826-compatible PM already implemented) Specific MIB definitions

    9. 12/12/2001 CESoPSN - Summary Encapsulation technique for emulation of low-rate TDM circuits over PSN PSN-invariant Does not mandate high-quality central network clock Based on a working implementation Tested with delay-sensitive applications over live IP backbones Allows to save link BW and PSN switching capacity: By packing multiple native delineation data chunks into a single packet By transmitting only outage indications during ES outages Defines OAM Detection and handling of defects PW Loopbacks Proposed for the WG review and acceptance as the WG document

    10. 12/12/2001 Questions?

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