draft-ietf-bmwg-fib-term-02.txt   draft-ietf-bmwg-fib-term-03.txt 
Benchmarking Methodology Working Group G. Trotter Benchmarking Methodology Working Group G. Trotter
Internet Draft Agilent Technologies Internet Draft Agilent Technologies
Document: draft-ietf-bmwg-fib-term-02.txt July 2001 Document: draft-ietf-bmwg-fib-term-03.txt September 2001
Category: Informational Category: Informational
Terminology for Forwarding Information Base (FIB) based Router Terminology for Forwarding Information Base (FIB) based Router
Performance Performance
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1]. all provisions of Section 10 of RFC2026 [1].
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months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet- Drafts as at any time. It is inappropriate to use Internet- Drafts as
reference material or to cite them other than as "work in progress." reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract
The forwarding performance of an IP router may be dependent upon or
may be linked to the composition and size of the forwarding
information base installed within a router. This document describes
the terms to be used in a methodology that determines the IP packet
forwarding performance of IP routers as a function of the forwarding
information base installed within a router.
Table of Contents Table of Contents
1. Introduction....................................................2 1. Introduction....................................................2
2. Overview........................................................2 2. Overview........................................................2
3. Existing Definitions............................................2 3. Existing Definitions............................................3
4. Definition Format...............................................3 4. Definition Format...............................................3
5. Definitions - parameters........................................3 5. Definitions - parameters........................................3
5.1 Network Prefix.................................................3 5.1 Network Prefix.................................................3
5.2 Network Prefix Length..........................................4 5.2 Network Prefix Length..........................................4
5.3 Forwarding Information Base (FIB)..............................4 5.3 Forwarding Information Base (FIB)..............................4
5.4 Forwarding Information Base Entry..............................5 5.4 Forwarding Information Base Entry..............................5
5.5 Forwarding Information Base Size...............................5 5.5 Forwarding Information Base Size...............................5
5.6 Longest Length Prefix Match Algorithm..........................6 5.6 Longest Length Prefix Match Algorithm..........................6
5.7 Forwarding Information Base Prefix Distribution................6 5.7 Forwarding Information Base Prefix Distribution................6
5.8 Per-Interface or Per-Card Forwarding Information Base..........7 5.8 Per-Interface or Per-Card Forwarding Information Base..........7
5.9 Per-Interface Forwarding Information Base Cache................7 Terminology for FIB based Router Performance Sept., 2001
5.10 Route Aggregation.............................................8
5.9 Per-Interface Forwarding Information Base Cache................8
5.10 Route Aggregation.............................................9
6. Definitions - metrics...........................................9 6. Definitions - metrics...........................................9
6.1 Maximum Forwarding Information Base Size.......................9 6.1 Maximum Forwarding Information Base Size.......................9
6.2 Forwarding Information Base Learning Time.....................10 6.2 Forwarding Information Base Learning Time.....................10
6.3 Forwarding Information Base-dependent Throughput..............10 6.3 Forwarding Information Base-dependent Throughput..............11
6.4 Forwarding Information Base-dependent Latency.................11 6.4 Forwarding Information Base-dependent Latency.................11
6.5 Forwarding Information Base-dependent Frame Loss Rate.........11 6.5 Forwarding Information Base-dependent Frame Loss Rate.........11
7. Security Considerations........................................12 7. Security Considerations........................................12
Terminology for FIB based Router Performance July, 2001
8. References.....................................................12 8. References.....................................................12
9. Acknowledgments................................................12 9. Acknowledgments................................................12
10. Author's Addresses............................................12 10. Author's Addresses............................................12
1. Introduction 1. Introduction
This document defines terms that are to be used in a methodology This document defines terms that are to be used in a methodology
that determines the IP packet forwarding performance of IP routers that determines the IP packet forwarding performance of IP routers
as a function of the forwarding information base installed within as a function of the forwarding information base installed within
the router. the router.
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the router. Tests may need to be performed up to the maximum FIB the router. Tests may need to be performed up to the maximum FIB
size (6.1). size (6.1).
