Global Routing Operations T. Evens
Internet-Draft S. Bayraktar
Updates: 7854 (if approved) M. Bhardwaj
Intended status: Standards Track Cisco Systems
Expires: August 27, 2018 P. Lucente
NTT Communications
February 23, 2018
Support for Local RIB in BGP Monitoring Protocol (BMP)
draft-ietf-grow-bmp-local-rib-01
Abstract
The BGP Monitoring Protocol (BMP) defines access to the Adj-RIB-In
and locally originated routes (e.g. routes distributed into BGP from
protocols such as static) but not access to the BGP instance Loc-RIB.
This document updates the BGP Monitoring Protocol (BMP) RFC 7854 by
adding access to the BGP instance Local-RIB, as defined in RFC 4271
the routes that have been selected by the local BGP speaker's
Decision Process. These are the routes over all peers, locally
originated, and after best-path selection.
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
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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 August 27, 2018.
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Current Method to Monitor Loc-RIB . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Per-Peer Header . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Peer Flags . . . . . . . . . . . . . . . . . . . . . . . 8
5. Loc-RIB Monitoring . . . . . . . . . . . . . . . . . . . . . 9
5.1. Per-Peer Header . . . . . . . . . . . . . . . . . . . . . 9
5.2. Peer UP Notification . . . . . . . . . . . . . . . . . . 9
5.2.1. Peer UP Information . . . . . . . . . . . . . . . . . 10
5.3. Peer Down Notification . . . . . . . . . . . . . . . . . 10
5.4. Route Monitoring . . . . . . . . . . . . . . . . . . . . 10
5.4.1. ASN Encoding . . . . . . . . . . . . . . . . . . . . 11
5.4.2. Granularity . . . . . . . . . . . . . . . . . . . . . 11
5.5. Route Mirroring . . . . . . . . . . . . . . . . . . . . . 11
5.6. Statistics Report . . . . . . . . . . . . . . . . . . . . 11
6. Other Considerations . . . . . . . . . . . . . . . . . . . . 11
6.1. Loc-RIB Implementation . . . . . . . . . . . . . . . . . 11
6.1.1. Multiple Loc-RIB Peers . . . . . . . . . . . . . . . 12
6.1.2. Filtering Loc-RIB to BMP Receivers . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8.1. BMP Peer Type . . . . . . . . . . . . . . . . . . . . . . 12
8.2. BMP Peer Flags . . . . . . . . . . . . . . . . . . . . . 13
8.3. Peer UP Information TLV . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . 13
9.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
The BGP Monitoring Protocol (BMP) suggests that locally originated
routes are locally sourced routes, such as redistributed or otherwise
added routes to the BGP instance by the local router. It does not
specify routes that are in the BGP instance Loc-RIB, such as routes
after best-path selection.
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Figure 1 shows the flow of received routes from one or more BGP peers
into the Loc-RIB.
+------------------+ +------------------+
| Peer-A | | Peer-B |
/-- | | ---- | | --\
| | Adj-RIB-In (Pre) | | Adj-RIB-In (Pre) | |
| +------------------+ +------------------+ |
| | | |
| Filters/Policy -| Filters/Policy -| |
| V V |
| +------------------ +------------------+ |
| | Adj-RIB-In (Post)| | Adj-RIB-In (Post)| |
| +------------------ +------------------+ |
| | | |
| Selected -| Selected -| |
| V V |
| +-----------------------------------------+ |
| | Loc-RIB | |
| +-----------------------------------------+ |
| |
| ROUTER/BGP Instance |
\----------------------------------------------------/
Figure 1: BGP peering Adj-RIBs-In into Loc-RIB
As shown in Figure 2, Locally originated follows a similar flow where
the redistributed or otherwise originated routes get installed into
the Loc-RIB based on the decision process selection.
