BGP FlowSpec Extensions for Routing Policy Distribution (RPD)
draft-li-idr-flowspec-rpd-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Zhenbin Li , Liang Ou , Yujia Luo , Sujian Lu , Huaimo Chen , Shunwan Zhuang , Nan Wu | ||
| Last updated | 2018-10-22 | ||
| Replaced by | draft-ietf-idr-rpd | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Call For Adoption By WG Issued | |
| Document shepherd | (None) | ||
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| Send notices to | (None) |
draft-li-idr-flowspec-rpd-03
Network Working Group Z. Li
Internet-Draft Huawei
Intended status: Standards Track L. Ou
Expires: April 25, 2019 Y. Luo
China Telcom Co., Ltd.
S. Lu
Tencent
H. Chen
S. Zhuang
N. Wu
Huawei
October 22, 2018
BGP FlowSpec Extensions for Routing Policy Distribution (RPD)
draft-li-idr-flowspec-rpd-03
Abstract
This document describes a mechanism to use BGP Flowspec address
family as routing-policy distribution protocol. This mechanism is
called BGP FlowSpec Extensions for Routing Policy Distribution (BGP-
FS RPD).
Requirements Language
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].
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 April 25, 2019.
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Copyright Notice
Copyright (c) 2018 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/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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3
3. Problem Statements . . . . . . . . . . . . . . . . . . . . . 4
3.1. Inbound Traffic Control . . . . . . . . . . . . . . . . . 4
3.2. Outbound Traffic Control . . . . . . . . . . . . . . . . 5
4. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 6
5. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 6
5.1. Traffic Actions for Routing Policy Distribution . . . . . 7
5.2. Option 1: BGP Policy Attribute . . . . . . . . . . . . . 7
5.2.1. Match Fields . . . . . . . . . . . . . . . . . . . . 8
5.2.2. Action Fields . . . . . . . . . . . . . . . . . . . . 13
5.2.3. Application Examples . . . . . . . . . . . . . . . . 15
5.3. Option 2: BGP Wide Community . . . . . . . . . . . . . . 19
5.3.1. New Wide Community Atoms . . . . . . . . . . . . . . 20
5.3.2. New Wide Community Actions . . . . . . . . . . . . . 26
5.3.3. Application Examples . . . . . . . . . . . . . . . . 27
5.4. Capability Negotiation . . . . . . . . . . . . . . . . . 34
6. Consideration . . . . . . . . . . . . . . . . . . . . . . . . 34
6.1. Route-Policy . . . . . . . . . . . . . . . . . . . . . . 34
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 35
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
9. Security Considerations . . . . . . . . . . . . . . . . . . . 36
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1. Normative References . . . . . . . . . . . . . . . . . . 36
11.2. Informative References . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
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1. Introduction
It is difficult to optimize traffic paths on a traditional IP network
because of:
o Heavy configuration and error prone. Traffic can only be adjusted
device by device. All routers that the traffic traverses need to
be configured. The configuration workload is heavy. The
operation is not only time consuming but also prone to
misconfiguration for Service Providers.
o Complex. The routing policies used to control network routes are
complex, posing difficulties to subsequent maintenance, high
maintenance skills are required.
It is desirable to have an automatic mechanism for setting up routing
policies, which can simplify the routing policies configuration.
This document describes extensions to BGP for Routing Policy
Distribution.
2. Definitions and Acronyms
BGP Flow Specification route: BGP Flow Specification routes are
defined in RFC 5575. Each BGP Flow Specification route contains BGP
Network Layer Reachability Information (NLRI) and Extended Community
Attributes, which carry traffic filtering rules and actions to be
taken on filtered traffic.
BGP Flow Specification peer relationship: A BGP Flow Specification
peer relationship is established between the device that generates
BGP Flow Specification routes and each network ingress that will
transmit the BGP Flow Specification routes. After receiving the BGP
Flow Specification routes, the peer delivers preferred BGP Flow
Specification routes to the forwarding plane. The routes are then
converted into traffic policies that control attack traffic.
o ACL:Access Control List
o BGP: Border Gateway Protocol
o FS: Flow Specification
o PBR:Policy-Based Routing
o RPD: Routing Policy Distribution
o VPN: Virtual Private Network
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3. Problem Statements
It is obvious that providers have the requirements to adjust their
business traffic from time to time because:
o Business development or network failure introduces link congestion
and overload.
o Network transmission quality is decreased as the result of delay,
loss and they need to adjust traffic to other paths.
o To control OPEX and CPEX, prefer the transit provider with lower
price.
3.1. Inbound Traffic Control
In the scenario below, for the reasons above, the provider of AS100
saying P may wish the inbound traffic from AS200 enters AS100 through
link L3 instead of the others. Since P doesn't have any
administration over AS200, so there is no way for P to modify the
route selection criteria directly.