When configuring the router for these measurements, the routes need When configuring the router for these measurements, the routes need
to be manually entered into the router, or advertised via a routing to be manually entered into the router, or advertised via a routing
protocol. It may take some period of time (the FIB learning time protocol. It may take some period of time (the FIB learning time
(6.2)) before the router learns all the routes. (6.2)) before the router learns all the routes.
When routes are advertised into the router, the routes should be When routes are advertised into the router, the routes should be
advertised in such a way so that route aggregation (5.10) does not advertised in such a way so that route aggregation (5.10) does not
Terminology for FIB based Router Performance Sept., 2001
occur. Also, the effect of a per-interface FIB cache (5.9) needs to occur. Also, the effect of a per-interface FIB cache (5.9) needs to
be taken into account. be taken into account.
3. Existing Definitions 3. Existing Definitions
[3] should be consulted before attempting to make use of this [3] should be consulted before attempting to make use of this
document. [2] contains discussions of a number of terms relevant to document. [2] contains discussions of a number of terms relevant to
the benchmarking of network interconnect devices and should also be the benchmarking of network interconnect devices and should also be
consulted. consulted.
Terminology for FIB based Router Performance July, 2001
4. Definition Format 4. Definition Format
The definition format is the equivalent to that defined in [3], and The definition format is the equivalent to that defined in [3], and
is repeated here for convenience: is repeated here for convenience:
X.x Term to be defined. (e.g., Latency) X.x Term to be defined. (e.g., Latency)
Definition: Definition:
The specific definition for the term. The specific definition for the term.
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Definition: Definition:
"A network prefix is . . . a contiguous set of bits at the "A network prefix is . . . a contiguous set of bits at the
more significant end of the address that defines a set of more significant end of the address that defines a set of
systems; host numbers select among those systems." systems; host numbers select among those systems."
(This definition is taken directly from section 2.2.5, (This definition is taken directly from section 2.2.5,
"Addressing Architecture", in [4].) "Addressing Architecture", in [4].)
Discussion: Discussion:
Network prefixes are represented as a 32 bit IP address with
a mask indicating the number of bits representing the network Terminology for FIB based Router Performance Sept., 2001
prefix. I.e. 141.184.128 /17 indicates that the network
prefix is 17 bits long (i.e. the network prefix length, see In the CIDR context, the network prefix is the network
(5.2)). component of an IP address. A common alternative to using a
bitwise mask to communicate this component is the use of
"slash (/) notation." Slash notation binds the notion of
network prefix length (see 5.2) in bits to an IP address.
E.g., 141.184.128.0/17 indicates the network component of
this IPv4 address is 17 bits wide.
Measurement units: Measurement units:
<n/a> <n/a>
Issues: Issues:
Terminology for FIB based Router Performance July, 2001
See Also: See Also:
Network Prefix Length (5.2) Network Prefix Length (5.2)
5.2 Network Prefix Length 5.2 Network Prefix Length
Definition: Definition:
The number of bits used to define the network prefix. The number of bits used to define the network prefix.
Network prefixes, using CIDR terminology, are typically Network prefixes, using CIDR terminology, are typically
referred to as 15.35.128.0 /17, indicating that the network referred to as 15.35.128.0 /17, indicating that the network
prefix is 17 bits long. prefix is 17 bits long.
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Definition: Definition:
As according to the definition in [4]: As according to the definition in [4]:
"The table containing the information necessary to forward IP "The table containing the information necessary to forward IP
Datagrams, in this document, is called the Forwarding Datagrams, in this document, is called the Forwarding
Information Base. At minimum, this contains the interface Information Base. At minimum, this contains the interface
identifier and next hop information for each reachable identifier and next hop information for each reachable
destination network prefix." destination network prefix."
Discussion: Discussion:
Terminology for FIB based Router Performance Sept., 2001
The forwarding information base describes a database indexing The forwarding information base describes a database indexing
network prefixes versus router port identifiers. network prefixes versus router port identifiers.
A forwarding information base consists of [FIB size (6.1)] A forwarding information base consists of [FIB size (6.1)]
FIB entries (5.4). FIB entries (5.4).
The forwarding information base is distinct from the "routing The forwarding information base is distinct from the "routing
table" (or, the Routing Information Base), which holds all table" (or, the Routing Information Base), which holds all
routing information received from routing peers. routing information received from routing peers.
