INTERNET-DRAFT G. Manhoudt Intended Status: Proposed Standard AimValley Expires: December 16, 2012 S. Roullot Alcatel-Lucent P. Roberts Alcatel-Lucent July 09, 2012 Transparent SDH/SONET over Packet draft-manhoudt-pwe3-tsop-00 Abstract This document describes the Transparent SDH/SONET over Packet (TSoP) mechanism to encapsulate Synchronous Digital Hierarchy (SDH) or Synchronous Optical NETwork (SONET) bit-streams in a packet format, suitable for Pseudowire (PW) transport over a packet switched network (PSN). The key property of the TSoP method is that it transports the SDH/SONET client signal in its entirety through the PW, i.e., no use is made of any specific characteristic of the SONET/SDH signal format, other than its bit rate. The TSoP transparency includes transporting the timing properties of the SDH/SONET client signal. This ensures a maximum of transparency and a minimum of complexity, both in implementation and during operation. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html Manhoudt et al. Expires December 16, 2012 [Page 1] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Manhoudt et al. Expires December 16, 2012 [Page 2] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5 2.1. Conventions Used in This Document . . . . . . . . . . . . 5 2.2. Acronyms and Terms . . . . . . . . . . . . . . . . . . . . 5 3. Emulated STM-N Services . . . . . . . . . . . . . . . . . . . 6 3.1 PSN-bound direction . . . . . . . . . . . . . . . . . . . . 8 3.1 CE-bound direction . . . . . . . . . . . . . . . . . . . . 9 4. TSoP Encapsulation Layer . . . . . . . . . . . . . . . . . . . 11 4.1. TSoP Packet Format . . . . . . . . . . . . . . . . . . . . 11 4.2. PSN/PW Headers . . . . . . . . . . . . . . . . . . . . . . 11 4.2.1 Transport over an MPLS(-TP) PSN . . . . . . . . . . . . 11 4.2.2 Transport over an IPv4/IPv6 PSN . . . . . . . . . . . . 12 4.3. TSoP Encapsulation Headers . . . . . . . . . . . . . . . . 12 4.3.1. Location and Order of TSoP Encapsulation Headers . . . 12 4.3.2. Usage and Structure of the TSoP Control Word . . . . . 14 4.3.3. Usage of the RTP Header . . . . . . . . . . . . . . . 15 5. TSoP Payload Field . . . . . . . . . . . . . . . . . . . . . . 17 6. TSoP Operation . . . . . . . . . . . . . . . . . . . . . . . . 17 6.1. Common Considerations . . . . . . . . . . . . . . . . . . 17 6.2. IWF Operation . . . . . . . . . . . . . . . . . . . . . . 17 6.2.1. PSN-Bound Direction . . . . . . . . . . . . . . . . . 17 6.2.2. CE-Bound Direction . . . . . . . . . . . . . . . . . . 18 6.3. TSoP Defects . . . . . . . . . . . . . . . . . . . . . . . 20 6.4. TSoP Performance Monitoring . . . . . . . . . . . . . . . 21 7. Quality of Service (QoS) Issues . . . . . . . . . . . . . . . 23 8. Congestion Control . . . . . . . . . . . . . . . . . . . . . . 23 9. Security Considerations . . . . . . . . . . . . . . . . . . . 24 10. Applicability Statements . . . . . . . . . . . . . . . . . . . 25 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . . 26 13.2. Informative References . . . . . . . . . . . . . . . . . . 27 Appendix A. Parameters to be configured to set up a TSoP PW . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30 Manhoudt et al. Expires December 16, 2012 [Page 3] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 1. Introduction This document describes the Transparent SDH/SONET over Packet (TSoP) method for encapsulating SDH or SONET signals with bit rates of 51.84 Mbit/s or N * 155.52 Mbit/s (where N = 1, 4, 16 or 64) for Pseudowire (PW) transport over a packet switched network (PSN), using circuit emulation techniques. The selected approach for this encapsulation scheme avoids using any particular signal characteristics of the SDH/SONET signal, other than its bit rate. This approach closely follows the SAToP method described in [RFC4553] for PW transport of E1, DS1, E3 or DS3 over a PSN. An alternative to the TSoP method for STM-N transport over PW is known as CEP (Circuit Emulation over Packet) and is described in [RFC4842]. The key difference between the CEP approach and the TSoP approach is that within CEP an incoming STM-N is terminated and demultiplexed to its constituent VCs (Virtual Containers). Subsequently, each VC is individually circuit emulated and encapsulated into a PW and transported over the PSN to potentially different destinations, where they are reassembled into (newly constructed) STM-N signals again. The TSoP approach, on the other hand, is to encapsulate the entire STM-N in a single circuit emulating Pseudowire and transport it to a single destination over the PSN. The essential difference between both methods is that CEP offers more routing flexibility and better bandwidth efficiency than TSoP at the cost of the loss of transparency (overhead, timing, scrambling) at the STM-N layer and at the cost of added complexity associated with the inclusion of what in essence is an SDH/SONET VC cross-connect function in the PEs. Within the context of this document, there is no difference between SONET [GR-253] signals, often denoted as OC-M, and SDH [G.707] signals, usually denoted as STM-N. For ease of reading, this document will only refer to STM-N, but any statement about an STM-N signal should be understood to apply equally to the equivalent OC-M signal, unless it is specifically mentioned otherwise. The equivalency can be described by the following relations between N and M: If N = 0 then M = 1 and if N >= 1 then M = 3 * N. The TSoP solution presented in this document conforms to the PWE3 architecture described in [RFC3985] and satisfies the relevant general requirements put forward in [RFC3916]. As with all PWs, TSoP PWs may be manually configured or set up using the PWE3 control protocol [RFC4447]. Manhoudt et al. Expires December 16, 2012 [Page 4] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 2. Terminology and Conventions 2.1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2.2. Acronyms and Terms The following acronyms used in this document are defined in [RFC3985], [RFC4197] and [RFC4553]: AC Attachment Circuit ATM Asynchronous Transfer Mode CE Customer Edge CES Circuit Emulation Service IWF Interworking Function NSP Native Service Processing PE Provider Edge PREP Pre-Processing PSN Packet Switched Network PW Pseudowire SDH Synchronous Digital Hierarchy SONET Synchronous Optical Network TDM Time Division Multiplexing In addition, the following specific terms are used in this document: LOF Loss Of Frame - A condition of an STM-N signal in which the frame pattern cannot be detected. Criteria for raising and clearing a LOF condition can be found in [G.783]. LOS Loss Of