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Traffic from PE1 to Prefix1
----------------------------------->
+-----------------+ +-------------------------+
| +---------+ | L1 | +----+ +----------+|
| |Speaker1 | +------------+ |IGW1| |policy ||
| +---------+ |** L2**| +----+ |controller||
| | ** ** | +----------+|
| +---+ | **** | |
| |PE1| | **** | |
| +---+ | ** ** | |
| +---------+ |** L3**| +----+ |
| |Speaker2 | +------------+ |IGW2| AS100 |
| +---------+ | L4 | +----+ |
| | | |
| AS200 | | |
| | | ... |
| | | |
| +---------+ | | +----+ +-------+ |
| |Speakern | | | |IGWn| |Prefix1| |
| +---------+ | | +----+ +-------+ |
+-----------------+ +-------------------------+
Prefix1 advertised from AS100 to AS200
<----------------------------------------
Inbound Traffic Control case
3.2. Outbound Traffic Control
In the scenario below, the provider of AS100 saying P prefers link L3
for the traffic to the destination Prefix2 among multiple exits and
links. This preference can be dynamic and changed frequently because
of the reasons above. So the provider P expects an efficient and
convenient solution.
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Traffic from PE2 to Prefix2
----------------------------------->
+-------------------------+ +-----------------+
|+----------+ +----+ |L1 | +---------+ |
||policy | |IGW1| +------------+ |Speaker1 | |
||controller| +----+ |** **| +---------+ |
|+----------+ |L2** ** | +-------+|
| | **** | |Prefix2||
| | **** | +-------+|
| |L3** ** | |
| AS100 +----+ |** **| +---------+ |
| |IGW2| +------------+ |Speaker2 | |
| +----+ |L4 | +---------+ |
| | | |
|+---+ | | AS200 |
||PE2| ... | | |
|+---+ | | |
| +----+ | | +---------+ |
| |IGWn| | | |Speakern | |
| +----+ | | +---------+ |
+-------------------------+ +-----------------+
Prefix2 advertised from AS200 to AS100
<----------------------------------------
Outbound Traffic Control case
4. Proposed Solution
BGP FlowSpec [RFC5575] leverages the BGP control plane to simplify
the distribution of filter rules. New filter rules can be injected
to all BGP peers simultaneously without changing router
configuration. Its typical application is for DDOS mitigation.
This document introduces a mechanism that uses BGP Flowspec as a
routing policy distribution protocol. It can be as powerful as the
device-based routing policy while still has the efficiency and
convenience of BGP Flowspec.
This draft will use the term BGP-FS RPD (or BGP RPD for short) as the
abbreviation of BGP Extensions for Routing Policy Distribution.
5. Protocol Extensions
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5.1. Traffic Actions for Routing Policy Distribution
The traffic-action extended community consists of 6 bytes of which
only the 2 least significant bits of the 6th byte (from left to
right) are currently defined in [RFC5575]: Terminal Action (bit 47)
and Sample (bit 46). This document defines Routing Policy
Distribution (RPD, or R for short) Flag (Bit 45). The 6th byte with
this newly defined flag is illustrated below:
40 41 42 43 44 45 46 47
+---+---+---+---+---+---+---+---+
| reserved | R | S | T |
+---+---+---+---+---+---+---+---+
Traffic-action with RPD (R) flag
RPD (R) Flag (Bit 45): When this bit is set, the corresponding
filtering rules will be used as Routing Policy.
5.2. Option 1: BGP Policy Attribute
This document defines and uses a new BGP attribute called the "BGP
Policy attribute". This is an optional BGP attribute. The format of
this attribute is defined as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attr Flag |Attr Type(TBD) | Attr Length ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Match fields (Variable) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Action fields (Variable) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of BGP Policy Attribute
Match fields: Match Fields define the matching criteria for the BGP
Policy Attribute.
Action fields: Action fields define the action being applied to the
target route.
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5.2.1. Match Fields
Match Fields define the matching criteria for the BGP Policy
Attribute. It has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Match Type (2 octets) | Length (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-TLVs (Variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Match Fields Format
Match Type:
1: Permit, specifies the permit mode of a match rule. If a route
matches the matching criteria of the BGP Policy Attribute, the
actions defined by the Action fields of the BGP Policy Attribute are
performed. If a route does not match the matching criteria for the
BGP Policy Attribute, then nothing needs to be done with this route.
2: Deny, specifies the deny mode of a match rule. In the deny mode,
If a route does not match the matching criteria of the BGP Policy
Attribute, the actions defined by the Action fields of the BGP Policy
Attribute are performed. If a route matches the matching criteria of
the BGP Policy Attribute, then nothing needs to be done with this
route.
Length: The total length of the Sub-TLVs in the Match fields.
The contents of Match fields are encoded as Sub-TLVs, where each Sub-
TLV has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (2 octets) | Length (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Values (Variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-TLV Format
Type: The Type field contains a value of 1-65534. The values 0 and
65535 are reserved for future use.
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Length: The Length field represents the total length of a given TLV's
value field in octets.
Values: The Value field contains the TLV value.
