Network Working Group N. Bahadur, Ed.
Internet-Draft R. Folkes, Ed.
Intended status: Informational Juniper Networks, Inc.
Expires: December 27, 2013 S. Kini
Ericsson
June 25, 2013
Routing Information Base Info Model
draft-nitinb-i2rs-rib-info-model-00
Abstract
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 install state into the
hardware; for packet forwarding. This draft specifies an information
model for the RIB, to build a standardized RIB model, using which an
external entity (external to the network device) can read and write
information from/to the RIB.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 27, 2013.
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 5
2. RIB data . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. RIB definition . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Routing tables . . . . . . . . . . . . . . . . . . . . . . 6
2.3. Route . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4. Nexthop . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4.1. Nexthop types . . . . . . . . . . . . . . . . . . . . 9
2.4.2. Nexthop list attributes . . . . . . . . . . . . . . . 10
2.4.3. Nexthop content . . . . . . . . . . . . . . . . . . . 10
2.4.4. Nexthop attributes . . . . . . . . . . . . . . . . . . 11
2.4.5. Special nexthops . . . . . . . . . . . . . . . . . . . 11
3. Reading from the RIB . . . . . . . . . . . . . . . . . . . . . 11
4. Writing to the RIB . . . . . . . . . . . . . . . . . . . . . . 12
5. Events and Notifications . . . . . . . . . . . . . . . . . . . 12
6. RIB grammar . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Using the RIB grammar . . . . . . . . . . . . . . . . . . . . 15
7.1. Using route preference and metric . . . . . . . . . . . . 15
7.2. Using different nexthops types . . . . . . . . . . . . . . 16
7.2.1. Tunnel nexthops . . . . . . . . . . . . . . . . . . . 16
7.2.2. Replication lists . . . . . . . . . . . . . . . . . . 16
7.2.3. Weighted lists . . . . . . . . . . . . . . . . . . . . 16
7.2.4. Protection lists . . . . . . . . . . . . . . . . . . . 17
7.2.5. Nexthop chains . . . . . . . . . . . . . . . . . . . . 17
7.2.6. Lists of lists . . . . . . . . . . . . . . . . . . . . 18
7.3. Solving optimized exit control . . . . . . . . . . . . . . 18
8. RIB operations at scale . . . . . . . . . . . . . . . . . . . 19
8.1. RIB reads . . . . . . . . . . . . . . . . . . . . . . . . 19
8.2. RIB writes . . . . . . . . . . . . . . . . . . . . . . . . 19
8.3. RIB events and notifications . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.1. Normative References . . . . . . . . . . . . . . . . . . . 20
12.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
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) populates the Routing information base (RIB) of the router.
The RIB is managed by the RIB manager and it 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 Figure 1.
+-------------+ +-------------+
|RIB-Client 1 | ...... |RIB-Client N |
+-------------+ +-------------+
^ ^
| |
+----------------------+
|
V
+---------------------+
|RIB-Manager |
| |
| +-----+ |
| | RIB | |
| +-----+ |
+---------------------+
^
|
+---------------------------------+
| |
V V
+-------------+ +-------------+
|FIB-Manager 1| |FIB-Manager M|
| +-----+ | .......... | +-----+ |
| | FIB | | | | FIB | |
| +-----+ | | +-----+ |
+-------------+ +-------------+
Figure 1: RIB-Manager, RIB-Clients and FIB-Managers
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 (
[I-D.atlas-i2rs-problem-statement]). Traditional protocol-based RIB
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population suffices for most use cases where distributed network
control works. However there are use cases in which the network
admins today configure static routes, policies and RIB import/export
rules on the routers. There is also a growing list of use cases (
[I-D.white-i2rs-use-case], [I-D.hares-i2rs-use-case-vn-vc] ) in which
a network admin might want to program the RIB based on data unrelated
to just routing (within that network's domain). It could be based on
routing data in adjacent domain or it could be based on load on
storage and compute in the given domain. Or it could simply be a
programmatic way of creating on-demand dynamic overlays between
compute hosts (without requiring the hosts to run traditional routing
protocols). If there was a standardized programmatic interface to a
RIB, it would fuel further networking applications targeted towards
specific niches.
