6man R. Bonica
Internet-Draft Juniper Networks
Intended status: Standards Track Y. Kamite
Expires: November 6, 2020 NTT Communications Corporation
T. Niwa
KDDI
A. Alston
Liquid Telecom
L. Jalil
Verizon
May 5, 2020

The IPv6 Compressed Routing Header (CRH)
draft-bonica-6man-comp-rtg-hdr-15

Abstract

This document defines two new Routing header types. Collectively, they are called the Compressed Routing Headers (CRH). Individually, they are called CRH-16 and CRH-32.

Status of This Memo

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Table of Contents

1. Introduction

IPv6 source nodes use Routing headers to specify the path that a packet takes to its destination. The IETF has defined several Routing header types. RH0 was the first to be defined and was deprecated because of security vulnerabilities.

This document defines two new Routing header types. Collectively, they are called the Compressed Routing Headers (CRH). Individually, they are called CRH-16 and CRH-32.

The CRH, like RH0, allows IPv6 source nodes to specify the path that a packet takes to its destination. The CRH differs from RH0 because:

The following are reasons for encoding the CRH in as few bytes as possible:

Section 9 of this document addresses security considerations. Appendix A of this document demonstrates how the CRH can be encoded in fewer bytes than RH0.

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 [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. The Compressed Routing Headers (CRH)

Both CRH versions (i.e., CRH-16 and CRH-32) contain the following fields:

In the CRH, the Type-specific data field contains a list of Segment Identifiers (SIDs). Each SID represents both of the following:

SIDs are listed in reverse order. So, the first SID in the list represents the final segment in the path. Because segments are listed in reverse order, the Segments Left field can be used as an index into the SID list. In this document, the "current SID" is the SID list entry referenced by the Segments Left field.

The first segment in the path can be omitted from the list. See Appendix B for examples.

In the CRH-16, each SID is encoded in 16-bits. In the CRH-32, each SID is encoded in 32-bits.

In all cases, the CRH MUST end on a 64-bit boundary. So, the Type- specific data field MUST be padded with zeros if the CRH would otherwise not end on a 64-bit boundary.

     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 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             SID[0]            |          SID[1]               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |                          .........
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   

Figure 1: CRH-16

     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 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +                             SID[0]                            +
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +                             SID[1]                            +
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                                                              //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    +                             SID[n]                            +
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   

Figure 2: CRH-32

4. The CRH Forwarding Information Base (CRH-FIB)

Each SID identifies a CRH-FIB entry.

Each CRH-FIB entry contains:

The IPv6 address represents an interface on the next segment endpoint. It MUST NOT be a link-local address. While the IPv6 address represents an interface on the next segment endpoint, it does not necessarily represent the interface through which the packet will arrive at the next segment endpoint.

The forwarding method specifies how the processing node will forward the packet to the next segment endpoint. The following are examples:

Some forwarding methods require method-specific parameters. For example, a forwarding method might require a parameter that identifies the interface through which the packet should be forwarded.

The CRH-FIB can be populated:

5. Processing Rules

The following rules describe CRH processing:

5.1. Computing Minimum CRH Length

The algorithm described in this section accepts the following CRH fields as its input parameters:

It yields L, the minimum CRH length. The minimum CRH length is measured in 8-octet units, not including the first 8 octets.

<CODE BEGINS>

switch(Routing Type) {
    case CRH-16:
        if (Segments Left <= 2)
            return(0)
        sidsBeyondFirstWord = Segments Left - 2;
        sidPerWord = 4;
    case CRH-32:
        if (Segments Left <= 1)
            return(0)
        sidsBeyondFirstWord = Segments Left - 1;
        sidsPerWord = 2;
    case default:
        return(0xFF);
    }

words = sidsBeyondFirstWord div sidsPerWord;
if (sidsBeyondFirstWord mod sidsPerWord)
    words++;

return(words)


<CODE ENDS>

6. Mutability

In the CRH, the Segments Left field is mutable. All remaining fields are immutable.

7. Applications And SIDs

A CRH contains one or more SIDs. Each SID is processed by exactly one node.

Therefore, a SID is not required to have domain-wide significance. Applications can:

8. Management Considerations

PING and TRACEROUTE both operate correctly in the presence of the CRH.

9. Security Considerations

Networks that process the CRH MUST mitigate the security vulnerabilities described in [RFC5095]. Their border routers SHOULD discard packets that satisfy the following criteria:

Many border routers cannot filter packets based upon the Segments Left value. These border routers MAY discard packets that satisfy the following criteria:

10. Implementation and Deployment Status

Juniper Networks has produced experimental implementations of the CRH on:

Liquid Telecom has deployed the CRH, on a limited basis, in their network. Other experimental deployments are in progress.

