One document matched: draft-ietf-i2rs-rib-info-model-08.xml
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<rfc category="info" docName="draft-ietf-i2rs-rib-info-model-08"
ipr="trust200902">
<front>
<title>Routing Information Base Info Model</title>
<author fullname="Nitin Bahadur" initials="N.B." role="editor"
surname="Bahadur">
<organization>Bracket Computing</organization>
<address>
<postal>
<street>150 West Evelyn Ave, Suite 200</street>
<city>Mountain View</city>
<region>CA</region>
<code>94041</code>
<country>US</country>
</postal>
<email>nitin_bahadur@yahoo.com</email>
</address>
</author>
<author fullname="Sriganesh Kini" initials="S.K." role="editor"
surname="Kini">
<organization>Ericsson</organization>
<address>
<email>sriganesh.kini@ericsson.com</email>
</address>
</author>
<author fullname="Jan Medved" initials="J.M." surname="Medved">
<organization>Cisco</organization>
<address>
<email>jmedved@cisco.com</email>
</address>
</author>
<!---->
<date day="19" month="October" year="2015" />
<area>Routing</area>
<workgroup>Network Working Group</workgroup>
<keyword>Internet-Draft</keyword>
<keyword>RIB</keyword>
<keyword>info model</keyword>
<abstract>
<t>Routing and routing functions in enterprise and carrier networks are
typically performed by network devices (routers and switches) using a
routing information base (RIB). Protocols and configuration push data
into the RIB and the RIB manager installs state into the hardware; for
packet forwarding. This draft specifies an information model for the RIB
to enable defining a standardized data model. Such a data model can be
used to define an interface to the RIB from an entity that may even be
external to the network device. This interface can be used to support
new use-cases being defined by the IETF I2RS WG.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction" toc="default">
<t>Routing and routing functions in enterprise and carrier networks are
traditionally performed in network devices. Traditionally routers run
routing protocols and the routing protocols (along with static config)
populate the Routing information base (RIB) of the router. The RIB is
managed by the RIB manager and the RIB manager provides a north-bound
interface to its clients i.e. the routing protocols to insert routes
into the RIB. The RIB manager consults the RIB and decides how to
program the forwarding information base (FIB) of the hardware by
interfacing with the FIB manager. The relationship between these
entities is shown in <xref target="rib-fib-interaction"></xref>.</t>
<figure align="center" anchor="rib-fib-interaction"
title="RIB manager, RIB clients and FIB managers">
<artwork align="left"><![CDATA[
+-------------+ +-------------+
|RIB client 1 | ...... |RIB client N |
+-------------+ +-------------+
^ ^
| |
+----------------------+
|
V
+---------------------+
|RIB manager |
| |
| +-----+ |
| | RIB | |
| +-----+ |
+---------------------+
^
|
+---------------------------------+
| |
V V
+-------------+ +-------------+
|FIB manager 1| |FIB manager M|
| +-----+ | .......... | +-----+ |
| | FIB | | | | FIB | |
| +-----+ | | +-----+ |
+-------------+ +-------------+
]]></artwork>
</figure>
<t>Routing protocols are inherently distributed in nature and each
router makes an independent decision based on the routing data received
from its peers. With the advent of newer deployment paradigms and the
need for specialized applications, there is an emerging need to guide
the router's routing function <xref
target="I-D.ietf-i2rs-problem-statement"></xref>. Traditional
network-device protocol-based RIB population suffices for most use cases
where distributed network control is used. However there are use cases
which the network operators currently address by configuring static
routes, policies and RIB import/export rules on the routers. There is
also a growing list of use cases <xref
target="I-D.white-i2rs-use-case"></xref>, <xref
target="I-D.hares-i2rs-use-case-vn-vc"></xref> in which a network
operator might want to program the RIB based on data unrelated to just
routing (within that network's domain). Programming the RIB could be
based on other information such as routing data in the adjacent domain
or the load on storage and compute in the given domain. Or it could
simply be a programmatic way of creating on-demand dynamic overlays
(e.g. GRE tunnels) between compute hosts (without requiring the hosts to
run traditional routing protocols). If there was a standardized publicly
documented programmatic interface to a RIB, it would enable further
networking applications that address a variety of use-cases <xref
target="I-D.ietf-i2rs-problem-statement"></xref>.</t>
<t>A programmatic interface to the RIB involves 2 types of operations -
reading from the RIB and writing (adding/modifying/deleting) to the RIB.
<xref target="I-D.white-i2rs-use-case"></xref> lists various use-cases
which require read and/or write manipulation of the RIB.</t>
<t>In order to understand what is in a router's RIB, methods like
per-protocol SNMP MIBs and show output screen scraping are used. These
methods are not scalable, since they are client pull mechanisms and not
proactive push (from the router) mechanisms. Screen scraping is error
prone (since the output format can change) and is vendor dependent.
Building a RIB from per-protocol MIBs is error prone since the MIB data
represent protocol data and not the exact information that went into the
RIB. Thus, just getting read-only RIB information from a router is a
hard task.</t>
<t>Adding content to the RIB from an external entity can be done today
using static configuration mechanisms provided by router vendors.