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/--------------------------------------------------------\
| |
| +----------+ +----------+ +----------+ +----------+ |
| | IS-IS | | OSPF | | Static | | BGP | |
| +----------+ +----------+ +----------+ +----------+ |
| | | | | |
| | | |
| | Redistributed or originated into BGP | |
| | | |
| | | | | |
| V V V V |
| +----------------------------------------------+ |
| | Loc-RIB | |
| +----------------------------------------------+ |
| |
| ROUTER/BGP Instance |
\--------------------------------------------------------/
Figure 2: Locally Originated into Loc-RIB
BGP instance Loc-RIB usually provides a similar, if not exact,
forwarding information base (FIB) view of the routes from BGP that
the router will use. The following are some use-cases for Loc-RIB
access:
o Adj-RIBs-In Post-Policy may still contain hundreds of thousands of
routes per-peer but only a handful are selected and installed in
the Loc-RIB as part of the best-path selection. Some monitoring
applications, such as ones that need only to correlate flow
records to Loc-RIB entries, only need to collect and monitor the
routes that are actually selected and used.
Requiring the applications to collect all Adj-RIB-In Post-Policy
data forces the applications to receive a potentially large
unwanted data set and to perform the BGP decision process
selection, which includes having access to the IGP next-hop
metrics. While it is possible to obtain the IGP topology
information using BGP-LS, it requires the application to implement
SPF and possibly CSPF based on additional policies. This is
overly complex for such a simple application that only needed to
have access to the Loc-RIB.
o It is common to see frequent changes over many BGP peers, but
those changes do not always result in the router's Loc-RIB
changing. The change in the Loc-RIB can have a direct impact on
the forwarding state. It can greatly reduce time to troubleshoot
and resolve issues if operators had the history of Loc-RIB
changes. For example, a performance issue might have been seen
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for only a duration of 5 minutes. Post troubleshooting this issue
without Loc-RIB history hides any decision based routing changes
that might have happened during those five minutes.
o Operators may wish to validate the impact of policies applied to
Adj-RIB-In by analyzing the final decision made by the router when
installing into the Loc-RIB. For example, in order to validate if
multi-path prefixes are installed as expected for all advertising
peers, the Adj-RIB-In Post-Policy and Loc-RIB needs to be
compared. This is only possible if the Loc-RIB is available.
Monitoring the Adj-RIB-In for this router from another router to
derive the Loc-RIB is likely to not show same installed prefixes.
For example, the received Adj-RIB-In will be different if add-
paths is not enabled or if maximum number of equal paths are
different from Loc-RIB to routes advertised.
This document adds Loc-RIB to the BGP Monitoring Protocol and
replaces Section 8.2 [RFC7854] Locally Originated Routes.
1.1. Current Method to Monitor Loc-RIB
Loc-RIB is used to build Adj-RIB-Out when advertising routes to a
peer. It is therefore possible to derive the Loc-RIB of a router by
monitoring the Adj-RIB-In Pre-Policy from another router. At scale
this becomes overly complex and error prone.
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/------------------------------------------------------\
| ROUTER1 BGP Instance |
| |
| +--------------------------------------------+ |
| | Loc-RIB | |
| +--------------------------------------------+ |
| | | |
| +------------------+ +------------------+ |
| | Peer-ROUTER2 | | Peer-ROUTER3 | |
| | Adj-RIB-Out (Pre)| | Adj-RIB-Out (Pre)| |
| +------------------+ +------------------+ |
| Filters/Policy -| Filters/Policy -| |
| V V |
| +-------------------+ +-------------------+ |
| | Adj-RIB-Out (Post)| | Adj-RIB-Out (Post)| |
| +-------------------+ +-------------------+ |
| | | |
\------------- | ------------------------ | -----------/
BGP | BGP |
Peer | Peer |
+------------------+ +------------------+
| Peer-ROUTER1 | | Peer-ROUTER1 |
/--| |--\ /--| | --\
| | Adj-RIB-In (Pre) | | | | Adj-RIB-In (Pre) | |
| +------------------+ | | +------------------+ |
| | | |
| ROUTER2/BGP Instance | | ROUTER3/BGP Instance |
\------------------------/ \-------------------------/
| |
v v
ROUTER2 BMP Feed ROUTER3 BMP Feed
Figure 3: Current method to monitor Loc-RIB
The setup needed to monitor the Loc-RIB of a router requires another
router with a peering session to the target router that is to be
monitored. As shown in Figure 3, the target router Loc-RIB is
advertised via Adj-RIB-Out to the BMP router over a standard BGP
peering session. The BMP router then forwards Adj-RIB-In Pre-Policy
to the BMP receiver.