Programming the RIB involves 2 parts - reading what's in the RIB and
adding/modifying/deleting contents of the RIB.
[I-D.white-i2rs-use-case] lists various use-cases which require read
and/or write manipulation of the RIB.
In order to understand what is in a router's RIB, methods like per-
protocol SNMP MIBs and show output screen scraping are being 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 output can change) and vendor dependent.
Building a RIB from per-protocol MIBs is error prone since the MIB
data represents 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.
Adding content to the RIB from an external entity can be done today
using static configuration support provided by router vendors.
However the mix of what can be modified in the RIB varies from vendor
to vendor and the way 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.
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. And that data model could then be used by an
external entity to program a router.
The rest of this document is organized as follows. Section 2.1 goes
into the details of what constitutes and can be programmed in a RIB.
The RIB grammar is specified in Section 6. Examples of using the RIB
grammar are shown in Section 7. Section 5 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
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events.
1.1. Conventions used in this document
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 [RFC2119].
2. RIB data
This section describes the details of a RIB. It makes forward
references to objects in the RIB grammar (Section 6).
2.1. RIB definition
A RIB contains one or more routing instances. On a network device, a
RIB is uniquely identified by its name. A routing instance can be in
only 1 RIB. A routing instance is a collection of routing tables,
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 other each. Layer 3
VPNs, Layer 2 VPNs and VPLS are modeled as routing instances. The
set of interfaces indicates which interfaces this RIB has control
over. The routing tables specify how incoming traffic is to be
forwarded. And the routing parameters control the information in the
routing tables. The intersection set of interfaces of 2 routing
instances MUST be the null set. In other words, an interface should
not be present in 2 routing instances. Thus a routing instance
describes the routing policy and parameters across a set of
interfaces.
A routing instance MUST contain the following mandatory fields.
o INSTANCE_NAME: A routing instance is identified by its name,
INSTANCE_NAME.
o INSTANCE_DISTINGUISHER: Each routing instance must have a unique
distinguisher associated with it. It enables one to distinguish
routes across routing instances. The route distinguisher MUST be
unique across all routing instances in a given network device.
How the INSTANCE_DISTINGUISHER is allocated and kept unique is
outside the scope of this document. The instance distinguisher
maps well to BGP route-distinguisher for virtual private networks
(VPNs). However, the same concept can be used for other use-cases
as well.
o routing-table-list: This is the list of routing tables associated
with this routing instance. Each routing instance can have
multiple tables to represent routes of different types. For
example, one would put IPv4 routes in one table and MPLS routes in
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another table.
A routing instance MAY contain the following optional fields.
o interface-list: This represents the list of interfaces in 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.
o ROUTER_ID: The router-id field identifies the router. This field
is to be used if one wants to virtualize a physical router into
multiple virtual routers. Each virtual router will have a unique
router-id.
o ISO_SYSTEM_ID: For IS-IS to operate on a router, a system
identifier is needed. This represents the same.
o as-data: The as-data fields is used when the routes in this
instance are to be tagged with certain autonomous system (AS)
characteristics. The RIB manager can use AS length as one of the
parameters for making path selection. as-data consists of a AS
number and an optional Confederation AS number ([RFC5065]).
2.2. Routing tables
A routing table is an entity that contains routes. A routing table
is identified by its name. The name MUST be unique within a RIB.
All routes in a given routing table MUST be of the same type (e.g.
IPv4). Each routing table MUST belong to some routing instance.
A routing table can be tagged with a MULTI_TOPOLOGY_ID. If a routing
instance is divided into multiple logical topologies, then the multi-
topology field is used to distinguish one topology from the other, so
as to keep routes from one topology independent of routes from
another topology.
If a routing instance contains multiple tables of the same type (e.g.