However the mix of what can be modified in the RIB varies from vendor to
vendor and the method of configuring it is also vendor dependent. This
makes it hard for an external entity to program a multi-vendor network
in a consistent and vendor-independent way.</t>
<t>The purpose of this draft is to specify an information model for the
RIB. Using the information model, one can build a detailed data model
for the RIB. That data model could then be used by an external entity to
program a network device.</t>
<t>The rest of this document is organized as follows. <xref
target="rib-data"> </xref> goes into the details of what constitutes and
can be programmed in a RIB. Guidelines for reading and writing the RIB
are provided in <xref target="rib-read"></xref> and <xref
target="rib-write"></xref> respectively. <xref target="events"></xref>
provides a high-level view of the events and notifications going from a
network device to an external entity, to update the external entity on
asynchronous events. The RIB grammar is specified in <xref
target="rib-grammar"></xref>. Examples of using the RIB grammar are
shown in <xref target="rib-examples"></xref>. <xref
target="rib-scale"></xref> covers considerations for performing RIB
operations at scale.</t>
<section title="Conventions used in this document">
<t>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 <xref
target="RFC2119"></xref>.</t>
</section>
</section>
<section anchor="rib-data" title="RIB data" toc="default">
<t>This section describes the details of a RIB. It makes forward
references to objects in the RIB grammar (<xref
target="rib-grammar"></xref>). A high-level description of the RIB
contents is as shown below.</t>
<figure anchor="rib-model" title="RIB model">
<artwork name="RIB model"><![CDATA[
routing-instance
| |
| |
0..N | | 1..N
| |
interface(s) RIB(s)
|
|
| 0..N
|
route(s)
]]></artwork>
</figure>
<section title="RIB definition">
<t>A RIB is an entity that contains routes. A RIB is identified by its
name and a RIB is contained within a routing instance (<xref
target="routing-instance"></xref>). The name MUST be unique within a
routing instance. All routes in a given RIB MUST be of the same type
(e.g. IPv4). Each RIB MUST belong to a routing instance.</t>
<t>A routing instance can have multiple RIBs. A routing instance can
even have two or more RIBs with the same type of routes (e.g. IPv6). A
typical case where this can be used is for multi-topology routing
(<xref target="RFC4915"></xref>, <xref target="RFC5120"></xref>).</t>
<t>Each RIB can be optionally associated with a ENABLE_IP_RPF_CHECK
attribute that enables Reverse path forwarding (RPF) checks on all IP
routes in that RIB. Reverse path forwarding (RPF) check is used to
prevent spoofing and limit malicious traffic. For IP packets, the IP
source address is looked up and the rpf interface(s) associated with
the route for that IP source address is found. If the incoming IP
packet's interface matches one of the rpf interface(s), then the IP
packet is forwarded based on its IP destination address; otherwise,
the IP packet is discarded.</t>
</section>
<section anchor="routing-instance" title="Routing instance">
<t>A routing instance, in the context of the RIB information model, is
a collection of RIBs, interfaces, and routing parameters. A routing
instance creates a logical slice of the router and allows different
logical slices; across a set of routers; to communicate with each
other. Layer 3 Virtual Private Networks (VPN), Layer 2 VPNs (L2VPN)
and Virtual Private Lan Service (VPLS) can be modeled as routing
instances. Note that modeling a Layer 2 VPN using a routing instance
only models the Layer-3 (RIB) aspect and does not model any layer-2
information (like ARP) that might be associated with the L2VPN.</t>
<t>The set of interfaces indicates which interfaces are associated
with this routing instance. The RIBs specify how incoming traffic is
to be forwarded. And the routing parameters control the information in
the RIBs. The intersection set of interfaces of 2 routing instances
MUST be the null set. In other words, an interface MUST NOT be present
in 2 routing instances. Thus a routing instance describes the routing
information and parameters across a set of interfaces.</t>
<t>A routing instance MUST contain the following mandatory
fields.<list style="symbols">
<t>INSTANCE_NAME: A routing instance is identified by its name,
INSTANCE_NAME. This MUST be unique across all routing instances in
a given network device.</t>
<t>rib-list: This is the list of RIBs associated with this routing
instance. Each routing instance can have multiple RIBs to
represent routes of different types. For example, one would put
IPv4 routes in one RIB and MPLS routes in another RIB.</t>
</list></t>
<t>A routing instance MAY contain the following optional fields.<list
style="symbols">
<t>interface-list: This represents the list of interfaces
associated with this routing instance. The interface list helps
constrain the boundaries of packet forwarding. Packets coming on
these interfaces are directly associated with the given routing
instance. The interface list contains a list of identifiers, with
each identifier uniquely identifying an interface.</t>
<t>ROUTER_ID: The router-id field identifies the network device in
control plane interactions with other network devices. This field
is to be used if one wants to virtualize a physical router into
multiple virtual routers. Each virtual router MUST have a unique
router-id. ROUTER_ID MUST be unique across all network devices in
a given domain.</t>
</list></t>
</section>
<section title="Route">
<t>A route is essentially a match condition and an action following
the match. The match condition specifies the kind of route (IPv4,
MPLS, etc.) and the set of fields to match on. <xref
target="route-model"></xref> represents the overall contents of a
route.</t>
<figure anchor="route-model" title="Route model">
<artwork name="Route model"><![CDATA[
route
| | |
+---------+ | +----------+
| | |
0..N | | |
route-attribute match nexthop
|
|
+-------+-------+-------+--------+
| | | | |
| | | | |
IPv4 IPv6 MPLS MAC Interface
]]></artwork>
</figure>
<t>This document specifies the following match types:<list
style="symbols">
<t>IPv4: Match on destination IP address in the IPv4 header</t>
<t>IPv6: Match on destination IP address in the IPv6 header</t>
<t>MPLS: Match on a MPLS label at the top of the MPLS label
stack</t>
<t>MAC: Match on MAC destination addresses in the ethernet
header</t>
<t>Interface: Match on incoming interface of the packet</t>
<t>IP multicast: Match on (S, G) or (*, G), where S and G are IP
addresses</t>
</list></t>
<t>Each route MUST have associated with it the following mandatory
route attributes.<list style="symbols">
<t>ROUTE_PREFERENCE: This is a numerical value that allows for
comparing routes from different protocols. Static configuration is
also considered a protocol for the purpose of this field. It is
also known as administrative-distance. The lower the value, the
higher the preference. For example there can be an OSPF route for
192.0.2.1/32 with a preference of 5. If a controller programs a
route for 192.0.2.1/32 with a preference of 2, then the
controller's route will be preferred by the RIB manager.