The current method introduces the need for additional resources:
o Requires at least two routers when only one router was to be
monitored.
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o Requires additional BGP peering to collect the received updates
when peering may have not even been required in the first place.
For example, VRF's with no peers, redistributed bgp-ls with no
peers, segment routing egress peer engineering where no peers have
link-state address family enabled.
Complexities introduced with current method in order to derive (e.g.
correlate) peer to router Loc-RIB:
o Adj-RIB-Out received as Adj-RIB-In from another router may have a
policy applied that filters, generates aggregates, suppresses more
specifics, manipulates attributes, or filters routes. Not only
does this invalidate the Loc-RIB view, it adds complexity when
multiple BMP routers may have peering sessions to the same router.
The BMP receiver user is left with the error prone task of
identifying which peering session is the best representative of
the Loc-RIB.
o BGP peering is designed to work between administrative domains and
therefore does not need to include internal system level
information of each peering router (e.g. the system name or
version information). In order to derive a Loc-RIB to a router,
the router name or other system information is needed. The BMP
receiver and user are forced to do some type of correlation using
what information is available in the peering session (e.g. peering
addresses, ASNs, and BGP-ID's). This leads to error prone
correlations.
o The BGP-ID's and session addresses to router correlation requires
additional data, such as router inventory. This additional data
provides the BMP receiver the ability to map and correlate the
BGP-ID's and/or session addresses, but requires the BMP receiver
to somehow obtain this data outside of BMP. How this data is
obtained and the accuracy of the data directly effects the
integrity of the correlation.
2. Terminology
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].
3. Definitions
o Adj-RIB-In: As defined in [RFC4271], "The Adj-RIBs-In contains
unprocessed routing information that has been advertised to the
local BGP speaker by its peers." This is also referred to as the
pre-policy Adj-RIB-In in this document.
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o Adj-RIB-Out: As defined in [RFC4271], "The Adj-RIBs-Out contains
the routes for advertisement to specific peers by means of the
local speaker's UPDATE messages."
o Loc-RIB: As defined in [RFC4271], "The Loc-RIB contains the routes
that have been selected by the local BGP speaker's Decision
Process." It is further defined that the routes selected include
locally originated and routes from all peers.
o Pre-Policy Adj-RIB-Out: The result before applying the outbound
policy to an Adj-RIB-Out. This normally represents a similar view
of the Loc-RIB but may contain additional routes based on BGP
peering configuration.
o Post-Policy Adj-RIB-Out: The result of applying outbound policy to
an Adj-RIB-Out. This MUST be what is actually sent to the peer.
4. Per-Peer Header
4.1. Peer Type
A new peer type is defined for Loc-RIB to distinguish that it
represents Loc-RIB with or without RD and local instances.
Section 4.2 [RFC7854] defines a Local Instance Peer type, which is
for the case of non-RD peers that have an instance identifier.
This document defines the following new peer type:
o Peer Type = TBD: Loc-RIB Instance Peer
4.2. Peer Flags
In section 4.2 [RFC7854], the "locally sourced routes" comment under
the L flag description is removed. Locally sourced routes MUST be
conveyed using the Loc-RIB instance peer type.
The per-peer header flags for Loc-RIB Instance Peer type are defined
as follows:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|F| Reserved |
+-+-+-+-+-+-+-+-+
o The F flag indicates that the Loc-RIB is filtered. This indicates
that the Loc-RIB does not represent the complete routing table.
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The remaining bits are reserved for future use. They SHOULD be
transmitted as 0 and their values MUST be ignored on receipt.