Signal - A condition of the STM-N attachment circuit in which the incoming signal has an insufficient energy level for reliable reception. Criteria for raising and clearing a LOS condition can be found in [G.783]. G-AIS Generic Alarm Indication Signal - A specific bit pattern that replaces the normal STM-N signal in the case of certain failure scenarios. The G-AIS pattern [G.709] is constructed by continuously repeating the 2047 bit pseudo random bit sequence based on the generating polynomial 1 + x^9 + x^11 according to [O.150]. NIM Non-Intrusive Monitor - A circuit that monitors a signal in a certain direction of transmission, without changing the binary content of it. A NIM can be used for Fault Management Manhoudt et al. Expires December 16, 2012 [Page 5] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 and Performance Monitoring purposes SF Signal Fail: A control signal, that exists internally in a system, to convey the failed state of an incoming signal, from a server layer process to the adjacent client layer process. See [G.783] LOPS Loss of Packet State - A defect that indicates that the PE at the receiving end of a TSoP carrying PW experiences an interruption in the stream of received TSoP packets. See [RFC5604] 3. Emulated STM-N Services The TSoP emulated STM-N service over a Pseudowire makes use of a bi- directional point-to-point connection over the PSN between two TSoP- IWF blocks, located in the PE nodes that terminate the PW that interconnects them, as shown in figure 1. The TSoP-IWF blocks each consist of two half-functions, a PSN-bound IWF and a CE-bound IWF, one for each direction of transmission. As the name implies, the PSN- bound part of the TSoP IWF performs the conversion of an STM-N bitstream to a packet flow, suitable for transport over the PSN and the CE-bound part of the TSoP-IWF performs the inverse operation. Manhoudt et al. Expires December 16, 2012 [Page 6] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 |<------------------ Emulated Service ----------------->| | | | |<-------------- Pseudowire ------------->| | | AC | | AC | |<---->| |<----- PSN ----->| |<---->| | | | | | | | . PE1 . . PE2 . | . +-----------+ +-----------+ . +---+ | | | | +---+ | |----->| PSN-bound |====> . . . ====>| CE-bound |----->| | | C | | IWF | | IWF | | C | | E | | _ _ _ | | _ _ _ | | E | | | | | | | | | | 1 | | | | | | 2 | | |<-----| CE-bound |<==== . . . <====| PSN-bound |<-----| | +---+ | | IWF | | IWF | | +---+ | +-----------+ +-----------+ | | TSoP-IWF TSoP-IWF | native native STM-N STM-N Figure 1. Overview of STM-N emulated service architecture The following list provides the STM-N services, as specified in [G.707] and [GR-253], that can be supported by a TSoP PW: 1. STM-0 or OC-1 (51.84 Mbit/s) 2. STM-1 or OC-3 (155.52 Mbit/s) 3. STM-4 or OC-12 (622.08 Mbit/s) 4. STM-16 or OC-48 (2488.32 Mbit/s) 5. STM-64 or OC-192 (9953.28 Mbit/s) The TSoP protocol used for emulation of STM-N services does not depend on the method in which the STM-N is delivered to the PE. For example, an STM-1 attachment circuit is treated in the same way regardless of whether it is a copper [G.703] or a fiber optic [G.707] link. Also, in case the STM-N is carried in an OTN signal [G.709], the functionality in the TSoP-IWF operates in the same way, but a PWE3 Pre-processing (PREP) functional block will be present between the AC and the PE to perform the OTN (de)multiplexing functions. The TSoP-IWF function in figure 1 is further broken down in functional blocks in figure 2. These individual functional blocks are described in the next two sections. Manhoudt et al. Expires December 16, 2012 [Page 7] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 AC TSoP-IWF PSN ------>|<------------------------------------------------->|<-------- +---------------------------------------------------+ | +-------+ | | +-------+ SF | PSN- | CE-side_ | | | |----->| bound | defect +--------+ | STM-N | | STM-N | +->| NIM |------------>| | | =========>| Rx | | +-------+ | | | | | |===0=======================>| PSN- | | Packet | +-------+ +--------+ | bound |===========> | | Subst. | | IWF | | | | Signal |===========>| | | | | Gen. | +-->| | | | +--------+ | +--------+ | | | | | PSN-bound direction | | - - - -|- - - - - - - - - - - - - - - - - -|- - - - - - - -|- - - - - | CE-bound direction | | | | | | +--------+ | PSN-side_ | | | G-AIS | | defect | | | Gen. |====+ | | | +--------+ | | | | | | +--------+ | | +--------+ | +---| | | | +-------+ | |<===+ | | | | | | | STM-N/ | No_Packet | CE- | | <=========| STM-N |<=====| G-AIS |<-----------| bound |<=========== STM-N | | Tx | | Switch | | IWF | | Packet | | | +-->| |<========0==| | | | +-------+ | +--------+ | | | | | | +----------+ | +--------+ | | | | optional | | | | +------| CE-bound |<---+ | | | NIM | | | +----------+ | +---------------------------------------------------+ Figure 2. TSoP functional block diagram 3.1 PSN-bound direction In the PSN-bound direction the STM-N signal is received from the CE via an AC by the STM-N Rx function. This function recovers the optical or electrical signal and converts it to a suitable internal format. In addition, it detects the LOS condition and it asserts the SF signal whenever this is the case. The STM-N Rx block is Manhoudt et al. Expires December 16, 2012 [Page 8] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 equivalent to the OSn_TT_Sk & OSn/RSn_A_Sk (in the case of an optical STM-N) or the ESn_TT_Sk & ESn/RSn_A_Sk (in the case of an electrical STM-N interface) function pairs defined in [G.783]. The CE-bound IWF segments the STM-N ingress bitstream, which it receives from the STM-N Rx function, in blocks of equal length. Each block of bits is supplied with the appropriate TSoP Encapsulation Headers and then delivered to the PSN Multiplexing layer to add the required headers for transport over the PSN. The PSN-bound NIM function controls the state of the CE-side_defect signal. It will assert this signal in case the SF signal is asserted or in case another defect is detected in the incoming STM-N signal. The inclusion of other defects than LOS in the CE-side_defect signal is OPTIONAL. When the CE-side_defect signal is asserted, the PSN-bound IWF will set the corresponding flag (L-bit) in the overhead of the affected packets. Packets in which the L-bit is set MUST have a substitution payload (created by the Substitution Signal Generator function) of the same length as the regular TSoP payload. This substitution payload is RECOMMENDED to be the G-AIS pattern or a fixed "all ones" pattern. Lastly, when the PSN-side_defect state is asserted, the PSN-bound IWF will set the corresponding flag (R-bit) in the overhead of all packets that are transmitted while this signal is in the asserted state. 