Preference should be used to dictate behavior. For more examples
of preference, see <xref target="route-preference"></xref>.</t>
</list></t>
<t>Each route can have associated with it one or more optional route
attributes.<list style="symbols">
<t>route-vendor-attributes: Vendors can specify vendor-specific
attributes using this. The details of this attribute is outside
the scope of this document.</t>
</list></t>
</section>
<section title="Nexthop">
<t>A nexthop represents an object resulting from a route lookup. For
example, if a route lookup results in sending the packet out a given
interface, then the nexthop represents that interface.</t>
<t>Nexthops can be fully resolved nexthops or unresolved nexthop. A
resolved nexthop has adequate information to send the outgoing packet
to the destination by forwarding it on an interface to a directly
connected neighbor. For example, a nexthop to a point-to-point
interface or a nexthop to an IP address on an Ethernet interface has
the nexthop resolved. An unresolved nexthop is something that requires
the RIB manager to determine the final resolved nexthop. For example,
a nexthop could be an IP address. The RIB manager would resolve how to
reach that IP address, e.g. is the IP address reachable by regular IP
forwarding or by a MPLS tunnel or by both. If the RIB manager cannot
resolve the nexthop, then the nexthop remains in an unresolved state
and is NOT a candidate for installation in the FIB. Future RIB events
can cause an unresolved nexthop to get resolved (like that IP address
being advertised by an IGP neighbor). Conversely resolved nexthops can
also become unresolved (e.g. in case of a tunnel going down) and hence
would no longer be candidates to be installed in the FIB.</t>
<t>When at least one of a route's nexthops is resolved, then the route
can be used to forward packets. Such a route is considered eligible to
be installed in the FIB and is henceforth referred to as a
FIB-eligible route. Conversely, when all the nexthops of a route are
unresolved that route can no longer be used to forward packets. Such a
route is considered ineligible to be installed in the FIB and is
henceforth referred to as a FIB-ineligible route. The RIB information
model allows an external entity to program routes whose nexthops may
be unresolved initially. Whenever an unresolved nexthop gets resolved,
the RIB manager will send a notification of the same (see <xref
target="events"></xref> ).</t>
<t>The overall structure and usage of a nexthop is as shown in the
figure below.</t>
<figure anchor="nexthop-model" title="Nexthop model">
<artwork name="Nexthop model"><![CDATA[
route
|
| 0..N
|
nexthop <-------------------------------+
| |
+-------+----------------------------+-------------+ |
| | | | | |
| | | | | |
base load-balance protection replicate chain |
| | | | | |
| |2..N |2..N |2..N |1..N |
| | | | | |
| | V | | |
| +------------->+<------------+-------------+ |
| | |
| +-------------------------------------+
|
+-------------------+
|
|
|
|
+---------------+--------+--------+--------------+
| | | |
| | | |
nexthop-id egress-interface logical-tunnel |
|
|
+---------------------------+
|
+--------------+-----------+
| | |
| | |
tunnel-encap tunnel-decap special-nexthop
]]></artwork>
</figure>
<t>Nexthops can be identified by an identifier to create a level of
indirection. The identifier is set by the RIB manager and returned to
the external entity on request. The RIB data-model SHOULD support a
way to optionally receive a nexthop identifier for a given nexthop.
For example, one can create a nexthop that points to a BGP peer. The
returned nexthop identifier can then be used for programming routes to
point to the same nexthop. Given that the RIB manager has created an
indirection for that BGP peer using the nexthop identifier, if the
transport path to the BGP peer changes, that change in path will be
seamless to the external entity and all routes that point to that BGP
peer will automatically start going over the new transport path.
Nexthop indirection using identifiers could be applied to not just
unicast nexthops, but even to nexthops that contain chains and nested
nexthops (<xref target="nexthop-types"></xref>).</t>
<section anchor="nexthop-types" title="Nexthop types">
<t>This document specifies a very generic, extensible and recursive
grammar for nexthops. Nexthops can be <list style="symbols">
<t>Interface nexthops - pointing to an interface</t>
<t>Tunnel nexthops - pointing to a tunnel</t>
<t>Replication lists - list of nexthops to which to replicate a
packet</t>
<t>Weighted lists - for load-balancing</t>
<t>Preference lists - for protection using primary and
backup</t>
<t>Nexthop chains - for chaining multiple operations or
attaching multiple headers</t>
<t>Lists of lists - recursive application of the above</t>
<t>Indirect nexthops - pointing to a nexthop identifier</t>
<t>Special nexthops - for performing specific well-defined
functions (e.g. drop)</t>
</list>It is expected that all network devices will have a limit
on how many levels of lookup can be performed and not all hardware
will be able to support all kinds of nexthops. RIB capability
negotiation becomes very important for this reason and a RIB
data-model MUST specify a way for an external entity to learn about
the network device's capabilities. Examples of when and how to use
various kinds of nexthops are shown in <xref
target="nexthop-examples"></xref>.</t>
<t>Tunnel nexthops allow an external entity to program static tunnel
headers. There can be cases where the remote tunnel end-point does
not support dynamic signaling (e.g. no LDP support on a host) and in
those cases the external entity might want to program the tunnel
header on both ends of the tunnel. The tunnel nexthop is kept
generic with specifications provided for some commonly used tunnels.