5. Loc-RIB Monitoring
Loc-RIB contains all routes from BGP peers as well as any and all
routes redistributed or otherwise locally originated. In this
context, only the BGP instance Loc-RIB is included. Routes from
other routing protocols that have not been redistributed, originated
by or into BGP, or received via Adj-RIB-In are not considered.
Loc-RIB in this context does not attempt to maintain a pre-policy and
post-policy representation. Loc-RIB is the selected and used routes,
which is equivalent to post-policy.
For example, VRF "Blue" imports several targets but filters out
specific routes. The end result of VRF "Blue" Loc-RIB is conveyed.
Even though the import is filtered, the result is complete for VRF
"Blue" Loc-RIB. The F flag is not set in this case since the Loc-RIB
is complete and not filtered to the BMP receiver.
5.1. Per-Peer Header
All peer messages that include a per-peer header MUST use the
following values:
o Peer Type: Set to TBD to indicate Loc-RIB Instance Peer.
o Peer Distinguisher: Zero filled if the Loc-RIB represents the
global instance. Otherwise set to the route distinguisher or
unique locally defined value of the particular instance the Loc-
RIB belongs to.
o Peer Address: Zero-filled. Remote peer address is not applicable.
The V flag is not applicable with Local-RIB Instance peer type
considering addresses are zero-filed.
o Peer AS: Set to the BGP instance global or default ASN value.
o Peer BGP ID: Set to the BGP instance global or RD (e.g. VRF)
specific router-id.
5.2. Peer UP Notification
Peer UP notifications follow section 4.10 [RFC7854] with the
following clarifications:
o Local Address: Zero-filled, local address is not applicable.
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o Local Port: Set to 0, local port is not applicable.
o Remote Port: Set to 0, remote port is not applicable.
o Sent OPEN Message: This is a fabricated BGP OPEN message.
Capabilities MUST include 4-octet ASN and all necessary
capabilities to represent the Loc-RIB route monitoring messages.
Only include capabilities if they will be used for Loc-RIB
monitoring messages. For example, if add-paths is enabled for
IPv6 and Loc-RIB contains additional paths, the add-paths
capability should be included for IPv6. In the case of add-paths,
the capability intent of advertise, receive or both can be ignored
since the presence of the capability indicates enough that add-
paths will be used for IPv6.
o Received OPEN Message: Repeat of the same Sent Open Message. The
duplication allows the BMP receiver to use existing parsing.
5.2.1. Peer UP Information
The following peer UP information TLV types are added:
o Type = TBD: VRF/Table Name. The Information field contains an
ASCII string whose value MUST be equal to the value of the VRF or
table name (e.g. RD instance name) being conveyed. The string
size MUST be within the range of 1 to 255 bytes.
The VRF/Table Name TLV is optionally included. For consistency,
it is RECOMMENDED that the VRF/Table Name always be included. The
default value of "global" SHOULD be used for the default Loc-RIB
instance with a zero-filled distinguisher. If the TLV is
included, then it SHOULD also be included in the Peer Down
notification.
5.3. Peer Down Notification
Peer down notification SHOULD follow the section 4.9 [RFC7854] reason
2.
The VRF/Table Name informational TLV SHOULD be included if it was in
the Peer UP.
5.4. Route Monitoring
Route Monitoring messages are used for initial synchronization of the
Loc-RIB. They are also used to convey incremental Loc-RIB changes.
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As defined in section 4.3 [RFC7854], "Following the common BMP header
and per-peer header is a BGP Update PDU."
5.4.1. ASN Encoding
Loc-RIB route monitor messages MUST use 4-byte ASN encoding as
indicated in PEER UP sent OPEN message (Section 5.2) capability.
5.4.2. Granularity
State compression and throttling SHOULD be used by a BMP sender to
reduce the amount of route monitoring messages that are transmitted
to BMP receivers. With state compression, only the final resultant
updates are sent.
For example, prefix 10.0.0.0/8 is updated in the Loc-RIB 5 times
within 1 second. State compression of BMP route monitor messages
results in only the final change being transmitted. The other 4
changes are suppressed because they fall within the compression
interval. If no compression was being used, all 5 updates would have
been transmitted.
