--- 1/draft-ietf-i2rs-rib-info-model-05.txt 2015-03-08 23:14:42.549204873 -0700 +++ 2/draft-ietf-i2rs-rib-info-model-06.txt 2015-03-08 23:14:42.601206188 -0700 @@ -1,108 +1,108 @@ Network Working Group N. Bahadur, Ed. Internet-Draft Bracket Computing Intended status: Informational R. Folkes, Ed. -Expires: July 31, 2015 Juniper Networks, Inc. +Expires: September 10, 2015 Juniper Networks, Inc. S. Kini, Ed. Ericsson J. Medved Cisco - January 27, 2015 + March 09, 2015 Routing Information Base Info Model - draft-ietf-i2rs-rib-info-model-05 + draft-ietf-i2rs-rib-info-model-06 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 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. -Status of this Memo +Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on July 31, 2015. + This Internet-Draft will expire on September 10, 2015. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1.1. Conventions used in this document . . . . . . . . . . . . 6 - 2. RIB data . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 2.1. RIB definition . . . . . . . . . . . . . . . . . . . . . . 6 - 2.2. Routing instance . . . . . . . . . . . . . . . . . . . . . 7 - 2.3. Route . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 2.4. Nexthop . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 2.4.1. Nexthop types . . . . . . . . . . . . . . . . . . . . 12 - 2.4.2. Nexthop list attributes . . . . . . . . . . . . . . . 13 - 2.4.3. Nexthop content . . . . . . . . . . . . . . . . . . . 13 - 2.4.4. Special nexthops . . . . . . . . . . . . . . . . . . . 14 - 3. Reading from the RIB . . . . . . . . . . . . . . . . . . . . . 14 - 4. Writing to the RIB . . . . . . . . . . . . . . . . . . . . . . 15 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1.1. Conventions used in this document . . . . . . . . . . . . 5 + 2. RIB data . . . . . . . . . . . . . . . . . . . . . . . . . . 5 + 2.1. RIB definition . . . . . . . . . . . . . . . . . . . . . 5 + 2.2. Routing instance . . . . . . . . . . . . . . . . . . . . 6 + 2.3. Route . . . . . . . . . . . . . . . . . . . . . . . . . . 7 + 2.4. Nexthop . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 2.4.1. Nexthop types . . . . . . . . . . . . . . . . . . . . 11 + 2.4.2. Nexthop list attributes . . . . . . . . . . . . . . . 12 + 2.4.3. Nexthop content . . . . . . . . . . . . . . . . . . . 12 + 2.4.4. Special nexthops . . . . . . . . . . . . . . . . . . 13 + 3. Reading from the RIB . . . . . . . . . . . . . . . . . . . . 14 + 4. Writing to the RIB . . . . . . . . . . . . . . . . . . . . . 14 5. Notifications . . . . . . . . . . . . . . . . . . . . . . . . 15 6. RIB grammar . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.1. Nexthop grammar explained . . . . . . . . . . . . . . . . 18 - 7. Using the RIB grammar . . . . . . . . . . . . . . . . . . . . 19 - 7.1. Using route preference . . . . . . . . . . . . . . . . . . 19 - 7.2. Using different nexthops types . . . . . . . . . . . . . . 19 + 7. Using the RIB grammar . . . . . . . . . . . . . . . . . . . . 18 + 7.1. Using route preference . . . . . . . . . . . . . . . . . 18 + 7.2. Using different nexthops types . . . . . . . . . . . . . 19 7.2.1. Tunnel nexthops . . . . . . . . . . . . . . . . . . . 19 7.2.2. Replication lists . . . . . . . . . . . . . . . . . . 19 - 7.2.3. Weighted lists . . . . . . . . . . . . . . . . . . . . 20 - 7.2.4. Protection lists . . . . . . . . . . . . . . . . . . . 20 - 7.2.5. Nexthop chains . . . . . . . . . . . . . . . . . . . . 21 - 7.2.6. Lists of lists . . . . . . . . . . . . . . . . . . . . 21 - 7.3. Performing multicast . . . . . . . . . . . . . . . . . . . 23 + 7.2.3. Weighted lists . . . . . . . . . . . . . . . . . . . 19 + 7.2.4. Protection . . . . . . . . . . . . . . . . . . . . . 20 + 7.2.5. Nexthop chains . . . . . . . . . . . . . . . . . . . 21 + 7.2.6. Lists of lists . . . . . . . . . . . . . . . . . . . 21 + 7.3. Performing multicast . . . . . . . . . . . . . . . . . . 23 8. RIB operations at scale . . . . . . . . . . . . . . . . . . . 24 8.1. RIB reads . . . . . . . . . . . . . . . . . . . . . . . . 24 - 8.2. RIB writes . . . . . . . . . . . . . . . . . . . . . . . . 24 - 8.3. RIB events and notifications . . . . . . . . . . . . . . . 24 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 24 + 8.2. RIB writes . . . . . . . . . . . . . . . . . . . . . . . 24 + 8.3. RIB events and notifications . . . . . . . . . . . . . . 24 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 - 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25 - 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 - 12.1. Normative References . . . . . . . . . . . . . . . . . . . 