IPv4), then a MULTI_TOPOLOGY_ID MUST be associated with each such
table. In other words, multiple tables MUST be used only when there
are multiple topologies. In a given routing instance,
MULTI_TOPOLOGY_ID MUST be unique across routing tables of the same
type.
Each route table can be optionally associated with a
ENABLE_IP_RPF_CHECK attribute that enables Reverse path forwarding
(RPF) checks on all IP routes in that table. 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
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destination address; otherwise, the IP packet is discarded.
2.3. Route
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. This document specifies the
following match types:
o IPv4: Match on destination IP in IPv4 header
o IPv6: Match on destination IP in IPv6 header
o MPLS: Match on a MPLS tag
o MAC: Match on ethernet destination addresses
o Interface: Match on incoming interface of packet
Each route can have associated with it one or more optional route
attributes.
o ROUTE_PREFERENCE: This is a numerical value that allows for
comparing routes from different protocols. 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
entered route will be preferred by the RIB manager. Preference
should be used to dictate behavior. For more examples of
preference, see Section 7.1.
o ROUTE_METRIC: Route preference is used for comparing routes from
different protocols. Route metric is used for comparing routes
learned by the same protocol. If a controller wishes to program 2
or more routes to the same destination, then it can use the metric
field to disambiguate the 2 routes. For more examples, see
Section 7.1.
o LOCAL_ONLY: This is a boolean value. If this is present, then it
means that this route should not be exported into other RIBs or
other route tables.
o rpf-check-interface: 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-check-interface
associated with the route for that IP source address is found. If
the incoming IP packet's interface matches one of the rpf-check-
interfaces, then the IP packet is forwarded based on its IP
destination address; otherwise, the IP packet is discarded. For
MPLS routes, there is no source address to be looked up, so the
usage is slightly different. For an MPLS route, a packet with the
specified MPLS label will only be forwarded if it is received on
one of the interfaces specified by the rpf-check-interface. If no
rpf-check-interface is specified, then matching packets are no
subject to this check. This field overrides the
ENABLE_IP_RPF_CHECK flag on the routing table and interfaces
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provided in this list are used for doing the RPF check.
o as-path: A route can have an as-path associated with it to
indicate which set of autonomous systems has to be traversed to
reach the final destination. The as-path attribute can be used by
the RIB manager in multiple ways. The RIB manager can choose
paths with lower as-path length. Or the RIB manager can choose to
not install paths going via a particular AS. How exactly the RIB
manager uses the as-path is outside the scope of this document.
For details of how the as-path is formed, see Section 5.1.2 of
[RFC4271] and Section 3 of [RFC5065].
o route-vendor-attributes: Vendors can specify vendor-specific
attributes using this. The details of this field is outside the
scope of this document.
2.4. Nexthop
A nexthop represents an object or action 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.
Nexthops can be fully resolved nexthops or unresolved nexthop. A
resolved nexthop is something that is ready for installation in the
FIB. For example, a nexthop that points to an interface. An
unresolved nexthop is something that requires the RIB manager to
figure out the final resolved nexthop. For example, a nexthop could
point to an IP address. The RIB manager has to resolve how to reach
that IP address - 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 stays in unresolved state and
is NOT a candidate for installation in the FIB. Future RIB events
can cause a nexthop to get resolved (like that IP address being
advertised by an IGP neighbor).
The RIB information model allows an external entity to program
nexthops that may be unresolved initially. Whenever a unresolved
nexthop gets resolved, the RIB manager will send a notification of
the same (see Section 5 ).
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
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peer will automatically start going over the new transport path.
Nexthop indirection using identifier could be applied to not just
unicast nexthops, but even to nexthops that contain chains and nested
nexthops (Section 2.4.1).
2.4.1. Nexthop types
This document specifies a very generic, extensible and recursive
grammar for nexthops. Nexthops can be
o Unicast nexthops - pointing to an interface
o Tunnel nexthops - pointing to a tunnel
o Replication lists - list of nexthops to which to replicate a
packet to
o Weighted lists - for load-balancing
o Protection lists - for primary/backup paths
o Nexthop chains - chaining headers, e.g. MPLS label over a GRE
header
o Lists of lists - recursive application of the above
o Indirect nexthops - pointing to a nexthop identifier
It is expected that all network devices will have a limit on
recursion 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 Section 7.2.