11. IANA Considerations

SID values 0-15 are reserved for future use. They may be assigned by IANA, based on IETF Consensus. IANA is requested to establish a "Registry of SRm6 Reserved SIDs". Values 0-15 are reserved for future use.

IANA is requested to make the following entries in the Internet Protocol Version 6 (IPv6) Parameters "Routing Type" registry:

     Suggested    
     Value            Description                           Reference
   ---------------------------------------------------------------------
       5    Compressed Routing Header (16-bit) (CRH-16)   This document
       6    Compressed Routing Header (32-bit) (CRH-32)   This document

12. Acknowledgements

Thanks to Dr. Vanessa Ameen, Fernando Gont, Naveen Kottapalli, Joel Halpern, Tony Li, Gerald Schmidt, Nancy Shaw, and Chandra Venkatraman for their contributions to this document.

13. Contributors

14. References

14.1. 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.
[RFC4443] Conta, A., Deering, S. and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", STD 89, RFC 4443, DOI 10.17487/RFC4443, March 2006.
[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.
[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, "Path MTU Discovery for IP version 6", STD 87, RFC 8201, DOI 10.17487/RFC8201, July 2017.

14.2. Informative References

[IANA-RH] , "Routing Headers"
[ISO10589-Second-Edition] , ""Intermediate system to Intermediate system intra-domain routeing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode Network Service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,", November 2001.
[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.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, December 1998.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006.
[RFC5340] Coltun, R., Ferguson, D., Moy, J. and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.

Appendix A. CRH Processing Examples

The CRH-16 and CRH-32 encode information more efficiently than RH0.

Routing Header Size (in Bytes) As A Function Of Routing Header Type and Number Of SIDs
SIDs RH0 CRH-16 CRH-32
1 24 8 8
2 40 8 16
3 56 16 16
4 72 16 24
5 88 16 24
6 104 16 32
7 120 24 32
8 136 24 40
9 152 24 40
10 168 24 48
11 184 32 48
12 200 32 52
13 216 32 52
14 232 32 56
15 248 40 56
16 264 40 60
17 280 40 60
18 296 40 64

Table 1 reflects Routing header size as a function of Routing header type and number of SIDs contained by the Routing header.

Appendix B. CRH Processing Examples

This appendix demonstrates CRH processing in the following scenarios:

 -----------                 -----------                 -----------                    
|Node: S    |               |Node: I1   |               |Node: I2   |      
|Loopback:  |---------------|Loopback:  |---------------|Loopback:  |                          
|2001:db8::a|               |2001:db8::1|               |2001:db8::2|               
 -----------                 -----------                 -----------                     
      |                                                       | 
      |                      -----------                      |
      |                     |Node: D    |                     |
       ---------------------|Loopback:  |---------------------
                            |2001:db8::b| 
                             -----------

Figure 3: Reference Topology

Figure 3 provides a reference topology that is used in all examples.

Node SIDs
SID IPv6 Address Forwarding Method
2 2001:db8::2 Least-cost path
11 2001:db8::b Least-cost path

Table 2 describes two entries that appear in each node's CRH-FIB.

B.1. The SID List Contains One Entry For Each Segment In The Path

In this example, Node S sends a packet to Node D, via I2. In this example, I2 appears in the CRH segment list.

As the packet travels from S to I2:
Source Address = 2001:db8::a Segments Left = 1
Destination Address = 2001:db8::2 SID[0] = 11
SID[1] = 2
As the packet travels from I2 to D:
Source Address = 2001:db8::a Segments Left = 0
Destination Address = 2001:db8::b SID[0] = 11
SID[1] = 2

B.2. The SID List Omits The First Entry In The Path

In this example, Node S sends a packet to Node D, via I2. In this example, I2 does not appear in the CRH segment list.

As the packet travels from S to I2:
Source Address = 2001:db8::a Segments Left = 1
Destination Address = 2001:db8::2 SID[0] = 11

As the packet travels from I2 to D:
Source Address = 2001:db8::a Segments Left = 0
Destination Address = 2001:db8::b SID[0] = 11

Authors' Addresses

Ron Bonica Juniper Networks 2251 Corporate Park Drive Herndon, Virginia 20171 USA EMail: rbonica@juniper.net
Yuji Kamite NTT Communications Corporation 3-4-1 Shibaura, Minato-ku Tokyo, 108-8118 Japan EMail: y.kamite@ntt.com
Tomonobu Niwa KDDI 3-22-7, Yoyogi, Shibuya-ku Tokyo, 151-0053 Japan EMail: to-niwa@kddi.com
Andrew Alston Liquid Telecom Nairobi, Kenya EMail: Andrew.Alston@liquidtelecom.com
Luay Jalil Verizon Richardson, Texas USA EMail: luay.jalil@one.verizon.com