As per Relevance of the word extension, we have this rfc below:
Network Working Group J.
Request For Comments: 1841 Cisco Systems, Inc
Category: Informational D.
Cisco Systems, Inc
A.
Cisco Systems, Inc
B.
Cisco Systems, Inc
K.
Cisco Systems, Inc
September 1995
PPP Network Control Protocol for LAN
Status of
This memo provides information for the Internet community. This
does not specify an Internet standard of any kind. Distribution
this memo is unlimited
Telecommunications infrastructure is improving to offer
bandwidth connections at lower cost. Access to the network
changing from modems to more intelligent devices. This
RFC discusses a PPP Network Control Protocol for one such
device. The protocol is the LAN extension interface protocol
Table of
1.0 Introduction ........................................... 3
1.1 LAN Extension Interface Topology ..................... 4
1.2 LAN Extension Interface Architecture ................. 5
1.3 LAN Extension Interface Protocol ..................... 6
2.0 LAN Extension Interface Protocol Control Packets........ 8
2.1 Startup Options ...................................... 8
2.2 Remote Command Options ............................... 14
2.3 Conditions for Sending PPP-LEX Packet ................ 17
3.0 Filter Protocol Type ................................... 18
3.1 LEX_RCMD_REQUEST - Filter Protocol Type............... 19
3.2 Response Packets - Filter Protocol Type............... 21
4.0 Filter MAC Address ..................................... 22
4.1 LEX_RCMD_REQUEST - Filter MAC Address ................ 23
4.2 Response Packets - Filter MAC Address................. 25
Chapman, et al Informational [Page 1]
RFC 1841 LAN Extension Interface Protocol September 1995
5.0 Set Priority ........................................... 27
5.1 LEX_RCMD_REQUEST - Set Priority ...................... 27
5.2 Response Packets - Set Priority ...................... 29
6.0 Disable LAN Extension Ethernet Interface ............... 30
6.1 LEX_RCMD_REQUEST - Disable LAN
Ethernet Interface ................................... 31
6.2 Response Packets - Disable LAN
Ethernet Interface ................................... 32
7.0 Enable LAN Extension Ethernet Interface ................ 33
7.1 LEX_RCMD_REQUEST - Enable LAN
Ethernet Interface ................................... 33
7.2 Response Packets - Enable LAN
Ethernet Interface ................................... 34
8.0 Reboot LAN Extension Interface Unit .................... 35
8.1 LEX_RCMD_REQUEST - Reboot LAN Extension
Unit ................................................. 35
8.2 Response Packets - Reboot LAN
Interface Unit ....................................... 36
9.0 Request Statistics ..................................... 37
9.1 LEX_RCMD_REQUEST - Request Statistics ................ 37
9.2 LEX_RCMD_ACK - Request Statistics .................... 39
9.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Request Statistics ....... 44
10.0 Download Request ...................................... 45
10.1 LEX_RCMD_REQUEST - Download Request ................. 46
10.2 Response Packets - Download Request.................. 48
11.0 Download Data ......................................... 49
11.1 LEX_RCMD_REQUEST - Download Request ................. 49
11.2 Response Packets - Download Data .................... 51
12.0 Download Status ....................................... 52
12.1 LEX_RCMD_REQUEST - Download Status .................. 53
12.2 LEX_RCMD_ACK - Download Status ...................... 54
12.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Download Status ......... 56
13.0 Inventory Request ..................................... 56
13.1 LEX_RCMD_REQUEST - Inventory Request ................ 57
13.2 LEX_RCMD_ACK - Inventory Request .................... 58
13.3 LEX_RCMD_NAK/LEX_RCMD_REJ - Inventory Request ....... 61
14.0 LAN Extension Interface Protocol Data Packets ......... 62
14.1 Frame Format ........................................ 62
14.2 Summary Field Descriptions........................... 63
Chapman, et al Informational [Page 2]
RFC 1841 LAN Extension Interface Protocol September 1995
NOTES ...................................................... 65
REFERENCES ................................................. 65
SECURITY CONSIDERATIONS .................................... 66
AUTHORS' ADDRESSES ......................................... 66
1.0
An increasing number of corporations allow their employees
telecommute to work due to local government regulations on
and air pollution. Additionally, many businesses are run out
internetworked home offices and small branch offices. With
changes in the workplace, more people and businesses require
access from small LANs
Today, routers serve the LAN-to-LAN traffic using high-speed
links such as leased lines, ISDN, or Frame Relay. This new breed
Internet users from home offices and small branch offices may have
different, less network-literate skill set than those connecting
to the Internet today. These new users need an alternative to
complex and hard-to-configure routers currently employed
connectivity. One such alternative is a LAN extension interface unit
A LAN extension interface unit is a hardware device installed
remote sites (such as a home office or small branch office)
connects a LAN across a WAN link to a router at a central site.
following sections introduce a LAN extension interface topology
architecture, and protocol
Chapman, et al Informational [Page 3]
RFC 1841 LAN Extension Interface Protocol September 1995
1.1 LAN Extension Interface
Figure 1 shows the topology of LAN extension interfaces. The
shows two LAN extension interface units connected via a WAN link to
central or "host router."