3.1 CE-bound direction In the CE-bound direction, the CE-bound IWF receives the PW packets from the PSN and strips off the PSN, PW, and TSoP encapsulation headers and writes the payload data in a buffer. The output data stream towards the CE is created by playing out this buffer with a suitable clock signal. The thus reconstructed STM-N signal is forwarded to the STM-N/G-AIS Switch function. The No_Packet signal is asserted by the CE-bound IWF in case the internal packet buffer empties due to lack of input packets from the PSN or in case a packet is missing or invalid. The PSN-side_defect signal is asserted by the CE-bound IWF in case the LOPS condition is detected by the CE-bound IWF (see section 6.2.2). The state of this signal controls the value of the R-bit in the overhead of the packets returned towards the far-end TSoP-IWF. The G-AIS Generator generates a G-AIS signal at the nominal frequency Manhoudt et al. Expires December 16, 2012 [Page 9] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 of the recovered STM-N signal, +/-20 ppm. The STM-N/G-AIS Switch normally takes its input from the CE-bound IWF and forwards the recovered STM-N signal towards the STM-N Tx funnction, but during the time that the No_Packet signal is asserted, it will select the G-AIS Generator as its active input and forward a G-AIS signal towards the STM-N Tx function. The CE-bound NIM function is an OPTIONAL function that can be used to detect additional defects in the recovered CE-bound STM-N signal. The presence of such defects (e.g. STM-N LOF) MAY be used as an additional reason for the STM-N/G-AIS Switch function to select the G-AIS signal as its active input. Lastly, the STM-N Tx function converts the internal signal that is output by the STM-N/G-AIS Switch block into a regular STM-N signal towards the CE via the AC. The STM-N Tx block is equivalent to the OSn_TT_So & OSn/RSn_A_So (in the case of an optical STM-N) or the ESn_TT_So & ESn/RSn_A_So (in the case of an electrical STM-N interface) function pairs defined in [G.783]. Manhoudt et al. Expires December 16, 2012 [Page 10] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 4. TSoP Encapsulation Layer 4.1. TSoP Packet Format The general format of TSoP packets during transport over the PSN is shown in Figure 3. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | | PSN/PW Headers | | ... | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | ... | | TSoP Encapsulation Headers | | ... | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | | | ... | | | | TSoP Payload Field | | | | ... | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3. Generic TSoP Packet Format 4.2. PSN/PW Headers A TSoP PW can be transported over different types of PSNs based on different switching technology. Below the transmission over MPLS and IPv4/IPv6 PSNs is described, but other methods are not precluded. The selected method will determine the format of the PSN/PW Headers part and influence the order of the fields in the TSoP Encapsulation Headers part. 4.2.1 Transport over an MPLS(-TP) PSN In case a TSoP PW is forwarded over an MPLS(-TP) PSN, a standard "bottom of stack" PW label as shown in figure 4 is prepended before the TSoP Encapsulation Headers. Subsequently, one or more MPLS(-TP) labels need to be pushed according to the standard MPLS transport methods outlined in [RFC3031] and [RFC3032]. Manhoudt et al. Expires December 16, 2012 [Page 11] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4. PW Label (S = 1) 4.2.2 Transport over an IPv4/IPv6 PSN Both UDP and L2TPv3 [RFC3931] can provide the PW demultiplexing mechanisms for TSoP PWs over an IPv4/IPv6 PSN. The PW label (figure 4) provides the demultiplexing function for an IPv4/IPv6 PSN as described in [RFC3985]. The total length of a TSoP packet for a specific PW MUST NOT exceed path MTU between the pair of PEs terminating this PW. TSoP implementations using an IPv4 PSN MUST mark the IPv4 datagrams they generate as "Don't Fragment" [RFC791] (see also [RFC4623]). 4.3. TSoP Encapsulation Headers 4.3.1. Location and Order of TSoP Encapsulation Headers The TSoP Encapsulation Headers MUST contain the TSoP Control Word (figure 7) and MUST contain a Minimum length RTP Header [RFC3550] (figure 8). The TSoP Encapsulation Headers must immediately follow the PSN/PW header, as shown in figure 3. In case the TSoP packets are transmitted over a PSN based on UDP over IPv4/IPv6 technology, the TSoP Encapsulation Headers have the RTP Header first and then the TSoP control word immediately next, as shown in figure 6. In case the TSoP packets are transmitted over a PSN based on a technology other than UDP over IPv4/IPv6, the TSoP Encapsulation Headers have the TSoP control word first and then the RTP header immediately next, as shown in figure 5. Note: This arrangement complies with the traditional usage of RTP for the IPv4/IPv6 PSN with UDP multiplexing while making TSoP PWs Equal Cost Multi-Path (ECMP)-safe for the MPLS PSN by providing for PW-IP packet discrimination (see [RFC3985]). Furthermore, it facilitates seamless stitching of L2TPv3-based and MPLS-based segments of TSoP PWs (see [RFC5254]). Manhoudt et al. Expires December 16, 2012 [Page 12] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | | PSN/PW Headers | | (Ethernet, MPLS(-TP), IPv4/IPv6 + L2TPv3, etc.) | | ... | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | TSoP Control Word | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | | +-- --+ | Minimum length RTP Header (see [RFC3550]) | +-- --+ | | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | ... | | TDM data (Payload) | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5. General TSoP Packet Format for all PSNs, other than an IPv4/IPv6 PSN with UDP PW Demultiplexing 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | | IPv4/IPv6 + UDP layer headers | | ... | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | | +-- --+ | Minimum length RTP Header (see [RFC3550]) | +-- --+ | | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | TSoP Control Word | +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ | ... | | TDM data (Payload) | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6. TSoP Packet Format for an IPv4/IPv6 PSN with UDP PW Demultiplexing Manhoudt et al. Expires December 16, 2012 [Page 13] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 4.3.2. Usage and Structure of the TSoP Control Word The purpose of the TSoP control word is to allow: 1. Detection of packet loss or misordering 2. Differentiation between PSN and attachment circuit problems as a cause for outage of the emulated service 3. Signaling of faults detected at the PW egress to the PW ingress The structure of the TSoP Control Word is in accordance with the general PW Control Word format specified in [RFC4385]. The TSoP CW format is shown in Figure 7 below. This TSoP Control Word MUST be present in each TSoP PW packet. