#31: lldpd reports incorrect maximum frame size
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Reporter: bernat | Owner: bernat
Type: defect | Status: new
Priority: minor | Component: core
Version: 0.4.1 | Keywords:
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Reported by Ben Harris in [http://bugs.debian.org/559314 #559314].
According to Wireshark, the LLDPDUs transmitted by lldpd include a
"Maximum Frame Size" TLV indicating a frame size of 1500 octets. This is
incorrect: According to IEEE Std 802.1AB-2005 (clause G.5.1):
a) If the MAC/PHY supports only the basic MAC frame format as defined in
3.1.1 of IEEE Std 802.3-2002, the maximum frame size field shall be set to
1518.
b) If the MAC/PHY supports an extension of the basic MAC frame format for
Tagged MAC frames as defined 3.5 of IEEE 802.3-2002, the maximum frame
size field shall be set to 1522.
c) If the MAC/PHY supports an extension of the MAC frame format that is
different from either of the above, the maximum frame size field shall be
set to the maximum value supported.
Thus, lldpd should set this field to 1518, 1522, or some other number
depending on the network driver's support for tagged VLANs and jumbo
frames. 1500 is definitely wrong, and it would be better for lldpd not to
include this TLV at all than to transmit incorrect information.
--
Ticket URL: <https://trac.luffy.cx/lldpd/ticket/31>
lldpd <https://trac.luffy.cx/lldpd/>
implementation of IEEE 802.1ab (LLDP)