The following TLVs are defined:
Type TBD1: BGP IPv4 Session (or IPv4 Session for short), whose TLV
contains the IPv4 local address/speaker and remote address/speaker of
a BGP session. Its TLV (or Sub-TLV) format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD1) | Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of IPv4 Session TLV
Type TBD2: BGP IPv6 Session (or IPv6 Session for short), whose TLV
contains the IPv6 local address/speaker and remote address/speaker of
a BGP session. Its TLV (or Sub-TLV) format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD2) | Length (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Local IPv6 Address (16 Bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Remote IPv6 Address (16 Bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of IPv6 Session TLV
Type TBD3: IPv4 Prefix Range, which represents a range of IPv4
prefixes. Its format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD3) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of IPv4 Prefix Range TLV
The IPv4 Prefix Range TLV (or Sub-TLV) contains a number of triple
<IPv4 Address, MaskLen, LeMaskLen>s. Each triple <IPv4 Address,
MaskLen, LeMaskLen> represents an IPv4 prefix range from IPv4-
Address/MaskLen to IPv4-Address/LeMaskLen. For example, triple
<10.10.0.0, 16, 16> represents prefixes 10.10.0.0/16 (i.e., from
10.10.0.0/16 to 10.10.0.0/16). Triple <20.20.15.0, 20, 24>
represents prefixes from 20.20.15.0/20 to 20.20.15.0/24.
The encoding of IPv4 Prefix Range may be optimized to the following
compact format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD3) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv4 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv4 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Compact Format of IPv4 Prefix Range TLV
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It contains a number of triple <MaskLen, LeMaskLen, IPv4 Prefix>s.
Each triple <MaskLen, LeMaskLen, IPv4 Prefix> represents an IPv4
prefix range from IPv4-Prefix/MaskLen to IPv4-Prefix/LeMaskLen.
LeMaskLen is the length of the prefix. For example, triple <16, 16,
10.10.0.0> represents prefixes 10.10.0.0/16 (i.e., from 10.10.0.0/16
to 10.10.0.0/16). Triple <20, 24, 20.20.15.0> represents prefixes
from 20.20.15.0/20 to 20.20.15.0/24.
Similarly, Type TBD4: IPv6 Prefix Range represents a range of IPv6
prefixes. Its format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD4) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 Address (16 Bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 Address (16 Bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of IPv6 Prefix Range TLV
The encoding of IPv6 Prefix Range may be optimized to the following
compact format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD4) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv6 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv6 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Compact Format of IPv6 Prefix Range TLV
Type TBD5: AS Path, which represents a sequence of AS numbers. For
an AS number occurs multiple times in a row in a path, it is
represented by the AS number and a count indicating the times that
the AS number occurs. Its format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD5) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count1 |
+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Countn |
+-+-+-+-+-+-+-+-+
Format of AS Path TLV
For example, AS Path "123456, 6553603, 6553603, 6553603" is
represented by AS1 = 123456, Count1 = 1, AS2 = 6553603, and Count2 =
3.
Type TBD6: Communities, which represents a list of communities
values. Its format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD6) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community 1 Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . . ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community n Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Communities TLV
5.2.2. Action Fields
Action fields define the action being applied to the targeted route.
It has the following format.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action Type (2 octets) | Length (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Action Values (Variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Action Fields Format
Action Type: The Action Type field contains a value of 1-65534. The
values 0 and 65535 are reserved for future use.
Action Length: The Action Length field represents the total length of
the Action Values in octets.
Action Values: The Action Values field contain parameters of the
action.
Supported format of the TLVs can be:
Type TBD7: Add AS Path, which indicates to add the sequence of AS
numbers represented in the TLV to AS Path. Its TLV (or Sub-TLV)
format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD7) | Length (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count1 |
+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Countn |
+-+-+-+-+-+-+-+-+
Format of Add AS Path TLV
When OP = 1, the sequence of AS numbers are added in the end of the
existing AS Path. When OP = 2, the sequence of AS numbers are added
in the front of the existing AS Path.
Type TBD8: Change Med, which indicates to change the Med according to
OP. Its TLV (or Sub-TLV) format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD8) | Length (5) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Change Med TLV
When OP = 1, assign the Value to the existing Med. When OP = 2, add
the Value to the existing Med. If the sum of them is greater than
the maximum value for Med, assign the maximum value to Med. When OP
= 3, subtract the Value from the existing Med. If the existing Med
minus the Value is less than 0, assign 0 to Med.
Type TBD9: Deny, which indicates Deny action. Its TLV (or Sub-TLV)
format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD9) | Length (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom Deny
5.2.3. Application Examples
5.2.3.1. Change Attributes
Multiple attributes of a route may be changed when it matches given
matching criteria. In the example below, the policy has the
following matching criteria:
o match 20.20.15.0/20 to 20.20.15.0/24
o match as-path 6553601 6553601
The actions to be applied are add 12345 to the existing MED and add
AS sequence 123456, 6553602, 6553602 to the end of existing AS Path.
These actions are listed as follows:
o apply MED = MED + 12345
o apply add as-path 123456, 6553602, 6553602
The corresponding BGP Policy Attribute Encoding for these is
illustrated below.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MatchType: 1 | Length: 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PrefxRange:TBD3 | Length: 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags (0) | MaskLen: 20 | LeMaskLen: 24 |IPv4 Prefix:20.|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|20.15 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Path: TBD5 | Length: 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP: 1 | AS 6553601 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS-Contiue | Count 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ActionType: 3 | Length: 24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Change MED: TBD8 | Length: 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP: 2 | Value: 12345 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Value-Contiue |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Add AS Path: TBD7 | Length: 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP: 1 | AS 123456 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS-Contiue | Count 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS 6553602 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count 2 |
+-+-+-+-+-+-+-+-+
Example BGP Policy Attribute Encoding for Change Attributes
5.2.3.2. Inbound Traffic Control
The traffic destined for Prefix1 needs to be scheduled to link
Speaker1 -> IGW2 for transmission.
