Network Working Group F. Xu
Internet-Draft Tencent
Intended status: Standards Track Y. Gu
Expires: January 8, 2020 S. Zhuang
Z. Li
Huawei
July 7, 2019
BGP Route Policy and Attribute Trace Using BMP
draft-xu-grow-bmp-route-policy-attr-trace-01
Abstract
The generation of BGP adj-rib-in, local-rib or adj-rib-out comes from
BGP protocol communication, and route policy processing. BGP
Monitoring Protocol (BMP) provides the monitoring of BGP adj-rib-in
[RFC7854], BGP local-rib [I-D.ietf-grow-bmp-local-rib] and BGP adj-
rib-out [I-D.ietf-grow-bmp-adj-rib-out]. However, there lacks
monitoring of how BGP routes are transformed from adj-rib-in into
local-rib and then adj-rib-out (i.e., the BGP route policy processing
procedures). This document describes a method of using BMP to trace
the change of BGP routes in correlation with responsible route
policies.
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 January 8, 2020.
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Copyright Notice
Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. BGP Route Policy and Attribute Trace Overview . . . . . . 3
1.2. Use cases . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extension of BMP for Route Policy and Attribute Trace . . . . 4
2.1. Common Header . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Per Peer Header . . . . . . . . . . . . . . . . . . . . . 4
2.3. Route Policy and Attribute Trace Message . . . . . . . . 4
2.3.1. VRF/Table Name TLV . . . . . . . . . . . . . . . . . 8
2.3.2. Pre Policy Attribute TLV . . . . . . . . . . . . . . 9
2.3.3. Post Policy Attribute TLV . . . . . . . . . . . . . . 9
2.3.4. Policy ID TLV . . . . . . . . . . . . . . . . . . . . 10
2.3.5. Optional TLV . . . . . . . . . . . . . . . . . . . . 11
3. Implementation Considerations . . . . . . . . . . . . . . . . 12
4. Implementation Example . . . . . . . . . . . . . . . . . . . 12
4.1. Route Distribution Tracking . . . . . . . . . . . . . . . 12
4.2. Route Leak Detection . . . . . . . . . . . . . . . . . . 16
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8. Normative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
The typical processing procedure after receiving a BGP Update Message
at a routing device is as follows: 1. Adding the pre-policy routes
into the pre-policy adj-rib-in (if any); 2. Filtering the pre-policy
routes through inbound route policies; 3. Selecting the BGP best
routes from the post-policy routes; 4. Adding the selected routes
into the BGP local-rib; 5-a. Adding the BGP best routes from local-
rib to the core routing table manager for selection; 5-b. Filtering
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the routes from BGP local-rib through outbound route policies w.r.t.
per peer or peer groups; 6. Sending the BGP adj-rib-out to the
target peer or peer groups. Details may vary by vendors. The BGP
Monitoring Protocol (BMP) can be utilized to monitor BGP routes in
forms of adj-rib-in, local-rib and adj-rib-out. However, the
complete procedure from inbound to outbound policy processing,
including other policies, e.g., route redistribution, route selection
and so on, is currently unobserved. For example, there are 10 policy
items (or nodes) configured under one outbound route policy per a
specific peer. By collecting the local-rib and adj-rib-out through
BMP, the operator finds that the outbound policy didn't work as
expected. However, it's hard to distinguish which one of the 10
policy items/nodes is responsible for the failure.
1.1. BGP Route Policy and Attribute Trace Overview
This document describes a method that records and reports how each
policy item/node processes the routes (e.g., changes the route
attribute). Each policy item/node processing is called an event
thereafter in this document. Compared with conventional BGP rib
entry, which consists of prefix/mask, route attributes, e.g., next
hop, MED, local preference, AS path, and so on, the event record
discussed in this document includes extra information, such as event
index, timestamp, policy information, and so on. For example, if a
route is processed by 5 policy items/nodes, there can be 5 event
records for the same prefix/mask. Each event is numbered in order of
time (e.g., the time of policy execution). The policy information
includes the policy name and item/node ID/name so that the server/
controller can map to the exact policy either directly from the
device or from the configurations collected at the server side.
This document defines a new BMP message type to carry the recorded
policy and route data. More detailed message format is defined in
Section 2. The message is called the BMP Route Policy and Attribute
Trace Message thereafter in this document.