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0|L|R|RSV|FRG| LEN | Sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7. Structure of the TSoP Control Word The use of Bits 0 to 3 is described in [RFC4385]. These bits MUST be set to zero unless they are being used to indicate the start of an Associated Channel Header (ACH). An ACH is needed if the state of the TSoP PW is being monitored using Virtual Circuit Connectivity Verification [RFC5085] or in case OAM functionality according to [RFC6371] is added. L (bit 4) - If this bit is set, it indicates that the STM-N data ingressing in the PSN-bound IWF is currently experiencing a fault condition. Once set, if the fault is rectified, the L-bit MUST be cleared. For each frame that is transmitted with L-bit = 1, the PSN-bound IWF MUST insert such an amount of substitution data in the TSoP payload field that the TSoP frame length, as it is during normal operation, is maintained. The CE-bound IWF MUST play out an amount of G-AIS data corresponding to the original TSoP Payload Field for each received packet with the L-bit set. Note: This document does not prescribe exactly which STM-N fault conditions are to be treated as invalidating the payload carried in the TSoP packets. An example of such a fault condition would be LOS. R (bit 5) - If this bit is set by the PSN-bound IWF, it indicates that its local CE-bound IWF is in the LOPS state, i.e., it has lost a preconfigured number of consecutive packets. The R-bit MUST be cleared by the PSN-bound IWF once its local CE-bound IWF Manhoudt et al. Expires December 16, 2012 [Page 14] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 has exited the LOPS state, i.e., has received a preconfigured number of consecutive packets. See also section 6.2.2. RSV (bits 6 to 7) - This field MUST be set to 0 by the PSN-bound IWF and MUST be ignored by the CE-bound IWF. RSV is reserved. FRG (bits 8 to 9) - This field MUST be set to 0 by the PSN-bound IWF and MUST be ignored by the CE-bound IWF. FRG is fragmentation; see [RFC4623]. LEN (bits 10 to 15) - This field MAY be used to carry the length of the TSoP packet (defined as the length of the TSoP Encapsulation Header + TSoP Payload Field) if it is less than 64 octets, and MUST be set to zero otherwise. When the LEN field is set to 0, the preconfigured size of the TSoP packet payload MUST be assumed to be as described in Section 5, and if the actual packet size is inconsistent with this length, the packet MUST be considered malformed. Sequence number (bits 16 to 31) - This field is used to enable the common PW sequencing function as well as detection of lost packets. It MUST be generated in accordance with the rules defined in Section 5.1 of [RFC3550] for the RTP sequence number: o Its space is a 16-bit unsigned circular space o Its initial value SHOULD be random (unpredictable). It MUST be incremented with each TSoP data packet sent in the specific PW. 4.3.3. Usage of the RTP Header A minimum length RTP Header as specified in [RFC3550] MUST be included in the TSoP Encapsulation Header. The reason for mandating the insertion of an RTP Header by the PSN-bound IWF is that it is expected that in most cases the CE-bound IWF will need to use the contained timestamps to be able to recover a clock signal of sufficient quality. By avoiding to make the presence of RTP Headers subject to configuration, the design of the of the CE-bound IWF can be simplified and another potential source of errors during commissioning is eliminated. The RTP Header fields in the list below (see also figure 8) MUST have the following specific values: V (version) = 2 P (padding) = 0 X (header extension) = 0 Manhoudt et al. Expires December 16, 2012 [Page 15] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 CC (CSRC count) = 0 M (marker) = 0 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V |P|X| CC |M| PT | Sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Timestamp | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8. Structure of the RTP Header field The PT (payload type) field is used as follows: 1. One PT value MUST be allocated from the range of dynamic values (see [RTP-TYPES]) for each direction of the PW. The same PT value MAY be reused for both directions of the PW and also reused between different PWs. 2. The PSN-bound IWF MUST set the PT field in the RTP header to the allocated value. 3. The CE-bound IWF MAY use the received value to detect malformed packets. The sequence number MUST be the same as the sequence number in the TSoP control word. The RTP timestamps are used for carrying timing information over the network. Their values MUST be generated in accordance with the rules established in [RFC3550]. A TSoP implementation MUST support RTP timestamping at the PW ingress with a nominal clock frequency of 25 MHz. This is also the default value. Other clock frequencies MAY be supported to generate the RTP Timestamps. Selection of the applicable clock frequency is done during commissioning of the PW that carries the emulated STM-N service. The SSRC (synchronization source) value in the RTP header MAY be used for detection of misconnections, i.e., incorrect interconnection of attachment circuits. In case this option is not used, this field should contain an all zero pattern. The usage of the options associated with the RTP Header (the timestamping clock frequency, selected PT and SSRC values) MUST be aligned between the two TSoP IWFs during Pseudowire commissioning. Manhoudt et al. Expires December 16, 2012 [Page 16] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 5. TSoP Payload Field In order to facilitate handling of packet loss in the PSN, all packets belonging to a given TSoP PW are REQUIRED to carry a fixed number of octets in its TSoP Payload Field. The TSoP Payload Field length MUST be defined during PW commissioning, MUST be the same for both directions of the PW, and MUST remain unchanged for the lifetime of the PW. All TSoP implementations MUST be capable of supporting the following TSoP Payload Field length: o STM-N (for N = 0, 1, 4, 16 and 64) - 810 octets Notes: 1. Whatever the selected payload size, TSoP does not assume alignment to any underlying structure imposed by TDM framing (octet, frame, or multiframe alignment). The STM-N signal remains scrambled through the TSoP encapsulation and decapsulation processes. 