The Policy Controller constructs a BGP-FS RPD route and pushes it to
all the IGW routers, the route carries:
1. Prefix1 in the Destination Prefix component of the BGP-FS NLRI;
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2. Flow Specification Traffic Action Extended Community with the
Routing Policy Distribution (R) Flag (Bit 45) set. When this bit
is set, the corresponding filtering rules will be used as Routing
Policies.
3. NO_ADVERTISE Community [RFC1997]
4. BGP Policy Attribute:
* Match Type: 2, Deny
* IPv4 Session Sub-TLV: Local BGP Speaker IGW2, Remote BGP Peer
Speaker1
* Action Type: Route-Prepend-AS
* Action Value: Prepend-AS times is 5
IGW1 processes the received BGP-FS RPD route as follows:
1. IGW1 gets the target prefix Prefix1 from the Destination Prefix
component in the BGP FS NLRI of the BGP FS RPD route;
2. IGW1 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW1 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW1 uses the target prefix Prefix1 to choose the matching
routes, in this case, IGW1 will choose the current best route of
Prefix1;
4. IGW1 gets the matching criteria from the BGP Policy Attribute:
Local BGP Speaker IGW2, Remote BGP Speaker1;
5. IGW1 gets the action from the BGP Policy Attribute: Route-
Prepend-AS, 5 times;
IGW1 checks the matching criteria and finds that it doesn't hits the
matching criteria: Local BGP Speaker IGW2, Remote BGP Speaker1, at
the same time the Match Type is "Deny" mode, so IGW1 sends the best
route of Prefix1 to Speaker1 and Speaker2 with performing the Action
instructions from the BGP-FS RPD route: Prepend Local AS 5 times.
IGW2 processes the received BGP FS RPD route as follows:
1. IGW2 gets the target prefix Prefix1 from the Destination Prefix
component in the BGP-FS NLRI of the BGP FS RPD route;
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2. IGW2 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW2 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW2 uses the target prefix Prefix1 to choose the matching
routes, in this case, IGW2 will choose the current best route of
Prefix1;
4. IGW2 gets the matching criteria from the BGP Policy Attribute:
Local BGP Speaker IGW2, Remote BGP Speaker1;
5. IGW2 gets the action from the BGP Policy Attribute: Route-
Prepend-AS, 5 times;
IGW2 checks the matching criteria and finds that there is a speaker
which hits the matching criteria: Local BGP Speaker IGW2, Remote BGP
Peer Speaker1, but the Match Type is "Deny" mode, so IGW2 sends the
best route of Prefix1 to Speaker1, without performing the Action
instructions from the BGP-FS RPD route. At the same time, IGW2 sends
the best route of Prefix1 to Speaker2 with performing the Action
instructions from the BGP-FS RPD route: Prepend Local AS 5 times.
In the similar manner, other IGWs will perform the same Action
instructions as IGW1. Then the traffic destined for Prefix1 has been
be scheduled to link L3 for transmission.
5.2.3.3. Outbound Traffic Control
In this scenario, if the bandwidth usage of a link exceeds the
specified threshold, the Policy Controller automatically identifies
which traffic needs to be scheduled and the Policy Controller
automatically calculates traffic control paths based on network
topology and traffic information.
For example, the outbound traffic destined for Prefix2 needs to be
scheduled to link IGW2 -> Speaker1 for transmission.
The Policy Controller sends a BGP-FS RPD route to IGW2, the route
carries:
1. Prefix2 in the Destination Prefix component of the BGP-FS NLRI;
2. Flow Specification Traffic Action Extended Community with the
Routing Policy Distribution (R) Flag (Bit 45) set. When this bit
is set, the corresponding filtering rules will be used as Routing
Policies.
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3. NO_ADVERTISE Community [RFC1997]
4. BGP Policy Attribute:
* Match Type: 1, Permit
* IPv4 Session Sub-TLV: Local BGP Speaker IGW2, Remote BGP Peer
Speaker1
* Action Type: Route-Preference
* Action Value: none
IGW2 processes the received BGP FS RPD route as follows:
1. IGW2 gets the target prefix Prefix2 from the Destination Prefix
component in the BGP-FS NLRI of the BGP FS RPD route;
2. IGW2 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW2 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW2 uses the target prefix Prefix2 to choose the matching
routes, in this case, the prefix Prefix2 has two more routes:
Prefix Next-Hop Local BGP Speaker Remote BGP Peer
Prefix2 Speaker1 IGW2 Speaker1
Prefix2 Speaker2 IGW2 Speaker2
...
4. IGW2 gets the matching criteria from the BGP Policy Attribute:
Local BGP Speaker IGW2, Remote BGP Peer Speaker1;
5. IGW2 gets the action from the BGP Policy Attribute: Route-
Preference;
So IGW2 chooses the BGP route received from Speaker1 instead of
Speaker2 as the best route and the outbound traffic destined for
Prefix2 can be scheduled to link L3 for transmission.
