6man R. Bonica Internet-Draft Juniper Networks Intended status: Standards Track N. So Expires: September 24, 2019 F. Xu Reliance Jio G. Chen Baidu Y. Zhu G. Yang China Telecom Y. Zhou ByteDance March 23, 2019 The IPv6 Compressed Routing Header (CRH) draft-bonica-6man-comp-rtg-hdr-03 Abstract This document defines the Compressed Routing Header (CRH). The CRH, like any other Routing header, contains a list of segment identifiers (SID). The CRH differs from other Routing headers in that its segment identifiers can be 8, 16 or 32 bits long. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 24, 2019. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. Bonica, et al. Expires September 24, 2019 [Page 1] Internet-Draft IPv6 Compressed Routing Header March 2019 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 3. The Compressed Routing Header (CRH) . . . . . . . . . . . . . 4 4. Segment Identifiers (SID) . . . . . . . . . . . . . . . . . . 6 5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 7 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.2. CRH Specific . . . . . . . . . . . . . . . . . . . . . . 7 5.2.1. Computing Minimum CRH Length . . . . . . . . . . . . 9 6. Mutability . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Management Considerationsinclude . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . 11 Appendix A. CRH Processing Examples . . . . . . . . . . . . . . 12 A.1. Loose Source Routing . . . . . . . . . . . . . . . . . . 13 A.2. Loose Source Routing Preserving The First SID . . . . . . 14 A.3. Strict Source Routing . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction An IPv6 [RFC8200] source node can steer a packet through a specific path to its destination. The source node defines the path as an ordered list of segments and encodes the path in an IPv6 Routing header. As per [RFC8200], all Routing headers includes the following fields: o Next Header - Identifies the header immediately following the Routing header. o Hdr Ext Len - Length of the Routing header. o Routing Type - Identifies the particular Routing header variant. Bonica, et al. Expires September 24, 2019 [Page 2] Internet-Draft IPv6 Compressed Routing Header March 2019 o Segments Left - The number of segments still to be traversed before reaching the destination. o Type-specific Data - Syntax and semantics are defined by the Routing Type. The following Routing types are currently defined: o Source Route (i.e., RH0) [RFC5095] (deprecated) o Type 2 Routing Header [RFC6275] o RPL Source Route Header [RFC6554] o Segment Routing Header (SRH) [I-D.ietf-6man-segment-routing-header] In each of the above-mentioned Routing Types, Type-specific Data contains a list of one or more segment identifiers (SID). Typically, a SID is an IPv6 address that identifies a segment endpoint. In the SRH, the SID may carry additional semantics. In all cases, the SID is 128 bits long. Therefore, routing headers can be very large. For example, an 88-byte Source Route header is required to specify a path that contains six segments. The same can be said of the SRH. Large Routing headers are undesirable for the following reasons: o Many ASIC-based forwarders copy the entire IPv6 extension header chain from buffer memory to on-chip memory. As the size of the IPv6 extension header chain increases, so does the cost of this copy. o Because Path MTU Discovery (PMTUD) [RFC8201] is not entirely reliable, many IPv6 hosts refrain from sending packets larger than the IPv6 minimum link MTU (i.e., 1280 bytes). When packets are small, the overhead imposed by large Routing headers becomes pronounced. This document defines the Compressed Routing Header (CRH). The CRH, like any other Routing header, contains a list of SIDs. The CRH differs from other Routing headers in that its SIDs can be 8, 16, or 32 bits long. Bonica, et al. Expires September 24, 2019 [Page 3] Internet-Draft IPv6 Compressed Routing Header March 2019 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. The Compressed Routing Header (CRH) Figure 1 depicts the CRH. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry |Com| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID List ........ +-+-+-+-+-+-+-+-+-+-+- Figure 1: Compressed Routing Header (CRH) The CRH contains the following fields: o Next Header - Defined in [RFC8200]. o Hdr Ext Len - Defined in [RFC8200]. o Routing Type - Defined in [RFC8200]. Value TBD by IANA. o Segments Left (SL) - Defined in [RFC8200]. o Last Entry - 8 bits. Represents the index (zero based), in the Segment List, of the last element of the Segment List.. o Com (Compression) - 2 bits. Represents the length of each entry in the SID List. Values are eight bits (0), sixteen bits (1), thirty-two bits (2), and reserved (3). o Reserved - SHOULD be set to zero by the sender. MUST be ignored by the receiver. o SID List - An zero-indexed list of SIDs. SIDs are listed in reverse order, with SID[0] representing the packet's ultimate Bonica, et al. Expires September 24, 2019 [Page 4] Internet-Draft IPv6 Compressed Routing Header March 2019 destination, SID[1] representing the previous segment endpoint and so forth. See Section 4 for SID details. Figure 2 through Figure 4 illustrate CRH encodings with Com equal to 0, 1 and 2. In all cases, the CRH MUST end on a 64-bit boundary. Therefore, the CRH MAY be padded with zeros. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry |Com| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID[0] | SID[1] | ......... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 2: Eight-bit Encoding (Com equals 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry |Com| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID[0] | SID[1] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| | ......... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Figure 3: Sixteen-bit Encoding (Com equals 1) Bonica, et al. Expires September 24, 2019 [Page 5] Internet-Draft IPv6 Compressed Routing Header March 2019 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry |Com| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + SID[0] + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + SID[1] + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + SID[n] + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Thirty-two bit Encoding (Com equals 2) 4. Segment Identifiers (SID) This document defines the following SID types: o Loosely routed o Strictly routed All SIDs, regardless of type, map to exactly one IPv6 address. The mapped address identifies an interface or set of interfaces (in the case of multicast) that terminate the segment. The address MUST be one of the following: o A globally scoped IPv6 unicast address [RFC4291]. o A Unique Local IPv6 Unicast Address (ULA) [RFC4193]. o A Multicast address [RFC4291]. A strictly routed SID also maps to a link interface. Nodes send packets through that interface in order to access the segment endpoint. SIDs are instantiated on nodes and their significance is limited to the node upon which they are instantiated. For example, assume that a SID is instantiated on multiple nodes. It can be loosely routed on one node and strictly routed on another. Likewise, it can map to a different globally scoped address on each node. See Appendix A for an example. Bonica, et al. Expires September 24, 2019 [Page 6] Internet-Draft IPv6 Compressed Routing Header March 2019 Forwarding nodes can learn the above-mentioned mappings from a central controller, from a distributed routing protocol or using any other means. The mechanisms that forwarding nodes use to learn the above-mentioned mappings are beyond the scope of this document. 5. Processing Rules 5.1. General [RFC8200] defines rules that apply to IPv6 extension headers, in general, and IPv6 Routing headers, in particular. All of these rules apply to the CRH. For example: o Extension headers (except for the Hop-by-Hop Options header) are not processed, inserted, or deleted by any node along a packet's delivery path, until the packet reaches the node (or each of the set of nodes, in the case of multicast) identified in the Destination Address field of the IPv6 header. o If, while processing a received packet, a node encounters a Routing header with an unrecognized Routing Type value, the required behavior of the node depends on the value of the Segments Left field. If Segments Left is zero, the node must ignore the Routing header and proceed to process the next header in the packet, whose type is identified by the Next Header field in the Routing header. If Segments Left is non-zero, the node must discard the packet and send an ICMP [RFC4443] Parameter Problem, Code 0, message to the packet's Source Address, pointing to the unrecognized Routing Type. o If, after processing a Routing header of a received packet, an intermediate node determines that the packet is to be forwarded onto a link whose link MTU is less than the size of the packet, the node must discard the packet and send an ICMP Packet Too Big message to the packet's Source Address. 5.2. CRH Specific When a node recognizes and processes a CRH, it executes the following procedure: o If the IPv6 Source Address is a link-local address, discard the packet. o If the IPv6 Source Address is a multicast address, discard the packet. Bonica, et al. Expires September 24, 2019 [Page 7] Internet-Draft IPv6 Compressed Routing Header March 2019 o If Segments Left equal 0, skip over the CRH and process the next header in the packet. o If Segments Left is greater than Last Entry plus one, send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Segments Left field, and discard the packet. o If Com is equal to (3) Reserved, send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Com field, and discard the packet. o If the IPv6 Hop Limit is less than or equal to 1, send an ICMP Time Exceeded -- Hop Limit Exceeded in Transit message to the Source Address and discard the packet. o Compute L, the minimum CRH length (See Section 5.2.1) o If L is greater than Hdr Ext Len, send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to the Last Entry field, and discard the packet. o Decrement Segments Left (i.e., SL). o Search for SID[SL] in the table that maps SID's to IPv6 addresses and interfaces. If SID[SL] cannot