1.2. Use cases
There are cases that a new policy is configured incorrectly, e.g.,
setting an incorrect community value, or policy placed in incorrect
order among other policies. These may result in incorrect route
attribute modification, best route selection mistake, or route
distribution mistake. With the correlated record of policy and
route, the server/controller is able to identify the unexpected route
change and its responsible policy. Considering the fact that the BGP
route policy impacts not only the route processing within the
individual device but also the route distribution to its peers, the
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route trace data of a single device is always analyzed in correlation
with such data collected from its peer devices.
Apart from the policy validation application, the route trace data
can also be analyzed to discover the route propagation path within
the network. With the route's inbound and outbound event records
collect from each related device, the server is able to find the
propagation path hop by hop. The identified path is helpful for
operators to better understand its network, and thus benefitting both
network troubleshooting and network planning.
2. Extension of BMP for Route Policy and Attribute Trace
2.1. Common Header
This document defines a new BMP message type to carry the Route
Policy and Attribute Trace data.
o Type = TBD: Route Policy and Attribute Trace Message
The new defined message type is indicated in the Message Type field
of the BMP common header.
2.2. Per Peer Header
The Route Policy and Attribute Trace Message is not per peer based,
thus it does not require the Per Peer Header.
2.3. Route Policy and Attribute Trace Message
The Route Policy and Attribute Trace Message format is defined as
follows:
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+---------------------------------------------------------------+
| Route Distinguisher |
+---------------------------------------------------------------+
| Prefix length |
+---------------------------------------------------------------+
| Prefix |
+---------------------------------------------------------------+
| Previous Hop Length |
+---------------------------------------------------------------+
| Previous Hop |
+---------------------------------------------------------------+
| Event count |
+---------------------------------------------------------------+
| Total event length |
+---------------------------------------------------------------+
| 1st Event |
+---------------------------------------------------------------+
| 2nd Event |
+---------------------------------------------------------------+
~ ~
+ ...... +
~ ~
+---------------------------------------------------------------+
| Last Event |
+---------------------------------------------------------------+
Figure 1: Route Policy and Attribute Trace Message format
o Route Distinguisher (8 Bytes): indicates the route distinguisher
(RD) related to the route.
o Prefix Length (1 Byte): indicates the length of the prefix.
o Prefix (Variable): indicates the monitored prefix, with the length
defined by Prefix Length field.
o Previous Hop Length (1 Byte): indicates the length of the
following Previous Hop field. If the BGP peer ID of previous hop
is IPv4, it is set to 4, and if the BGP peer ID of the previous
hop is an IPv6, it is set to 16.
o Previous Hop (Variable): indicates the BGP peer ID where this
route is learnt from. If the route is locally generated, then
field is zero filled.
o Event Count (1 Byte): indicates the total number of policy
processing event recorded in this message.
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o Total event length (2 Byte): indicates the total length of the
following fields including all events, where the total number is
indicated by the Event Count field.
o 1 ~ Last event: indicates each event, stacked one by one in order
of time. The event format is further defined as follows.
+---------------------------------------------------------------+
| Single event length |
+---------------------------------------------------------------+
| Event index |
+---------------------------------------------------------------+
| Timestamp(seconds) |
+---------------------------------------------------------------+
| Timestamp(microseconds) |
+---------------------------------------------------------------+
| Policy Classification |
+---------------------------------------------------------------+
| Peer ID |
+---------------------------------------------------------------+
| Peer AS |
+---------------------------------------------------------------+
| Path Identifier |
+---------------------------------------------------------------+
| Peer AFI |
+---------------------------------------------------------------+
| Peer SAFI |
+---------------------------------------------------------------+
| VRF/Table Name TLV |
+---------------------------------------------------------------+
| Pre Policy Attribute TLV |
+---------------------------------------------------------------+
| Post Policy Attribute TLV |
+---------------------------------------------------------------+
| Policy ID TLV |
+---------------------------------------------------------------+
| Optional TLV |
+---------------------------------------------------------------+
Figure 2: Event format
o Single event length (2 Byte): indicates the total length of a
single policy process event, including the following fields that
belong to this event.
o Event index (1 Byte): indicates the sequence number of this event,
staring from 1 and increases by 1 for each event recorded in
order.