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.
Nexthop 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 a 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.
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2.4.2. Nexthop list attributes
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 kinds of attributes are
specified:
o PROTECTION_PREFERENCE: This provides a primary/backup like
preference. The preference is an integer value that should be set
to 1 or 2. Nexthop members with a preference of 1 are preferred
over those with preference of 2. The network device SHOULD create
a list of nexthops with preference 1 (primary) and another list of
nexthops with preference 2 (backup) and SHOULD pre-program the
forwarding plane with both the lists. In case if all the primary
nexthops fail, then traffic MUST be switched over to members of
the backup nexthop list. All members in a list MUST either have a
protection preference specified or all members in a list MUST NOT
have a protection preference specified.
o LOAD_BALANCE_WEIGHT: This is used for load-balancing. Each list
member MUST be assigned a weight. The weight is a percentage
number from 1 to 99. The weight determines how much traffic is
sent over a given list member. If one of the members nexthops in
the list is not active, then the weight value of that nexthop
SHOULD be distributed among the other active members. How the
distribution is done is up to the network device and not in the
scope of the document. In other words, traffic should always be
load-balanced even if there is a failure. After a failure, the
external entity SHOULD re-program the nexthop list with updated
weights so as to get a deterministic behavior among the remaining
list members. 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.
2.4.3. Nexthop content
At the lowest level, a nexthop can point to a:
o identifier: This is an identifier returned by the network device
representing another nexthop or another nexthop chain.
o INTERFACE_IDENTIFIER: This represents a physical, logical or
virtual interface on the network device.
o address: This can be an IP address or MAC address or ISO address.
An optional table name can also be specified to indicate the table
in which the address is to be looked up further. By default the
table will be the same in which the route lookup was performed.
o tunnel encap: This can be an encap representing an IP tunnel or
MPLS tunnel or others as defined in this document
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o ROUTING_TABLE_NAME: This is a routing table that exists in the
RIB. A nexthop pointing to a table indicates that the route
lookup needs to continue in the specified table. This is a way to
perform chained lookups.
2.4.4. Nexthop attributes
Certain information is encoded implicitly in the nexthop and does not
need to be specified by the controller. For example, when a IP
packet is forwarded out, the IP TTL is decremented by default. Same
applies for an MPLS packet. Similarly, when an IP packet is sent
over an ethernet interface, any ARP processing is handled implicitly
by the network device and does not need to be programmed by an
external device.
A nexthop can have some attributes associated with it. The purpose
of the attributes is to either override implicit behavior (like that
related to TTL processing) or to guide the network device to perform
something specific. Vendor specific attributes can also be
specified. The details of vendor specific attributes is outside the
scope of this document.
2.4.5. Special nexthops
This document specifies certain special nexthops. The purpose of
each of them is explained below:
o DISCARD: This indicates that the network device should drop the
packet and increment a drop counter.
o 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).
o 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.
3. Reading from the RIB
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.
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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.
4. Writing to the RIB
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.
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 MUST support requesting identifiers for nexthops and
collecting the identifiers back in the response.
Route programming in the RIB SHOULD result in a return code that
contains the following attributes:
o Installed - Yes/No (Indicates whether the route got installed in
the FIB)
o Active - Yes/No (Indicates whether a route is fully resolved and
is a candidate for selection)
o Reason - E.g. Not authorized
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 identifier by a nexthop-identifier should be
unaffected when the contents of that nexthop changes.
5. Events and Notifications
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:
o Route change notification, with return code as specified in
Section 4
o Nexthop resolution status (resolved/unresolved) notification
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6. RIB grammar
This section specifies the RIB information model in Routing Backus-
Naur Form ([RFC5511]).
<rib> ::= <RIB_NAME> <routing-instance> [<routing-instance> ...]