The forwarding information base contains unique paths only The forwarding information base contains unique paths only
(i.e. does not contain secondary paths). (i.e. does not contain secondary paths).
Terminology for FIB based Router Performance July, 2001
Measurement units: Measurement units:
<none> <none>
Issues: Issues:
See Also: See Also:
forwarding information base entry (5.4) forwarding information base entry (5.4)
forwarding information base size (5.5) forwarding information base size (5.5)
forwarding information base prefix distribution (5.6) forwarding information base prefix distribution (5.6)
maximum forwarding information base size (6.1) maximum forwarding information base size (6.1)
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See Also: See Also:
forwarding information base (5.3) forwarding information base (5.3)
forwarding information base size (5.5) forwarding information base size (5.5)
forwarding information base prefix distribution (5.6) forwarding information base prefix distribution (5.6)
maximum forwarding information base size (6.1) maximum forwarding information base size (6.1)
5.5 Forwarding Information Base Size 5.5 Forwarding Information Base Size
Definition: Definition:
Terminology for FIB based Router Performance Sept., 2001
Refers to the number of forwarding information base entries Refers to the number of forwarding information base entries
within a forwarding information base. within a forwarding information base.
Discussion: Discussion:
The number of entries within a forwarding information base is The number of entries within a forwarding information base is
one of the key elements that may influence the forwarding one of the key elements that may influence the forwarding
performance of a router. Generally, the more entries within performance of a router. Generally, the more entries within
the forwarding information base, the longer it could take to the forwarding information base, the longer it could take to
find the longest matching network prefix within the find the longest matching network prefix within the
forwarding information base. forwarding information base.
Measurement units: Measurement units:
Number of routes Number of routes
Terminology for FIB based Router Performance July, 2001
Issues: Issues:
See Also: See Also:
forwarding information base (5.3) forwarding information base (5.3)
forwarding information base entry (5.4) forwarding information base entry (5.4)
forwarding information base prefix distribution (5.6) forwarding information base prefix distribution (5.6)
maximum forwarding information base size (6.1) maximum forwarding information base size (6.1)
5.6 Longest Length Prefix Match Algorithm 5.6 Longest Length Prefix Match Algorithm
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forwarding information base. forwarding information base.
Discussion: Discussion:
Network prefixes within the forwarding information base could Network prefixes within the forwarding information base could
be all of a single network prefix length, but, more be all of a single network prefix length, but, more
realistically, the network prefix lengths will be distributed realistically, the network prefix lengths will be distributed
across some range. across some range.
Individual performance measurements will be made against FIBs Individual performance measurements will be made against FIBs
populated with the same network prefix length, as well as populated with the same network prefix length, as well as
Terminology for FIB based Router Performance Sept., 2001
against FIBs with some distribution of network prefix against FIBs with some distribution of network prefix
lengths. lengths.
The distribution of network prefix lengths may have an impact The distribution of network prefix lengths may have an impact
on the forwarding performance of a router. The longer the on the forwarding performance of a router. The longer the
network prefix length, the longer it will take for a router network prefix length, the longer it will take for a router
to perform the longest length prefix match algorithm, and to perform the longest length prefix match algorithm, and
potentially the lower the performance of the router. potentially the lower the performance of the router.
Measurement units: Measurement units:
The forwarding information base prefix distribution is The forwarding information base prefix distribution is
expressed by a list of network prefix lengths and the expressed by a list of network prefix lengths and the
percentage of entries within the forwarding information base percentage of entries within the forwarding information base
with a particular network prefix length. For example, a with a particular network prefix length. For example, a
Terminology for FIB based Router Performance July, 2001
forwarding information base prefix distribution is forwarding information base prefix distribution is
represented as: represented as:
{[/16, 100], [/20, 360], [/24, 540]} {[/16, 100], [/20, 360], [/24, 540]}
This indicates that 100 of the entries within the forwarding This indicates that 100 of the entries within the forwarding
information base have a 16 bit network prefix length, 360 information base have a 16 bit network prefix length, 360
have a 20 bit network prefix length, and 540 have a 24 bit have a 20 bit network prefix length, and 540 have a 24 bit
network prefix length. network prefix length.