25 - 12.2. Informative References . . . . . . . . . . . . . . . . . . 25 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 + 12.1. Normative References . . . . . . . . . . . . . . . . . . 25 + 12.2. Informative References . . . . . . . . . . . . . . . . . 25 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 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) 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 @@ -205,32 +205,29 @@ "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). A high-level description of the RIB contents is as shown below. routing-instance - | | | | 0..N | | 1..N | | - interface(s) RIB(s) - | | | 0..N - + | route(s) Figure 2: RIB model 2.1. RIB definition A RIB is an entity that contains routes. A RIB is identified by its name and a RIB is contained within a routing instance (Section 2.2). 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 @@ -295,51 +296,53 @@ a given domain. 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. Figure 3 represents the overall contents of a route. route - | | | +---------+ | +----------+ | | | - 0..N | | | 1..N - - route-attribute match nexthop-list + 0..N | | | + route-attribute match nexthop | | +-------+-------+-------+--------+ | | | | | | | | | | IPv4 IPv6 MPLS MAC Interface - (Unicast/Multicast) - Figure 3: Route model This document specifies the following match types: + o IPv4: Match on destination IP address in the IPv4 header + o IPv6: Match on destination IP address in the IPv6 header o MPLS: Match on a MPLS label at the top of the MPLS label stack + o MAC: Match on MAC destination addresses in the ethernet header + o Interface: Match on incoming interface of the packet + o IP multicast: Match on (S, G) or (*, G), where S and G are IP - prefixes + addresses Each route MUST have associated with it the following mandatory route attributes. + o 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 Section 7.1. @@ -383,49 +387,48 @@ 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 Section 5 ). The overall structure and usage of a nexthop is as shown in the figure below. route - | | 0..N - - nexthop-list - | - +------------------+------------------+ - 1..N | | + nexthop <-----------------+ | | - - nexthop-list-member special-nexthop - - | + +-------+----------------------------+ | + | | | | | + | | | | | + base load-balance protection replicate | + | | | | | + | |2..N |2 |2..N | + | | V | | + | +------------->+<------------+ | + | | | + | +-----------------------+ | - - nexthop-chain - + +-------------------+ + | | + | nexthop-chain + | | + special-nexthop | 1..N | - 1..N | - - nexthop - + nexthop-chain-member | | - +--------+------+------------------+------------------+ + +---------------+--------+---------+------------------+ | | | | | | | | - nexthop-id egress-interface logical-tunnel tunnel-encap Figure 4: Nexthop model 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 @@ -435,31 +438,42 @@ 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 (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 Interface nexthops - pointing to an interface + o Tunnel nexthops - pointing to a tunnel + o Replication lists - list of nexthops to which to replicate a packet + o Weighted lists - for load-balancing - o Protection lists - for primary/backup paths + + o Preference lists - for protection using primary and backup + o Nexthop chains - for 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 + o Special nexthops - for performing specific well-defined functions + (e.g. drop) + 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 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 @@ -478,89 +492,94 @@ 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. 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 (primary) or 2 (backup). Only when all the primary nexthops - fail is the traffic re-routed through the backup nexthops. This - attribute must be specified for all the members of a list or none - of them. - o LOAD_BALANCE_WEIGHT: This is used for load-balancing. Each list + individual member of the list. Two attributes are specified: + + o 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. + + o 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. - A nexthop list MAY contain elements that have both - PROTECTION_PREFERENCE and LOAD_BALANCE_WEIGHT set. When both are - set, it means under normal operation the network device should load - balance the traffic over all FIB-eligible nexthops of the current - protection preference. - 2.4.3. Nexthop content At the lowest level, a nexthop