5.3. Option 2: BGP Wide Community
The BGP wide community is defined in
[I-D.ietf-idr-wide-bgp-communities]. It can be used to facilitate
the delivery of new network services, and be extended easily for
distributing different kinds of routing policies.
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This section describes an alternative extension to BGP protocol,
which extends the BGP wide community for distributing routing
policies. A few of new wide community atoms and new actions are
defined below.
5.3.1. New Wide Community Atoms
A wide community Atom is a TLV (or sub-TLV), which may be included in
a BGP wide community container (or BGP wide community for short).
The format of the TLV (or sub-TLV) and 8 wide community Atoms are
defined in [I-D.ietf-idr-wide-bgp-communities]. 3 new wide community
Atoms will be defined in this document. For your reference, the
format of the TLV is illustrated below:
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
+-+-+-+-+-+-+-+-+
| Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Wide Community Atom TLV
Some of the existing 8 wide community Atoms (from Type 1 to 8) and 9
new wide community Atoms (from TBD1 to TBD9) are listed as follows:
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+------+---------------------------------------------------------+
| Type | Description |
+------+---------------------------------------------------------+
| 1 | Autonomous System Number List |
| 2 | IPv4 Prefix (1 octet prefix length + prefix) List |
| . | . |
| : | : |
| 8 | UTF-8 String |
| TBD1 | BGP IPv4 Session (local address and remote address) |
| TBD2 | BGP IPv6 Session (local address and remote address) |
| TBD3 | IPv4 Prefix Range |
| TBD4 | IPv6 Prefix Range |
| TBD5 | AS Path |
| TBD6 | Communities |
| TBD7 | Add AS-Path |
| TBD8 | Change MED |
| TBD9 | Deny |
+------+---------------------------------------------------------+
Existing and New Wide Community Atoms
The wide community Atom BGP IPv4 Session contains the IPv4 local
address and remote address of a BGP session. Its format is
illustrated below:
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
+-+-+-+-+-+-+-+-+
| Type (TBD1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom BGP IPv4 Session
The wide community Atom BGP IPv6 Session contains the IPv6 local
address and remote address of a BGP session. Its format is
illustrated below:
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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
+-+-+-+-+-+-+-+-+
| Type (TBD2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Local IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Remote IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom BGP IPv6 Session
The wide community Atom IPv4 Prefix Range represents a range of IPv4
prefixes. Its format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD3) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom IPv4 Prefix Range
It contains a number of triple <IPv4 Address, MaskLen, LeMaskLen>s.
Each triple <IPv4 Address, MaskLen, LeMaskLen> represents an IPv4
prefix range from IPv4-Address/MaskLen to IPv4-Address/LeMaskLen.
For example, triple <10.10.0.0, 16, 16> represents prefixes
10.10.0.0/16 (i.e., from 10.10.0.0/16 to 10.10.0.0/16). Triple
<20.20.15.0, 20, 24> represents prefixes from 20.20.15.0/20 to
20.20.15.0/24. Note that MaskLen must be less than or equal to
LeMaskLen except for LeMaskLen = 0, in this case, triple
<IPv4-Address, MaskLen, 0> represents prefix IPv4-Address/MaskLen.
The encoding of Atom IPv4 Prefix Range may be optimized as the format
below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD3) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv4 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv4 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Compact Format of Atom IPv4 Prefix Range
It contains a number of triple <MaskLen, LeMaskLen, IPv4 Prefix>s.
Each triple <MaskLen, LeMaskLen, IPv4 Prefix> represents an IPv4
prefix range from IPv4-Prefix/MaskLen to IPv4-Prefix/LeMaskLen.
LeMaskLen is the length of the prefix. For example, triple <16, 16,
10.10.0.0> represents prefixes 10.10.0.0/16 (i.e., from 10.10.0.0/16
to 10.10.0.0/16). Triple <20, 24, 20.20.15.0> represents prefixes
from 20.20.15.0/20 to 20.20.15.0/24
Similarly, the wide community Atom IPv6 Prefix Range represents a
range of IPv6 prefixes. Its format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD4) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 Address (16 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom IPv6 Prefix Range
The encoding of Atom IPv6 Prefix Range may be optimized as the format
below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD4) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv6 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen | LeMaskLen | IPv6 Prefix ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Compact Format of Atom IPv6 Prefix Range
The wide community Atom AS Path represents a sequence of AS numbers.
For an AS number occurs multiple times in a row in a path, it is
represented by the AS number and a count indicating the times that
the AS number occurs. Its format is illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD5) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count1 |
+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Countn |
+-+-+-+-+-+-+-+-+
Format of Atom AS Path
For example, AS Path "123456, 6553603, 6553603, 6553603" is
represented by AS1 = 123456, Count1 = 1, AS2 = 6553603, and Count2 =
3.
The wide community Atom Communities represents a list of communities
values. Its format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD6) | Length (Variable) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community 1 Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ . . . ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community n Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom Communities
The wide community Atom Add AS Path indicates to add the sequence of
AS numbers represented in the Atom to AS Path. Its format is
illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD7) | Length (Variable) | OP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count1 |
+-+-+-+-+-+-+-+-+
~ . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Countn |
+-+-+-+-+-+-+-+-+
Format of Atom Add AS Path
When OP = 1, the sequence of AS numbers are added in the end of the
existing AS Path. When OP = 2, the sequence of AS numbers are added
in the front of the existing AS Path.
