Dissemination of Flow Specification Rules for IPv6
draft-ietf-idr-flow-spec-v6-12
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8956.
|
|
|---|---|---|---|
| Authors | Christoph Loibl , Robert Raszuk , Susan Hares | ||
| Last updated | 2020-07-10 (Latest revision 2020-04-20) | ||
| Replaces | draft-raszuk-idr-flow-spec-v6 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
INTDIR Telechat review
(of
-17)
Ready with Nits
RTGDIR Last Call review
(of
-17)
Has Issues
|
||
| Stream | WG state | WG Consensus: Waiting for Write-Up | |
| Document shepherd | Jie Dong | ||
| Shepherd write-up | Show Last changed 2020-06-23 | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | Jie Dong <jie.dong@huawei.com> |
draft-ietf-idr-flow-spec-v6-12
IDR Working Group C. Loibl, Ed.
Internet-Draft next layer Telekom GmbH
Intended status: Standards Track R. Raszuk, Ed.
Expires: January 11, 2021 Bloomberg LP
S. Hares, Ed.
Huawei
July 10, 2020
Dissemination of Flow Specification Rules for IPv6
draft-ietf-idr-flow-spec-v6-12
Abstract
Dissemination of Flow Specification Rules I-D.ietf-idr-rfc5575bis
provides a protocol extension for propagation of traffic flow
information for the purpose of rate limiting or filtering. I-D.ietf-
idr-rfc5575bis specifies those extensions for IPv4 protocol data
packets only.
This specification extends I-D.ietf-idr-rfc5575bis and defines
changes to the original document in order to make it also usable and
applicable to IPv6 data packets.
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 January 11, 2021.
Copyright Notice
Copyright (c) 2020 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
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(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
1.1. Definitions of Terms Used in This Memo . . . . . . . . . 3
2. IPv6 Flow Specification encoding in BGP . . . . . . . . . . . 3
3. IPv6 Flow Specification components . . . . . . . . . . . . . 4
3.1. Type 1 - Destination IPv6 Prefix . . . . . . . . . . . . 4
3.2. Type 2 - Source IPv6 Prefix . . . . . . . . . . . . . . . 4
3.3. Type 3 - Next Header . . . . . . . . . . . . . . . . . . 4
3.4. Type 7 - ICMPv6 type . . . . . . . . . . . . . . . . . . 5
3.5. Type 8 - ICMPv6 code . . . . . . . . . . . . . . . . . . 5
3.6. Type 12 - Fragment . . . . . . . . . . . . . . . . . . . 5
3.7. Type 13 - Flow Label (new) . . . . . . . . . . . . . . . 6
3.8. Encoding Example . . . . . . . . . . . . . . . . . . . . 6
4. Ordering of Flow Specifications . . . . . . . . . . . . . . . 8
5. Validation Procedure . . . . . . . . . . . . . . . . . . . . 8
6. IPv6 Traffic Filtering Action changes . . . . . . . . . . . . 8
6.1. Redirect IPv6 (rt-redirect-ipv6) Type/Sub-Type 0x80/TBD . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix A. Example python code: flow_rule_cmp_v6 . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
The growing amount of IPv6 traffic in private and public networks
requires the extension of tools used in the IPv4 only networks to be
also capable of supporting IPv6 data packets.
In this document authors analyze the differences of IPv6 [RFC8200]
flows description from those of traditional IPv4 packets and propose
subset of new encoding formats to enable Dissemination of Flow
Specification Rules [I-D.ietf-idr-rfc5575bis] for IPv6.
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This specification should be treated as an extension of base
[I-D.ietf-idr-rfc5575bis] specification and not its replacement. It
only defines the delta changes required to support IPv6 while all
other definitions and operation mechanisms of Dissemination of Flow
Specification Rules will remain in the main specification and will
not be repeated here.
1.1. Definitions of Terms Used in This Memo
AFI - Address Family Identifier.
AS - Autonomous System.
NLRI - Network Layer Reachability Information.
SAFI - Subsequent Address Family Identifier.
VRF - Virtual Routing and Forwarding instance.
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.
2. IPv6 Flow Specification encoding in BGP
The [I-D.ietf-idr-rfc5575bis] defines new SAFIs 133 (Dissemination of
Flow Specification) and 134 (L3VPN Dissemination of Flow
Specification) applications in order to carry corresponding to each
such application Flow Specification.
