RFC 2336 (rfc2336) - Page 2 of 5
Classical IP to NHRP Transition
Alternative Format: Original Text Document
RFC 2336 Classical IP and ARP over ATM to NHRP July 1998
It is reasonable to expect that ATMARP Clients and NHRP Clients will
initially coexist within a LIS. Thus, it is necessary to define a
graceful transition, including a period of coexistance, from the use
of ATMARP to the use of NHRP for address resolution in the LIS
[1][2]. In short, NHSs will be required to respond to ATMARP Client
queries in a fashion which will permit continued use of the ATMARP
Client within the LIS during the ATMARP to NHRP transition period.
Note that this document places no protocol requirements upon
ATMARP[1] servers.
For the following, it will be assumed that the reader is familiar
with the terminology as described in [1][2][3].
2. Service Requirements
If NHRP is to be used in a LIS then only NHSs will be used in the
LIS; that is, there will not be a mixture of NHSs and ATMARP servers
within the same LIS. Since ATMARP servers will not be able to
understand NHCs and since, as described below, NHSs will respond to
ATMARP Clients, this is a reasonable simplifying restriction.
This document will only address SVC based environments and will not
address PVC environments. This document will refer only to ATM AAL5
as the NBMA and IP as the protocol layer since ATMARP only addresses
these protocols.
2.1 NHRP Server Requirements
If NHRP Servers (NHS) are to be deployed in a LIS which contains both
ATMARP Clients and NHRP Clients then NHSs MUST respond to
ATMARP_Requests sent by ATMARP Clients in the same fashion that an
ATMARP Server would respond as described in [1]. To do this, the NHS
MUST first recognize the LLC/SNAP ATMARP code point with LLC=0xAA-
AA-03, OUI=0x00-00-00, and ethertype=0x08-06. Further, the NHS MUST
recognize the packet formats described in Section 8.7 of [1].
However, since this document does not extend to PVC environments,
NHSs MUST only receive/respond to values of ar$op of 1,2,10
(Decimal). If an NHS receives an ATMARP message with ar$op values
other than those previously noted then the NHS MUST discard the
packet and MUST NOT take any further action.
When an NHS receives a valid (as defined in the previous paragraph)
ATMARP_Request packet, the NHS MUST follow the rules described in
Section 8.4 of [1] with the following additional processing:
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