Figure 1 LAN Extension Interface
-----------------------------------------
-----------------------------------------
Virtual Interface Virtual
123.123.78.1 123.123.89.1
.........................................
Serial 0 Serial
-----------------------------------------
|<---- WAN Link ---->|
------------------ ------------------
| LAN Extension | | LAN Extension |
| Interface Unit | | Interface Unit |
------------------ ------------------
| |
------------------ ------------------
| |
------------ ------------
| End node | | End node |
------------ ------------
123.123.78.2 123.123.46.2
Each LAN extension interface unit maps to a virtual interface at
host router. The virtual interface mirrors the characteristics of
LAN extension interface unit. To the routing protocols, the
interface looks just like a local interface, but with the
of a serial line. The virtual interface keeps the state (up or down
of the LAN extension interface unit, and identifies each
extension interface unit by its MAC address
A LAN extension interface protocol transfers MAC frames from the
extension interface unit across the serial line to the host router
At the termination point in the router, the router routes
packets. This topology uses only one subnet per remote LAN
than two, as is the case when routers exist on both ends of a
link. Figure 1 shows this subnetting structure. The IP addresses
the virtual interfaces on the router are in the same subnet as the
addresses of the end nodes on the LAN of the LAN extension
unit. The LAN extension interface unit itself has no IP address
Chapman, et al Informational [Page 4]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN extension interface units resemble bridges, but with
following distinct differences
* LAN extension interface units always depend on a host router
They cannot operate standalone or even back-to-back with
LAN extension interface units
* LAN extension interface units need not employ any spanning
algorithm
* (LAN extension interface units transfer MAC frames across
serial line (like bridges), but a router can either route
bridge the LAN extension interface data packets
1.2 LAN Extension Interface
Figure 2 shows the basic LAN extension interface architecture
Figure 2 LAN Extension Interface
Router LAN Extension
------------------- -------------------
| Network Layer | | MAC Layer |
------------------- -------------------
| |
------------------- -------------------
| |Virtual Interface| | Filters | |
| ------------------- ------------------- |
| | | |
| ------------------- ------------- |
| | PPP | | RCMD | |
| | | | Handler | |
| ------------------- ------------- |
| | | |
| ------------------- ------------------- |
| |Serial Interface | | PPP | |
| ------------------- ------------------- |
| | | |
| | ------------------- |
| | | Serial Interface| |
| | ------------------- |
| | WAN Link | |
| --------------------------------------- |
| |
| Outbound Inbound |
--------------> <---------------
Chapman, et al Informational [Page 5]
RFC 1841 LAN Extension Interface Protocol September 1995
In the inbound direction (from the remote LAN, to the LAN
interface unit, across the WAN link, to the host router), the
extension interface unit can filter received frames to optimize
utilization. The LAN extension interface unit can filter frames
protocol type or by MAC address. Frames that pass through the
extension interface filters go to the WAN protocol state machine.
Figure 2, this state machine is PPP. The LAN extension interface
adds PPP encapsulation and forwards the packet to the router via
WAN serial link
Upon receiving the frame, the host router decapsulates the PPP
and passes the packet to the virtual interface. From there
virtual interface handles the packet like any packet received on
local interface -- by routing or bridging the packet to
interface, depending on configuration
In the outbound direction (from the host router, across the WAN link
to the LAN extension interface unit, to the LAN), the host router'
virtual interface builds the full MAC header, before adding
encapsulation. The router then sends the packet across the WAN
link to the LAN extension interface unit. The LAN extension
unit strips the PPP header and forwards the packet directly onto
LAN. The host router has already determined that the packet needs
be forwarded to the LAN extension interface unit, hence there is
need for additional filtering or processing at that end
Embedded in the data stream is a control stream for configuring
managing the LAN extension interface unit from the host router.
virtual interface makes the remote LAN extension interface
appear like a local router interface to the routing protocols
Configuration commands and statistics gathering commands are
on the router to the virtual interface. The virtual interface
the LAN extension interface remote commands into encoded messages
transfers them in-band with the data packets. The LAN
interface unit decodes the remote commands and executes them
Responses are similarly formatted messages sent by the LAN
interface unit to the host router. The remote command messages use
different encapsulation type than the data packets, as
later in this document in the "LAN Extension Interface
Control Packets" and "LAN Extension Interface Protocol Data Packets
sections
1.3 LAN Extension Interface
To accommodate this LAN extension interface architecture, a
Network Control Protocol (NCP) for PPP exists. This NCP is
PPP-LEX. The basic functionality of PPP-LEX is to encapsulate
Chapman, et al Informational [Page 6]
RFC 1841 LAN Extension Interface Protocol September 1995
extension interface control and data packets. The IETF has
two new protocol types for these functions, as shown in Table 1.