Implementations wishing to exchange IPv6 Flow Specifications MUST use
BGP's Capability Advertisement facility to exchange the Multiprotocol
Extension Capability Code (Code 1) as defined in [RFC4760]. While
[I-D.ietf-idr-rfc5575bis] specifies Flow Specification for IPv4
(AFI=1) only, the (AFI, SAFI) pair carried in the Multiprotocol
Extension Capability MUST be: (AFI=2, SAFI=133) for IPv6 Flow
Specification, and (AFI=2, SAFI=134) for VPNv6 Flow Specification.
For both SAFIs the indication to which address family they are
referring to will be recognized by AFI value (AFI=1 for IPv4 or
VPNv4, AFI=2 for IPv6 and VPNv6 respectively).
It needs to be observed that such choice of proposed encoding is
compatible with filter validation against routing reachability
information as described in Section 6 of [I-D.ietf-idr-rfc5575bis].
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3. IPv6 Flow Specification components
The following components are redefined or added for the purpose of
accommodating the IPv6 header encoding. Unless otherwise specified
all other components defined in [I-D.ietf-idr-rfc5575bis]
Section 4.2.2 also apply to IPv6 Flow Specification.
3.1. Type 1 - Destination IPv6 Prefix
Encoding: <type (1 octet), length (1 octet), offset (1 octet), prefix
(variable)>
Defines the destination prefix to match. The offset has been defined
to allow for flexible matching on part of the IPv6 address where it
is required to skip (don't care) of N first bits of the address.
This can be especially useful where part of the IPv6 address consists
of an embedded IPv4 address and matching needs to happen only on the
embedded IPv4 address. The encoded prefix contains enough octets for
the bits used in matching (length minus offset bits).
3.2. Type 2 - Source IPv6 Prefix
Encoding: <type (1 octet), length (1 octet), offset (1 octet), prefix
(variable)>
Defines the source prefix to match. The length, offset and prefix
are the same as in Section 3.1
3.3. Type 3 - Next Header
Encoding: <type (1 octet), [numeric_op, value]+>
Contains a list of {numeric_op, value} pairs that are used to match
the last Next Header ([RFC8200] Section 3) value octet in IPv6
packets.
This component uses the Numeric Operator (numeric_op) described in
[I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 3 component values
SHOULD be encoded as single byte (numeric_op len=00).
Note: While IPv6 allows for more then one Next Header field in the
packet the main goal of Type 3 flow specification component is to
match on the subsequent IP protocol value. Therefore the definition
is limited to match only on last Next Header field in the packet.
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3.4. Type 7 - ICMPv6 type
Encoding: <type (1 octet), [numeric_op, value]+>
Defines a list of {numeric_op, value} pairs used to match the type
field of an ICMPv6 packet (see also [RFC4443] Section 2.1).
This component uses the Numeric Operator (numeric_op) described in
[I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 7 component values
SHOULD be encoded as single byte (numeric_op len=00).
In case of the presence of the ICMPv6 type component only ICMPv6
packets can match the entire Flow Specification. The ICMPv6 type
component, if present, never matches when the packet's last Next
Header field value is not 58 (ICMPv6), if the packet is fragmented
and this is not the first fragment, or if the system is unable to
locate the transport header. Different implementations may or may
not be able to decode the transport header.
3.5. Type 8 - ICMPv6 code
Encoding: <type (1 octet), [numeric_op, value]+>
Defines a list of {numeric_op, value} pairs used to match the code
field of an ICMPv6 packet (see also [RFC4443] Section 2.1).
This component uses the Numeric Operator (numeric_op) described in
[I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 8 component values
SHOULD be encoded as single byte (numeric_op len=00).
In case of the presence of the ICMPv6 code component only ICMPv6
packets can match the entire Flow Specification. The ICMPv6 code
component, if present, never matches when the packet's last Next
Header field value is not 58 (ICMPv6), if the packet is fragmented
and this is not the first fragment, or if the system is unable to
locate the transport header. Different implementations may or may
not be able to decode the transport header.
3.6. Type 12 - Fragment
Encoding: <type (1 octet), [bitmask_op, bitmask]+>
Defines a list of {bitmask_op, bitmask} pairs used to match specific
IP fragments.
This component uses the Bitmask Operator (bitmask_op) described in
[I-D.ietf-idr-rfc5575bis] Section 4.2.1.2. The Type 12 component
bitmask MUST be encoded as single byte bitmask (bitmask_op len=00).
