0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 21 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that requests the download
status of the LAN extension interface unit.
Table 21 Field Values for LEX_RCMD_REQUEST Packet - Download Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 4 octets
Option-Data None
12.2 LEX RCMD_REQUEST - Download Status
When the LAN extension interface unit correctly receives the Download
Status LEX_RCMD_REQUEST packet, it returns a LEX_RCMD_ACK packet
containing the appropriate status information in the Option-Data
field.
Figure 17 shows the frame format for the Download Status LEX_RCMD_ACK
packet. The LAN extension interface unit transmits the fields from
left to right.
Figure 17 LEX_RCMD_ACK Packet Frame Format - Download Status
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete descriptions of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 22 provides a summary of these fields
when sending a status information to the host router.
Table 22 Field Values for LEX_RCMD_ACK Packet - Download Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x41 (LEX_RCMD_ACK packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 14 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 6 octets
Option-Data Status information. See the following
"Option-Data Field Descriptions" section
for details.
Option-Data Field Descriptions
The Option-Data field uses the Status field to send the download
status to the host router. The Status field reports the following
status information:
* 1 - Acknowledgment that no errors occurred
* 3 - Sequence error occurred
* 6 - Flash write error occurred
* 7 - Checksum error
12.3 LEX RCMD_NAK/LEX RCMD_REJ - Download Status
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for information on when the LAN extension interface
unit sends a Download Status LEX_RCMD_NAK packet and Download Status
LEX_RCMD_REJ packet.
The frame format for these two response packets mirror the frame
format of the Download Status LEX_RCMD_REQUEST packet. Table 23
summarizes the field values of the Download Status LEX_RCMD_NAK and
LEX_RCMD_REJ packets.
Table 23 Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets - Download
Status
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x0A (Download Status)
Option-Flags None
Option-Length 4 octets
Option-Data None
13.0 Inventory Request
The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
of 0x0B to the LAN extension interface unit to request inventory
information. The host router may use this remote command option to
accomplish the following:
* Distinguish between different versions of the LAN extension
interface unit for determining their capabilities
* Determine whether a new version of Flash code should be downloaded
13.1 LEX RCMD_REQUEST - Inventory Request
Figure 18 shows the frame format for a LEX_RCMD_REQUEST packet with
an Inventory Request remote command option. The host router transmits
the fields from left to right.
Figure 18 LEX_RCMD_REQUEST Packet Frame Format - Inventory Request
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags | Option-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 24 provides a summary of these fields
when sending a LEX_RCMD_REQUEST packet that requests inventory
information.
Table 24 Field Values for LEX_RCMD_REQUEST Packet-Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x40 (LEX_RCMD_REQUEST packet)
Identifier Valid values: 0x01-0xFF
Length 12 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 4 octets
Option-Data None
13.2 LEX RCMD_ACK - Inventory Request
When it correctly receives the Inventory Request remote command
option and retrieves the inventory information, the LAN extension
interface unit responds with an acknowledgment. This acknowledgment
contains the requested inventory information in the Option-Data
field.
Figure 19 shows the frame format for the Inventory Request
LEX_RCMD_ACK packet.
Figure 19 LEX_RCMD_ACK Packet Frame Format - Inventory Request
PPP Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF03 | Protocol-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2 octets) (2)
LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1) (2)
LAN Extension Interface Remote Command Option
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1) (1)
----------------------------------------------->
6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Length | Option-Data |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2)
Where the Option-Data field contains the following fields:
(32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flash Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HW Version | PROM Major Ver| PROM Minor Ver|Flash Major Ver|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flash Minor Ver| FLAGS | RAM Major Ver | RAM Minor Ver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Mac Address (6 octets) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field Descriptions
For a complete description of the fields in the PPP Header, the LAN
Extension Interface Protocol Header, and the LAN Extension Interface
Remote Command Option, refer to the "Remote Command Options" section
earlier in this document. Table 25 provides a summary of these fields
when acknowledging a LEX_RCMD_REQUEST packet that requests inventory
information.