Table 1 IETF Protocol Types for PPP-
Protocol Type
0x8041 Encapsulates control
0x0041 Encapsulates data packets (MAC frames
PPP is a natural choice for a LAN extension interface
because it allows for negotiating a specific control protocol
options at connection time. This means that network administrators
not have to statically configure the router interface for
interfaces. Rather, remote interfaces negotiate the link
connection time
The LAN extension interface protocol employs PPP link operation
described in RFC 1331, which reads as follows
In order to establish communications of a point-to-point link
each end of the PPP link must first send [Link Control Protocol
LCP packets to configure and test the data link. After the
has been established,the peer may be authenticated. Then PPP
send NCP packets to choose and configure one or more network
protocols. Once each of the chosen network-layer protocols
been configured, datagrams from each network layer protocol can
sent over the link
The link will remain configured for communications until
LCP or NCP packets close the link down, or until some
event occurs (an inactivity timer expires or network
intervention). (References, [1])
Thus, the LAN extension interface unit and the host router
PPP-LCP packets at connection time to dynamically configure and
the WAN serial link. Once the link reaches an "opened" state, the
extension interface unit and host router exchange PPP-LEX NCP
to configure the LAN extension interface protocol. Once it
configured, the NCP (PPP-LEX) reaches an "opened" state, and
carries the PPP-LEX control and data packets across the serial link
At this point, link traffic is a any combination of LCPs, PPP-
NCPs, PPP-LEX control packets, and PPP-LEX data packets
Note that the LAN extension interface protocol is not a
protocol. The only similarity to the PPP Bridging Control
(References. [2]) is that the LAN extension interface protocol
encapsulates MAC frames
Chapman, et al Informational [Page 7]
RFC 1841 LAN Extension Interface Protocol September 1995
The following sections detail PPP-LEX control packets and
packets
2.0 LAN Extension Interface Protocol Control
There are two types of PPP-LEX control packets, as follows
* Startup options
* Remote command options
The startup options packet is the first PPP-LEX NCP packet that
LAN extension interface unit sends to the host router after the
has reached an "opened" state. This required startup options
configures the LAN extension interface protocol and puts the PPP-
NCP in an "opened" state
Remote command options are the PPP-LEX NCP packets that control
functioning and statistics gathering of the LAN extension
protocol
2.1 Startup
The LAN extension interface unit sends a startup options packet
the host router to negotiate the following startup options
* MAC
* MAC
* LAN
The MAC Type startup option informs the host router of the type
media that the LAN extension interface unit is connected to.
example, the LAN extension interface unit may be connected to
Ethernet LAN or a Token Ring LAN. Currently, only Ethernet
supported. The MAC type tells the host router what type of
the LAN extension interface unit is prepared to receive. If the
router rejects the MAC type, the LAN extension interface unit
the Configure-Request again
The MAC Address startup option sends the MAC address of the
extension interface unit to the host router to authenticate the
extension interface unit and bind it to the corresponding
interface at the host router. The host router also inserts the
address in outbound packets. The MAC address is represented in
802.3 canonical format
The LAN Extension startup option establishes the network
protocol (NCP) as PPP-LEX and provides the host router with the
extension interface protocol version number
Chapman, et al Informational [Page 8]
RFC 1841 LAN Extension Interface Protocol September 1995
Each startup option is transmitted in a series of three fields
Option-Type, Option-Length, and Option-Data fields. The fields
concatenated in the startup options Configure-Request packet
Frame
Figure 3 shows a summary of the frame format for the startup
packet. The LAN extension interface unit sends this startup
packet to the host router. The LAN extension interface unit
these fields from left to right
Figure 3 Startup Options Frame Format (Configure-Request
PPP
<-------------------------------------------------------------->
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address | Control | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
LAN Extension Interface Protocol
<-------------------------------------------------------------->
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 octet) (1) (2)
LAN Extension Interface Startup
<-------------------------------------------------------------->
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-Length | Option-Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1)
This PPP-specified field is one octet and contains the
sequence 11111111 (hexadecimal 0xFF), the All-Stations address.
does not assign individual station addresses. The All-
address must be recognized and received by all devices. For
information on this field, refer to "The Point-to-Point
(PPP) for the Transmission of Multi-protocol Datagrams over Point
to-Point Links." (References, [1])
Chapman, et al Informational [Page 9]
RFC 1841 LAN Extension Interface Protocol September 1995
This PPP-specified field is one octet and contains the
sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI
command with the P/F bit set to zero
For more information on this field, refer to "The Point-to-
Protocol (PPP) for the Transmission of Multi-protocol Datagrams
Point-to Point Links." (References, [1])
Protocol-
The Protocol-Type field is two octets and contains the IETF-
protocol type value. Valid LAN extension interface protocol
values are as follows
* 0x8041 (for control packets
* 0x0041 (for data packets
Because the startup options packet encapsulates LAN
interface control data, the valid value for this field is 0x8041.
The Code field is one octet and identifies the type of LCP
that the LAN extension interface packet is sending. Valid values
as follows
* 0x01 - Configure-
* 0x02 - Configure-
* 0x03 - Configure-
* 0x04 - Configure-
The LAN extension interface unit initiates the startup
packet; therefore, the valid value for this field is 1.
