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NOTE: If you choose to configure a high Maximum Receive Unit (MRU) range for NetWare Link/PPP, you might need to edit the STARTUP.NCF file to redefine the Maximum Physical Receive Packet parameter. The Maximum Physical Receive Packet parameter defined in the STARTUP.NCF file must be large enough to accommodate the configured NetWare Link/PPP MRU Maximum Size value plus 10 bytes.
NetWare Link/PPP ensures that both send and receive data frames are never outside the configured MRU range. Through negotiation with the remote peer, the data frames are never smaller than the configured minimum MRU or larger than the configured maximum MRU. If the remote PPP peer requires frames outside the range, the connection is not established.
NetWare Link/PPP provides three parameters that control MRU negotiation with the remote data-link peer. The minimum and maximum MRU parameters establish a window or range of MRU values that are acceptable to the NetWare Link/PPP interface. The optimal MRU value establishes the preferred MRU value that the NetWare Link/PPP interface tries to establish.
The Internet PPP specification defines a default MRU size of 1,500 bytes. IP can run with 1,500-byte datagrams because it can support fragmentation of the stream to fit the data-link MRU. However, source route bridging does not support fragmentation. Therefore, when providing connectivity between bridged token ring LANs, you should reconfigure the NetWare Link/PPP interface to support a 4,500-byte MRU for the token ring LANs.
Using the bridged token ring example, the minimum and optimal MRU values should be set to 4,500 bytes. This configuration change forces the negotiated MRU value to 4,500 bytes, or the connection is not established.
If you are using IPX routing over NetWare Link/PPP to connect two token ring LANs, a negotiated MRU size of 4,500 bytes is preferred because it allows full-size token ring packets to be exchanged. A smaller MRU is still usable because the IPX packet size is automatically adjusted to the smaller NetWare Link/PPP MRU. In this case, you could configure the MRU Optimal Size parameter to 4,500 and leave the MRU Maximum Size and MRU Minimum Size parameters at their default values of 4,500 and 600, respectively. This approach starts the MRU negotiation with the remote PPP system at 4,500, but allows the acceptance of any value proposed by the remote system within the range of 600 to 4,500.
To configure MRU parameters, complete the following steps:
Load NIASCFG, then select the following parameter path:
Select Configure NIAS > Protocols and Routing > Network Interfaces
Scroll to a configured PPP interface, then select it.
The PPP Network Interface Configuration menu is displayed.
Select PPP Negotiations Options .
The PPP Negotiations Options menu is displayed.
Select MRU Maximum Size , then enter a value.
This parameter specifies the largest MRU size that PPP accepts for the local interface during link negotiation with a remote peer. This value, combined with the MRU Minimum Size value, defines the upper and lower limits used during MRU negotiation. The remote PPP peer must agree to a value within these limits to establish a connection.
Select MRU Optimal Size, then enter a value.
This parameter specifies the preferred MRU size that PPP proposes for the local interface during link negotiation with a remote peer. The actual negotiated MRU value can be anywhere within the range established by the MRU Minimum Size and the MRU Maximum Size parameters.
Select MRU Minimum Size , enter a value, then press Esc to confirm your configuration entries and return to the PPP Network Interface Configuration menu.
This parameter specifies the smallest MRU size that PPP accepts for the local interface during link negotiation with a remote peer. This value, combined with the MRU Maximum Size value, defines the upper and lower limits used during MRU negotiation. The remote PPP peer must agree to a value within these limits to establish a connection.
Press Esc to return to the Internetworking Configuration menu; save your changes when prompted.
If you want these changes to take effect immediately, select Reinitialize System .
If you want to configure other parameters, do so now, then reinitialize the system when you are finished.
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