Table 25 Field Values for LEX_RCMD_ACK Packet - Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code 0x41 (LEX_RCMD_ACK packet)
Identifier The same value as that sent by
LEX_RCMD_REQUEST packet
Length 34 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 26 octets
Option-Data Inventory data. See the following
"Option-Data Field Descriptions" section
for details.
Option-Data Field Descriptions
The Option-Data field of the LEX_RCMD_ACK packet uses the following
fields to send inventory data to the host router about the LAN
extension interface unit.
* Flash Size
This field contains the LAN extension interface unit's Flash size in
bytes.
* Serial Number
This field provides the LAN extension interface unit's serial number.
This is an unassigned, 32-bit number.
* HW Version
This field contains the version number of the LAN extension interface
hardware unit.
* PROM Major Ver
This field contains part of the version number of the PROM image.
"Major" indicates which major software release this revision belongs
to. For example, if the PROM version number is 1.2, then the major
version number is 1.
* PROM Minor Ver
This field contains part of the version number of the PROM image.
"Minor" indicates which minor software release this revision belongs
to. For example, if the PROM version number is 1.2, then the minor
version number is 2.
* Flash Major Ver
This field contains the "major" version number of the Flash image.
For example, if the Flash image version number is 1.2, then the major
version number is 1.
* Flash Minor Ver
This field contains the "minor" version number of the Flash image.
For example, if the Flash image version number is 1.2, then the minor
version number is 2.
* FLAGS
FLAGS report the boot status of the LAN extension interface unit. The
flags are as follows:
- 0x01 - Running PROM image
- 0x02 - Running Flash image
- 0x04 - PROM image passed checksum
- 0x08 - Flash image passed checksum
* RAM Major Ver
This field contains the "major" version number of the running image
in RAM. For example, if the RAM image version number is 1.2, then the
major version number is 1.
* RAM Minor Ver
This field contains the "minor" version number of the running image
in RAM. For example, if the RAM image version number is 1.2, then the
minor version number is 2.
* MAC Address
The MAC Address is the LAN extension interface unit's burned-in MAC
address in canonical format. This field is six octets.
13.3 LEX RCMD_NAK/LEX RCMD_REJ - Inventory Request
Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
in this document for information on when the LAN extension interface
unit sends an Inventory Request LEX_RCMD_NAK packet and Inventory
Request LEX_RCMD_REJ packet.
The frame format of these two response packets mirrors that of the
request. Table 26 summarizes the field values for such Inventory
Request LEX_RCMD_NAK/LEX_RCMD_REJ packets.
Table 26 Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
Inventory Request
Field Value
Address/Control 0xFF03 (Broadcast address/Unnumbered
information)
Protocol-Type 0x8041 (Control packet)
Code Valid values:
* 0x42 (LEX_RCMD_NAK packet)
* 0x43 (LEX_RCMD_REJ packet)
Identifier The same value as that sent by the
LEX_RCMD_REQUEST packet
Length 12 octets
Option-Type 0x0B (Inventory Request)
Option-Flags None
Option-Length 4 octets
Option-Data None
14.0 LAN Extension Interface Protocol Data Packets
When the PPP-LEX NCP is in an "opened" state, the LAN extension
interface unit and the host router also exchange PPP-LEX data packets
(as well as control packets). There is only one type of PPP-LEX data
packet. This data packet is a subset of the PPP-BCP packet format.
The format subsetting is such that a PPP-BCP implementation will
successfully process a LAN extension interface protocol packet. The
differences are as follows:
* LAN ID field will not be present.
* LAN FCS field will never be present (that is, the F flag will
always be off [=0]).
* LAN ID flag (I) will always be off.
* Pad field for the serial link will never be present, and the
count field will be 0.
For detailed information on PPP-BCP packets, refer to the "PPP
Bridging Control Protocol (BCP)" RFC. (References, [2])
14.1 Frame Format
Figure 20 shows the frame format for a PPP-LEX data packet. The MAC
frame is transferred except for the FCS field. The LAN extension
interface unit computes the FCS for packets transferred to the LAN
and strips the FCS for packets destined for the host router.