The Identifier field is one octet and contains a randomly
value. The value aids matching requests and replies. It
recommended that a non-zero value be used for the identifier.
is, zero could be used in the future for unsolicited messages
the LAN extension interface unit. Valid values are 0x01-0xFF
Chapman, et al Informational [Page 10]
RFC 1841 LAN Extension Interface Protocol September 1995
The Length field is two octets and indicates the length of the
packet in octets, including the Code, Identifier, Length, and
options fields
Option-
The Option-Type field is one octet and identifies the startup
being negotiated. Valid values are as follows
* 0x01 - MAC
* 0x03 - MAC
* 0x05 - LAN
Option-
The Option-Length field is one octet and specifies the length of
startup option fields, including the Option-Type, Option-Data,
Option-Length fields
Option-
The Option-Data field contains the data relating to the
specified in the Option-Type field. That is, if the Option-Type
specifies MAC type (0x01), then the Option-Data field contains
MAC type (Ethernet, Token Ring, and so on). If the Option-Type
specifies MAC address (0x03), then the Option-Data field contains
actual MAC address. If the Option-Type field specifies LAN
(0x05), then the Option-Data field contains LAN extension
software information. The following table defines the contents of
Option-Data field for each possible Option-Type field value
Option-Type Field Value Option-
0x01 (MAC Type) The most up-to-date value of the MAC type
specified in the most recent "
Numbers" RFC. The current valid value
that RFC follows
* 0x01: IEEE 802.3/Ethernet with
0x03 (MAC Address) The burned-in MAC address in IEEE 802.3
canonical format
0x05 (LAN Extension) The LAN extension interface protocol
number. 0x01 is the current protocol
supported
Chapman, et al Informational [Page 11]
RFC 1841 LAN Extension Interface Protocol September 1995
In the Configure-Request packet that it sends to the host router,
LAN extension interface unit concatenates the Option-Type, Option
Data, and Option-Length fields for each startup option, as shown
Figure 4. The LAN extension interface unit transmits these
from left to right
Figure 4 Sample Startup Options Configure-Request
PPP
<-------------------------------------------------------------->
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFF | 0x03 | 0x8041 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Control Protocol-
LAN Extension Interface Protocol
<-------------------------------------------------------------->
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 | 0x09 | 0x12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Identifier
LAN Extension Interface Startup
<------------------------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 | 0x03 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-
------------------------------>
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0x01 |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-
Chapman, et al Informational [Page 12]
RFC 1841 LAN Extension Interface Protocol September 1995
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x03 | 0x08 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-Length |
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0A 0A 0A 0A 0B 0C |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
---------- Option-Data --------|
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x05 | 0x03 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-Type Option-
4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0x01 |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-
In Figure 4, the Address field always contains 0xFF, and the
field always contains 0x03. The Protocol-Type field value is 0x8041
because the startup options packet is a LAN extension
control packet. The Code field value is 0x01 because the
extension interface unit is sending an LCP Configure-Request
to configure or negotiate PPP-LEX. The Identifier field contains
randomly generated number. The Length field gives the total length
the entire packet
The first startup option is the MAC Type startup option. The Option
Type value for MAC Type is 0x01. The Option-Length field value
the MAC type startup option is 3 octets. The Option-Data field
is 0x01 because, in this example, the LAN extension interface
connects to an Ethernet LAN using 802.3 canonical addresses
The next startup option transmitted is the MAC Address. Its Option
Type field value is 0x03, its Option-Length field value is 8 octets
and its Option-Data field value is the actual MAC address
Lastly, the LAN Extension startup option is transmitted. Its Option
Type field value is 0x05, its Option-Length field value is 3 octets
and its Option-Data field value is the LAN extension
protocol version number (0x01).
Chapman, et al Informational [Page 13]
RFC 1841 LAN Extension Interface Protocol September 1995
The host router responds to this LCP Configure-Request packet with
LCP Configure-Ack packet, Configure-Nak packet, or Configure-
packet. For more information on these packets, refer to "The Point
to-Point Protocol (PPP) for the Transmission of Multi-
Datagrams over Point-to-Point Links" RFC. (References, [1])
2.2 Remote Command
Once the host router responds to the startup options Configure
Request packet with a Configure-Ack packet, the PPP-LEX NCP is in
"opened" state, and the LAN extension interface unit and the
router freely exchange PPP-LEX data packets and remote
options packets
The host router initiates PPP-LEX remote command options packets
control the configuration of the LAN extension interface unit and
gather statistics. There are 11 types of remote command options
the host router can send in a LEX_RCMD_REQUEST packet to the
extension interface unit. The LAN extension interface unit
to a LEX_RCMD_REQUEST packet with a LEX_RCMD_ACK, LEX_RCMD_NAK,
LEX_RCMD_REJ packet
Frame
Figure 5 shows a summary of the frame format for a remote
options packet. These fields are transmitted from left to right
Figure 5 Remote Command Options Frame
PPP
<-------------------------------------------------------------->
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address | Control | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (1) (2)
LAN Extension Interface Protocol
<-------------------------------------------------------------->
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 octet) (1) (2)
Chapman, et al Informational [Page 14]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command
<--------------------------------
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option-Type | Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(1 octet) (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)
This PPP-specified field is a single octet and contains the
sequence 11111111 (hexadecimal 0xFF), the All-Stations address.
does not assign individual station addresses. The All-
address must be recognized and received by all devices. For
information on this field, refer to "The Point-to-Point
(PPP) for the Transmission of Multi-protocol Datagrams over Point
to-Point Links." (References, [1])
This PPP-specified field is a single octet and contains the
sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI
command with the P/F bit set to zero
For more information on this field, refer to "The Point-to-
Protocol (PPP) for the Transmission of Multi-protocol Datagrams
Point-to Point Links." (References, [1])
Note: Hereafter the Address and Control fields will be
together as a 2-octet field containing "0xFF03".