can be one of: + o identifier: This is an identifier returned by the network device representing another nexthop or another nexthop chain. + o 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. + o 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. + * 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. o EGRESS_INTERFACE and IP address: This can be used in cases e.g. where the IP address is a link-local address. + o EGRESS_INTERFACE and MAC address: The egress interface must be an ethernet interface. Address resolution is not required for this nexthop. + o 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 specified 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. + o 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). + o 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. 2.4.4. 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 @@ -604,50 +627,58 @@ 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. 5. 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 6. RIB grammar This section specifies the RIB information model in Routing Backus- - Naur Form [RFC5511]. + Naur Form [RFC5511]. 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. ::= [] [] ::= ( ...) ::= ( ...) ::= [ ... ] [ENABLE_IP_RPF_CHECK] ::= | | | - ::= + ::= [] [] ::= ( | | | | ) + ::= | | + | | + ::= | | | | - ::= ( | | ( )) ::= ::= ::= ::= ( | | ( )) @@ -649,26 +680,21 @@ ::= ::= ( | | ( )) ::= ::= ::= ::= | | - ::= - ::= - ::= - ::= [] - [] ::= | | ::= <> ::= <> ::= <> ::= <> @@ -665,45 +691,56 @@ [] ::= | | ::= <> ::= <> ::= <> ::= <> - ::= | - (( ) ...) | - ( ...) + ::= | + | + | + - ::= [] - [] + ::= + ( ) ... + is a number between 1 and 99. + ::= - ::= ( | - ) - [] - ::= [] - [] + = + ( )... + Each should have a unique value within a + . - ::= ( ...) - ::= | - ::= ( | | + ::= ... + + ::= | + + ::= ... + ::= | + + ::= | + | | | ( ( | )) | ( ) | ( []) | | ) - ::= | - ::= | | + ::= + + ::= | + + ::= | | ( []) ::= ::= | | | | | ::= ( ) | ( ) | ( ) | ( ) | ( ) | @@ -725,40 +762,26 @@ ::= ( | ) [] ::= ( | ) [] Figure 5: RIB rBNF grammar 6.1. Nexthop grammar explained - A nexthop-list can be a special-nexthop like DISCARD or it can be - complex nexthop containing one or more lists. The nexthop-list has - recursion built-in to address complex use-cases like the one defined - in Section 7.2.6. When recursion is used, one can specify the - attributes if one desires load-balancing or - primary/backup like feature. If neither attribute is specified, then - it implies that multicast (send to all) is desired. - - Protection preference and load balancing are also associated with the - nexthop-list-member. See Section 7.2.6 for an example. - - Specifying the nexthop attributes ( or - ) at the beginning of the construct - helps clearly indicate whether one is defining a set of constructs - for doing protection or load balancing or multicast. Placing the - attribute at the inner level would cause issues since the - attribute would need to be consistent (and duplicated) across various - members of (for example) the load-balance list and only after parsing - the inner level one would realize that it was load- - balancing that the caller desired. + 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 Section 7.2.6. 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 Using route preference a client can pre-install alternate paths in @@ -781,175 +804,169 @@ 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 + 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. A replication list (at the simplest level) can be represented as: - ::= [ ... ] + ::= [ ... ] The above can be derived from the grammar as follows: - ::= [ ...] - ::= [ ...] - ::= [ ... ] + ::= + ::= ... 7.2.3. Weighted lists 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 LOAD_BALANCE_WEIGHT associated with it. + nexthop MUST have a NEXTHOP_LB_WEIGHT associated with it. A weighted list (at the simplest level) can be represented as: - ::= ( ) - [( )... ] + ::= ( ) + [( )... ] The above can be derived from the grammar as follows: - ::= [ ...] - ::= ( ) - [( - ) ...] - ::= ( ) - [( ) ... ] - ::= ( ) - [( )... ] + ::= + ::= + + ( ) ... + ::= ( ) + ( ) ... -7.2.4. Protection lists +7.2.4. Protection - Protection lists are similar to weighted lists. A protection list - specifies a set of primary nexthops and a set of backup nexthops. - The attribute indicates which nexthop is - primary and which is backup. + A primary/backup protection can be represented as: - A protection list can be represented as: + ::= <1> <2> ) - ::= ( ) - [( )... ] +The above can be derived from the