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o Timestamp (8 Bytes): indicates the time when the policy of this
event starts execution, expressed in seconds and microseconds
since midnight (zero hour), January 1, 1970 (UTC).
o Peer ID (4 Bytes): indicates the BGP Peer ID where this policy is
configured under. This field is used in combination with the
Policy Direction field. If the Policy Direction field is set to
"0000", meaning Inbound policy, then this field is set to the BGP
Peer ID where the route is received from; if the Policy Direction
field is set to "0001", meaning Outbound policy, then this field
is set to the BGP Peer ID where the route is distributed to; If
the Policy Direction field is set to "0010", "0010","0100" meaning
Redistribution/Network/Aggregation policy, then this field is set
to all zeros.
o Peer AS (4 Bytes): indicates the AS number of the BGP Peer that
defined the Peer ID field.
o Policy Classification (1 Byte): indicates the category of the
policy. Currently 5 policy categories are defined: "0000"
indicating the Inbound policy, "0001" indicating the Outbound
policy, "0010" indicating the Redistribution policy (e.g., route
import from other sources, like ISIS/OSPF), "0011" indicates the
Route Leak policy (route leaking from the global routing table to
a VRF or from a VRF to the global routing table, or between VRFs),
"0100" indicates the Network policy (BGP network installment and
advertisement), "0101" indicating the Aggregation policy. More
categories can be defined.
o
+--------------------------------+
| Value |Policy Classification|
+--------------------------------+
| 00000000 | Inbound policy |
| 00000001 | Outbound policy |
| 00000010 | Redistribution |
| 00000011 | Route Leak |
| 00000100 | Network |
| 00000101 | Aggregation |
+----------+---------------------+
Table 1: Policy Classification
o Path Identifier (4 Bytes): used to distinguish multiple BGP paths
for the same prefix. If there's no path ID, this field is zero
filled.
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o Peer AFI (2 Bytes)/Peer SAFI (1 Byte): indicates the AFI/SAFI of
the route. The AFI/SAFI information varies for the same route
under different policy processing event. For example, an IPv4
Unicast route is received from a CE router at the PE router
through eBGP, an RD is attached to this IPv4 Unicast route and
making it a VPNv4 route, and then this VPNv4 route is distributed
to the RR. During this process, the AFI/SAFI information changes
from IPv4 Unicast (1/1) to VPNv4 (1/128) at the inbound policy and
outbound policy.
o VRF/Table Name TLV (Variable): indicates the VRF name or table
name of the route. The format of the VRF/Table Name TLV is
further defined in Figure 3. The VRF/Table Name TLV is non-
optional.
o Pre-policy Attribute TLV (Variable): include the BGP route
atttributes before the policy is executed. The format of the Pre-
policy Attribute TLV is further defined in Figure 4. The Pre-
policy Attribute TLV is optional.
o Post-policy Attribute TLV (Variable): include the BGP route
atttributes after the policy is executed. The format of the Post-
policy Attribute TLV is further defined in Figure 5. The Post-
policy Attribute TLV is optional.
o Policy ID TLV (Variable): indicates the ID of the route policy of
this event, which is user specific or vendor specific, which can
be used for mapping to the actual policy content. The policy
content data retrieval is out of the scope of this document. The
format of the Policy ID TLV is further defined in Figure 6. The
Policy ID TLV is optional.
o Optional TLV (Variable): leaves for future extension. The
Optioanl TLV is optional.
2.3.1. VRF/Table Name TLV
+-------------------------------+-------------------------------+
| Type = TBD1 | VRF/Table name length |
+-------------------------------+-------------------------------+
| VRF/Table name |
+---------------------------------------------------------------+
Figure 3: VRF/Table name TLV
o Type = TBD1 (2 Byte): indicates the type of VRF/Table name TLV.
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o VRF/Table name length (2 Byte): indicates the length of the VRF/
Table name field.
o VRF/Table name (Variable): indicates the VRF or table name of this
route in the format of ASCII string. The string size MUST be
within the range of 1 to 255 bytes. The VRF/Table name varies for
the same route under different events. For example, an IPv4
Unicast route is received from a CE router at the PE router
through iBGP, an RD is attached to this IPv4 route (under VRF A)
and making it a VPNv4 route, and then this VPNv4 route (under the
Global routing table) is distributed to the RR. During the whole
process, the VRF/Table name changes from VRF A to the Global
routing Table name at the inbound event and outbound event.