Protocol-
The Protocol-Type field is two octets and contains the IETF-
protocol type value. Valid LAN extension interface protocol
values follow
* 0x8041 (for control packets
* 0x0041 (for data packets
Chapman, et al Informational [Page 15]
RFC 1841 LAN Extension Interface Protocol September 1995
Because the remote command options packet encapsulates LAN
interface control data, the valid value for this field is 0x8041.
The Code field is one octet and identifies the type of PPP-
packet. Valid values are as follows
* 0x40 - LEX_RCMD_REQUEST
* 0x41 - LEX_RCMD_ ACK
* 0x42 - LEX_RCMD_NAK
* 0x43 - LEX_RCMD_REJ
The host router sends the LEX_RCMD_REQUEST packet, and the
extension interface unit sends the LEX_RCMD_ACK, LEX_RCMD_NAK,
LEX_RCMD_REJ packets
The Identifier field is one octet and contains a randomly
value. The value aids matching requests and replies. It
recommended that a non-zero value be used for the identifier.
is, zero could be used in the future for unsolicited messages
the LAN extension interface unit. Valid values are 0x01-0xFF
The Length field is two octets and indicates the length in octets
the entire packet, including the Code, Identifier, Length, and
command options fields
Option-
The Option-Type field is one octet and identifies the remote
option being transmitted. Valid values are as follows
* 0x01 - Filter Protocol
* 0x02 - Filter MAC
* 0x03 - Set
* 0x04 - Disable LAN Extension Ethernet
* 0x05 - Enable LAN Extension Ethernet
* 0x06 - Reboot LAN Extension Interface
* 0x07 - Request
* 0x08 - Download
* 0x09 - Download
* 0x0A - Download
* 0x0B- Inventory
Chapman, et al Informational [Page 16]
RFC 1841 LAN Extension Interface Protocol September 1995
Each remote command option is discussed in detail in its own
later in this document
Option-
This field is one octet and further specifies the remote
option, containing specific actions that must be followed
Option-
The Option-Length field is two octets and specifies the length
octets of the remote command option fields, including the Option
Type, Option-Flags, Option-Length, and Option-Data fields
Option-
Option-Data field contains data relating to the remote command
specified in the Option-Type field
2.3 Conditions for Sending PPP-LEX
This section describes the general conditions under which PPP-
packet types are sent. For specific information by remote command
refer to the appropriate remote command section later in
document
LEX RCMD_REQUEST
The host router sends LEX_RCMD_REQUEST packets to the LAN
interface unit to initiate a remote command request. Until the
router receives a LEX_RCMD_ACK, LEX_RCMD_NAK, or LEX_RCMD_REJ
from the LAN extension interface unit, the host router continues
send the LEX_RCMD_REQUEST packet a default number of times, at
point the host router times out
LEX_RCMD_ACK
The LAN extension interface unit responds to a LEX_RCMD_
packet with a LEX_RCMD_ACK packet when it correctly receives
request and is able to perform the request
LEX RCMD_NAK
The LAN extension interface unit responds to a LEX_RCMD_
packet with a LEX_RCMD_NAK packet when the LAN extension
unit recognizes all the elements of the remote command option,
some elements are not acceptable. Upon receipt of a LEX_RCMD_
packet, the host router immediately stops sending the request
Chapman, et al Informational [Page 17]
RFC 1841 LAN Extension Interface Protocol September 1995
LEX RCMD_REJ
The LAN extension interface unit responds to a LEX_RCMD_
packet with a LEX_RCMD_REJ packet when the Option-Type value in
request packet is invalid. Invalid Option-Type values are those
than 0x01 or greater than 0x0B. Currently, this is the only
under which the LAN extension interface unit sends a LEX_RCMD_
packet. Upon receipt of a LEX_RCMD_REJ packet, the host
immediately stops sending the request
The following sections detail each of the 11 remote command options
The sections provide a general description of the option and
specify the option's Option-Type, Option-Flags, Option-Length,
Option-Data fields. In addition, the sections describe the
messages from the LAN extension interface unit
3.0 Filter Protocol
The host router sends a LEX_RCMD_REQUEST packet with an Option-
of 0x01 to the LAN extension interface unit to configure the
extension interface unit to filter inbound packets by protocol type
A protocol type filter determines whether or not the LAN
interface unit forwards packets of a specific protocol type to
host router. A protocol type filter consists of a 16-bit value, 16-
bit mask, and a permit or deny field. (See the "Option-Data
Descriptions" section for more information on these filter fields.)