Figure 20 PPP-LEX Data Packet Frame Format
(8 bits) (8 bits) (8 bits) (8 bits)
+-+-+-+-+-+-+-+-+
| HDLC FLAG |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF | 0x03 | 0x0041 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| F|I|Z|0| Pad | Mac Type | Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source MAC Address | Length/Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LLC Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (Serial) HDLC CRC | HDLC FLAG |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
14.2 Summary Field Descriptions
HDLC FLAG
HDLC Frame delimiter.
0xFF
This Address field contains the broadcast address.
0x03
This Control field contains unnumbered information.
0x0041
This field contains the IETF-assigned protocol type value for a
PPP-LEX data packet. In this case this field will always contain
0x0041.
Flags
The flags F, I, Z, 0 have the following meanings:
* F: Set bit F if the LAN FCS field is present. Because PPP-LEX
data packets do not contain the LAN FCS field, this bit should
not be set (field=0).
* I: Set bit I if the LAN ID field is present. Because PPP-LEX
data packets do not contain the field, this bit should not be
set (field=0).
* Z: Set bit Z if IEEE 802.3 Pad must be zero filled to minimum
size.
* 0: Reserved, must be zero.
Pad
Any PPP frame may have padding inserted in the Optional Data Link
Layer Padding field. The value tells the receiving system how many
pad octets to strip off. The LAN extension interface protocol does
not support the Optional Data Link Layer Padding field, so the
value of this field should be zero.
MAC Type
This field contains the most up-to-date value of the MAC type as
specified in the most recent "Assigned Numbers" RFC. The current
value is as follows:
* 1: IEEE 802.3/Ethernet with canonical addresses
Destination MAC Address
This field is 6 octets and contains the MAC address of the
destination system as defined by IEEE. The MAC Type field defines
the bit ordering.
Source MAC Address
This field is 6 octets and contains the MAC address of the
destination system as defined by IEEE. The MAC Type field defines
the bit ordering.
Length/Type
This field is any Ethernet protocol type (See RFC1700 in the
references "Assigned Numbers"). For IEEE 802.3 frames, this is a
length field.
LLC Data
This field is the remainder of the MAC frame which is (or would be
if it were present) protected by the LAN FCS.
(Serial) HDLC CRC
This is a 16 bit Cyclic Redundancy Check field.
For complete information on the above fields and their relationship
to PPP-BCP packets, refer to the "PPP Bridging Control Protocol
(BCP)" RFC. (References, [2])
Notes
1. The LAN extension interface protocol does allow the segmentation
of individual LAN packets across the serial link. Each LAN
packet must be transmitted across the serial link as one PPP-LEX
encapsulation.
2. MAC addresses in PPP-LEX packets should be in canonical format.
References
[1] Simpson, W., "The Point-To-Point Protocol (PPP) for the
Transmission of Multi-protocol Datagrams over Point-To-Point
Links", RFC1331, Daydreamer, May 1992.
[2] Baker, F., and R. Bowen, "PPP Bridging Control Protocol (BCP)",
RFC1638, ACC, IBM, June 1994.
[3] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
1334, Lloyd & Associates, Daydreamer, October 1992.
[4] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC1700,
USC/Information Sciences Institute, October 1994.
[5] Reynolds, J., and J. Postel, "Standard for the transmission of IP
datagrams over IEEE 802 networks", RFC1042, USC/Information
Sciences Institute, February 1988.
Security Considerations
Security issues are not discussed in this memo.
Authors' Addresses
Joelle Bafile Chapman, Technical Writer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: joelle@cisco.com
Dave Coli, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: dcoli@cisco.com
Andy Harvey, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: agh@cisco.com
Bent Jensen, Engineering Manager
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
EMail: bent@cisco.com
Kevin Rowett, Software Engineer
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706