be found in that table, send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to SID[SL], and discard the packet. o Copy the address associated with SID[SL] to the IPv6 Destination Address. o If the IPv6 Destination address is a multicast address and SL is greater than zero, send an ICMP Parameter Problem, Code 0, message to the Source Address, pointing to Segment List [SL], and discard the packet. o Decrement the IPv6 Hop Limit. o If SID[SL] is a loosely routed segment, resubmit the packet to the IPv6 module for transmission to the new destination. o If SID[SL] is a strictly routed segment, forward the packet through the interface that is associated with SID[SL]. The above stated rules are demonstrated in Appendix A. Bonica, et al. Expires September 24, 2019 [Page 8] Internet-Draft IPv6 Compressed Routing Header March 2019 5.2.1. Computing Minimum CRH Length The algorithm described in this section accepts the following CRH fields as its input parameters: o Compression (Com). o Last Entry. It yields L, the minimum CRH length. The minimum CRH length is measured in 8-octet units, not including the first 8 octets. if (Com == 0 ) { /* Eight bit encoding */ L = ( ( Last Entry + 1 ) / 8 ); if ( ( Last Entry + 1 ) % 8 ) L++; } elsif (Com == 1 ) { /* Sixteen bit encoding */ L = ( ( Last Entry + 1 ) / 4 ); if ( ( Last Entry + 1 ) % 4 ) L++; } elsif (Com == 2 ) { /* Thirty-two bit encoding */ L = ( ( Last Entry + 1 ) / 2 ); if ( ( Last Entry + 1 ) % 2 ) L++; } else { /* Invalid Com */ L = 0xFF } return(L) 6. Mutability The Segments Left field is mutable and MAY be decremented by processing nodes. All remaining fields are immutable. Bonica, et al. Expires September 24, 2019 [Page 9] Internet-Draft IPv6 Compressed Routing Header March 2019 7. Management Considerationsinclude PING and TRACEROUTE [RFC2151] both operate correctly in the presence of the CRH. 8. Security Considerations The CRH can be used within trusted domains only. In order to enforce this requirement, domain edge routers MUST do one of the following: o Discard all inbound packets that contain a CRH o Authenticate [RFC4302] [RFC4303] all inbound packets that contain a CRH 9. IANA Considerations This document makes the following registration in the Internet Protocol Version 6 (IPv6) Parameters "Routing Type" registry maintained by IANA: Value Description Reference ------------------------------------------------------------ TBD Compressed Routing Header (CRH) This document 10. Acknowledgements Thanks to Joel Halpern, Gerald Schmidt, Nancy Shaw and Chandra Venkatraman for their comments. 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI 10.17487/RFC4302, December 2005, . Bonica, et al. Expires September 24, 2019 [Page 10] Internet-Draft IPv6 Compressed Routing Header March 2019 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, . [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", STD 89, RFC 4443, DOI 10.17487/RFC4443, March 2006, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., "Path MTU Discovery for IP version 6", STD 87, RFC 8201, DOI 10.17487/RFC8201, July 2017, . 11.2. Informative References [I-D.ietf-6man-segment-routing-header] Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-segment-routing-header-16 (work in progress), February 2019. [RFC2151] Kessler, G. and S. Shepard, "A Primer On Internet and TCP/ IP Tools and Utilities", FYI 30, RFC 2151, DOI 10.17487/RFC2151, June 1997, . [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, . [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation of Type 0 Routing Headers in IPv6", RFC 5095, DOI 10.17487/RFC5095, December 2007, . Bonica, et al. Expires September 24, 2019 [Page 11] Internet-Draft IPv6 Compressed Routing Header March 2019 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011, . [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 Routing Header for Source Routes with the Routing Protocol for Low-Power and Lossy Networks (RPL)", RFC 6554, DOI 10.17487/RFC6554, March 2012, . Appendix A. CRH Processing Examples This appendix provides examples of CRH processing in the following applications: o Loose source routing (Appendix A.1) o Loose source routing preserving the first SID (Appendix A.2) o Strict source routing (Appendix A.3) ----------- 2001:db8:0:2/64 |Node: I2 | 2001:db8:0:4/64 ----------------------|Loopback: |-------------------- | ::2 |2001:db8::2| ::1 | | ----------- | | ::1 :: 2| ----------- ----------- ----------- |Node: S |2001:db8:0:1/64|Node: I1 |2001:db8:0:3/64|Node: I3 | |Loopback |---------------|Loopback: |---------------|Loopback: | |2001:db8::a| ::1 ::2 |2001:db8::1| ::1 ::2 |2001:db8::3| ----------- ----------- ----------- | ::1 ----------- | |Node: D | 2001:db8:0:b/64 | |Loopback: |--------------------- |2001:db8::b| ::2 ----------- Figure 5: Reference Topology Figure 5 provides a reference topology that is used in all examples. Bonica, et al. Expires September 24, 2019 [Page 12] Internet-Draft IPv6 Compressed Routing Header March 2019 +--------------------+-----+--------------+ | Instantiating Node | SID | IPv6 Address | +--------------------+-----+--------------+ | All | 