A LEX_RCMD_REQUEST packet can contain 0 to 200 (depending on
size) protocol type filters. When a LEX_RCMD_REQUEST packet
multiple filters, they are concatenated
The LAN extension interface unit applies the protocol type filters
each inbound packet's protocol type field in the order in which
filters exist in the filter table. A packet must be permitted by
of the filters before the LAN extension interface unit can
the packet across the serial link
The following example is a filtering algorithm
if (protocol_type_field & (~filter_mask)) == filter_value
if (permit/deny_field == PERMIT)
else
The protocol type filter should also be applied to the DIX type
field of Ethernet II frames as well as to IEEE 802.2 SNAP packets
Chapman, et al Informational [Page 18]
RFC 1841 LAN Extension Interface Protocol September 1995
3.1 LEX RCMD_REQUEST-Filter Protocol
Figure 6 shows a frame format summary of a LEX_RCMD_REQUEST
for the Filter Protocol Type remote command option. The host
transmits the fields from left to right
Figure 6 LEX_RCMD_REQUEST Packet Frame Format - Filter Protocol
PPP
<-------------------------------------------------------------->
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
<-------------------------------------------------------------->
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
<--------------------------------
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 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (16 bits) | Value (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Permit/Deny (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chapman, et al Informational [Page 19]
RFC 1841 LAN Extension Interface Protocol September 1995
Summary Field
For a complete description of the fields in the PPP Header, the
Extension Interface Protocol Header, and the LAN Extension
Remote Command Options, refer to the "Remote Command Options"
earlier in this document. The following table provides a summary
these fields when sending a LEX_RCMD_REQUEST packet that
the LAN extension interface unit to filter by protocol type
Table 2 Field Values for LEX_RCMD_REQUEST Packet-Filter Protocol
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code 0x40 (LEX_RCMD_REQUEST packet
Identifier Valid values: 0x01-0
Length Minimum length = 12
Maximum length = 1212
Option-Type 0x01 (Filter Protocol Type
Option-Flags
Option-Length Minimum length = 4
Maximum length = 1204
Option-Data Zero or more filters to be applied
the LAN extension interface unit. See
following "Option-Data Field Descriptions
for details
Option-Data Field
The following three Option-Data fields are used in conjunction
specify a protocol type filter
*
The Value field contains a 16-bit value that is any Ethernet
code. Refer to the "Assigned Numbers" RFC for valid Ethernet
codes. (References, [4]).
*
The Mask field contains a 16-bit "wild card" mask. That is,
field contains a 16-bit number whose ones bits correspond to the
code bits to be ignored during the comparison. Thus, the
excludes bits from the comparison in the protocol type filter
Chapman, et al Informational [Page 20]
RFC 1841 LAN Extension Interface Protocol September 1995
* Permit/
The Permit/Deny field determines whether a protocol type
permits or denies inbound frames to pass to the host router. A
value is a non-zero value that allows frames of a specific
type to pass to the host router. A deny value is a zero value
does not allow frames of a specific protocol type to pass to the
router
Implementation
Each LEX_RCMD_REQUEST packet is a complete specification of
protocol type filters and replaces any previously
filters
Note the following special cases
* A LEX_RCMD_REQUEST packet with an Option-Length field
to four (without any filter entries) instructs the LAN
interface unit to turn off protocol type filtering. All
protocol types are forwarded
* A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in
Value field, 0xFFFF in the Mask field, and a positive value in
Permit/Deny field means that if previous filters in the filter
do not permit the inbound packet then this filter entry will.
filter entry is typically the last filter in a list of
contained within the Option-Data field
* A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in
Value field, 0xFFFF in the Mask field, and a zero in
Permit/Deny field, means that the LAN extension interface unit
deny all protocol types. This filter is typically the last filter
a list of filters contained within the Option-Data field
3.2 Response Packets - Filter Protocol
The following packets are valid responses to the Filter Protocol
LEX_RCMD_REQUEST packet
* LEX_RCMD_ACK - Filter Protocol
The LAN extension interface unit sends a LEX_RCMD_ACK packet
response to the Filter Protocol Type LEX_RCMD_REQUEST packet when
LAN extension interface unit correctly receives the Filter
Type remote command option and applies all filter entries to
filter table. All filter entries are returned to the host router
the LEX_RCMD_ACK packet
Chapman, et al Informational [Page 21]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD_NAK - Filter Protocol
The LAN extension interface unit sends a LEX_RCMD_NAK packet
response to the Filter Protocol Type LEX_RCMD_REQUEST packet when
request contains an incorrect number of bytes in the filter or
there are no more filter entries available. The LAN
interface unit continues to use the previous filter table (that is
the filter table that existed prior to the receipt of the request).
The host router should signal an error to the user/
administrator. All filter entries are returned to the host router
the LEX_RCMD_NAK packet
* LEX_RCMD-REJ - Filter Protocol
See the "Conditions for Sending PPP-LEX Packets" section earlier
this document for more information on this packet type
Table 3 summarizes the field values of Filter Protocol
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets
Table 3 Field Values for Response Packets - Filter Protocol
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code Valid values
* 0x41 (LEX_RCMD_ACK packet
* 0x42 (LEX_RCMD_NAK packet
* 0x43 (LEX_RCMD_REJ packet
Identifier The same value as that sent by
LEX_RCMD_REQUEST
Length The same value as that sent by
LEX_RCMD_REQUEST
Option-Type 0x01 (Filter Protocol Type
Option-Flags
Option-Length The same value as that sent by
LEX_RCMD_REQUEST
Option-Data The filter entries sent in
LEX_RCMD_REQUEST
4.0 Filter MAC
The host router sends a LEX_RCMD_REQUEST packet with an Option-
of 0x02 to the LAN extension interface unit to configure the
extension interface unit to filter inbound packets by source
address. A MAC address filter determines whether or not the
extension interface unit forwards packets with a specific source
Chapman, et al Informational [Page 22]
RFC 1841 LAN Extension Interface Protocol September 1995
address to the host router. A MAC address filter consists of
address, a MAC address mask, and a permit or deny field. (See
"Option-Data Field Descriptions" section later in this section
more information on these filter fields.)