2. With a payload size of 810 octets, the STM-N emulated service over the PSN will have a nominal packet rate of 8000 packets/s when N = 0 and a nominal packet rate of 24000*N packets/s for N >= 1. TSoP uses the following ordering for packetization of the TDM data: o The order of the payload octets corresponds to their order on the attachment circuit. o Consecutive bits coming from the attachment circuit fill each payload octet starting from most significant bit to least significant. 6. TSoP Operation 6.1. Common Considerations Edge-to-edge emulation of an STM-N service using TSoP is only possible when the two PW attachment circuits are of the same type, i.e., both are STM-N with equal N. 6.2. IWF Operation 6.2.1. PSN-Bound Direction Manhoudt et al. Expires December 16, 2012 [Page 17] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 Once the PW is commisioned, the PSN-bound TSoP IWF operates as follows: The ingressing STM-N bit-stream is segmented, such that each segment contains the configured number of payload octets per packet. This forms the TSoP Payload Field. The STM-N bit-stream MUST NOT be descrambled before segmentation and packetization for PW transport. Subsequently, the TSoP Encapsulation Headers are prepended according to the rules in section 4.3. Lastly, the PSN/PW Headers are added to the packetized service data, and, depending on the applicable PSN technology, a Frame Check Sum is added. The resulting packets are transmitted over the PSN. 6.2.2. CE-Bound Direction Once the PW is commissioned, the CE-bound TSoP IWF operates as follows: Each time a valid TSoP packet is received from the PSN, its sequence number is checked to determine its relative position in the stream of received packets. Packets that are received out-of-order MAY be reordered. Next, the data in the fixed length TSoP payload field of each packet is written into a (jitter) buffer in the order indicated by its sequence number. In case data is missing due to a lost packet or a packet that could not be re-ordered, an equivalent amount of dummy data (G-AIS pattern) is substituted. Subsequently, the STM-N stream towards the CE is reconstructed by playing out the buffer content with a clock that is reconstructed to have the same average frequency as the STM-N clock at the PW ingress. In addition, this clock signal must have such properties that the following requirements can be met: o A reconstructed SDH-type STM-N signal delivered to an Attachment Circuit MUST meet [G.825] jitter and wander requirements, or, o A reconstructed SONET-type OC-M signal delivered to an Attachment Circuit MUST meet [GR-253] jitter and wander requirements. The size of the buffer in the CE-bound TSoP IWF SHOULD be configurable to allow accommodation to the PSN specific packet delay variation. The CE-bound TSoP IWF SHOULD use the sequence number in the TSoP Manhoudt et al. Expires December 16, 2012 [Page 18] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 Control Word for detection of lost and misordered packets. The sequence numbers in the RTP Header MAY be used instead. Note: A valid sequence number can be always found in bits 16 - 31 of the first 32-bit word immediately following the PW demultiplexing header regardless of the specific PSN type, multiplexing method, location of the RTP header, etc. This approach simplifies implementations supporting multiple encapsulation types as well as implementation of multi-segment (MS) PWs using different encapsulation types in different segments. The CE-bound TSoP IWF MAY reorder misordered packets. Misordered packets that can not be reordered MUST be discarded and treated the same way as lost packets. The payload of received TSoP packets marked with the L-bit set MUST be replaced by the equivalent number of bits from the G-AIS pattern. Likewise, the payload of each lost or malformed (see section 6.3) TSoP packet MUST be replaced with the equivalent number of bits from the G-AIS pattern. Before a TSoP PW has been commissioned and after a PW has been decommissioned, the IWF MUST play out the G-AIS pattern to its STM-N attachment circuit. Once a TSoP PW has been commissioned, the CE-bound IWF begins to receive TSoP packets and to store their payload in the buffer, but continues to play out the G-AIS pattern to its TDM attachment circuit. This intermediate state persists until a preconfigured degree of filling (for example half of the CE-bound IWF buffer) has been reached by writing consecutive TSoP packets or until a preconfigured intermediate state timer (started when the TSoP commissioning is complete) expires. Each time an STM-N signal is replaced by a G-AIS signal at the same nominal bitrate, this signal may start at an arbitrary point in its repeating 2047-bit sequence. Once the starting point is selected, the G-AIS signal is sent uninterrupted until the condition that invoked it has been removed. The frequency of the clock that is used to generate this G-AIS signal MUST have an accuracy that is better than +/- 20 ppm relative to the nominal STM-N frequency. Once the preconfigured amount of the STM-N data has been received, the CE-bound TSoP IWF enters its normal operational state where it continues to receive TSoP packets and to store their payload in the buffer while playing out the contents of the jitter buffer in accordance with the required clock. In this state, the CE-bound IWF performs clock recovery, MAY monitor PW defects, and MAY collect PW Manhoudt et al. Expires December 16, 2012 [Page 19] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 performance monitoring data. The CE-bound IWF enters the LOPS defect state in case it detects the loss of a preconfigured number of consecutive packets or if the intermediate state timer expires before the required amount of TDM data has been received. While in this state, the local PSN-bound TSoP IWF SHOULD mark every packet it transmits with the R-bit set. The CE-bound IWF leaves the LOPS defect state and transits to the normal state once a preconfigured number of consecutive valid TSoP packets have been received (successfully reordered packets contribute to the count of consecutive packets). The RTP timestamps inserted in each TSoP packet at the PW ingress allow operation in differential mode provided that both PW ingress and PW egress IWFs have a local clock that is traceable to a common timing source. The use of adaptive mode clocking mode, i.e., recovering the STM-N clock in the CE-bound IWF by essentially averaging the arrival times of the TSoP packets from the PSN without using RTP information, is not recommended for TSoP-based circuit emulation. 