<routing-instance> ::= <INSTANCE_NAME> <INSTANCE_DISTINGUISHER>
[<interface-list>] <routing-table-list>
[<ROUTER_ID>] [<ISO_SYSTEM_ID>]
[<as-data>]
<as-data> ::= <AS_NUMBER> [<CONFEDERATION_AS>]
<interface-list> ::= (<INTERFACE_IDENTIFIER> ...)
<routing-table-list> ::= (<routing-table> ...)
<routing-table> ::= <routing-instance-name> <ROUTING_TABLE_NAME>
<table-family>
[<route> ... ] [<MULTI_TOPOLOGY_ID>]
[ENABLE_IP_RPF_CHECK]
<table-family> ::= <IPV4_TABLE_FAMILY> | <IPV6_TABLE_FAMILY> |
<MPLS_TABLE_FAMILY> | <IEEE_MAC_TABLE_FAMILY>
<route> ::= <ROUTING_TABLE_NAME> <match>
<nexthop-list> [<route-attributes>]
[<route-vendor-attributes>]
<match> ::= <ipv4-route> | <ipv6-route> | <mpls-route> |
<mac-route> | <interface-route>
<ipv4-route> ::= <IPV4_ADDRESS> <IPV4_PREFIX_LENGTH>
<ipv6-route> ::= <IPV6_ADDRESS> <IPV6_PREFIX_LENGTH>
<mpls-route> ::= <MPLS> ( <MPLS_LABEL> ... )
<mac-route> ::= <IEEE_MAC> ( <MAC_ADDRESS> )
<interface-route> ::= <INTERFACE> <INTERFACE_IDENTIFIER>
<route-attributes> ::= [<ROUTE_PREFERENCE>] [<ROUTE_METRIC>]
[<LOCAL_ONLY>]
[<address-family-route-attributes>]
<address-family-route-attributes> ::= <ip-route-attributes> |
<mpls-route-attributes> |
<ethernet-route-attributes>
<ip-route-attributes> ::= [<as-path>] [<rpf-check-interface>]
<as-path> ::= (<as-path-segment-type> <as-list>) [<as-path> ...]
<as-path-segment-type> ::= <AS_SET> | <AS_SEQUENCE> |
<AS_CONFED_SEQUENCE> | <AS_CONFED_SET>
<as-list> ::= (<AS_NUMBER> ...) [<as-path>]
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<rpf-check-interface> ::= <interface-list>
<mpls-route-attributes> ::= [<rpf-check-interface>]
<ethernet-route-attributes> ::= <>
<route-vendor-attributes> ::= <>
<nexthop-list> ::= <special-nexthop> |
((<nexthop-list-member>) |
([<nexthop-list-member> ... ] <nexthop-list> ))
<nexthop-list-member> ::= (<nexthop-chain> |
<nexthop-chain-identifier> )
[<nexthop-list-member-attributes>]
<nexthop-list-member-attributes> ::= [<PROTECTION_PREFERENCE>]
[<LOAD_BALANCE_WEIGHT>]
<nexthop-chain> ::= (<nexthop> ...)
<nexthop-chain-identifier> ::= <NEXTHOP_NAME> | <NEXTHOP_ID>
<nexthop> ::= (<nexthop-identifier> | <INTERFACE_IDENTIFIER> |
(<nexthop-address> [<ROUTING_TABLE_NAME>]
[<EGRESS_INTERFACE>]) |
(<tunnel-encap> [<ROUTING_TABLE_NAME>]
[<EGRESS_INTERFACE>) |
<ROUTING_TABLE_NAME>)
[<nexthop-attributes>]
[<nexthop-vendor-attributes>]
<nexthop-identifier> ::= <NEXTHOP_NAME> | <NEXTHOP_ID>
<nexthop-address> ::= (<IPv4> <ipv4-address>) |
(<IPV6> <ipv6-address>) |
(<IEEE_MAC> <IEEE_MAC_ADDRESS>) |
(<ISO> <ISO_ADDRESS>)
<special-nexthop> ::= <DISCARD> | <DISCARD_WITH_ERROR> |
(<RECEIVE> [<COS_VALUE>] [<rate-limiter>])
<rate-limiter> ::= <>
<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>]
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[<FLOW_LABEL>] [<HOP_LIMIT>]
<mpls-header> ::= (<mpls-label-operation> ...)