A LEX_RCMD_REQUEST packet can contain 0 to 100 (depending on
size) MAC address filters. When a LEX_RCMD_REQUEST packet
multiple filters, they are concatenated
The LAN extension interface unit applies MAC address filters to
inbound packet's source MAC address in the order in which the
exist in the filter entry list. A packet must be permitted by one
the filters before the LAN extension interface unit can forward
packet across the serial link
4.1 LEX RCMD_REQUEST - Filter MAC
Figure 7 shows a frame format summary of a LEX_RCMD_REQUEST
for the Filter MAC Address remote command option. The host
transmits the fields from left to right
Figure 7 LEX_RCMD_REQUEST Packet Frame Format - Filter MAC
PPP
<-------------------------------------------------------------->
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
<-------------------------------------------------------------->
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)
Chapman, et al Informational [Page 23]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command
<--------------------------------
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 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address Mask (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Permit/Deny (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field
For a complete description of the fields in the PPP Header, the
Extension Interface Protocol Header, and the LAN Extension
Remote Command Options, refer to the "Remote Command Options"
earlier in this document. Table 4 provides a summary of these
when sending a LEX_RCMD_REQUEST packet that configures the
extension interface unit to filter by source MAC address
Table 4 Field Values for LEX_RCMD_REQUEST Packet - Filter MAC
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code 0x40 (LEX_RCMD_REQUEST packet
Identifier Valid values: 0x01-0
Length Minimum length = 12
Maximum length = 1412
Option-Type 0x02 (Filter MAC Address
Option-Flags
Option-Length Minimum length = 4
Chapman, et al Informational [Page 24]
RFC 1841 LAN Extension Interface Protocol September 1995
Maximum length = 1404
Option-Data Zero or more filters to be applied at
LAN extension interface unit. See
following "Option-Data Field
section for details
Option-Data Field
The following three Option-Data fields are used in conjunction
specify a MAC address filter
* MAC
The MAC Address field contains a 48-bit IEEE 802.3 MAC address
canonical format
* MAC Address
The MAC Address Mask field contains a "wild card" mask. The mask is
48-bit hexadecimal number whose ones bits correspond to the
address bits to be ignored during the comparison. The mask
bits from the comparison in the MAC address filter
* Permit/
The Permit/Deny field determines whether or not a MAC address
permits or denies inbound frames of a specific MAC address to pass
the host router. A permit value is a non-zero value that
frames of a specific MAC address to pass to the host router. A
value is a zero value that does not allow frames of a specific
address to pass to the host router
Implementation
Each LEX_RCMD_REQUEST packet is a complete specification of all
address filters and replaces any previously established filters
A LEX_RCMD_REQUEST packet with an Option-Length field equal to
(without any filter entries) instructs the LAN extension
unit to turn off filtering. All MAC addresses, except
destination addresses cached in the self-learning filter,
forwarded
4.2 Response Packets - Filter MAC
The following packets are valid responses to the Filter MAC
LEX_RCMD_REQUEST packet
Chapman, et al Informational [Page 25]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD_ACK - Filter MAC
The LAN extension interface unit sends a LEX_RCMD_ACK packet
response to a Filter MAC Address LEX_RCMD_REQUEST packet when the
extension interface unit correctly receives the Filter MAC
remote command option and applies the entries to its filter table
All MAC address filter entries are returned in the LEX_RCMD_
packet
* LEX_RCMD_NAK - Filter MAC
The LAN extension interface unit sends a LEX_RCMD_NAK packet
response to the Filter MAC Address LEX_RCMD_REQUEST packet when
request contains an incorrect number of bytes in the filter or
there are no more filter entries available. The LAN
interface unit continues to use the previous filter table (that is
the filter table that existed prior to the receipt of the request).