The wide community Atom Change Med indicates to change the Med
according to OP. Its format is illustrated below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD8) | Length (5) | OP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom Change Med
When OP = 1, assign the Value to the existing Med. When OP = 2, add
the Value to the existing Med. If the sum of them is greater than
the maximum value for Med, assign the maximum value to Med. When OP
= 3, subtract the Value from the existing Med. If the existing Med
minus the Value is less than 0, assign 0 to Med.
The wide community Atom Deny indicates Deny action. Its format is
illustrated below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD9) | Length (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Format of Atom Deny
5.3.2. New Wide Community Actions
A Registered Wide BGP Community Value may indicate an action. For
example, value 17 indicates "PREPEND N TIMES BY AS" as defined in
draft [I-D.ietf-idr-registered-wide-bgp-communities]. 2 new values
for actions are defined in this document. Some of the existing
values (from 1 to 24) and the two new values are listed below:
+-------+-------------------------------------------------------+
| Value | Description |
+-------+-------------------------------------------------------+
| 1 | BLACKHOLE |
| 2 | SOURCE FILTER |
| . | . |
| : | : |
| 24 | FREE POOL |
| TBD11 | change attributes |
| TBD12 | no advertise |
+-------+-------------------------------------------------------+
Existing and New Wide Communities Values
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When action "change attributes" is used, multiple attributes can be
changed. The parameters and operations for the action are
represented by the Atoms related to the operations. These Atoms are
included in a BGP Wide Community Parameter(s) TLV. The Atoms may be
"Add AS-Path" and "Change MED".
5.3.3. Application Examples
5.3.3.1. Change Attributes
Multiple attributes of a route may be changed when it matches given
criteria. In the example below, the policy has the following
matching criteria:
o match 20.20.15.0/20 to 20.20.15.0/24
o match as-path 6553601 6553601
The actions to be applied are add 12345 to the existing MED and add
AS sequence 123456, 6553602, 6553602, 6553602, 6553602 to the end of
existing AS Path. These actions are listed as follows:
o apply MED = MED + 12345
o apply add as-path 123456, 6553602, 6553602, 6553602, 6553602
The corresponding BGP Wide Community Encoding for these is
illustrated below.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Container Type: 1 |Flags |0|1| Reserved(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length: 71 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community: Change Attributes TBD11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AS 64496 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Context AS 64496 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target TLV: 1 | Length: 18 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PrefxRange:TBD3| Length: 6 | Flags (0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaskLen: 20 | LeMaskLen: 24 |IPv4 Prefix: 20.20. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|.15 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Path: TBD5 | Length: 6 | OP: 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS 6553601 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ExcTargetTLV: 2| Length: 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Param TLV: 3| Length: 32 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ChangeMED: TBD8| Length: 5 | OP: 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value: 12345 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|AddASPath: TBD7| Length: 11 | OP: 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS 123456 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS 6553602 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count 4 |
+-+-+-+-+-+-+-+-+
Example BGP Wide Community Encoding for Change Attributes
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5.3.3.2. Inbound Traffic Control
As required in the case, traffic from PE1 to Prefix1 need to enter
through L3, so IGWs except IGW2 should prepend ASN list to Prefix1
when populating to AS100. As shown in figure below, community
"PREPEND N TIMES BY AS" and "Exclude Target(s) TLV" are be used.
The encoding example using BGP Wide Community:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Container Type: 1 |Flags |0|1| Reserved(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length: 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community: PREPEND N TIMES BY AS 17 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AS 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Context AS 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ExcTargetTLV: 2| Length: 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|IPv4Sess: TBD1 | Length: 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Address/Speaker #IGW2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Address/Speaker #Speaker1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Param TLV: 3 | Length: 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Integer: 4 | Length: 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prepend # 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Example encoding for Inbound Traffic Control case
"PREPEND N TIMES BY AS" Wide Community has been defined in
[I-D.ietf-idr-registered-wide-bgp-communities].
The traffic destined for Prefix1 needs to be scheduled to link
Speaker1 -> IGW2 for transmission.
The Policy Controller constructs a BGP RPD route and pushes it to all
the IGW routers, the route carries:
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1. Prefix1 in the Destination Prefix component of the BGP-FS NLRI;
2. Flow Specification Traffic Action Extended Community with the
Routing Policy Distribution (R) Flag (Bit 45) set. When this bit
is set, the corresponding filtering rules will be used as Routing
Policies.