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router. By doing this, destination address / network prefix router. By doing this, destination address / network prefix
lookups can be performed on the interface or card, unloading lookups can be performed on the interface or card, unloading
a router's CPU. a router's CPU.
Measurement units: Measurement units:
<n/a> <n/a>
Issues: Issues:
See Also: See Also:
Terminology for FIB based Router Performance Sept., 2001
forwarding information base (5.3) forwarding information base (5.3)
per-interface forwarding information base cache (5.9) per-interface forwarding information base cache (5.9)
5.9 Per-Interface Forwarding Information Base Cache 5.9 Per-Interface Forwarding Information Base Cache
Definition: Definition:
A subset of a forwarding information base, installed on a A subset of a forwarding information base, installed on a
router's interface card to speed the destination address / router's interface card to speed the destination address /
network prefix lookup process. network prefix lookup process.
Discussion: Discussion:
Prior to installing a complete copy of the forwarding Prior to installing a complete copy of the forwarding
information base on each interface of a router, a popular information base on each interface of a router, a popular
technique for speeding destination address lookups is to technique for speeding destination address lookups is to
Terminology for FIB based Router Performance July, 2001
install a cache of frequently used routes on a router's install a cache of frequently used routes on a router's
interface. interface.
The most frequently used routes are placed in the forwarding The most frequently used routes are placed in the forwarding
information base cache. IP packets whose destination address information base cache. IP packets whose destination address
does not match a network prefix within the per-interface does not match a network prefix within the per-interface
forwarding information base cache are forwarded to a router's forwarding information base cache are forwarded to a router's
central processor for lookup in the complete forwarding central processor for lookup in the complete forwarding
information base. information base.
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forwarding performance of the router. forwarding performance of the router.
Measurement units: Measurement units:
<n/a> <n/a>
Issues: Issues:
See Also: See Also:
forwarding information base (5.3) forwarding information base (5.3)
per-interface forwarding information base (5.8) per-interface forwarding information base (5.8)
Terminology for FIB based Router Performance Sept., 2001
5.10 Route Aggregation 5.10 Route Aggregation
Definition: Definition:
The ability of a router to collapse many forwarding The ability of a router to collapse many forwarding
information base entries into a single entry. information base entries into a single entry.
Discussion: Discussion:
A router may aggregate routes in a forwarding information A router may aggregate routes in a forwarding information
base into a single entry to conserve space. base into a single entry to conserve space.
When advertising routes into a router to perform benchmarking When advertising routes into a router to perform benchmarking
tests as a function of the forwarding information base tests as a function of the forwarding information base
installed within the router, it is necessary to ensure that a installed within the router, it is necessary to ensure that a
router does not aggregate routes. router does not aggregate routes.
Terminology for FIB based Router Performance July, 2001
Thus, when routes are advertised to the router or installed Thus, when routes are advertised to the router or installed
statically, care must be taken to ensure that the router does statically, care must be taken to ensure that the router does
not aggregate routes. not aggregate routes.
For example, if advertising a set of /24 network prefixes For example, if advertising a set of /24 network prefixes
into a particular port on the router, 256 consecutive /24 into a particular port on the router, 256 consecutive /24
routes, sharing a common leading 16 bits, should not be routes, sharing a common leading 16 bits, should not be
advertised on a single port. If this is done, then the advertised on a single port. If this is done, then the
router will install a single entry within the forwarding router will install a single entry within the forwarding
information base indicating that all networks matching a information base indicating that all networks matching a
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6.1 Maximum Forwarding Information Base Size 6.1 Maximum Forwarding Information Base Size
Definition: Definition:
The maximum number of forwarding information base entries The maximum number of forwarding information base entries
that can be supported within the forwarding information base. that can be supported within the forwarding information base.
The Maximum Forwarding Information Base Size is the size over The Maximum Forwarding Information Base Size is the size over
which all entries can and are used to forward traffic. which all entries can and are used to forward traffic.
Discussion: Discussion:
Terminology for FIB based Router Performance Sept., 2001
It is useful to know the maximum forwarding information base It is useful to know the maximum forwarding information base
size for a router as it will be an indicator of the ability size for a router as it will be an indicator of the ability
of the router to function within the given application space, of the router to function within the given application space,
and whether the router will be able to handle projected and whether the router will be able to handle projected
network growth. network growth.