It is expected that the data-model will model these tunnel types
with complete accuracy.</t>
<t>Nexthop chains <xref target="nexthop-chains"></xref>, is a way to
perform multiple operations on a packet by logically combining them.
For example, one can chain together "decapsulate MPLS header" and
"send it out a specific EGRESS_INTERFACE". Chains can be used to
specify multiple headers over a packet, before a packet is
forwarded. One simple example is that of MPLS over GRE, wherein the
packet has an inner MPLS header followed by a GRE header followed by
an IP header. The outermost IP header is decided by the network
device whereas the MPLS header and GRE header are specified by the
controller. Not every network device will be able to support all
kinds of nexthop chains and an arbitrary number of header chained
together. The RIB data-model SHOULD provide a way to expose nexthop
chaining capability supported by a given network device.</t>
</section>
<section title="Nexthop list attributes">
<t>For nexthops that are of the form of a list(s), attributes can be
associated with each member of the list to indicate the role of an
individual member of the list. Two attributes are specified:<list
style="symbols">
<t>NEXTHOP_PREFERENCE: This is used for protection schemes. It
is an integer value between 1 and 99. A lower value indicates
higher preference. To download a primary/standby pair to the
FIB, the nexthops that are resolved and have two highest
preferences are selected. Each <NEXTHOP_PREFERENCE> should
have a unique value within a <nexthop-protection> <list
style="symbols">
<t></t>
</list>(<xref target="rib-grammar"></xref>).</t>
<t>NEXTHOP_LB_WEIGHT: This is used for load-balancing. Each list
member MUST be assigned a weight between 1 and 99. The weight
determines the proportion of traffic to be sent over a nexthop
used for forwarding as a ratio of the weight of this nexthop
divided by the weights of all the nexthops of this route that
are used for forwarding. To perform equal load-balancing, one
MAY specify a weight of "0" for all the member nexthops. The
value "0" is reserved for equal load-balancing and if applied,
MUST be applied to all member nexthops.</t>
</list></t>
</section>
<section title="Nexthop content">
<t>At the lowest level, a nexthop can be one of:<list
style="symbols">
<t>identifier: This is an identifier returned by the network
device representing a nexthop. This can be used as a way of
re-using a nexthop when programming complex nexthops.</t>
<t>EGRESS_INTERFACE: This represents a physical, logical or
virtual interface on the network device. Address resolution must
not be required on this interface. This interface may belong to
any routing instance.</t>
<t>IP address: A route lookup on this IP address is done to
determine the egress interface. Address resolution may be
required depending on the interface. <list style="symbols">
<t>An optional RIB name can also be specified to indicate
the RIB in which the IP address is to be looked up. One can
use the RIB name field to direct the packet from one domain
into another domain. By default the RIB will be the same as
the one that route belongs to.</t>
</list></t>
<t>EGRESS_INTERFACE and IP address: This can be used in cases
e.g. where the IP address is a link-local address.</t>
<t>EGRESS_INTERFACE and MAC address: The egress interface must
be an ethernet interface. Address resolution is not required for
this nexthop.</t>
<t>tunnel encap: This can be an encap representing an IP tunnel
or MPLS tunnel or others as defined in this document. An
optional egress interface can be chained to the tunnel encap to
indicate which interface to send the packet out on. The egress
interface is useful when the network device contains Ethernet
interfaces and one needs to perform address resolution for the
IP packet.</t>
<t>tunnel decap: This is to specify decapsulating a tunnel
header. After decap, further lookup on the packet can be done
via chaining it with another nexthop. The packet can also be
sent out via a EGRESS_INTERFACE directly.</t>
<t>logical tunnel: This can be a MPLS LSP or a GRE tunnel (or
others as defined in this document), that is represented by a
unique identifier (E.g. name).</t>
<t>RIB_NAME: A nexthop pointing to a RIB indicates that the
route lookup needs to continue in the specified RIB. This is a
way to perform chained lookups.</t>
</list></t>
</section>
<section title="Special nexthops">
<t>This document specifies certain special nexthops. The purpose of
each of them is explained below:<list style="symbols">
<t>DISCARD: This indicates that the network device should drop
the packet and increment a drop counter.</t>
<t>DISCARD_WITH_ERROR: This indicates that the network device
should drop the packet, increment a drop counter and send back
an appropriate error message (like ICMP error).</t>
<t>RECEIVE: This indicates that that the traffic is destined for
the network device. For example, protocol packets or OAM
packets. All locally destined traffic SHOULD be throttled to
avoid a denial of service attack on the router's control plane.