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0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 0 | 0 | 0 | 0 |LF |FF |IsF| 0 |
+---+---+---+---+---+---+---+---+
Figure 1: Fragment Bitmask Operand
Bitmask values:
IsF - Is a fragment - match if IPv6 Fragment Header ([RFC8200]
Section 4.5) Fragment Offset is not 0
FF - First fragment - match if IPv6 Fragment Header ([RFC8200]
Section 4.5) Fragment Offset is 0 AND M flag is 1
LF - Last fragment - match if IPv6 Fragment Header ([RFC8200]
Section 4.5) Fragment Offset is not 0 AND M flag is 0
0 - MUST be set to 0 on NLRI encoding, and MUST be ignored during
decoding
3.7. Type 13 - Flow Label (new)
Encoding: <type (1 octet), [numeric_op, value]+>
Contains a list of {numeric_op, value} pairs that are used to match
the 20-bit Flow Label IPv6 header field ([RFC8200] Section 3).
This component uses the Numeric Operator (numeric_op) described in
[I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 13 component values
SHOULD be encoded as 1-, 2-, or 4-byte quantities (numeric_op len=00,
len=01 or len=10).
3.8. Encoding Example
3.8.1. Example 1
The following example demonstrates the prefix encoding for: "all
packets to ::1234:5678:9A00:0/64-104 from 100::/8 and port 25".
+--------+-------------------------+-------------+----------+
| length | destination | source | port |
+--------+-------------------------+-------------+----------+
| 0x0f | 01 68 40 12 34 56 78 9A | 02 08 00 01 | 04 81 19 |
+--------+-------------------------+-------------+----------+
Decoded:
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+-------+------------+------------------------------+
| Value | | |
+-------+------------+------------------------------+
| 0x0f | length | 16 octets (len<240 1-octet) |
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
| 0x68 | length | 104 bit |
| 0x40 | offset | 64 bit |
| 0x12 | prefix | |
| 0x34 | prefix | |
| 0x56 | prefix | |
| 0x78 | prefix | |
| 0x9A | prefix | |
| 0x02 | type | Type 2 - Source IPv6 Prefix |
| 0x08 | length | 8 bit |
| 0x00 | offset | 0 bit |
| 0x01 | prefix | |
| 0x04 | type | Type 4 - Port |
| 0x81 | numeric_op | end-of-list, value size=1, = |
| 0x19 | value | 25 |
+-------+------------+------------------------------+
This constitutes a NLRI with a NLRI length of 16 octets.
3.8.2. Example 2
The following example demonstrates the prefix encoding for: "all
packets to ::1234:5678:9A00:0/65-104".
+--------+-------------------------+
| length | destination |
+--------+-------------------------+
| 0x08 | 01 68 41 24 68 ac f1 34 |
+--------+-------------------------+
Decoded:
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+-------+------------+------------------------------+
| Value | | |
+-------+------------+------------------------------+
| 0x08 | length | 8 octets (len<240 1-octet) |
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
| 0x68 | length | 104 bit |
| 0x41 | offset | 65 bit |
| 0x24 | prefix | starting with the 66ths bit |
| 0x68 | prefix | |
| 0xac | prefix | |
| 0xf1 | prefix | |
| 0x34 | prefix | |
+-------+------------+------------------------------+
This constitutes a NLRI with a NLRI length of 8 octets.
4. Ordering of Flow Specifications
The definition for the order of traffic filtering rules from
[I-D.ietf-idr-rfc5575bis] Section 5.1 can be reused with new
consideration for the IPv6 prefix offset. As long as the offsets are
equal, the comparison is the same, retaining longest-prefix-match
semantics. If the offsets are not equal, the lowest offset has
precedence, as this flow matches the most significant bit.
The code in Appendix A shows a Python3 implementation of the
resulting comparison algorithm. The full code was tested with Python
3.7.2 and can be obtained at https://github.com/stoffi92/draft-ietf-
idr-flow-spec-v6/tree/master/flowspec-cmp [1].
5. Validation Procedure
The validation procedure is the same as specified in
[I-D.ietf-idr-rfc5575bis] Section 6 with the exception that item a)
of the validation procedure should now read as follows:
a) A destination prefix component with offset=0 is embedded in the
Flow Specification
6. IPv6 Traffic Filtering Action changes
Traffic Filtering Actions from [I-D.ietf-idr-rfc5575bis] Section 7
can also be applied to IPv6 Flow Specifications. To allow an IPv6
address specific route-target, a new Traffic Filtering Action IPv6
address specific extended community is specified in Section 6.1
below:
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6.1. Redirect IPv6 (rt-redirect-ipv6) Type/Sub-Type 0x80/TBD
The redirect IPv6 address specific extended community allows the
traffic to be redirected to a VRF routing instance that lists the
specified IPv6 address specific route-target in its import policy.
