The IPv6 Compact Routing Header (CRH)
draft-bonica-6man-comp-rtg-hdr-29
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| Authors | Ron Bonica , Yuji Kamite , Andrew Alston , Daniam Henriques , Luay Jalil | ||
| Last updated | 2022-11-14 | ||
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draft-bonica-6man-comp-rtg-hdr-29
6man R. Bonica
Internet-Draft Juniper Networks
Intended status: Standards Track Y. Kamite
Expires: 18 May 2023 NTT Communications Corporation
A. Alston
D. Henriques
Liquid Telecom
L. Jalil
Verizon
14 November 2022
The IPv6 Compact Routing Header (CRH)
draft-bonica-6man-comp-rtg-hdr-29
Abstract
This document defines two new Routing header types. Collectively,
they are called the Compact Routing Headers (CRH). Individually,
they are called CRH-16 and CRH-32.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 18 May 2023.
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Copyright (c) 2022 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 (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. The Compressed Routing Headers (CRH) . . . . . . . . . . . . 3
4. The CRH Forwarding Information Base (CRH-FIB) . . . . . . . . 4
5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Computing Minimum CRH Length . . . . . . . . . . . . . . 6
6. Mutability . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Applications And SIDs . . . . . . . . . . . . . . . . . . . . 7
8. Management Considerations . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Implementation and Deployment Status . . . . . . . . . . . . 8
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
14.1. Normative References . . . . . . . . . . . . . . . . . . 9
14.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. CRH Processing Examples . . . . . . . . . . . . . . 11
A.1. The SID List Contains One Entry For Each Segment In The
Path . . . . . . . . . . . . . . . . . . . . . . . . . . 12
A.2. The SID List Omits The First Entry In The Path . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
IPv6 [RFC8200] source nodes use Routing headers to specify the path
that a packet takes to its destination. The IETF has defined several
Routing header types [IANA-RH]. This document defines two new
Routing header types. Collectively, they are called the Compact
Routing Headers (CRH). Individually, they are called CRH-16 and CRH-
32.
The CRH allows IPv6 source nodes to specify the path that a packet
takes to its destination. The CRH:
* Can be encoded in relatively few bytes.
* Is designed to operate within a limited domain. (See Section 9).
The following are reasons for encoding the CRH in as few bytes as
possible:
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* Many ASIC-based forwarders copy headers from buffer memory to on-
chip memory. As header sizes increase, so does the cost of this
copy.
* 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 is excessive.
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 Headers (CRH)
Both CRH versions (i.e., CRH-16 and CRH-32) contain the following
fields:
* Next Header - Defined in [RFC8200].
* Hdr Ext Len - Defined in [RFC8200].
* Routing Type - Defined in [RFC8200]. (CRH-16 value is 5. CRH-32
value is 6).
* Segments Left - Defined in [RFC8200].
* Type-specific Data - Described in [RFC8200].
In the CRH, the Type-specific data field contains a list of Segment
Identifiers (SIDs). Each SID represents both of the following:
* A segment of the path that the packet takes to its destination.
* An entry in the CRH Forwarding Information Base (CRH-FIB)
(Section 4).
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.
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The first segment in the path can be omitted from the list. See
Appendix A for examples.
In the CRH-16 (Figure 1), each SID is encoded in 16-bits. In the
CRH-32 (Figure 2), 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:
* An IPv6 address.
* A topological function.
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* Arguments for the topological function. (Optional).
The first ten bits of the IPv6 address MUST NOT be fe00. That prefix
is reserved for link-local [RFC6890] addresses.
The topological function specifies how the processing node forwards
the packet to the next segment endpoint. The following are examples:
* Forward the packet through the least-cost path to the next segment
endpoint.
* Forward the packet through a specified interface.
* Encapsulate the packet in another IPv6 header of any type (e.g.,
MPLS, IPv6) and forward either through the least cost path or a
specified interface.
Some topological functions require parameters. For example, a
topological function might require a parameter that identifies the
interface through which the packet should be forwarded.
The CRH-FIB can be populated:
* By an operator, using a Command Line Interface (CLI).
* By a controller, using the Path Computation Element (PCE)
Communication Protocol (PCEP) [RFC5440] or the Network
Configuration Protocol (NETCONF) [RFC6241].
* By a distributed routing protocol [ISO10589-Second-Edition],
[RFC5340], [RFC4271].
5. Processing Rules
The following rules describe CRH processing:
* If Segments Left equals 0, skip over the CRH and process the next
header in the packet.
* If Hdr Ext Len indicates that the CRH is larger than the
implementation can process, discard the packet and send an ICMPv6
[RFC4443] Parameter Problem, Code 0, message to the Source
Address, pointing to the Hdr Ext Len field.
* Compute L, the minimum CRH length ( Section 5.1).
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* If L is greater than Hdr Ext Len, discard the packet and send an
ICMPv6 Parameter Problem, Code 0, message to the Source Address,
pointing to the Segments Left field.
* Decrement Segments Left.
* Search for the current SID in the CRH-FIB. In this document, the
"current SID" is the SID list entry referenced by the Segments
Left field.
* If the search does not return a CRH-FIB entry, discard the packet
and send an ICMPv6 Parameter Problem, Code 0, message to the
Source Address, pointing to the current SID.
* If Segments Left is greater than 0 and the CRH-FIB entry contains
a multicast address, discard the packet and send an ICMPv6
Parameter Problem, Code 0, message to the Source Address, pointing
to the current SID.