As a benchmarking value, it is necessary to discover this As a benchmarking value, it is necessary to discover this
value so that performance measurements can be made up to the value so that performance measurements can be made up to the
maximum possible forwarding information base size. maximum possible forwarding information base size.
Measurement units: Measurement units:
Number of routes Number of routes
Issues: Issues:
Terminology for FIB based Router Performance July, 2001
Could this value vary with the forwarding information base Could this value vary with the forwarding information base
prefix distribution? prefix distribution?
See Also: See Also:
forwarding information base (5.3) forwarding information base (5.3)
forwarding information base entry (5.4) forwarding information base entry (5.4)
forwarding information base size (5.5) forwarding information base size (5.5)
forwarding information base prefix distribution (5.6) forwarding information base prefix distribution (5.6)
6.2 Forwarding Information Base Learning Time 6.2 Forwarding Information Base Learning Time
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When performing benchmarking tests that take the forwarding When performing benchmarking tests that take the forwarding
information base into account, time must be allocated for the information base into account, time must be allocated for the
router to process the routing information and to install the router to process the routing information and to install the
complete forwarding information base within itself, before complete forwarding information base within itself, before
performance measurements are made. performance measurements are made.
Measurement units: Measurement units:
Prefixes per second. Prefixes per second.
Terminology for FIB based Router Performance Sept., 2001
Issues: Issues:
See Also: See Also:
forwarding information base (5.3) forwarding information base (5.3)
6.3 Forwarding Information Base-dependent Throughput 6.3 Forwarding Information Base-dependent Throughput
Definition: Definition:
Throughput, as defined in [3], used in a context where the Throughput, as defined in [3], used in a context where the
forwarding information base influences the throughput. forwarding information base influences the throughput.
Discussion: Discussion:
Terminology for FIB based Router Performance July, 2001
This definition for FIB-dependent throughput is added to This definition for FIB-dependent throughput is added to
distinguish the context of this measurement from that defined distinguish the context of this measurement from that defined
in [3]. in [3].
Measurement units: Measurement units:
See [3]. See [3].
Issues: Issues:
See Also: See Also:
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forwarding information base-dependent throughput (6.3) forwarding information base-dependent throughput (6.3)
forwarding information base-dependent frame loss rate (6.5) forwarding information base-dependent frame loss rate (6.5)
6.5 Forwarding Information Base-dependent Frame Loss Rate 6.5 Forwarding Information Base-dependent Frame Loss Rate
Definition: Definition:
Frame Loss Rate, as defined in [3], used in a context where Frame Loss Rate, as defined in [3], used in a context where
the forwarding information base influences the throughput. the forwarding information base influences the throughput.
Discussion: Discussion:
Terminology for FIB based Router Performance Sept., 2001
This definition for FIB-dependent frame loss rate is added to This definition for FIB-dependent frame loss rate is added to
distinguish the context of this measurement from that defined distinguish the context of this measurement from that defined
in [3]. in [3].
Measurement units: Measurement units:
See [3]. See [3].
Issues: Issues:
See Also: See Also:
forwarding information base-dependent throughput (6.3) forwarding information base-dependent throughput (6.3)
forwarding information base-dependent latency (6.4) forwarding information base-dependent latency (6.4)
Terminology for FIB based Router Performance July, 2001
7. Security Considerations 7. Security Considerations
As this document is solely for the purpose of providing metric As this document is solely for the purpose of providing metric
methodology and describes neither a protocol nor a protocols methodology and describes neither a protocol nor a protocols
implementation, there are no security considerations associated with implementation, there are no security considerations associated with
this document. this document.
8. References 8. References
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Agilent Technologies (Canada) Inc. Agilent Technologies (Canada) Inc.
#2500 4710 Kingsway #2500 4710 Kingsway
Burnaby, British Columbia Burnaby, British Columbia
Canada Canada
V5H 4M2 V5H 4M2
Phone: +1 604 454 3516 Phone: +1 604 454 3516
Email: Guy_Trotter@agilent.com Email: Guy_Trotter@agilent.com
Full Copyright Statement Full Copyright Statement
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This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
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Terminology for FIB based Router Performance July, 2001
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and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
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Terminology for FIB based Router Performance July, 2001
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