2.3.2. Pre Policy Attribute TLV
+-------------------------------+-------------------------------+
| Type = TBD2 | Pre Policy Attr. length |
+-------------------------------+-------------------------------+
| Pre Policy Attribute sub TLVs |
+---------------------------------------------------------------+
Figure 4: Pre Policy Attribute TLV
o Type = TBD2 (2 Byte): indicates the type of Pre Policy Attribute
TLV.
o Pre Policy Attribute length (2 Byte): indicates the total length
of the following Pre Policy Attribute sub TLVs.
o Pre Policy Attribute sub TLVs (Variable): include the BGP route
attributes before the policy is executed.
2.3.3. Post Policy Attribute TLV
+-------------------------------+-------------------------------+
| Type = TBD3 | Post Policy Attr. length |
+-------------------------------+-------------------------------+
| Post Policy Attribute sub TLVs |
+---------------------------------------------------------------+
Figure 5: Post Policy Attribute TLV
o Type = TBD3 (2 Byte): indicates the type of Pre Policy Attribute
TLV.
o Pre Policy Attribute length (2 Byte): indicates the total length
of the following Pre Policy Attribute sub TLVs.
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o Pre Policy Attribute sub TLVs (Variable): include the BGP route
attributes before the policy is executed.
2.3.4. Policy ID TLV
The Route Policy and Attribute Trace Message is not per peer based,
thus it does not require the Per Peer Header.
+------------------------+---------------------------+
| Type = TBD4 | Policy ID length |
+----------------------------------------------------+
|M| Res. | Policy Count |
+----------------------------------------------------+
| 1st Policy |C|R| Res. |
+----------------------------------------------------+
~ | ~
+ ... | ... +
~ | ~
+----------------------------------------------------+
| Last Policy |C|R| Res. |
+----------------------------------------------------+
Figure 6: Policy ID TLV
Considering the chaining and recursion of polices and policy items,
the Policy ID TLV is defined as follows.
o Type = TBD4 (2 Byte): indicates the type of Policy ID TLV.
o Policy ID length (2 Byte): indicates the length of the Policy ID
value field that follows it. The Policy ID value field includes
the Reserved bits, the Flag bits, Policy Count field, and Policy
field.
o Flag bit M (1 bit): indicates if the route in this event is
matched (once or multiple times) or not by any policies. "0" means
no match and "1" means elsewise. The remaining 7 bits are
reserved for future extension.
o Policy Count (1 Byte): indicates the number of policies (in the
format of Policy name + Item ID) carried in this event.
o 1st ~ Last Policy (Variable): indicates the Policy name and the
Item ID of each policy match.
o Flag bit C (1 bit): indicates if the next subsequent policy has
chaining relationship to the current policy. "1" means it's
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chaining relationship and "0" means elsewise. For the flag byte
following the Last Policy field, the C bit SHALL be set to "0".
o Flag bit R (1 bit): indicates if the next subsequent policy has
recursioning relationship to the current policy. "1" means it's
recursioning relationship and "0" means elsewise. For the flag
byte following the Last Policy field, the R bit SHALL be set to
"0".
+----------------------------------------+
| Policy Name length |
+----------------------------------------+
| Policy Name |
+----------------------------------------+
| Item ID length |
+----------------------------------------+
| Item ID |
+----------------------------------------+
Figure 7: Policy field format
The Policy ID field consists of the Route Policy Name and the Route
Policy Item ID. The Policy name and Item ID are in the format of
ASCII string, the length of both fields are indicated by the Policy
Name length (2 Bytes) and Item length (1 Byte) fields, respectively.
2.3.5. Optional TLV
+-------------------------------+-------------------------------+
| Type = TBD5 | Length |
+-------------------------------+-------------------------------+
| Value |
+---------------------------------------------------------------+
Figure 8: Optional TLV
The Optional TLV remains to be defined. One or more Optional TLV
types can be defined. One or more Optional TLVs can be used.
One possible way of utilizing the Optional TLV is to define a string
Type TLV. The String Type TLV allows flexible textual expression of
user-specific information without requiring structural format. Some
examples:
o The Policy ID TLV is defined as optional, considering that users
may don't want detailed information about the policy but only the
result and/or the reasons. Using a string type TLV, one may
express "Route rejected due to inbound filtering". However, such
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expression still requires the tracking of policy processing in
realtime, it's just another form of tracking representation to the
BMP server and the user.
o Another possible application is for route leak detection. One may
express the business relations as "P2C", "P2P" and so on, with the
inbound filtering event or the outbound filtering event. Detailed
usage is discussed in Section 4.2.