3. NO_ADVERTISE Community [RFC1997]
4. Wide BGP Community Attribute:
PREPEND N TIMES BY AS:
Type: 0x0001 S = src AS #
F = 0x80 C = 0x00000000
H = 0 T = none
L = 36 octets E = Type_TBD (BGP IPv4 session)
R = 17 P = Type_4 (0x05)
Where "BGP IPv4 session" Atom TLV contains:
The BGP session IPv4 local address: Local BGP Speaker IGW2
The BGP session IPv4 peer address: Remote BGP Peer Speaker1
IGW1 processes the received BGP-FS RPD route as follows:
1. IGW1 gets the target prefix Prefix1 from the Destination Prefix
component in the BGP FS NLRI of the BGP FS RPD route;
2. IGW1 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW1 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW1 uses the target prefix Prefix1 to choose the matching
routes, in this case, IGW1 will choose the current best route of
Prefix1;
4. IGW1 gets the action type from the Wide BGP Community Attribute:
PREPEND N TIMES BY AS;
5. IGW1 gets the matching criteria from the Wide BGP Community
Attribute: Exclude the BGP IPv4 session: <Local BGP Speaker IGW2,
Remote BGP Speaker1>;
6. IGW1 gets the parameter for "PREPEND N TIMES BY AS" from the Wide
BGP Community Attribute: 5 times;
IGW1 checks the matching criteria and finds that it doesn't hits the
exclude matching criteria: Local BGP Speaker IGW2, Remote BGP
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Speaker1, so IGW1 sends the best route of Prefix1 to Speaker1 and
Speaker2 with performing the Action instructions from the BGP-FS RPD
route: Prepend Local AS 5 times.
IGW2 processes the received BGP FS RPD route as follows:
1. IGW2 gets the target prefix Prefix1 from the Destination Prefix
component in the BGP-FS NLRI of the BGP FS RPD route;
2. IGW2 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW2 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW2 uses the target prefix Prefix1 to choose the matching
routes, in this case, IGW2 will choose the current best route of
Prefix1;
4. IGW2 gets the action type from the Wide BGP Community Attribute:
PREPEND N TIMES BY AS;
5. IGW2 gets the matching criteria from the BGP Policy Attribute:
Exclude the BGP IPv4 session: <Local BGP Speaker IGW2, Remote BGP
Speaker1>;
6. IGW2 gets the parameter for "PREPEND N TIMES BY AS" from the Wide
BGP Community Attribute: 5 times;
IGW2 checks the matching criteria and finds that there is a speaker
which hits the exclude matching criteria: Local BGP Speaker IGW2,
Remote BGP Peer Speaker1, so IGW2 sends the best route of Prefix1 to
Speaker1 without performing the Action instructions from the BGP-FS
RPD route, at the same time, IGW2 sends the best route of Prefix1 to
Speaker2 with performing the Action instructions from the BGP-FS RPD
route: Prepend Local AS 5 times.
In the similar manner, other IGWs will perform the same Action
instructions as IGW1. Then the traffic destined for Prefix1 has been
be scheduled to link L3 for transmission.
5.3.3.3. Outbound Traffic Control
As required in the case, traffic from PE2 to Prefix2 need to exit
through L3, so IGWs should prefer the route from IGW2 to Speaker1.
As shown in figure below, community "LOCAL PREFERENCE" and "Target(s)
TLV" are be used.
The encoding example using BGP Wide Community:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Container Type: 1 |Flags |0|1| Reserved(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length: 36 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Community: LOCAL PREFERENCE 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source AS 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Context AS 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TargetTLV: 1 | Length: 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4Sess:TBD1| Length: 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Address/Speaker #IGW2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Address/Speaker #Speaker1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Param TLV: 3 | Length: 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Integer: 4 | Length: 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Increment # 100 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Example encoding for Outbound Traffic Control case
"LOCAL PREFERENCE" Wide Community has been defined in
[I-D.ietf-idr-registered-wide-bgp-communities].
In this scenario, if the bandwidth usage of a link exceeds the
specified threshold, the Policy Controller automatically identifies
which traffic needs to be scheduled and the Policy Controller
automatically calculates traffic control paths based on network
topology and traffic information.
For example, the outbound traffic destined for Prefix2 needs to be
scheduled to link IGW2 -> Speaker1 for transmission.
The Policy Controller sends a BGP-FS RPD route to IGW2, the route
carries:
1. Prefix2 in the Destination Prefix component of the BGP-FS NLRI;
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2. Flow Specification Traffic Action Extended Community with the RPD
(R) Flag (Bit 45) set. When this bit is set, the corresponding
filtering rules will be used as Routing Policies.
3. NO_ADVERTISE Community [RFC1997]
4. Wide BGP Community Attribute:
LOCAL PREFERENCE:
Type: 0x0001 S = src AS #
F = 0x80 C = 0x00000000
H = 0 T = Type_TBD (BGP IPv4 session)
L = 36 octets E = none
R = 20 P = Type_4 (0x64)
Where "BGP IPv4 session" Atom TLV contains:
The BGP session IPv4 local address: Local BGP Speaker IGW2
The BGP session IPv4 peer address: Remote BGP Peer Speaker1
IGW2 processes the received BGP FS RPD route as follows:
1. IGW2 gets the target prefix Prefix2 from the Destination Prefix
component in the BGP-FS NLRI of the BGP FS RPD route;
2. IGW2 identifies the Routing Policy Distribution (R) Flag carrying
in the Flow Specification Traffic Action Extended Community, then
IGW2 knows that the corresponding filtering rules will be used as
Routing Policies.