6.3. TSoP Defects In addition to the LOPS state defined above, the CE-bound TSoP IWF MAY detect the following defects: o Stray packets o Malformed packets o Excessive packet loss rate o Buffer overrun o Buffer underrun o Remote packet loss Corresponding to each defect is a defect state of the IWF, a detection criterion that triggers transition from the normal operation state to the appropriate defect state, and an alarm that MAY be reported to the management system and thereafter cleared. Alarms are only reported when the defect state persists for a preconfigured amount of time (typically 2.5 seconds) and MUST be cleared after the corresponding defect is undetected for a second preconfigured amount of time (typically 10 seconds). The trigger and release times for the various alarms may be independent. Stray packets MAY be detected by the PSN and PW demultiplexing layers. The SSRC field in the RTP header MAY be used for this purpose as well. Stray packets MUST be discarded by the CE-bound IWF, and their detection MUST NOT affect mechanisms for detection of Manhoudt et al. Expires December 16, 2012 [Page 20] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 packet loss. Malformed packets are detected by mismatch between the expected packet size and the actual packet size inferred from the PSN and PW demultiplexing layers (taking the value of the L-bit into account). Differences between the received PT value and the PT value allocated for this direction of the PW MAY also be used for this purpose. Malformed, in-order packets MUST be discarded by the CE-bound IWF and replacement data generated as with lost packets. Excessive packet loss rate is detected by computing the average packet loss rate over a configurable amount of time and comparing it with preconfigured raise and clear thresholds. Buffer overrun is detected in normal operational state when the (jitter) buffer of the CE-bound IWF cannot accommodate newly arrived TSoP packets. Buffer underrun can detected in normal operational state when the (jitter) buffer of the CE-bound IWF has insufficient data to maintain playing out the STM-N signal towards the CE at the recovered clock rate. In this situation G-AIS MUST be substituted until the buffer fill has reached its preconfigured degree of filling again. Remote packet loss is indicated by reception of packets with their R-bit set. 6.4. TSoP Performance Monitoring Performance monitoring (PM) parameters are routinely collected for STM-N services and provide an important maintenance mechanism in SDH networks. However, STM-N level PM data provides the information over the performance of the end-to-end STM-N connection, which may extend well beyond the part in which it is carried over a TSoP Pseudowire. It may be important to be able to measure the performance of a TSoP Pseudowire section, which forms a part of the STM-N end-to-end connection, in isolation. For that reason a set of packet level counters are specified that can be used to assess the performance of the TSoP Pseudowire section. Collection of the TSoP PW performance monitoring data is OPTIONAL and, if implemented, is only performed after the CE-bound IWF has exited its intermediate state. The following counters are defined: ENCAP_TXTOTAL_PKTS - The total number of TSoP packets that is transmitted towards the PSN by the PSN-bound IWF function. This includes packets with the L-bit set. Manhoudt et al. Expires December 16, 2012 [Page 21] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 DECAP_RXTOTAL_PKTS - The total number of TSoP packets that is received from the PSN by the CE-bound IWF function. This includes malformed packets, out-of-order packets and packets with the L-bit set. DECAP_REORDERED_PKTS - The number of out-of-order TSoP packets that is received from the PSN by the CE-bound IWF, based on the received sequence numbers, for which the ordering could be corrected by the CE-bound IWF. DECAP_MISSING_PKTS - The number of TSoP packets that did not arrive at the CE-bound IWF from the PSN, based on the received sequence numbers. DECAP_MALFORMED_PKTS - The number of TSoP packets that is received from the PSN by the CE-bound IWF function which contains one of the following RTP related errors: TSoP Payload Field length mismatch, PT-value mismatch (if checked) and/or SSRC mismatch (if checked). DECAP_OUTOFORDER_PKTS - The number of out-of-order TSoP packets that is received from the PSN by the CE-bound IWF, based on the received sequence numbers, for which the ordering could not be corrected by the CE-bound IWF. DECAP_OVERRUN_PKTS - The number of packets that is received from the PSN that is dropped by the CE-bound IWF due to the fact that the (jitter) buffer has insufficient capacity to store the TSoP Payload Field content. DECAP_UNDERRUN_BITS - The number of bits that is not played out towards the CE by the CE-bound IWF because the (jitter) buffer is empty at the moment they need to be played out. DECAP_PLAYEDOUT_PKTS - The number of packets that has been successfully played out towards the CE by the CE-bound IWF containing valid STM-N payload including the packets that have been received with the L-bit containing substituted data. Packets which are lost in transmission over the PSN or packets which discarded by the CE-bound IWF due to some error condition are not counted. Note that packets with the L-bit set are considered normal data from the perspective of TSoP Pseudowire Performance Monitoring, since in such cases the location of the fault is before the signal ingresses the PSN-bound IWF, so outside the scope of the TSoP PW. Manhoudt et al. Expires December 16, 2012 [Page 22] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 7. Quality of Service (QoS) Issues TSoP SHOULD employ existing QoS capabilities of the underlying PSN. If the PSN providing connectivity between PE devices is Diffserv-enabled and provides a PDB [RFC3086] that guarantees low jitter and low loss, the TSoP PW SHOULD use this PDB in compliance with the admission and allocation rules the PSN has put in place for that PDB (e.g., marking packets as directed by the PSN). If the PSN is Intserv-enabled, then GS (Guaranteed Service) [RFC2212] with the appropriate bandwidth reservation SHOULD be used in order to provide a bandwidth guarantee equal or greater than that of the aggregate TDM traffic. 