3. Implementation Considerations
Considering the data amount of monitoring the route and policy trace
of all routes from all BMP clients, users MAY trigger the monitoring
at any user-specific time. Users MAY configure locally at the BMP
client to monitor only user-specific routes or all the routes. In
addition, users MAY configure locally at the BMP client whether to
report the TLVs that are optional according to their own
requirements, i.e., the Pre Policy Attribute TLV, Post Policy
Attribute TLV, Policy ID TLV, and Optional TLV.
Successive recored events from one device MAY be encapsulated in one
Route Policy and Attribute Trace Message or multiple Route Policy and
Attribute Trace Messages per the user configuration.
4. Implementation Example
4.1. Route Distribution Tracking
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+----------+
+------>+BMP server+<-------+
| +--+-------+ |
+ ^ ^ |
Event 1,2,3 +-----+ | +
+ + + Event 9,10,11
| Event 4,5 Event 6,7,8 +
| + + |
| | | |
10.1.1.1/32 ****|****|**********|***********|*****
+---------> * | | | | AS0*
+-----+ * | | +--+--+ | *
| CE1 ++eBGP+ * | +--------->+ RR +------+ | *
+-----+ | * | | | ++----+ | | *
AS1 | * | | | ^ iBGP | | *
| * | | ++----+ | 65000:10 | | * 10.1.1.1/32
10.1.1.1/32 +----------> PE2 +---+10.1.1.1/32| | * +----------->
+---------> * | | +-----+ | | * +-----+
+-----+ * | | iBGP | | * +eBGP+>+ CE4 |
| CE2 ++eBGP+ * | | iBGP 65000:10 + | * | +-----+
+-----+ | * | +65000:10 10.1.1.1/32 | * | AS4
AS2 | * | 10.1.1.1/32 + | * |
| * ++----+ +--v-++ * |
+-----+ +-----> PE1 | | PE3 +------+ +-----+
| CE3 ++eBGP+-----> | | +------+eBGP+>+ CE5 |
+-----+ * +-----+ +-----+ * +-----+
10.1.1.1/32 * * 10.1.1.1/32
+--------> ************************************** +----------->
AS3 AS5
Figure 9: Route Policy and Attribute Trace record implementation example
We take the network shown in Figure 9 as an example to show how to
use Route Policy and Attribute Trace Messages to recover the
footprint of the route propagation. Notice that only basic events
required for footprint recovery are illustrated here. Also notice
that the event index shown in Figure 9, 10, 11 are for illustration
purpose, and may not reflect the actual indexing.
Suppose a prefix 10.1.1.1/32 is sent from both CE2 and CE3 to PE1
through eBGP peering, PE1 processes the two Update messages through
inbound policies. Such procedure is recorded as two events, namely
Event 1 and Event 2. Then PE1 selects the route from CE2 as the best
route, add it to VRF 1, and then distribute the VPNv4 route to RR.
The distribution procedure is recorded by PE1 as Event 3. As an
example, the Route Policy and Attribute Trace Message of Event 1, 2,
3 is listed as follows. Only fields related to footprint recovery
are listed in the message shown below. Specifically, the Previous
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Hop information is carried in Event 3 when outbounding the route,
indicating that the outbounded route is learnt from CE2. The same
prefix is sent from CE1 to PE2, added to VRF 1 and then distributed
to RR in the form of VPNv4 route. Two events, Event 4 (inbound) and
Event 5 (outbound) are recorded by PE2. Now for RR, prefix
10.1.1.1/32 is received from both PE1 and PE2 in the form of VPNv4
route. RR selects the route from PE1 as the best route, and
distribute it to PE3. Three events, Event 6 (PE2 inbound), Event 7
(PE1 inbound), Event 8 (PE3 outbound) are recorded in this case. PE3
receives the VPNv4 route from RR, adds it to VRF 1 and then
distribute the IPv4 route to CE4 and CE5, respectively. Here, three
events are recorded, Event 9 (RR inbound), Event 10 (CE4 outbound)
and Event 11 (CE5 outbound).