<mpls-label-operation> ::= (<MPLS_PUSH> <MPLS_LABEL> [<S_BIT>]
[<TOS_VALUE>] [<TTL_VALUE>]) |
(<MPLS_POP> [<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>]
<nexthop-attributes> ::= [<NEXTHOP_ADDRESS_FAMILY>]
[<nexthop-flags>]
<NEXTHOP_ADDRESS_FAMILY> ::= <IPV4> | <IPV6> | <ISO> | <IEEE MAC>
<nexthop-flags> ::= [<NO_DECREMENT_TTL>] [<NO_PROPAGATE_TTL>]
<nexthop-vendor-attributes> ::= <>
7. Using the RIB grammar
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.
7.1. Using route preference and metric
Using route preference one can pre-install protection paths in the
network. For example, if OSPF has a route preference of 10, then one
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 goes away (for any
reason), the protection path will get installed in the FIB.
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.
Route metric is used to disambiguate between 2 or more routes to the
same destination with the same preference and in the same route
table. One usage of this is to install 2 routes, each with a
different nexthop. The preferred nexthop is given a better metric
than the other one. This results in traffic being forwarded to the
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preferred nexthop. If the preferred nexthop fails, then the RIB
manager will automatically install a route to the other nexthop.
7.2. Using different nexthops types
The RIB grammar allows one to create a variety of nexthops. This
section describes uses for certain types of nexthops.
7.2.1. Tunnel nexthops
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.
7.2.2. Replication lists
One can create a replication list for replication 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.
A replication list (at the simplest level) can be represented as:
<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= <nexthop-chain> [<nexthop-chain> ...]
<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
7.2.3. Weighted lists
A weighted list is used to load-balance traffic among a set of
nexthops. A weighted list is very similar to a replication list,
with the difference that each member nexthop MUST have a
LOAD_BALANCE_WEIGHT associated with it.
A weighted list (at the simplest level) can be represented as:
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<nexthop-list> ::= (<nexthop> <LOAD_BALANCE_WEIGHT>)
[(<nexthop> <LOAD_BALANCE_WEIGHT>)... ]
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= (<nexthop-chain> <nexthop-list-member-attributes>)
[(<nexthop-chain>
<nexthop-list-member-attributes>) ...]
<nexthop-list> ::= (<nexthop-chain> <LOAD_BALANCE_WEIGHT>)
[(<nexthop-chain> <LOAD_BALANCE_WEIGHT>) ... ]
<network-list> ::= (<nexthop> <LOAD_BALANCE_WEIGHT>)
[(<nexthop> <LOAD_BALANCE_WEIGHT>)... ]
7.2.4. Protection lists
Protection lists are similar to weighted lists. A protection list
specifies a set of primary nexthops and a set of backup nexthops.
The <PROTECTION_PREFERENCE> attribute indicates which nexthop is
primary and which is backup.
A protection list can be represented as:
<nexthop-list> ::= (<nexthop> <PROTECTION_PREFERENCE>)
[(<nexthop> <PROTECTION_PREFERENCE>)... ]
A protection list can also be a weighted list. In other words,
traffic can be load-balanced among the primary nexthops of a
protection list. In such a case, the list will look like:
<nexthop-list> ::= (<nexthop> <PROTECTION_PREFERENCE>
<LOAD_BALANCE_WEIGHT>)
[(<nexthop> <PROTECTION_PREFERENCE>
<LOAD_BALANCE_WEIGHT>)... ]
7.2.5. Nexthop chains
A nexthop chain is a nexthop that puts 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 allows an external entity to break up the
programming of the nexthop into independent pieces - one per
encapsulation.