An optional rate-limiter can be specified to indicate how to
throttle traffic destined for the control plane. The description
of the rate-limiter is outside the scope of this document.</t>
</list></t>
</section>
</section>
</section>
<section anchor="rib-read" title="Reading from the RIB">
<t>A RIB data-model MUST allow an external entity to read entries, for
RIBs created by that entity. The network device administrator MAY allow
reading of other RIBs by an external entity through access lists on the
network device. The details of access lists are outside the scope of
this document.</t>
<t>The data-model MUST support a full read of the RIB and subsequent
incremental reads of changes to the RIB. An external agent SHOULD be
able to request a full read at any time in the lifecycle of the
connection. When sending data to an external entity, the RIB manager
SHOULD try to send all dependencies of an object prior to sending that
object.</t>
</section>
<section anchor="rib-write" title="Writing to the RIB">
<t>A RIB data-model MUST allow an external entity to write entries, for
RIBs created by that entity. The network device administrator MAY allow
writes to other RIBs by an external entity through access lists on the
network device. The details of access lists are outside the scope of
this document.</t>
<t>When writing an object to a RIB, the external entity SHOULD try to
write all dependencies of the object prior to sending that object. The
data-model SHOULD support requesting identifiers for nexthops and
collecting the identifiers back in the response.</t>
<t>Route programming in the RIB MUST result in a return code that
contains the following attributes:<list style="symbols">
<t>Installed - Yes/No (Indicates whether the route got installed in
the FIB)</t>
<t>Active - Yes/No (Indicates whether a route is fully resolved and
is a candidate for selection)</t>
<t>Reason - E.g. Not authorized</t>
</list>The data-model MUST specify which objects are modify-able
objects. A modify-able object is one whose contents can be changed
without having to change objects that depend on it and without affecting
any data forwarding. To change a non-modifiable object, one will need to
create a new object and delete the old one. For example, routes that use
a nexthop that is identified by a nexthop identifier should be
unaffected when the contents of that nexthop changes.</t>
</section>
<section anchor="events" title="Notifications">
<t>Asynchronous notifications are sent by the network device's RIB
manager to an external entity when some event occurs on the network
device. A RIB data-model MUST support sending asynchronous
notifications. A brief list of suggested notifications is as below:<list
style="symbols">
<t>Route change notification, with return code as specified in <xref
target="rib-write"></xref></t>
<t>Nexthop resolution status (resolved/unresolved) notification</t>
</list></t>
</section>
<section anchor="rib-grammar" title="RIB grammar">
<t>This section specifies the RIB information model in Routing
Backus-Naur Form <xref target="RFC5511"></xref>. This grammar is
intended to help the reader better understand the english text
description in order to derive a data model. However it may not provide
all the detail provided by the english text. When there is a lack of
clarity in the grammar the english text will take precedence.</t>
<figure anchor="rib-grammar-details" title="RIB rBNF grammar">
<artwork><![CDATA[
<routing-instance> ::= <INSTANCE_NAME>
[<interface-list>] <rib-list>
[<ROUTER_ID>]
<interface-list> ::= (<INTERFACE_IDENTIFIER> ...)
<rib-list> ::= (<rib> ...)
<rib> ::= <RIB_NAME> <rib-family>
[<route> ... ]
[ENABLE_IP_RPF_CHECK]
<rib-family> ::= <IPV4_RIB_FAMILY> | <IPV6_RIB_FAMILY> |
<MPLS_RIB_FAMILY> | <IEEE_MAC_RIB_FAMILY>
<route> ::= <match> <nexthop>
[<route-attributes>]
[<route-vendor-attributes>]
<match> ::= <IPV4> <ipv4-route> | <IPV6> <ipv6-route> |
<MPLS> <MPLS_LABEL> | <IEEE_MAC> <MAC_ADDRESS> |
<INTERFACE> <INTERFACE_IDENTIFIER>
<route-type> ::= <IPV4> | <IPV6> | <MPLS> | <IEEE_MAC> | <INTERFACE>
<ipv4-route> ::= <ip-route-type>
(<destination-ipv4-address> | <source-ipv4-address> |
(<destination-ipv4-address> <source-ipv4-address>))
<destination-ipv4-address> ::= <ipv4-prefix>
<source-ipv4-address> ::= <ipv4-prefix>
<ipv4-prefix> ::= <IPV4_ADDRESS> <IPV4_PREFIX_LENGTH>
<ipv6-route> ::= <ip-route-type>
(<destination-ipv6-address> | <source-ipv6-address> |
(<destination-ipv6-address> <source-ipv6-address>))
<destination-ipv6-address> ::= <ipv6-prefix>
<source-ipv6-address> ::= <ipv6-prefix>
<ipv6-prefix> ::= <IPV6_ADDRESS> <IPV6_PREFIX_LENGTH>
<ip-route-type> ::= <SRC> | <DEST> | <DEST_SRC>
<route-attributes> ::= <ROUTE_PREFERENCE> [<LOCAL_ONLY>]
[<address-family-route-attributes>]
<address-family-route-attributes> ::= <ip-route-attributes> |
<mpls-route-attributes> |
<ethernet-route-attributes>
<ip-route-attributes> ::= <>
<mpls-route-attributes> ::= <>
<ethernet-route-attributes> ::= <>
<route-vendor-attributes> ::= <>
<nexthop> ::= <nexthop-base> | <nexthop-lb> |
<nexthop-protection> | <nexthop-replicate> |
<nexthop-chain>
<nexthop-base> ::= <NEXTHOP_ID> |
<nexthop-special> |
<EGRESS_INTERFACE> |
<ipv4-address> | <ipv6-address> |
(<EGRESS_INTERFACE>
(<ipv4-address> | <ipv6-address>)) |
(<EGRESS_INTERFACE> <IEEE_MAC_ADDRESS>) |
<tunnel-encap> | <tunnel-decap> |
<logical-tunnel> |
<RIB_NAME>)
<EGRESS_INTERFACE> ::= <INTERFACE_IDENTIFIER>
<nexthop-special> ::= <DISCARD> | <DISCARD_WITH_ERROR> |
(<RECEIVE> [<COS_VALUE>])
<nexthop-lb> ::= <NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop) ...