8. Congestion Control As explained in [RFC3985], the PSN carrying the PW may be subject to congestion. TSoP PWs represent inelastic constant bit-rate (CBR) flows and cannot respond to congestion in a TCP-friendly manner prescribed by [RFC2914], although the percentage of total bandwidth they consume remains constant. Unless appropriate precautions are taken, undiminished demand of bandwidth by TSoP PWs can contribute to network congestion that may impact network control protocols. Whenever possible, TSoP PWs SHOULD be carried across traffic- engineered PSNs that provide either bandwidth reservation and admission control or forwarding prioritization and boundary traffic conditioning mechanisms. IntServ-enabled domains supporting Guaranteed Service (GS) [RFC2212] and DiffServ-enabled domains [RFC2475] supporting Expedited Forwarding (EF) [RFC3246] provide examples of such PSNs. Such mechanisms will negate, to some degree, the effect of the TSoP PWs on the neighboring streams. In order to facilitate boundary traffic conditioning of TSoP traffic over IP PSNs, the TSoP IP packets SHOULD NOT use the DiffServ Code Point (DSCP) value reserved for the Default Per-Hop Behavior (PHB) [RFC2474]. If TSoP PWs run over a PSN providing best-effort service, they SHOULD monitor packet loss in order to detect "severe congestion". If such a condition is detected, a TSoP PW SHOULD shut down bi-directionally for some period of time as described in Section 6.5 of [RFC3985]. Note that: 1. The TSoP IWF can inherently provide packet loss measurement since Manhoudt et al. Expires December 16, 2012 [Page 23] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 the expected rate of arrival of TSoP packets is fixed and known 2. The results of the TSoP packet loss measurement may not be a reliable indication of presence or absence of severe congestion if the PSN provides enhanced delivery. For example: a) If TSoP traffic takes precedence over non-TSoP traffic, severe congestion can develop without significant TSoP packet loss. b) If non-TSoP traffic takes precedence over TSoP traffic, TSoP may experience substantial packet loss due to a short-term burst of high-priority traffic. 3. The STM-N services emulated by the TSoP PWs have high availability objectives (see [G.829]) that MUST be taken into account when deciding on temporary shutdown of TSoP PWs. This specification does not define the exact criteria for detecting "severe congestion" using the TSoP packet loss rate or the specific methods for bi-directional shutdown the TSoP PWs (when such severe congestion has been detected) and their subsequent re-start after a suitable delay. This is left for further study. However, the following considerations may be used as guidelines for implementing the TSoP severe congestion shutdown mechanism: 1. If the TSoP PW has been set up using either PWE3 control protocol [RFC4447] or L2TPv3 [RFC3931], the regular PW teardown procedures of these protocols SHOULD be used. 2. If one of the TSoP PW end points stops transmission of packets for a sufficiently long period, its peer (observing 100% packet loss) will necessarily detect "severe congestion" and also stop transmission, thus achieving bi-directional PW shutdown. 9. Security Considerations TSoP does not enhance or detract from the security performance of the underlying PSN; rather, it relies upon the PSN mechanisms for encryption, integrity, and authentication whenever required. TSoP PWs share susceptibility to a number of Pseudowire layer attacks and will use whatever mechanisms for confidentiality, integrity, and authentication are developed for general PWs. These methods are beyond the scope of this document. Although TSoP PWs MUST employ an RTP header to achieve an explicit transfer of timing information, SRTP (see [RFC3711]) mechanisms are NOT RECOMMENDED as a substitute for PW layer security. Manhoudt et al. Expires December 16, 2012 [Page 24] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 Misconnection detection capabilities of TSoP increase its resilience to misconfiguration. Random initialization of sequence numbers, in both the control word and the optional RTP header, makes known-plaintext attacks on encrypted TSoP PWs more difficult. Encryption of PWs is beyond the scope of this document. 10. Applicability Statements TSoP is an encapsulation layer intended for carrying SDH STM-N circuits over the PSN in a structure-agnostic and fully transparent fashion. TSoP fully complies with the principle of minimal intervention, minimizing overhead and computational power required for encapsulation. TSoP provides sequencing and synchronization functions needed for emulation of STM-N bit-streams, including detection of lost or misordered packets and perform the appropriate compensation. Furthermore, explicit timing information is provided by the presence of an RTP timestamp in each TSoP packet. STM-N bit-streams carried over TSoP PWs may experience delays exceeding those typical of native SDH networks. These delays include the TSoP packetization delay, edge-to-edge delay of the underlying PSN, and the delay added by the jitter buffer. It is recommended to estimate both delay and delay variation prior to setup of a TSoP PW. TSoP carries STM-N streams over PSN in their entirety, including any control plane data contained within the data. Consequently, the emulated STM-N services are sensitive to the PSN packet loss. Appropriate generation of replacement data can be used to prevent shutting down the CE STM-N interface due to occasional packet loss. Other effects of packet loss on this interface (e.g., errored blocks) cannot be prevented. TSoP provides for effective fault isolation by forwarding the local attachment circuit failure indications to the remote attachment circuit. TSoP provides for a carrier-independent ability to detect misconnections and malformed packets via the PT and SSRC fields in the RTP Header. This feature increases resilience of the emulated service to misconfiguration. Being a constant bit rate (CBR) service, TSoP cannot provide TCP Manhoudt et al. Expires December 16, 2012 [Page 25] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 friendly behavior under network congestion. Faithfulness of a TSoP PW may be increased by exploiting QoS features of the underlying PSN. TSoP does not provide any mechanisms for protection against PSN outages, and hence its resilience to such outages is limited. However, lost-packet replacement and packet reordering mechanisms increase resilience of the emulated service to fast PSN rerouting events. 