[dhcwg] Question on RFC2131 / RFC1541
Andrew W Elble <aweits@rit.edu> Mon, 11 December 2017 23:43 UTC
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From: Andrew W Elble <aweits@rit.edu>
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Date: Mon, 11 Dec 2017 18:43:52 -0500
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Subject: [dhcwg] Question on RFC2131 / RFC1541
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I'm wondering about the re-use of XID at time T1. RFC1541 had a clear explanation as to what was expected of XID at renewal. RFC2131 is lacking that language. RFC7513 seems to contain a reference to the use of a new TID/XID at renewal time. Should clients be re-using the same XID that was used in the initial DHCPDISCOVER at renewal? RFC7513 6.4.3.5: Event: EVE_DHCP_RENEW - A DHCPv4 Renew or a DHCPv6 Renew message is received "In such case, a new TID will be used by the client. The TID field of the corresponding entries MUST be set to the new TID. Note that TID check will not be performed on such messages." RFC2131 4.1: Constructing and sending DHCP messages "The 'xid' field is used by the client to match incoming DHCP messages with pending requests. A DHCP client MUST choose 'xid's in such a way as to minimize the chance of using an 'xid' identical to one used by another client. For example, a client may choose a different, random initial 'xid' each time the client is rebooted, and subsequently use sequential 'xid's until the next reboot. Selecting a new 'xid' for each retransmission is an implementation decision. A client may choose to reuse the same 'xid' or select a new 'xid' for each retransmitted message" RFC1531/RFC1541 4.4.4: Reacquisition and expiration "At time T1 after the client accepts the lease on its network address, the client moves to RENEWING state and sends (via unicast) a DHCPREQUEST message to the server to extend its lease. The client generates a random transaction identifier and inserts that identifier into the 'xid' field in the DHCPREQUEST. The client records the local time at which the DHCPREQUEST message is sent for computation of the lease expiration time. The client MUST NOT include a 'server identifier' in the DHCPREQUEST message." Thanks, Andy -- Andrew W. Elble aweits@discipline.rit.edu Infrastructure Engineer, Communications Technical Lead Rochester Institute of Technology PGP: BFAD 8461 4CCF DC95 DA2C B0EB 965B 082E 863E C912
- [dhcwg] Question on RFC2131 / RFC1541 Andrew W Elble
- Re: [dhcwg] Question on RFC2131 / RFC1541 Ted Lemon