RPL Ethernet Multicast Packet Format for Filtering (96525)

SUMMARY

Depending upon the physical layout and traffic volume of your network, you may want to filter Remote Program Load (RPL) multicast packets from crossing over routers and bridges. This would especially make sense if your diskless workstations are all located on the same subnet as your Remoteboot server(s).

Token ring networks do not have to be concerned with this extra traffic burden because the RPL packets are not broadcasted, but rather two local FIND frames are sent out first and subsequent FIND frames are sent with necessary routing information.

Ethernet networks, on the other hand, are vulnerable to this broadcast traffic. However, the following ethernet RPL packet formats will provide the required byte patterns to filter out the initial RPL multicast FIND frame on your ethernet network.

MORE INFORMATION

Ethernet RPL FIND Multicast Packet Format

dlc header consisting of:

  destination multicast address       6 bytes   03 00 02 00 00 00
  source address                      6 bytes   net adapter specific
  frame length                        2 bytes   00 56

llc header consisting of:

  destination sap                     1 byte    FC
  source sap                          1 byte    FC
  frame type (UI)                     1 byte    03

start of FIND frame consisting of:

  data length                         2 bytes   00 53
  FIND command                        2 bytes   00 01

The following is a sample sniffer trace that shows actual FIND and FOUND packets from a RPL conversation:

Sniffer Network Analyzer data from 30-Oct-92 at 09:06:00, file A:RPLBOOT.ENC, Page 1


- - - - - - - - - - - - - - - - Frame 94 - - - - - - - - - - - - - - -
-

SUMMARY  Delta T     Destination   Source        Summary
    94   75.8943  030002000000    SHELDON<00>      RPL C Find

RPL:  ----- RPL Find frame -----
RPL:
RPL:  Type = 1 (Find)
RPL:  Correlator = 00000000
RPL:  Maximum frame size = 2048
RPL:  Connection class = X1
RPL:         .... 0... = Broadcast to functional address
RPL:         .... .0.. = Broadcast to group
RPL:         .... ..0. = Cannot accept frames from connection-oriented
services
RPL:         .... ...1 = Type 1 (can accept unnumbered frames)
RPL:  Ring adapter address = 3Com  B083C0, SHELDON<00>
RPL:  SAP value = FC
RPL:  Search vector = 00280004
RPL:  No filename for this request
RPL:  Machine configuration data = FC81007000000008
Sniffer Network Analyzer data from 30-Oct-92 at 09:06:00, file
A:RPLBOOT.ENC, Page 5


RPL:  Equipment flags = 4463
RPL:  Memory size = 267
RPL:  Engineering Change level = ""
RPL:  Adapter id = 0000
RPL:  Adapter EC level = ".........."
RPL:
RPL:  [Normal end of "RPL Find frame".]
RPL:

ADDR  HEX                                                ASCII
0000  03 00 02 00 00 00 00 60  8C B0 83 C0 00 56 FC FC
.......`.....V..
0010  03 00 53 00 01 00 08 40  03 00 00 00 00 00 10 00
..S....@........
0020  08 00 06 40 09 08 00 00  06 40 0A 00 01 00 0A 40
...@.....@.....@
0030  06 00 60 8C B0 83 C0 00  05 40 07 FC 00 28 00 04
..`......@...(..
0040  00 24 C0 05 FC 81 00 70  00 00 00 08 44 63 02 67
.$.....p....Dc.g
0050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
................
0060  00 00 00 00                                       ....



- - - - - - - - - - - - - - - - Frame 95 - - - - - - - - - - - - - - -


SUMMARY  Delta T     Destination   Source        Summary
    95    0.0342  SHELDON<00>     MULE             RPL R Found

RPL:  ----- RPL Found frame -----
RPL:
RPL:  Type = 2 (Found)
RPL:  Correlator = 00000000
RPL:  Response code = 00
RPL:  Destination address = 3Com  B083C0, SHELDON<00>
RPL:  Source address = 3Com  4D222E, MULE
RPL:  Maximum frame size = 1508
RPL:  Connection class = X1
RPL:         .... 0... = Broadcast to functional address
RPL:         .... .0.. = Broadcast to group
RPL:         .... ..0. = Cannot accept frames from connection-oriented
services
RPL:         .... ...1 = Type 1 (can accept unnumbered frames)
RPL:  SAP value of loader = F8
RPL:
RPL:  [Normal end of "RPL Found frame".]
RPL:

ADDR  HEX                                                ASCII
0000  00 60 8C B0 83 C0 02 60  8C 4D 22 2E 00 3D FC FC
.`.....`.M"..=..
0010  03 00 3A 00 02 00 08 40  03 00 00 00 00 00 05 40
..:....@.......@
0020  0B 00 00 0A 40 0C 00 60  8C B0 83 C0 00 0A 40 06
....@..`......@.
0030  02 60 8C 4D 22 2E 00 10  00 08 00 06 40 09 05 E4
.`.M".......@...
0040  00 06 40 0A 00 01 00 05  40 07 F8                 ..@.....@..