If several local instances match this criteria, the choice between
them is a local matter (for example, the instance with the lowest
Route Distinguisher value can be elected).
This extended community uses the same encoding as the IPv6 address
specific Route Target extended community [RFC5701] Section 2 with the
high-order octet of the Type always set to 0x80 and the Sub-Type
always TBD.
Interferes with: All BGP Flow Specification redirect Traffic
Filtering Actions (with itself and those specified in
[I-D.ietf-idr-rfc5575bis] Section 7.4).
7. Security Considerations
No new security issues are introduced to the BGP protocol by this
specification over the security considerations in
[I-D.ietf-idr-rfc5575bis]
8. IANA Considerations
This section complies with [RFC7153]
IANA is requested to create and maintain a new registry entitled:
"Flow Spec IPv6 Component Types" containing the initial entries as
specified in Table 1.
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+-------+-------------------------+-----------------+
| Value | Name | Reference |
+-------+-------------------------+-----------------+
| 1 | Destination IPv6 Prefix | [this document] |
| 2 | Source IPv6 Prefix | [this document] |
| 3 | Next Header | [this document] |
| 4 | Port | [this document] |
| 5 | Destination port | [this document] |
| 6 | Source port | [this document] |
| 7 | ICMPv6 type | [this document] |
| 8 | ICMPv6 code | [this document] |
| 9 | TCP flags | [this document] |
| 10 | Packet length | [this document] |
| 11 | DSCP | [this document] |
| 12 | Fragment | [this document] |
| 13 | Flow Label | [this document] |
+-------+-------------------------+-----------------+
Table 1: Registry: Flow Spec IPv6 Component Types
In order to manage the limited number space and accommodate several
usages, the following policies defined by [RFC8126] are used:
+--------------+------------------------+
| Type Values | Policy |
+--------------+------------------------+
| 0 | Reserved |
| [1 .. 127] | Specification Required |
| [128 .. 254] | Expert Review |
| 255 | Reserved |
+--------------+------------------------+
Table 2: Flow Spec IPv6 Component Types Registration Policy
Guidance for Experts:
128-254 requires Expert Review as the registration policy. The
Experts are expected to check the clarity of purpose and use of
the requested code points. The Experts must also verify that
any specification produced in the IETF that requests one of
these code points has been made available for review by the IDR
working group and that any specification produced outside the
IETF does not conflict with work that is active or already
published within the IETF. It must be pointed out that
introducing new component types may break existing
implementations of this protocol. Unused and available for
assignment via documented procedures.
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IANA maintains a registry entitled "Generic Transitive Experimental
Use Extended Community Sub-Types". For the purpose of this work,
IANA is requested to assign a new value:
+------------+----------------------------------------+-------------+
| Sub-Type | Name | Reference |
| Value | | |
+------------+----------------------------------------+-------------+
| TBD | Flow spec rt-redirect-ipv6 | [this |
| | format | document] |
+------------+----------------------------------------+-------------+
Table 3: Registry: Generic Transitive Experimental Use Extended
Community Sub-Types
9. Acknowledgements
Authors would like to thank Pedro Marques, Hannes Gredler and Bruno
Rijsman, Brian Carpenter, and Thomas Mangin for their valuable input.
10. Contributors
Danny McPherson
Verisign, Inc.
Email: dmcpherson@verisign.com
Burjiz Pithawala
Individual
Email: burjizp@gmail.com
Andy Karch
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: akarch@cisco.com
11. References
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11.1. Normative References
[I-D.ietf-idr-rfc5575bis]
Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
draft-ietf-idr-rfc5575bis-25 (work in progress), May 2020.
[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>.
[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>.
[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>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[RFC5701] Rekhter, Y., "IPv6 Address Specific BGP Extended Community
Attribute", RFC 5701, DOI 10.17487/RFC5701, November 2009,
<https://www.rfc-editor.org/info/rfc5701>.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP
Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
March 2014, <https://www.rfc-editor.org/info/rfc7153>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
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[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>.