11. IANA Considerations IANA is requested to assign a new MPLS Pseudowire (PW) type for the following TSoP encapsulated services: PW type Description Reference -------- -------------- ---------- 0x0020 STM-0 or OC-1 RFC XXXX 0x0021 STM-1 or OC-3 RFC XXXX 0x0022 STM-4 or OC-12 RFC XXXX 0x0023 STM-16 or OC-48 RFC XXXX 0x0024 STM-64 or OC-192 RFC XXXX The above value is suggested as the next available value and has been reserved for this purpose by IANA. RFC Editor: Please replace RFC XXXX above with the RFC number of this document and remove this note. 12. Acknowledgements The authors of this document are much indebted to the authors of [RFC4553]. This latter RFC has been used as a template and example for the current document. Moreover, many paragraphs and sentences have been copied from this RFC without alteration or with only slight modification into the current document. Furthermore, we thank Zhu Bao, Jeff Towne, Willem van den Bosch and Matthew Bocci for their valuable feedback. 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Manhoudt et al. Expires December 16, 2012 [Page 26] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [G.707] ITU-T Recommendation G.707/Y.1322 (01/2007) - Network node interface for the synchronous digital hierarchy (SDH) [G.783] ITU-T Recommendation G.783 (03/2006) - Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks [O.150] ITU-T Recommendation O.150 (05/1996) - General requirements for instrumentation for performance measurement on digital transmission equipment [G.825] ITU-T Recommendation G.825 (03/2000) - The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH) [GR-253] Telcordia GR-253-CORE - Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria (September 2000) 13.2. Informative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001. [RFC3916] Xiao, X., Ed., McPherson, D., Ed., and P. Pate, Ed., "Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3)", RFC 3916, September 2004. [RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005. [RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005. [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006. [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and Manhoudt et al. Expires December 16, 2012 [Page 27] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006. [RFC4553] Vainshtein, A., Ed., and YJ. Stein, Ed., "Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)", RFC 4553, June 2006. [RFC4623] Malis, A. and M. Townsley, "Pseudowire Emulation Edge-to- Edge (PWE3) Fragmentation and Reassembly", RFC 4623, August 2006. [RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig, "Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)", RFC 4842, April 2007. [RFC5085] Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007. [RFC5254] Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed., "Requirements for Multi-Segment Pseudowire Emulation Edge- to-Edge (PWE3)", RFC 5254, October 2008. [RFC5604] Nicklass, O., "Managed Objects for Time Division Multiplexing (TDM) over Packet Switched Networks (PSNs)", RFC 5604, July 2009. [RFC6371] Busi, I., Ed., and D. Allan, Ed., "Operations, Administration, and Maintenance Framework for MPLS-Based Transport Networks", RFC 6371, September 2011. [G.709] ITU-T Recommendation G.709/Y.1331 (12/2009) - Interfaces for the Optical Transport Network (OTN) [G.829] ITU-T Recommendation G.829 (12/2002) - Error performance events for SDH multiplex and regenerator sections [802.1Q] IEEE Std. 802.1Q-2011, "Media Access Control (MAC) Bridges and Virtual Bridge Local Area Networks", 31 August 2011 [MEF 8] Metro Ethernet Forum - Implementation Agreement for the Emulation of PDH Circuits over Metro Ethernet Networks (October 2004) [RTP-TYPE] RTP PARAMETERS, Manhoudt et al. Expires December 16, 2012 [Page 28] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 Appendix A. Parameters to be configured to set up a TSoP PW The following parameters of the TSoP IWF MUST be agreed upon between the peer IWFs during the PW setup. Such an agreement can be reached via manual configuration or via one of the PW set-up protocols: 1. Type of attachment circuit, i.e., the value of N of the STM-N signal, which corresponds to a bit rate as mentioned in section 3. 2. Payload size, i.e., the (constant) number of octets that is transmitted in the TSoP Payload Field of each TSoP packet. The default value is 810 octets. 3. Timestamping clock frequency: 25 MHz (default) or an alternative value. 4. The configurability of the following parameters (see section 6.2.2) governing the behavior of the CE-bound IWF buffer is optional: a) The maximum amount of payload data that may be stored in the CE-bound IWF payload buffer b) The desired degree of filling of the CE-bound IWF buffer in steady state (typically 50% of the configured buffer size) c) The "intermediate state" timer, i.e., the maximum amount of time that the CE-bound IWF waits before after the first TSoP packet has been received, before it starts to play out data from the buffer towards the CE 5. The content of the following RTP header fields must be provided by the user: a) The 7-bit RTP Payload Type (PT) value; any value can be assigned to be used with TSoP PWs. Default is an all zero pattern. b) The 32-bit Synchronization Source (SSRC) value. Default is an all zero pattern. 6. The order of the RTP Header and TSoP-CW Header must be defined. This may be derived from the applied PSN transport technology, see section 4.3 7. The number of TSoP packets that must be missed consecutively before the CE-bound IWF enters the LOPS defect state (default 10) and the number of TSoP packets that must be received consecutively Manhoudt et al. Expires December 16, 2012 [Page 29] INTERNET DRAFT Transparent SDH/SONET over Packet July 09, 2012 to clear the LOPS defect state (default 2). See section 4.3.2 and [RFC5604] 8. To support the optional excessive packet loss event by the CE-bound IWF, the following parameters must be configured: a) The length of the observation period for detecting excessive packet loss. Default value is 10 s. b) The minimum number of lost packets that is to be detected in the observation interval before an excessive packet loss alarm is raised. Default value is 30% of the expected packets. c) The maximum number of lost packets that is to be detected in the observation interval to clear an excessive packet loss alarm. Default value is 1% of the expected packets. Authors' Addresses Gert Manhoudt AimValley B.V Utrechtseweg 38 1213 TV Hilversum The Netherlands E-mail: gmanhoudt@aimvalley.nl Stephan Roullot Alcatel-Lucent Centre de Villarceaux Route de Villejust 91620 Nozay France E-mail: stephan.roullot@alcatel-lucent.com Peter Roberts Alcatel-Lucent 600 March Road Kanata, Ontario, K2K 2E6 Canada E-mail: peter.roberts@alcatel-lucent.com Manhoudt et al. 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