AS4637 BGP Routing Table Analysis Report

Active BGP entries (FIB)

Table Size Metrics

The trend of the size of the BGP Forwarding Table (FIB). Also the underlying BGP Routing Table (RIB). The RIB/FIB ratio is a function of the number of BGP peering sessions at the sample point. Some RIB entries are marked as unusable as an outcome of protocol operation, and these categories of unusable advertisements are tracked.

Address Span Metrics

The total span of address space advertised in the BGP table, and the relationship of this value to the number and size of address prefix objects in the table.

More Specifics

The characteristics of more specific advertisements - where an advertisement is associated with a sub-span of address space of another advertisement. The metrics also look at the degree of similarity of the AS paths of the specific advertisements to the encompassing aggregate.

AS Numbers

The time trend of the number of unique AS numbers advertised within the BGP table. The associated metrics characterise AS's into origin only, transit only, or mixed (origin and transit), and also look at the trends of advertised address space as related to the number of ASes.

AS Paths

The time trend of the number of unique AS Paths advertised within the BGP table. The associated metrics look at trends of average path length, and BGP table entries per path.

Prefix Length Distributions

The time trend of the distribution of BGP Table entries by address prefix length.

Root Prefix Length Distributions

The time trend of the distribution of Root BGP Table entries by address prefix length.

AS Diameter Reports

The time trend of the reacahbility of addresses and AS's using AS distance from the sample point to the origin AS as the diameter metric.

BGP Update Reports

Compares the current BGP Table with the previous table and reports on the number of changes in the FIB. These changes are further categorised into announcements, withdrawls and path changes, and further categorised by prefix length.

Path Updates - Breakdown by Update Type

Examines those updates that involved a change of AS Path and breaks this down into five categories:

• A change of origin AS (origin)
• A change in the origin's nexthop AS (remote change)
• A change in the transit AS path (transit)
• A change in the firsthop AS (Local change)
• A change in AS prepending (Traffic Engineering)

AS Announcement Reports

The time trend of total span of address space advertised by ASes, using truncated prefix length as the span metric.

AS Connectivity Reports

This set of reports lists all visible AS's using a number of ordering criteria. The reports order AS's by the total span of addresses originated by an AS, the total span of addresses reachable via an AS, and the totspan of roiginating plus transit addresses via each AS. Each AS in an AS path has an adjacent AS closer to the sample point, and an adjacent AS further from the sample point. The number of such pairwise adjacencies is reported for each AS. The average AS Connectivity Degree is the average number of adjacent AS's for an AS.

Aggregation Reports

This set of reports lists all potential aggregation of a number of specific routes into an aggregate route. The aggregation criteria include a match of the original AS path, which may include prepended AS's, a match of the reduced AS Path, and a match on the Origin AS only. As this view is taken from a single sample point, this list is not definitive, and the report will propose potential aggregation actions which may not be feasible for the Origin AS. The report also applies a prefix length filter to all prefixes, accepting only those prefixes which pass the following ruleset:

• 24.0.0.0/8 accept prefix length <=20
• 61.0.0.0/8 accept prefix length <= 20
• 63.0.0.0/8 accept prefix length <= 20
• 64.0.0.0/8 accept prefix length <= 20
• 65.0.0.0/8 accept prefix length <= 20
• 66.0.0.0/8 accept prefix length <= 20
• 0.0.0.0/1 (0.0.0.0/8 through 126.0.0.0/8) accept prefix length <= 19
• 128.0.0.0/2 (128.0.0.0/8 through 191.0.0.0/8) accept prefix length <= 16
• 192.0.0.0/8 through 204.0.0.0/8 accept prefix length <=24
• 205.0.0.0/8 through 255.0.0.0/8 accept prefix length <=20

BGP Reports

Report Index

• AS1221 Telstra
• AS4637 Reach
• AS6447 Route-Views.Oregon-ix.net

BGP data obtained from the boundary of AS4637.

Report last updated at Thu Jun 7 09:40:28 2007 (Australian Eastern Time).

Data prior to 11 April 97 interpreted from data gathered by Erik-Jan Bos, SURFnet.

BGP table analyser written and maintained by Geoff Huston.

Footnote

The reports are organized in the table in two parts:
• The name is a reference to a graph of the data. If the data is a single series then this is a simple time-series plot. If the data is a multi-series vector, the first graph is a compound graph of the time series of each element in the vector, the second is a relative plot using a common start point and looking at the relative change in the value of each element of the vector. The third is a relative plot, normalizing the start point to zero and looking at the absolute change in each element of the vector. The last isa distribution graph.
• The value is a reference to the text raw data file. The text file uses a column format, with the first column representing the measurement time. The time base is the number of seconds since 1 January 1970 UTC. If you wish to convert this to Microsoft Excel time format, then divide this time measurement by 86400 and add 25569, and then add the local offset to UTC

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