<nexthop-protection> = <NEXTHOP_PREFERENCE> <nexthop>
(<NEXTHOP_PREFERENCE> <nexthop>)...
<nexthop-replicate> ::= <nexthop> <nexthop> ...
<nexthop-chain> ::= <nexthop> ...
<logical-tunnel> ::= <tunnel-type> <TUNNEL_NAME>
<tunnel-type> ::= <IPV4> | <IPV6> | <MPLS> | <GRE> | <VxLAN> | <NVGRE>
<tunnel-encap> ::= (<IPV4> <ipv4-header>) |
(<IPV6> <ipv6-header>) |
(<MPLS> <mpls-header>) |
(<GRE> <gre-header>) |
(<VXLAN> <vxlan-header>) |
(<NVGRE> <nvgre-header>)
<ipv4-header> ::= <SOURCE_IPv4_ADDRESS> <DESTINATION_IPv4_ADDRESS>
<PROTOCOL> [<TTL>] [<DSCP>]
<ipv6-header> ::= <SOURCE_IPV6_ADDRESS> <DESTINATION_IPV6_ADDRESS>
<NEXT_HEADER> [<TRAFFIC_CLASS>]
[<FLOW_LABEL>] [<HOP_LIMIT>]
<mpls-header> ::= (<mpls-label-operation> ...)
<mpls-label-operation> ::= (<MPLS_PUSH> <MPLS_LABEL> [<S_BIT>]
[<TOS_VALUE>] [<TTL_VALUE>]) |
(<MPLS_SWAP> <IN_LABEL> <OUT_LABEL>
[<TTL_ACTION>])
<gre-header> ::= <GRE_IP_DESTINATION> <GRE_PROTOCOL_TYPE> [<GRE_KEY>]
<vxlan-header> ::= (<ipv4-header> | <ipv6-header>)
[<VXLAN_IDENTIFIER>]
<nvgre-header> ::= (<ipv4-header> | <ipv6-header>)
<VIRTUAL_SUBNET_ID>
[<FLOW_ID>]
<tunnel-decap> ::= ((<IPV4> <IPV4_DECAP> [<TTL_ACTION>]) |
(<IPV6> <IPV6_DECAP> [<HOP_LIMIT_ACTION>]) |
(<MPLS> <MPLS_POP> [<TTL_ACTION>]))
]]></artwork>
</figure>
<section title="Nexthop grammar explained">
<t>A nexthop is used to specify the next network element to forward
the traffic to. It is also used to specify how the traffic should be
load-balanced, protected using preference or multicasted using
replication. This is explicitly specified in the grammar. The nexthop
has recursion built-in to address complex use-cases like the one
defined in <xref target="lists-of-lists"></xref>.</t>
<t></t>
</section>
</section>
<section anchor="rib-examples" title="Using the RIB grammar">
<t>The RIB grammar is very generic and covers a variety of features.
This section provides examples on using objects in the RIB grammar and
examples to program certain use cases.</t>
<section anchor="route-preference" title="Using route preference">
<t>Using route preference a client can pre-install alternate paths in
the network. For example, if OSPF has a route preference of 10, then
another client can install a route with route preference of 20 to the
same destination. The OSPF route will get precedence and will get
installed in the FIB. When the OSPF route is withdrawn, the alternate
path will get installed in the FIB.</t>
<t>Route preference can also be used to prevent denial of service
attacks by installing routes with the best preference, which either
drops the offending traffic or routes it to some monitoring/analysis
station. Since the routes are installed with the best preference, they
will supersede any route installed by any other protocol.</t>
</section>
<section anchor="nexthop-examples"
title="Using different nexthops types">
<t>The RIB grammar allows one to create a variety of nexthops. This
section describes uses for certain types of nexthops.</t>
<section title="Tunnel nexthops">
<t>A tunnel nexthop points to a tunnel of some kind. Traffic that
goes over the tunnel gets encapsulated with the tunnel encap. Tunnel
nexthops are useful for abstracting out details of the network, by
having the traffic seamlessly route between network edges. At the
end of a tunnel, the tunnel will get decapsulated. Thus the grammar
supports two kinds of operations, one for encap and another for
decap.</t>
</section>
<section anchor="replication-list" title="Replication lists">
<t>One can create a replication list for replicating traffic to
multiple destinations. The destinations, in turn, could be complex
nexthops in themselves - at a level supported by the network device.
Point to multipoint and broadcast are examples that involve
replication.</t>
<t>A replication list (at the simplest level) can be represented
as:</t>
<figure>
<artwork><![CDATA[
<nexthop> ::= <NEXTHOP_REPLICATE> <nexthop> [ <nexthop> ... ]
The above can be derived from the grammar as follows:
<nexthop> ::= <nexthop-replicate>
<nexthop> ::= <NEXTHOP_REPLICATE> <nexthop> <nexthop> ...