A simple example of MPLS over GRE can be represented as:
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<nexthop-list> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
The above can be derived from the grammar as follows:
<nexthop-list> ::= <nexthop-list-member> [<nexthop-list-member> ...]
<nexthop-list> ::= <nexthop-chain>
<nexthop-list> ::= <nexthop> [ <nexthop> ... ]
<nexthop-list> ::= <tunnel-encap> (<nexthop> [ <nexthop> ...])
<nexthop-list> ::= <tunnel-encap> (<tunnel-encap>)
<nexthop-list> ::= (<MPLS> <mpls-header>) (<GRE> <gre-header>)
7.2.6. Lists of lists
Lists of lists is a complex construct. One example of usage of such
a construct is to replicate traffic to multiple destinations, with
high availability. In other words, for each destination you have a
primary and backup nexthop (replication list) to ensure there is no
traffic drop in case of a failure. So the outer list is a list of
destinations and the inner lists are replication lists of primary/
backup nexthops.
7.3. Solving optimized exit control
In case of optimized exit control, a controller wants to control the
edge device (and optionally control the outgoing interface on that
edge device) that is used by a server to send traffic out. This can
be easily achieved by having the controller program the edge router
(Eg. 192.0.2.10) and the server along the following lines:
Server:
<route> ::= <routing-table-name> <match> (<edge-router>
<edge-router-interface>)
<route> ::= <routing-table-name> <198.51.100.1/16>
(<GRE> <gre-header>)
(<MPLS> <mpls-header>)
<route> ::- <routing-table-name> <198.51.100.1/16>
(<GRE> <192.0.2.10> <GRE_PROTOCOL_MPLS>)
(<MPLS_PUSH> <100>)
Edge Router:
<route> ::= <mpls-routing-table> <mpls-route> <nexthop>
<route> ::= <mpls-routing-table> (<MPLS> <100>) <interface-10>
In the above case, the label 100 identifies the egress interface
on the edge router.
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8. RIB operations at scale
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.
8.1. RIB reads
Bulking (grouping of multiple objects in a single message) MUST be
supported when a network device sends RIB data to an external entity.
8.2. RIB writes
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.
8.3. RIB events and notifications
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.
9. Security Considerations
All interactions between a RIB manager and an external entity MUST be
authenticated. The RIB manager MUST protect itself against a denial
of service attack by a rouge 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.
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.
10. IANA Considerations
This document does not generate any considerations for IANA.
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11. Acknowledgements
The authors would like to thank Alia Atlas, Edward Crabbe, Hariharan
Ananthakrishnan, Jeff Haas and Ina Minei 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, Sriganesh Kini,
Susan Hares, Fabian Schneider and Nitin Bahadur.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
12.2. Informative References
[I-D.atlas-i2rs-problem-statement]
Atlas, A., Nadeau, T., and D. Ward, "Interface to the
Routing System Problem Statement",
draft-atlas-i2rs-problem-statement-00 (work in progress),
February 2013.
[I-D.hares-i2rs-use-case-vn-vc]
Hares, S., "Use Cases for Virtual Connections on Demand
(VCoD) and Virtual Network on Demand using Interface to
Routing System", draft-hares-i2rs-use-case-vn-vc-00 (work
in progress), February 2013.
[I-D.white-i2rs-use-case]
White, R., Hares, S., and R. Fernando, "Use Cases for an
Interface to the Routing System",
draft-white-i2rs-use-case-00 (work in progress),
February 2013.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065, August 2007.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
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Authors' Addresses
Nitin Bahadur (editor)
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
US
Phone: +1 408 745 2000
Email: nitinb@juniper.net
URI: www.juniper.net
Ron Folkes (editor)
Juniper Networks, Inc.
1194 N. Mathilda Avenue
Sunnyvale, CA 94089
US
Phone: +1 408 745 2000
Email: ronf@juniper.net
URI: www.juniper.net
Sriganesh Kini
Ericsson
Email: sriganesh.kini@ericsson.com
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