3. IGW2 uses the target prefix Prefix2 to choose the matching
routes, in this case, the prefix Prefix2 has two more routes:
Prefix Next-Hop Local BGP Speaker Remote BGP Peer
--------------------------------------------------------
Prefix2 Speaker1 IGW2 Speaker1
Prefix2 Speaker2 IGW2 Speaker2
...
4. IGW2 gets the action type from the Wide BGP Community Attribute:
LOCAL PREFERENCE;
5. IGW2 gets the matching criteria from the Wide BGP Community
Attribute: Local BGP Speaker IGW2, Remote BGP Peer Speaker1;
6. IGW2 gets the parameter for "LOCAL PREFERENCE" from the Wide BGP
Community Attribute: increment 100;
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So IGW2 chooses the BGP route received from Speaker1 instead of
Speaker2 as the best route and the outbound traffic destined for
Prefix2 can be scheduled to link L3 for transmission.
5.4. Capability Negotiation
It is necessary to negotiate the capability to support BGP Extensions
for Routing Policy Distribution (RPD). The BGP RPD Capability is a
new BGP capability [RFC5492]. The Capability Code for this
capability is to be specified by the IANA. The Capability Length
field of this capability is variable. The Capability Value field
consists of one or more of the following tuples:
+--------------------------------------------------+
| Address Family Identifier (2 octets) |
+--------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
+--------------------------------------------------+
| Send/Receive (1 octet) |
+--------------------------------------------------+
BGP RPD Capability
The meaning and use of the fields are as follows:
Address Family Identifier (AFI): This field is the same as the one
used in [RFC4760].
Subsequent Address Family Identifier (SAFI): This field is the same
as the one used in [RFC4760].
Send/Receive: This field indicates whether the sender is (a) willing
to receive Routing Policies from its peer (value 1), (b) would like
to send Routing Policies to its peer (value 2), or (c) both (value 3)
for the <AFI, SAFI>.
6. Consideration
6.1. Route-Policy
Routing policies are used to filter routes and control how routes are
received and advertised. If route attributes, such as reachability,
are changed, the path along which network traffic passes changes
accordingly.
When advertising, receiving, and importing routes, the router
implements certain policies based on actual networking requirements
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to filter routes and change the attributes of the routes. Routing
policies serve the following purposes:
o Control route advertising: Only routes that match the rules
specified in a policy are advertised.
o Control route receiving: Only the required and valid routes are
received. This reduces the size of the routing table and improves
network security.
o Filter and control imported routes: A routing protocol may import
routes discovered by other routing protocols. Only routes that
satisfy certain conditions are imported to meet the requirements
of the protocol.
o Modify attributes of specified routes Attributes of the routes:
that are filtered by a routing policy are modified to meet the
requirements of the local device.
o Configure fast reroute (FRR): If a backup next hop and a backup
outbound interface are configured for the routes that match a
routing policy, IP FRR, VPN FRR, and IP+VPN FRR can be
implemented.
Routing policies are implemented using the following procedures:
1. Define rules: Define features of routes to which routing policies
are applied. Users define a set of matching rules based on
different attributes of routes, such as the destination address
and the address of the router that advertises the routes.
2. Implement the rules: Apply the matching rules to routing policies
for advertising, receiving, and importing routes.
7. Contributors
The following people have substantially contributed to the definition
of the BGP-FS RPD and to the editing of this document:
Peng Zhou
Huawei
Email: Jewpon.zhou@huawei.com
8. IANA Considerations
TBD.
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9. Security Considerations
TBD.
10. Acknowledgements
The authors would like to thank Acee Lindem, Jeff Haas, Jie Dong,
Haibo Wang, Lucy Yong, Qiandeng Liang, Zhenqiang Li for their
comments to this work.
11. References
11.1. Normative References
[I-D.ietf-idr-wide-bgp-communities]
Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S.,
and P. Jakma, "BGP Community Container Attribute", draft-
ietf-idr-wide-bgp-communities-05 (work in progress), July
2018.
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<https://www.rfc-editor.org/info/rfc1997>.
[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>.
[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>.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
2009, <https://www.rfc-editor.org/info/rfc5492>.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
<https://www.rfc-editor.org/info/rfc5575>.
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11.2. Informative References
[I-D.ietf-idr-registered-wide-bgp-communities]
Raszuk, R. and J. Haas, "Registered Wide BGP Community
Values", draft-ietf-idr-registered-wide-bgp-communities-02
(work in progress), May 2016.
Authors' Addresses
Zhenbin Li
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Liang Ou
China Telcom Co., Ltd.
109 West Zhongshan Ave,Tianhe District
Guangzhou 510630
China
Email: oul@gsta.com
Yujia Luo
China Telcom Co., Ltd.
109 West Zhongshan Ave,Tianhe District
Guangzhou 510630
China
Email: luoyuj@gsta.com
Sujian Lu
Tencent
Tengyun Building,Tower A ,No. 397 Tianlin Road
Shanghai, Xuhui District 200233
China
Email: jasonlu@tencent.com
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Huaimo Chen
Huawei
Boston, MA
USA
Email: Huaimo.chen@huawei.com
Shunwan Zhuang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: zhuangshunwan@huawei.com
Nan Wu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: eric.wu@huawei.com
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