A BMP receiver SHOULD expect that Loc-RIB route monitoring
granularity can be different by BMP sender implementation.
5.5. Route Mirroring
Route mirroring is not applicable to Loc-RIB.
5.6. Statistics Report
Not all Stat Types are relevant to Loc-RIB. The Stat Types that are
relevant are listed below:
o Stat Type = 8: (64-bit Gauge) Number of routes in Loc-RIB.
o Stat Type = 10: Number of routes in per-AFI/SAFI Loc-RIB. The
value is structured as: 2-byte AFI, 1-byte SAFI, followed by a 64-
bit Gauge.
6. Other Considerations
6.1. Loc-RIB Implementation
There are several methods to implement Loc-RIB efficiently. In all
methods, the implementation emulates a peer with Peer UP and DOWN
messages to convey capabilities as well as Route Monitor messages to
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convey Loc-RIB. In this sense, the peer that conveys the Loc-RIB is
a local router emulated peer.
6.1.1. Multiple Loc-RIB Peers
There MUST be multiple emulated peers for each Loc-RIB instance, such
as with VRF's. The BMP receiver identifies the Loc-RIB's by the peer
header distinguisher and BGP ID. The BMP receiver uses the VRF/
Table Name from the PEER UP information to associate a name to the
Loc-RIB.
In some implementations, it might be required to have more than one
emulated peer for Loc-RIB to convey different address families for
the same Loc-RIB. In this case, the peer distinguisher and BGP ID
should be the same since it represents the same Loc-RIB instance.
Each emulated peer instance MUST send a PEER UP with the OPEN message
indicating the address family capabilities. A BMP receiver MUST
process these capabilities to know which peer belongs to which
address family.
6.1.2. Filtering Loc-RIB to BMP Receivers
There maybe be use-cases where BMP receivers should only receive
specific routes from Loc-RIB. For example, IPv4 unicast routes may
include IBGP, EBGP, and IGP but only routes from EBGP should be sent
to the BMP receiver. Alternatively, it may be that only IBGP and
EBGP that should be sent and IGP redistributed routes should be
excluded. In these cases where the Loc-RIB is filtered, the F flag
is set to 1 to indicate to the BMP receiver that the Loc-RIB is
filtered.
7. Security Considerations
It is not believed that this document adds any additional security
considerations.
8. IANA Considerations
This document requests that IANA assign the following new parameters
to the BMP parameters name space [1].
8.1. BMP Peer Type
This document defines a new peer type (Section 4.1):
o Peer Type = TBD: Loc-RIB Instance Peer
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8.2. BMP Peer Flags
This document defines a new flag (Section 4.2) and proposes that peer
flags are specific to the peer type:
o The F flag indicates that the Loc-RIB is filtered. This indicates
that the Loc-RIB does not represent the complete routing table.
8.3. Peer UP Information TLV
This document defines the following new BMP PEER UP informational
message TLV types (Section 5.2.1):
o Type = TBD: VRF/Table Name. The Information field contains an
ASCII string whose value MUST be equal to the value of the VRF or
table name (e.g. RD instance name) being conveyed. The string
size MUST be within the range of 1 to 255 bytes.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[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>.
9.2. URIs
[1] https://www.iana.org/assignments/bmp-parameters/bmp-
parameters.xhtml
Acknowledgements
The authors would like to thank John Scudder for his valuable input.
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Authors' Addresses
Tim Evens
Cisco Systems
2901 Third Avenue, Suite 600
Seattle, WA 98121
USA
Email: tievens@cisco.com
Serpil Bayraktar
Cisco Systems
3700 Cisco Way
San Jose, CA 95134
USA
Email: serpil@cisco.com
Manish Bhardwaj
Cisco Systems
3700 Cisco Way
San Jose, CA 95134
USA
Email: manbhard@cisco.com
Paolo Lucente
NTT Communications
Siriusdreef 70-72
Hoofddorp, WT 2132
NL
Email: paolo@ntt.net
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