]]></artwork>
</figure>
</section>
<section title="Weighted lists">
<t>A weighted list is used to load-balance traffic among a set of
nexthops. From a modeling perspective, a weighted list is very
similar to a replication list, with the difference that each member
nexthop MUST have a NEXTHOP_LB_WEIGHT associated with it.</t>
<t>A weighted list (at the simplest level) can be represented
as:</t>
<figure>
<artwork><![CDATA[
<nexthop> ::= <NEXTHOP_LOAD_BALANCE> (<nexthop> <NEXTHOP_LB_WEIGHT>)
[(<nexthop> <NEXTHOP_LB_WEIGHT>)... ]
The above can be derived from the grammar as follows:
<nexthop> ::= <nexthop-lb>
<nexthop> ::= <NEXTHOP_LOAD_BALANCE>
<NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop>) ...
<nexthop> ::= <NEXTHOP_LOAD_BALANCE> (<NEXTHOP_LB_WEIGHT> <nexthop>)
(<NEXTHOP_LB_WEIGHT> <nexthop>) ...
]]></artwork>
</figure>
</section>
<section title="Protection">
<t>A primary/backup protection can be represented as:</t>
<figure>
<artwork><![CDATA[
<nexthop> ::= <NEXTHOP_PROTECTION> <1> <interface-primary>
<2> <interface-backup>)
The above can be derived from the grammar as follows:
<nexthop> ::= <nexthop-protection>
<nexthop> ::= <NEXTHOP_PROTECTION> (<NEXTHOP_PREFERENCE> <nexthop>
(<NEXTHOP_PREFERENCE> <nexthop>)...)
<nexthop> ::= <NEXTHOP_PROTECTION> (<NEXTHOP_PREFERENCE> <nexthop>
(<NEXTHOP_PREFERENCE> <nexthop>))
<nexthop> ::= <NEXTHOP_PROTECTION> ((<NEXTHOP_PREFERENCE> <nexthop-base>
(<NEXTHOP_PREFERENCE> <nexthop-base>))
<nexthop> ::= <NEXTHOP_PROTECTION> (<1> <interface-primary>
(<2> <interface-backup>))
]]></artwork>
</figure>
<t>Traffic can be load-balanced among multiple primary nexthops and
a single backup. In such a case, the nexthop will look like:</t>
<figure>
<artwork><![CDATA[
<nexthop> ::= <NEXTHOP_PROTECTION> (<1>
(<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop-base>
(<NEXTHOP_LB_WEIGHT> <nexthop-base>) ...))
<2> <nexthop-base>)
]]></artwork>
</figure>
<t>A backup can also have another backup. In such a case, the list
will look like:</t>
<figure>
<artwork><![CDATA[
<nexthop> ::= <NEXTHOP_PROTECTION> (<1> <nexthop>
<2> <NEXTHOP_PROTECTION>(<1> <nexthop> <2> <nexthop>))
]]></artwork>
</figure>
</section>
<section anchor="nexthop-chains" title="Nexthop chains">
<t>A nexthop chain is a way to perform multiple operations on a
packet by logically combining them. For example, when a VPN packet
comes on the WAN interface and has to be forwarded to the correct
VPN interface, one needs to POP the VPN label before sending the
packet out. Using a nexthop chain, one can chain together "pop MPLS
header" and "send it out a specific EGRESS_INTERFACE". </t>
<figure>
<artwork><![CDATA[
The above example can be derived from the grammar as follows:
<nexthop-chain> ::= <nexthop> <nexthop>
<nexthop-chain> ::= <nexthop-base> <nexthop-base>
<nexthop-chain> ::= <tunnel-decap> <EGRESS_INTERFACE>
<nexthop-chain> ::= (<MPLS> <MPLS_POP>) <interface-outgoing>
]]></artwork>
</figure>
<t>Elements in a nexthop-chain are evaluated left to right.</t>
<t>A nexthop chain can also be used to put one or more headers on an
outgoing packet. One example is a Pseudowire - which is MPLS over
some transport (MPLS or GRE for instance). Another example is VxLAN
over IP. A nexthop chain thus allows an external entity to break up
the programming of the nexthop into independent pieces - one per
encapsulation.</t>
<t>A simple example of MPLS over GRE can be represented as:</t>
<figure>
<artwork><![CDATA[
<nexthop-chain> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
<interface-outgoing>
The above can be derived from the grammar as follows:
<nexthop-chain> ::= <nexthop> <nexthop> <nexthop>
<nexthop-chain> ::= <nexthop-base> <nexthop-base> <nexthop-base>
<nexthop-chain> ::= <tunnel-encap> <tunnel-encap> <EGRESS_INTERFACE>
<nexthop-chain> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
<interface-outgoing>
]]></artwork>
</figure>
</section>
<section anchor="lists-of-lists" title="Lists of lists">
<t>Lists of lists is a complex construct. One example of usage of
such a construct is to replicate traffic to multiple destinations,
with load balancing. In other words, for each branch of the
replication tree, there are multiple interfaces on which traffic
needs to be load-balanced on. So the outer list is a replication
list for multicast and the inner lists are weighted lists for load
balancing. Lets take an example of a network element has to
replicate traffic to two other network elements. Traffic to the
first network element should be load balanced equally over two
interfaces outgoing-1-1 and outgoing-1-2. Traffic to the second
network element should be load balanced over three interfaces
outgoing-2-1, outgoing-2-2 and outgoing-2-3 in the ratio
20:20:60.</t>
<figure>
<artwork><![CDATA[
This can be derived from the grammar as follows:
<nexthop> ::= <nexthop-replicate>
<nexthop> ::= <NEXTHOP_REPLICATE> (<nexthop> <nexthop>...)