1 | 2001:db8::1 | | All | 2 | 2001:db8::2 | | All | 3 | 2001:db8::3 | | All | 10 | 2001:db8::a | | All | 11 | 2001:db8::b | +--------------------+-----+--------------+ Table 1: Loosely Routed SIDs Table 1 provides mappings for loosely routed SIDs. These mappings are instantiated on all nodes in the reference topology. +--------------------+-----+-----------------+-----------+ | Instantiating Node | SID | IPv6 Address | Interface | +--------------------+-----+-----------------+-----------+ | S | 129 | 2001:db8:0:1::2 | S -> I1 | | S | 130 | 2001:db8:0:2::2 | S -> I2 | | I1 | 129 | 2001:db8:0:3::2 | I1 -> I3 | | I2 | 129 | 2001:db8:0:4::2 | I2 -> I3 | | I3 | 129 | 2001:db8:0:b::2 | I3 -> D | +--------------------+-----+-----------------+-----------+ Table 2: Strictly Routed SIDs Table 2 provides mappings for strictly routed SIDs. These mappings are available on the instantiating node only. A.1. Loose Source Routing In this example, Node S sends a packet to Node D, specifying loose source route through Node I3. In this example, the first node in the path, I3, does not appear in the CRH segment list. Therefore, the destination node may not be able to send return traffic through the same path. +-------------------------------------+-------------------+ | As the packet travels from S to I3: | | +-------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 0 | | Destination Address = 2001:db8::3 | Segments Left = 1 | | | SID[0] = 11 | +-------------------------------------+-------------------+ Bonica, et al. Expires September 24, 2019 [Page 13] Internet-Draft IPv6 Compressed Routing Header March 2019 +-------------------------------------+-------------------+ | As the packet travels from I3 to D: | | +-------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 0 | | Destination Address = 2001:db8::b | Segments Left = 0 | | | SID[0] = 11 | +-------------------------------------+-------------------+ A.2. Loose Source Routing Preserving The First SID In this example, Node S sends a packet to Node D, specifying loose source route through Node I3. In this example, the first node in the path, I3, appears in the CRH segment list. Therefore, the destination node can send return traffic through the same path. +-------------------------------------+-------------------+ | As the packet travels from S to I3: | | +-------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 1 | | Destination Address = 2001:db8::3 | Segments Left = 1 | | | SID[0] = 11 | | | SID[1] = 3 | +-------------------------------------+-------------------+ +-------------------------------------+-------------------+ | As the packet travels from I3 to D: | | +-------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 1 | | Destination Address = 2001:db8::b | Segments Left = 0 | | | SID[0] = 11 | | | SID[1] = 3 | +-------------------------------------+-------------------+ A.3. Strict Source Routing In this example, Node S sends a packet to Node D, specifying the strict source route through I1 and I3. +---------------------------------------+-------------------+ | As the packet travels from S to I1: | | +---------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 1 | | Destination Address = 2001:db8:0:1::2 | Segments Left = 2 | | | SID[0] = 129 | | | SID[1] = 129 | +---------------------------------------+-------------------+ Bonica, et al. Expires September 24, 2019 [Page 14] Internet-Draft IPv6 Compressed Routing Header March 2019 +---------------------------------------+-------------------+ | As the packet travels from I1 to I3: | | +---------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 1 | | Destination Address = 2001:db8:0:3::2 | Segments Left = 1 | | | SID[0] = 129 | | | SID[1] = 129 | +---------------------------------------+-------------------+ +---------------------------------------+-------------------+ | As the packet travels from I3 to D: | | +---------------------------------------+-------------------+ | Source Address = 2001:db8::a | Last Entry = 1 | | Destination Address = 2001:db8:0:b::2 | Segments Left = 0 | | | SID[0] = 129 | | | SID[1] = 129 | +---------------------------------------+-------------------+ Authors' Addresses Ron Bonica Juniper Networks 2251 Corporate Park Drive Herndon, Virginia 20171 USA Email: rbonica@juniper.net Ning So Reliance Jio 3010 Gaylord PKWY, Suite 150 Frisco, Texas 75034 USA Email: Ning.So@ril.com Fengman Xu Reliance Jio 3010 Gaylord PKWY, Suite 150 Frisco, Texas 75034 USA Email: Fengman.Xu@ril.com Bonica, et al. Expires September 24, 2019 [Page 15] Internet-Draft IPv6 Compressed Routing Header March 2019 Gang Chen Baidu No.10 Xibeiwang East Road Haidian District Beijing 100193 P.R. China Email: phdgang@gmail.com Yongqing Zhu China Telecom 109 West Zhongshan Ave, Tianhe District Guangzhou P.R. China Email: zhuyq.gd@chinatelecom.cn Guangming Yang China Telecom 109 West Zhongshan Ave, Tianhe District Guangzhou P.R. China Email: yanggm.gd@chinatelecom.cn Yifeng Zhou ByteDance Building 1, AVIC Plaza, 43 N 3rd Ring W Rd Haidian District Beijing 100000 P.R. China Email: yifeng.zhou@bytedance.com Bonica, et al. Expires September 24, 2019 [Page 16]