The host router should signal an error to the user/
administrator. All filter entries are returned in the LEX_RCMD_
packet
* LEX_RCMD-REJ - Filter MAC
See the "Conditions for Sending PPP-LEX Packets" section earlier
this document for more information on this packet type
Table 5 summarizes the field values of Filter MAC
LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets
Table 5 Field Values for Response Packets - Filter MAC
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code Valid values
* 0x41 (LEX_RCMD_ACK packet
* 0x42 (LEX_RCMD_NAK packet
* 0x43 (LEX_RCMD_REJ packet
Identifier The same value as that sent by
LEX_RCMD_REQUEST
Length The same value as that sent by
LEX_RCMD_REQUEST
Option-Type 0x02 (Filter MAC Address
Option-Flags
Option-Length The same value as that sent by
LEX_RCMD_REQUEST
Option-Data The filter entries sent in
Chapman, et al Informational [Page 26]
RFC 1841 LAN Extension Interface Protocol September 1995
LEX_RCMD_REQUEST
5.0 Set
The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x03
to the LAN extension interface unit to establish the sending
of different protocol type packets from the LAN extension
unit to host router. There are four levels of priority
*
*
*
*
Packets are classified according to protocol type and then are
to one of four output queues on the LAN extension interface unit
correspond to the above priority levels. When the LAN
interface unit is ready to transmit a packet, it scans the
queues in order, from the highest to lowest, to find the
priority packet
5.1 LEX RCMD_REQUEST - Set
To establish priority queues for each protocol type, the host
sends a Set Priority LEX_RCMD_REQUEST packet. Figure 8 shows a
format summary of such a LEX_RCMD_REQUEST packet. The host
transmits the fields from left to right
Figure 8 LEX_RCMD_REQUEST Packet Frame Format - Set
PPP
<-------------------------------------------------------------->
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
<-------------------------------------------------------------->
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)
Chapman, et al Informational [Page 27]
RFC 1841 LAN Extension Interface Protocol September 1995
LAN Extension Interface Remote Command
<--------------------------------
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 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol Type (16 bits) | Protocol Value (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Summary Field
For a complete descriptions of the fields in the PPP Header, the
Extension Interface Protocol Header, and the LAN Extension
Remote Command Options, refer to the "Remote Command Options"
earlier in this document. The following table provides a summary
these fields when sending a LEX_RCMD_REQUEST packet that
priority queuing
Table 6 Field Values for LEX_RCMD_REQUEST Packet - Set
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code 0x40 (LEX_RCMD_REQUEST packet
Identifier Valid values: 0x01-0
Length Minimum length = 12
Maximum length = 1028
Option-Type 0x03 (Set Priority
Option-Flags
Option-Length Minimum length = 4
Maximum length = 1020
Option-Data Protocol Type and Priority Value. See
following "Option-Data Field Description
section for details
Chapman, et al Informational [Page 28]
RFC 1841 LAN Extension Interface Protocol September 1995
Option-Data Field
The following Option-Data fields set the priority queuing
different protocol type packets
* Protocol
The Protocol Type field contains a 16-bit number that is any
type code. See the most recent "Assigned Numbers" RFC for the
Ethernet type code
* Priority
The Priority Value field specifies the priority queue for
protocol type specified in the Protocol Type field. Valid values
as follows
- 0 - High priority
- 1 - Medium priority
- 2 - Normal priority
- 3 - Low priority
Sending a LEX_RCMD_REQUEST packet with an Option-Length of four (
priority entries) disables priority queuing. When disabled, the
extension interface unit transfers all packets at a normal (2)
priority level. When a new priority is specified, it overwrites
previous setting
5.2 Response Packets - Set
The following packets are valid responses to the Set
LEX_RCMD_REQUEST packet
* LEX_RCMD_ACK - Set
See the "Conditions for Sending PPP-LEX Packets" section earlier
this document for more information on this packet type
* LEX_RCMD_NAK - Set
The LAN extension interface unit sends a LEX_RCMD_NAK packet
response to the Set Priority LEX_RCMD_REQUEST packet when the
contains an incorrect number of bytes in the message, when
resources are not available, or when the specified priority
invalid
Chapman, et al Informational [Page 29]
RFC 1841 LAN Extension Interface Protocol September 1995
* LEX_RCMD-REJ - Set
See the "Conditions for Sending PPP-LEX Packets" section earlier
this document for more information on this packet type. Table 7
summarizes the field values of Set Priority LEX_RCMD_ACK
LEX_RCMD_NAK, and LEX_RCMD_REJ packets
Table 7 Field Values for Response Packets - Set
Field
Address/Control 0xFF03 (Broadcast address/
information
Protocol-Type 0x8041 (Control packet
Code Valid values
* 0x41 (LEX_RCMD_ACK packet
* 0x42 (LEX_RCMD_NAK packet
* 0x43 (LEX_RCMD_REJ packet
Identifier A randomly generated value that aids
matching requests with
Length Minimum length = 12
Maximum length = 1028
Option-Type 0x03 (Set Priority
Option-Flags
Option-Length Minimum length = 4
Maximum length = 1020
Option-Data Protocol Type and Priority Value
in the LEX_RCMD_REQUEST
6.0 Disable LAN Extension Ethernet
The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x04
to the LAN extension interface unit to disable the LAN
Ethernet interface. This remote command option stops data
from the LAN extension interface unit to the host router
troubleshooting or for reconfiguring the LAN extension
unit. This remote command option only affects data traffic. PPP-
control packets can still be transferred over the serial link
Chapman, et al Informational [Page 30]
RFC 1841 LAN Extension Interface Protocol September 1995
6.1 LEX RCMD_REQUEST - Disable LAN Extension Ethernet
Figure 9 shows a frame format summary of a LEX_RCMD_REQUEST
for the Disable LAN Extension Ethernet Interface remote
option. The host router transmits the fields from left to right
Figure 9 LEX_RCMD_REQUEST Packet Frame Format -
Disable LAN Extension Ethernet
PPP
<-------------------------------------------------------------->
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
<-------------------------------------------------------------->
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
<-------------------------------------------------------------->
0 1 2 3 4 5 6 7 8 9 0 1 2 