* Copy the IPv6 address from the CRH-FIB entry to the Destination
Address field in the IPv6 header.
* Decrement the IPv6 Hop Limit.
* Submit the packet, its topological function and its parameters to
the IPv6 module. See NOTE.
NOTE: By default, the IPv6 module determines the next-hop and
forwards the packet. However, the topological function may elicit
another behavior. For example, the IPv6 module may forward the
packet through a specified interface.
5.1. Computing Minimum CRH Length
The algorithm described in this section accepts the following CRH
fields as its input parameters:
* Routing Type (i.e., CRH-16 or CRH-32).
* Segments Left.
It yields L, the minimum CRH length. The minimum CRH length is
measured in 8-octet units, not including the first 8 octets.
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<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:
* Allocate SIDs so that they have domain-wide significance.
* Allocate SIDs so that they have node-local significance.
8. Management Considerations
PING and TRACEROUTE [RFC2151] both operate correctly in the presence
of the CRH.
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9. Security Considerations
Networks that process the CRH MUST NOT accept packets containing the
CRH from outside of there limited domain.. Their border routers
SHOULD discard packets that satisfy the following criteria:
* The packet contains a CRH
* The Segments Left field in the CRH has a value greater than 0
* The Destination Address field in the IPv6 header represents an
interface that resides inside of the network.
Many border routers cannot filter packets based upon the Segments
Left value. These border routers MAY discard packets that satisfy
the following criteria:
* The packet contains a CRH
* The Destination Address field in the IPv6 header represents an
interface that resides inside of the network.
10. Implementation and Deployment Status
Juniper Networks has produced experimental implementations of the CRH
on:
* A LINUX-based software platform
* The MX-series (ASIC-based) router
Liquid Telecom has deployed the CRH, on a limited basis, in their
network. Other experimental deployments are in progress.
11. IANA Considerations
This document makes the following registrations in the "Internet
Protocol Version 6 (IPv6) Parameters" "Routing Types" subregistry
maintained by IANA:
+-------+------------------------------+---------------+
| Value | Description | Reference |
+=======+==============================+===============+
| 5 | CRH-16 | This document |
+-------+------------------------------+---------------+
| 6 | CRH-32 | This document |
+-------+------------------------------+---------------+
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12. Acknowledgements
Thanks to Dr. Vanessa Ameen, Fernando Gont, Naveen Kottapalli, Joel
Halpern, Tony Li, Gerald Schmidt, Nancy Shaw, Ketan Talaulikar, and
Chandra Venkatraman for their contributions to this document.
13. Contributors
Gang Chen
Baidu
No.10 Xibeiwang East Road Haidian District
Beijing 100193 P.R. China
Email: phdgang@gmail.com
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
Gyan Mishra
Verizon
Silver Spring, Maryland, USA
Email: hayabusagsm@gmail.com
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,
<https://www.rfc-editor.org/info/rfc2119>.
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[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,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[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,
<https://www.rfc-editor.org/info/rfc8201>.
14.2. Informative References
[IANA-RH] IANA, "Routing Headers",
<https://www.iana.org/assignments/ipv6-parameters/
ipv6-parameters.xhtml#ipv6-parameters-3>.
[ISO10589-Second-Edition]
International Organization for Standardization,
""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,
<https://www.rfc-editor.org/info/rfc2151>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
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[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<https://www.rfc-editor.org/info/rfc6890>.
Appendix A. CRH Processing Examples
This appendix demonstrates CRH processing in the following scenarios:
* The SID list contains one entry for each segment in the path
(Appendix A.1).
* The SID list omits the first entry in the path (Appendix A.2).
----------- ----------- -----------
|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.
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+=====+==============+===================+
| SID | IPv6 Address | Forwarding Method |
+=====+==============+===================+
| 2 | 2001:db8::2 | Least-cost path |
+-----+--------------+-------------------+
| 11 | 2001:db8::b | Least-cost path |
+-----+--------------+-------------------+
Table 1: Node SIDs
Table 1 describes two entries that appear in each node's CRH-FIB.
A.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 |
+-------------------------------------+-------------------+
Table 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 |
+-------------------------------------+-------------------+
Table 3
A.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.
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+=====================================+===================+
| As the packet travels from S to I2: | |
+=====================================+===================+
| Source Address = 2001:db8::a | Segments Left = 1 |
+-------------------------------------+-------------------+
| Destination Address = 2001:db8::2 | SID[0] = 11 |
+-------------------------------------+-------------------+
Table 4
+=====================================+===================+
| As the packet travels from I2 to D: | |
+=====================================+===================+
| Source Address = 2001:db8::a | Segments Left = 0 |
+-------------------------------------+-------------------+
| Destination Address = 2001:db8::b | SID[0] = 11 |
+-------------------------------------+-------------------+
Table 5
Authors' Addresses
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, Virginia 20171
United States of America
Email: rbonica@juniper.net
Yuji Kamite
NTT Communications Corporation
3-4-1 Shibaura, Minato-ku,
108-8118
Japan
Email: y.kamite@ntt.com
Andrew Alston
Liquid Telecom
Nairobi
Kenya
Email: Andrew.Alston@liquidtelecom.com
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Daniam Henriques
Liquid Telecom
Johannesburg
South Africa
Email: daniam.henriques@liquidtelecom.com
Luay Jalil
Verizon
Richardson, Texas
United States of America
Email: luay.jalil@one.verizon.com
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