grammar as follows: - 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: + ::= + ::= ( + ( )...) + ::= ( + ( )) + ::= (( + ( )) + ::= (<1> + (<2> )) - ::= ( - ) - [( - )... ] + Traffic can be load-balanced among multiple primary nexthops and a + single backup. In such a case, the nexthop will look like: + + ::= (<1> + ( + ( + ( ) ...)) + <2> ) + + A backup can also have another backup. In such a case, the list will + look like: + + ::= (<1> + <2> <3> ) 7.2.5. Nexthop chains - A nexthop chain is a nexthop that puts one or more headers on an + A nexthop chain specifies how 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 allows an external entity to break up the programming of the nexthop into independent pieces - one per encapsulation. Elements in a nexthop-chain are evaluated left to right. A simple example of MPLS over GRE can be represented as: - ::= ( ) ( ) + ::= ( ) ( + ) The above can be derived from the grammar as follows: - ::= [ ...] - ::= - ::= [ ... ] - ::= ( [ ...]) - ::= () - ::= ( ) ( ) + ::= [ ...] + ::= ( + ) + ::= ( ) + ::= ( ) ( + ) 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 multicast - list and the inner lists are protection lists of primary/backup - nexthops. - - ::= ( ) - ( ) - - The above can be derived from the grammar as follows: - - ::= () () - ::= ( ) - () - ::= (( ) - )) - () - ::= (( ) - ( )) - () - ::= (( <1>) ( <2>)) - () - ::= (( <1>) ( <2>)) - () - ::= (( <1>) ( <2>)) - () - ::= (( <1>) ( <2>)) () - - // Like above, the member on the right can be expanded - to give: - - ::= (( <1>) ( <2>)) - (( <1>) ( <2>)) - - Above, eth1 and eth3 are primary multicast interfaces and eth2 and eth4 - are their respective backup interfaces. - - Another example of list of lists would be ECMP (load-balancing - traffic across 2 nexthops), wherein each nexthop itself is an - aggregated high-level interface (i.e. load-balance the traffic across - the components of the nexthop itself). See below for the derivation. - - ::= () (( <0.5> <0.5>) <0.5>) - -The above asks for sending 50% traffic to eth1 interface, -25% (50% of 50%) to eth2 and 25% to eth3. - - ::= ( ::= (( ) - ( ) - ::= (( <0.5>) ( <0.5>) - ::= (( <0.5>) ( <0.5>) - ::= (( <0.5>) ( <0.5>) - ::= (( <0.5>) ( <0.5>) - ::= (( <0.5>) ( <0.5>) - ::= (( <0.5>) ( <0.5>) + 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. - ::= (( <0.5>) - (( ) <0.5>) - ::= (( <0.5>) - (( <0.5> <0.5>) <0.5>) - ::= (( <0.5>) - (( <0.5> <0.5>) <0.5>) - ::= (( <0.5>) (( <0.5> <0.5>) <0.5>) +This can be derived from the grammar as follows: -One can make this example even more complicated by adding protection -nexthops for one or more of the eth interfaces. + ::= + ::= ( ...) + ::= ( ) + ::= (( ) + ( )) + ::= (( + ( + ( ) ...)) + (( + ( + ( ) ...)) + ::= (( + ( + ( ))) + (( + ( + ( ) + ( ))) + ::= (( + ( ) + ( ))) + (( + ( ) + ( ) + ( ))) + ::= (( + ( ) + ( ))) + (( ( ) + ( ) + ( ))) + ::= + (( + (50 ) + (50 ))) + (( + (20 ) + (20 ) + (60 ))) 7.3. Performing multicast 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. In PIM-based multicast, the packets are IP forwarded on an IP @@ -1026,39 +1043,36 @@ 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.hares-i2rs-use-case-vn-vc] Hares, S. and M. Chen, "Use Cases for Virtual Connections on Demand (VCoD) and Virtual Network on Demand (VNoD) - using Interface to Routing System", - draft-hares-i2rs-use-case-vn-vc-03 (work in progress), - July 2014. + using Interface to Routing System", draft-hares-i2rs-use- + case-vn-vc-03 (work in progress), July 2014. [I-D.ietf-i2rs-problem-statement] Atlas, A., Nadeau, T., and D. Ward, "Interface to the - Routing System Problem Statement", - draft-ietf-i2rs-problem-statement-06 (work in progress), - January 2015. + Routing System Problem Statement", draft-ietf-i2rs- + problem-statement-06 (work in progress), January 2015. [I-D.white-i2rs-use-case] White, R., Hares, S., and A. Retana, "Protocol Independent - Use Cases for an Interface to the Routing System", - draft-white-i2rs-use-case-06 (work in progress), - July 2014. + Use Cases for an Interface to the Routing System", draft- + white-i2rs-use-case-06 (work in progress), July 2014. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. - Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", - RFC 4915, June 2007. + Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC + 4915, June 2007. [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, February 2008. [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax Used to Form Encoding Rules in Various Routing Protocol Specifications", RFC 5511, April 2009. Authors' Addresses