+---------------------------------------------------------------+
| RD: 65000:10 |
+---------------------------------------------------------------+
| Prefix: 10.1.1.1/32 |
+---------------------------------------------------------------+
| Previous hop: CE2 |
+---------------------------------------------------------------+
| Event count: 2 |
+---------------------------------------------------------------+
| Event 1 |
+---------------------------------------------------------------+
| Timestamp 1 |
+---------------------------------------------------------------+
| Inbound policy |
+---------------------------------------------------------------+
| Peer ID: CE2 |
+---------------------------------------------------------------+
| Peer AS: AS2 |
+---------------------------------------------------------------+
| Path ID: 0 |
+---------------------------------------------------------------+
| AFI/SAFI: IPv4 Unicast |
+---------------------------------------------------------------+
| VRF/Table name: VRF 1 |
+---------------------------------------------------------------+
| Pre Policy Attributes |
+---------------------------------------------------------------+
| Post Policy Attributes |
+---------------------------------------------------------------+
| Policy ID: WC1, node 101 |
+---------------------------------------------------------------+
| Event 3 |
+---------------------------------------------------------------+
| Timestamp 3 |
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+---------------------------------------------------------------+
| Outbound policy |
+---------------------------------------------------------------+
| Peer ID: RR |
+---------------------------------------------------------------+
| Peer AS: AS0 |
+---------------------------------------------------------------+
| Path ID: 0 |
+---------------------------------------------------------------+
| AFI/SAFI: VPNv4 |
+---------------------------------------------------------------+
| VRF/Table name: Global/Default |
+---------------------------------------------------------------+
| Pre Policy Attributes |
+---------------------------------------------------------------+
| Post Policy Attributes |
+---------------------------------------------------------------+
| Policy ID: RR1, node 200 |
+---------------------------------------------------------------+
Figure 10: Event 1,3 data view
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+---------------------------------------------------------------+
| RD: 65000:10 |
+---------------------------------------------------------------+
| Prefix: 10.1.1.1/32 |
+---------------------------------------------------------------+
| Previous hop: CE3 |
+---------------------------------------------------------------+
| Event count: 1 |
+---------------------------------------------------------------+
| Event 2 |
+---------------------------------------------------------------+
| Timestamp 2 |
+---------------------------------------------------------------+
| Inbound policy |
+---------------------------------------------------------------+
| Peer ID: CE3 |
+---------------------------------------------------------------+
| Peer AS: AS3 |
+---------------------------------------------------------------+
| Path ID: 0 |
+---------------------------------------------------------------+
| AFI/SAFI: IPv4 Unicast |
+---------------------------------------------------------------+
| VRF/Table name: VRF 1 |
+---------------------------------------------------------------+
| Pre Policy Attributes |
+---------------------------------------------------------------+
| Post Policy Attributes |
+---------------------------------------------------------------+
| Policy ID: WC1, node 102 |
+---------------------------------------------------------------+
Figure 11: Event 2 data view
The BMP server can use the collected events to recover the route
footprint. The key information required from recovery is the
Timestamp of each event, and the Previous Hop of the route. The
Timestamp allows the server to identify the order of each event,
while the Previous Hop information, combined with the outbound peer
information, allows the server to recover the route propagation hop
by hop.
4.2. Route Leak Detection
Reusing Figure 9, the Optional TLV of the RoFT Message can be
utilized to carry user-specific strings. We present a route leak
detection example here.
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Suppose, a route leak happens (10.1.1.1/32: AS2 --> AS0 --> AS4).
The Bussiness relationships between ASes are shown in Table 2.
+----------------+--------------+
| Neighbor ASes | Bussiness |
| | Relationship |
+-------------------------------+
| AS 1 : AS 0 | P2C |
+-------------------------------+
| AS 2 : AS 0 | P2C |
+-------------------------------+
| AS 3 : AS 0 | P2C |
+-------------------------------+
| AS 0 : AS 4 | C2P |
+-------------------------------+
| AS 0 : AS 5 | P2C |
+----------------+--------------+
Table 2: Bussiness Relationship
To detect the route leak, the BMP server analyzes the events with
bussiness relationship information reported from the ingress device
and egress device of AS0 (regarding a specific route)). In this
example, regarding 10.1.1.1/32, data from PC1 and PE3 are analized.