<nexthop> ::= <NEXTHOP_REPLICATE> (<nexthop> <nexthop>)
<nexthop> ::= <NEXTHOP_REPLICATE> ((<NEXTHOP_LOAD_BALANCE> <nexthop-lb>)
(<NEXTHOP_LOAD_BALANCE> <nexthop-lb>))
<nexthop> ::= <NEXTHOP_REPLICATE> ((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop>) ...))
((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop>) ...))
<nexthop> ::= <NEXTHOP_REPLICATE> ((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop>)))
((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>
(<NEXTHOP_LB_WEIGHT> <nexthop>)
(<NEXTHOP_LB_WEIGHT> <nexthop>)))
<nexthop> ::= <NEXTHOP_REPLICATE> ((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>)
(<NEXTHOP_LB_WEIGHT> <nexthop>)))
((<NEXTHOP_LOAD_BALANCE>
(<NEXTHOP_LB_WEIGHT> <nexthop>)
(<NEXTHOP_LB_WEIGHT> <nexthop>)
(<NEXTHOP_LB_WEIGHT> <nexthop>)))
<nexthop> ::= <NEXTHOP_REPLICATE>
((<NEXTHOP_LOAD_BALANCE>
(50 <outgoing-1-1>)
(50 <outgoing-1-2>)))
((<NEXTHOP_LOAD_BALANCE>
(20 <outgoing-2-1>)
(20 <outgoing-2-2>)
(60 <outgoing-2-3>)))
]]></artwork>
</figure>
<t></t>
</section>
</section>
<section title="Performing multicast">
<t>IP multicast involves matching a packet on (S, G) or (*, G), where
both S (source) and G (group) are IP prefixes. Following the match,
the packet is replicated to one or more recipients. How the recipients
subscribe to the multicast group is outside the scope of this
document.</t>
<t>In PIM-based multicast, the packets are IP forwarded on an IP
multicast tree. The downstream nodes on each point in the multicast
tree is one or more IP addresses. These can be represented as a
replication list ( <xref target="replication-list"></xref> ).</t>
<t>In MPLS-based multicast, the packets are forwarded on a point to
multipoint (P2MP) label-switched path (LSP). The nexthop for a P2MP
LSP can be represented in the nexthop grammar as a
<logical-tunnel> (P2MP LSP identifier) or a replication list (
<xref target="replication-list"></xref>) of <tunnel-encap>, with
each tunnel encap representing a single mpls downstream nexthop.</t>
</section>
</section>
<section anchor="rib-scale" title="RIB operations at scale">
<t>This section discusses the scale requirements for a RIB data-model.
The RIB data-model should be able to handle large scale of operations,
to enable deployment of RIB applications in large networks.</t>
<section title="RIB reads">
<t>Bulking (grouping of multiple objects in a single message) MUST be
supported when a network device sends RIB data to an external entity.
Similarly the data model MUST enable a RIB client to request data in
bulk from a network device.</t>
</section>
<section title="RIB writes">
<t>Bulking (grouping of multiple write operations in a single message)
MUST be supported when an external entity wants to write to the RIB.
The response from the network device MUST include a return-code for
each write operation in the bulk message.</t>
</section>
<section title="RIB events and notifications">
<t>There can be cases where a single network event results in multiple
events and/or notifications from the network device to an external
entity. On the other hand, due to timing of multiple things happening
at the same time, a network device might have to send multiple events
and/or notifications to an external entity. The network device
originated event/notification message MUST support bulking of multiple
events and notifications in a single message.</t>
</section>
</section>
<section title="Security Considerations">
<t>All interactions between a RIB manager and an external entity MUST be
authenticated and authorized. The RIB manager MUST protect itself
against a denial of service attack by a rogue external entity, by
throttling request processing. A RIB manager MUST enforce limits on how
much data can be programmed by an external entity and return error when
such a limit is reached.</t>
<t>The RIB manager MUST expose a data-model that it implements. An
external agent MUST send requests to the RIB manager that comply with
the supported data-model. The data-model MUST specify the behavior of
the RIB manager on handling of unsupported data requests.</t>
</section>
<section title="IANA Considerations">
<t>This document does not generate any considerations for IANA.</t>
</section>
<section title="Acknowledgements">
<t>The authors would like to thank Ron Folkes, Jeffrey Zhang,
the working group co-chairs and reviewers on their comments and
suggestions on this draft. The following people contributed to
the design of the RIB model as part of the I2RS Interim meeting
in April 2013 - Wes George, Chris Liljenstolpe, Jeff Tantsura,
Susan Hares and Fabian Schneider.</t>
</section>
</middle>
<back>
<references title="Normative References">
&RFC2119;
</references>
<references title="Informative References">
&RFC4915;
&RFC5120;
&RFC5511;
&I2RS-USE-CASES;
&I2RS-PROBLEM-STATEMENT;
&I2RS-VN-VC;
</references>
</back>
</rfc>
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