Global Routing Operations T. Evens
Internet-Draft S. Bayraktar
Intended Status: Standards Track M. Bhardwaj
Expires: September 11, 2017 Cisco Systems
March 10, 2017 P. Lucente
NTT Communications
Support for Local RIB in BGP Monitoring Protocol (BMP)
draft-evens-grow-bmp-local-rib-00
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
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Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Current Method to Monitor Loc-RIB . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Per-Peer Header . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Peer Type . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Peer Flags . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Loc-RIB Monitoring . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Per-Peer Header . . . . . . . . . . . . . . . . . . . . . 8
5.2. Peer UP Notification . . . . . . . . . . . . . . . . . . . 8
5.2.1. Peer UP Information . . . . . . . . . . . . . . . . . 9
5.3. Peer Down Notification . . . . . . . . . . . . . . . . . . 9
5.4. Route Monitoring . . . . . . . . . . . . . . . . . . . . . 9
5.5. Route Mirroring . . . . . . . . . . . . . . . . . . . . . . 9
5.6 Statistics Report . . . . . . . . . . . . . . . . . . . . . 9
6. Other Considerations . . . . . . . . . . . . . . . . . . . . . 10
6.1. Loc-RIB Implementation . . . . . . . . . . . . . . . . . . 10
6.1.1 Multiple Loc-RIB Peers . . . . . . . . . . . . . . . . . 10
6.1.2 Filtering Loc-RIB to BMP Receivers . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.2. Normative References . . . . . . . . . . . . . . . . . . . 11
9.3. Informative References . . . . . . . . . . . . . . . . . . 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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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.
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
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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.
/--------------------------------------------------------\
| |
| +----------+ +----------+ +----------+ +----------+ |
| | 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
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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 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. While it
is possible to derive the Loc-RIB, it is also error prone and
complex.
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. 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.
Unnecessary resources needed for current method:
o Requires at least two routers when only one router was to be
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monitored.
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 erroneous 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].
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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.
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 would match what is in the
local RIB.
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
This document defines the following new peer type:
o Peer Type = 3: Loc-RIB Instance Peer
4.2. Peer Flags
In section 4.2 [RFC7854], the "locally sourced routes" comment in 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
+-+-+-+-+-+-+-+-+
|V|F| Reserved |
+-+-+-+-+-+-+-+-+
o The V flag indicates that the Peer address is an IPv6 address.
For IPv4 peers, this is set to 0.
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o The F flag indicates that the Loc-RIB is filtered. This
indicates that the Loc-RIB does not represent the complete
routing table.
The remaining bits are reserved for future use. They MUST 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 or received
via Adj-RIB-In are not considered.
5.1. Per-Peer Header
All peer messages that include a per-peer header MUST use the
following values:
o Peer Type: Set to 3 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 as remote peer address is not
applicable.
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.
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
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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 Type is added:
o Type = 3: VRF Name. The Information field contains an ASCII
string whose value MUST be equal to the value of the VRF name
(e.g. RD instance name) configured. This type is only relevant and
used when the Loc-RIB represents a VRF/RD instance.
It is RECOMMENDED that the VRF Name be defined as "global" for the
global/default Loc-RIB instance.
5.3. Peer Down Notification
Peer down notification SHOULD follow the section 4.9 [RFC7854] reason
2.
5.4. Route Monitoring
Route Monitoring messages are used for initial synchronization of the
Loc-RIB. They are also used for incremental updates upon every
change to the RIB. State compression on interval, such as 1 or
greater seconds, can mask critical RIB changes. Therefore state
compression SHOULD be avoided. If the Loc-RIB changes, a route
monitor message should be sent.
As defined in section 4.3 [RFC7854], "Following the common BMP header
and per-peer header is a BGP Update PDU."
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
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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
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 Name
from the PEER UP to name 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
partial.
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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 peer types
to the BMP parameters name space [1].
o Peer Type = 3: Loc-RIB Instance Peer
9. References
9.1. URIs
[1] https://www.iana.org/assignments/bmp-parameters/bmp-
parameters.xhtml
9.2. 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, <http://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, <http://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, <http://www.rfc-
editor.org/info/rfc7854>.
9.3. Informative References
[I-ID.ietf-grow-bmp-adj-rib-out] TBD.
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Acknowledgments
TBD.
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 2132 WT
NL
Email: paolo@ntt.net
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