The bussiness relationship can be expressed in strings, such as "P2C"
or "P2P". At PE1, when 10.1.1.1/32 is received from CE2 and going
through the inbound policy, PE1 uses the Optional TLV (more
specifically the String Type TLV) to carry the text "Bussiness
Relationship: P2C" in the Inound Policy event. On the other hand, at
PE3, when 10.1.1.1/32 goes through the outbound policy and then sent
to CE4, PE3 adds the "Bussiness Relationship: P2C", using the
Optional TLV, in the Outbound Policy event. More specifically, the
format of the above mentioned two events are listed in Figure 12
(Event 1) and Figure 13 (Event 10), respecitvely.
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+---------------------------------------------------------------+
| RD: 65000:10 |
+---------------------------------------------------------------+
| Prefix: 10.1.1.1/32 |
+---------------------------------------------------------------+
| Previous hop: CE2 |
+---------------------------------------------------------------+
| Event count: 1 |
+---------------------------------------------------------------+
| Event 1 |
+---------------------------------------------------------------+
| Timestamp 1 |
+---------------------------------------------------------------+
| Inbound policy |
+---------------------------------------------------------------+
| Peer ID: CE2 |
+---------------------------------------------------------------+
| Peer AS: AS2 |
+---------------------------------------------------------------+
| Path ID: 0 |
+---------------------------------------------------------------+
| AFI/SAFI: IPv4 Unicast |
+---------------------------------------------------------------+
| VRF/Table name: VRF 1 |
+---------------------------------------------------------------+
| Pre Policy Attributes |
+---------------------------------------------------------------+
| Post Policy Attributes |
+---------------------------------------------------------------+
| Policy ID: WC1, node 101 |
+---------------------------------------------------------------+
| Optional TLV: "Bussiness Relationship: P2C" |
+---------------------------------------------------------------+
Figure 12: Event 1 data view
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+---------------------------------------------------------------+
| RD: 65000:10 |
+---------------------------------------------------------------+
| Prefix: 10.1.1.1/32 |
+---------------------------------------------------------------+
| Previous hop: RR |
+---------------------------------------------------------------+
| Event count: 1 |
+---------------------------------------------------------------+
| Event 10 |
+---------------------------------------------------------------+
| Timestamp 10 |
+---------------------------------------------------------------+
| Outbound policy |
+---------------------------------------------------------------+
| Peer ID: CE4 |
+---------------------------------------------------------------+
| Peer AS: AS4 |
+---------------------------------------------------------------+
| Path ID: 0 |
+---------------------------------------------------------------+
| AFI/SAFI: IPv4 Unicast |
+---------------------------------------------------------------+
| VRF/Table name: VRF 3 |
+---------------------------------------------------------------+
| Pre Policy Attributes |
+---------------------------------------------------------------+
| Post Policy Attributes |
+---------------------------------------------------------------+
| Policy ID: OB1, node 300 |
+---------------------------------------------------------------+
| Optional TLV: "Bussiness Relationship: C2P" |
+---------------------------------------------------------------+
Figure 13: Event 10 data view
The BMP server can use the two Optional TLVs from Event 1 and Event
10 to detect the route leak. What's more, the repsonsible
configurations are directly shown in the two events, i.e., the
Inbound policy at PE1: "Policy ID: WC1, node 101", the Outbound
policy at PE3: "Policy ID: OB1, node 300". No need to correlate with
other data sources, the user can detect the leak and figure out the
root cause.
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5. Acknowledgements
TBD.
6. IANA Considerations
TBD.
7. Security Considerations
TBD.
8. Normative References
[I-D.ietf-grow-bmp-adj-rib-out]
Evens, T., Bayraktar, S., Lucente, P., Mi, K., and S.
Zhuang, "Support for Adj-RIB-Out in BGP Monitoring
Protocol (BMP)", draft-ietf-grow-bmp-adj-rib-out-06 (work
in progress), June 2019.
[I-D.ietf-grow-bmp-local-rib]
Evens, T., Bayraktar, S., Bhardwaj, M., and P. Lucente,
"Support for Local RIB in BGP Monitoring Protocol (BMP)",
draft-ietf-grow-bmp-local-rib-04 (work in progress), June
2019.
[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>.
[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>.
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/info/rfc7854>.
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Authors' Addresses
Feng Xu
Tencent
Guangzhou
China
Email: oliverxu@tencent.com
Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: guyunan@huawei.com
Shunwan Zhuang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: zhuangshunwan@huawei.com
Zhenbin Li
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
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