Multicast Data Statistics
Multicast Packet Statistics shows a multicast data table (from rvtrace -addrinfo). The text below introduces important concepts. Multicast Packet Statistics—Column Headings describes the columns in detail.
Figure 150: Multicast Packet Statistics
Notice that the rows divide visually into six groups, as indicated by a number in the Port column and an asterisk (*).
The first row (immediately after the table and column headings, and before the four groups) is a network total row; the word Totals in the Address column is a visual cue. This row shows the grand total of multicast and broadcast packets on the network during the interval. For example, the Data column shows the total number of data packets that rvtrace detected on the network during the interval.
The remaining rows display more fine-grained information about those packets—grouping them by UDP service, destination address, and source address.
A number in the Port column indicates the UDP service for its row, and the group of rows that follow it. A blank in this column means that the row has the same port as the row above, and is part of the same subtotal group. Notice how the pattern of numbers and blanks in the Port column visually indicates the subtotal groups.
* flags a row as a destination subtotal row. A blank (space character) in this column flags a row as a source row. Each group begins with a destination subtotal row, followed by one or more source rows.
Each destination subtotal row is the heading and subtotal for the source rows that follow it. For example, consider the destination row with 20000 in the Port column, and 224.1.1.12 in the Address column. The Data column indicates 20 packets on UDP service 20000 sent to the multicast group 224.1.1.12. The two subsequent source rows indicate that those 20 packets came from two sources—the daemon or IPM with SCid 39365 at 10.101.2.102 sent 10 packets, while SCid 39364 at the same host sent another 10 packets. The subtotal 20 in turn contributes to the grand total 51 in the first row.
A destination subtotal row governs the source rows below it (until the next destination subtotal row). That is, the UDP service (port) and address in the governing row apply to those source rows. Similarly, the governing row address implies either multicast or broadcast protocol, and this protocol also applies to the statistics in the source rows that it governs. (Naturally, all of this information also applies to the governing row itself.)
Each source row shows a very narrow subset of packet activity during the interval—packets on a specific UDP service (port), with a specific destination address, and originating at a specific source (IP address). The Address column shows the source; the UDP service and destination address are specified in the governing row (that is, the nearest preceding destination subtotal row).
In destination rows numbers in statistics columns count packets with the destination specified in the Address column.
In source rows numbers in statistics columns count packets originating from the IP address in the Address column.
In network total rows, numbers in statistics columns represent the packet totals for the network during the interval.
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Column |
Description |
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In destination subtotal rows, this column contains a UDP port number indicating the Rendezvous service for the group of rows that it begins. In source rows this column is blank; the service in the nearest preceding destination row also applies to the source row. |
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* |
Asterisk ( Blank in this column indicates a source row. |
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In destination rows this column shows the destination address shared among a group of packets. It can be an IP address or a multicast group. In source rows this column shows the IP address from which group of packets originate. In network total rows, this column contains the word |
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Service communication ID. In source rows, this value differentiates the source of packets when several daemons or IPM instances on the same host computer reuse the same service port. Zero in this column indicates that the source is the only sender on that service and host. In destination rows this column is blank. |
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Data packets. This column shows the number of multicast or broadcast data packets. |
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Data bytes. This column sums the number of payload bytes over the data packets (as counted in the Data column). |
Null
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Null packets. When a Rendezvous daemon has no data packets to transmit, it periodically sends null packets to maintain continuity. This column displays the number of null packets that |
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Retransmitted data packets.
For statistics concerning retransmission requests and rejections, see Multicast Retransmit Statistics. |
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Retransmitted bytes. This column sums the number of payload bytes over the retransmitted data packets (as counted in the Rdata column). |
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Sequence gaps.
For more information, see Gaps Diagnoses. |
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Bad packets. This column shows the number of packets that lack UDP checksums, or are corrupt in some other way. Warning See Bad Packets. |
R
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Reliability. A numeric value indicates the reliability of a specific service on a specific host. Hyphen ( |
Gaps Diagnoses
A sequence gap can occur in two situations:
| • | rvtrace misses one or more packets; that is, the hardware or operating system on which rvtrace is running drops one or more packets. |
| • | The network infrastructure drops one or more packets between their source and rvtrace. |
To determine which of these two situations has actually occurred, check the Rdata values within the interval and in subsequent intervals. If Rdata remains at zero, then it is likely that rvtrace alone is missing packets. If Rdata is non-zero, then it is likely that the network infrastructure is dropping packets (Rdata is non-zero because other daemons on the network are requesting retransmission of the missing packets).