11.2. URIs
[1] https://github.com/stoffi92/draft-ietf-idr-flow-spec-
v6/tree/master/flowspec-cmp
Appendix A. Example python code: flow_rule_cmp_v6
<CODE BEGINS>
"""
Copyright (c) 2020 IETF Trust and the persons identified as authors
of draft-ietf-idr-flow-spec-v6. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
"""
import itertools
import collections
import ipaddress
EQUAL = 0
A_HAS_PRECEDENCE = 1
B_HAS_PRECEDENCE = 2
IP_DESTINATION = 1
IP_SOURCE = 2
FS_component = collections.namedtuple('FS_component',
'component_type value')
class FS_IPv6_prefix_component:
def __init__(self, prefix, offset=0,
component_type=IP_DESTINATION):
self.offset = offset
self.component_type = component_type
# make sure if offset != 0 that non of the
# first offset bits are set in the prefix
self.value = prefix
if offset != 0:
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i = ipaddress.IPv6Interface(
(self.value.network_address, offset))
if i.network.network_address != \
ipaddress.ip_address('0::0'):
raise ValueError('Bits set in the offset')
class FS_nlri(object):
"""
FS_nlri class implementation that allows sorting.
By calling .sort() on a array of FS_nlri objects these
will be sorted according to the flow_rule_cmp algorithm.
Example:
nlri = [ FS_nlri(components=[
FS_component(component_type=4,
value=bytearray([0,1,2,3,4,5,6])),
]),
FS_nlri(components=[
FS_component(component_type=5,
value=bytearray([0,1,2,3,4,5,6])),
FS_component(component_type=6,
value=bytearray([0,1,2,3,4,5,6])),
]),
]
nlri.sort() # sorts the array accorinding to the algorithm
"""
def __init__(self, components = None):
"""
components: list of type FS_component
"""
self.components = components
def __lt__(self, other):
# use the below algorithm for sorting
result = flow_rule_cmp_v6(self, other)
if result == B_HAS_PRECEDENCE:
return True
else:
return False
def flow_rule_cmp_v6(a, b):
"""
Implementation of the flowspec sorting algorithm in
draft-ietf-idr-flow-spec-v6.
"""
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for comp_a, comp_b in itertools.zip_longest(a.components,
b.components):
# If a component type does not exist in one rule
# this rule has lower precedence
if not comp_a:
return B_HAS_PRECEDENCE
if not comp_b:
return A_HAS_PRECEDENCE
# Higher precedence for lower component type
if comp_a.component_type < comp_b.component_type:
return A_HAS_PRECEDENCE
if comp_a.component_type > comp_b.component_type:
return B_HAS_PRECEDENCE
# component types are equal -> type specific comparison
if comp_a.component_type in (IP_DESTINATION, IP_SOURCE):
if comp_a.offset < comp_b.offset:
return A_HAS_PRECEDENCE
if comp_a.offset < comp_b.offset:
return B_HAS_PRECEDENCE
# both components have the same offset
# assuming comp_a.value, comp_b.value of type
# ipaddress.IPv6Network
# and the offset bits are reset to 0 (since they are
# not represented in the NLRI)
if comp_a.value.overlaps(comp_b.value):
# longest prefixlen has precedence
if comp_a.value.prefixlen > \
comp_b.value.prefixlen:
return A_HAS_PRECEDENCE
if comp_a.value.prefixlen < \
comp_b.value.prefixlen:
return B_HAS_PRECEDENCE
# components equal -> continue with next
# component
elif comp_a.value > comp_b.value:
return B_HAS_PRECEDENCE
elif comp_a.value < comp_b.value:
return A_HAS_PRECEDENCE
else:
# assuming comp_a.value, comp_b.value of type
# bytearray
if len(comp_a.value) == len(comp_b.value):
if comp_a.value > comp_b.value:
return B_HAS_PRECEDENCE
if comp_a.value < comp_b.value:
return A_HAS_PRECEDENCE
# components equal -> continue with next
# component
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Internet-Draft IPv6 Flow Specification July 2020
else:
common = min(len(comp_a.value),
len(comp_b.value))
if comp_a.value[:common] > \
comp_b.value[:common]:
return B_HAS_PRECEDENCE
elif comp_a.value[:common] < \
comp_b.value[:common]:
return A_HAS_PRECEDENCE
# the first common bytes match
elif len(comp_a.value) > len(comp_b.value):
return A_HAS_PRECEDENCE
else:
return B_HAS_PRECEDENCE
return EQUAL
<CODE ENDS>
Authors' Addresses
Christoph Loibl (editor)
next layer Telekom GmbH
Mariahilfer Guertel 37/7
Vienna 1150
AT
Phone: +43 664 1176414
Email: cl@tix.at
Robert Raszuk (editor)
Bloomberg LP
731 Lexington Ave
New York City, NY 10022
USA
Email: robert@raszuk.net
Susan Hares (editor)
Huawei
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
Loibl, et al. Expires January 11, 2021 [Page 16]