Layer Two Tunneling Protocol "L2TP"
2003-03
2023-12-06
Unless otherwise noted, the registrations in this registry are applicable
in the context of the IETF Vendor ID .
Control Message Attribute Value Pairs
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
To maximize extensibility while still permitting interoperability, a
uniform method for encoding message types and bodies is used
throughout L2TP. This encoding will be termed AVP (Attribute-Value
Pair).
0
Message Type AVP
Also, see Message Type AVP values below
1
Result Code AVP
Also, see Result Code AVP values below
2
Protocol Version AVP
3
Framing Capabilities AVP
Also, see Framing Field definition below
4
Bearer Capabilities AVP
Also, see Bearer Field definition below
5
Tie Breaker AVP
6
Firmware Revision AVP
7
Host Name AVP
8
Vendor Name AVP
9
Assigned Tunnel ID AVP
10
Receive Window Size AVP
11
Challenge AVP
12
Q.931 Cause Code AVP
13
Response AVP
14
Assigned Session ID AVP
15
Call Serial Number AVP
16
Minimum BPS AVP
17
Maximum BPS AVP
18
Bearer Type AVP
Also, see Bearer Field definition below
19
Framing Type AVP
Also, see Framing Field definition below
20
Reserved
21
Called Number AVP
22
Calling Number AVP
23
Sub-Address AVP
24
(Tx) Connect Speed BPS AVP
25
Physical Channel ID AVP
26
Initial Received LCP CONFREQ AVP
27
Last Sent LCP CONFREQ AVP
28
Last Received LCP CONFREQ AVP
29
Proxy Authen Type AVP
Also, see Proxy Authen Type AVP Values below
30
Proxy Authen Name AVP
31
Proxy Authen Challenge AVP
32
Proxy Authen ID AVP
33
Proxy Authen Response AVP
34
Call Errors AVP
35
ACCM AVP
36
Random Vector AVP
37
Private Group ID AVP
38
Rx Connect Speed AVP
39
Sequencing Required AVP
40
Rx Minimum BPS
41
Rx Maximum BPS
42
Service Category
Also, see Service Category AVP Flag Fields
below
43
Service Name
44
Calling Sub-Address
45
VPI/VCI Identifier
46
PPP Disconnect Cause Code
Also, see PPP Disconnect Cause Code Values
below
47
CCDS AVP
48
SDS AVP
49
LCP Want Options
50
LCP Allow Options
51
LNS Last Sent LCP Confreq
52
LNS Last Received LCP Confreq
53
Modem On-Hold Capable AVP
54
Modem On-Hold Status AVP
55
PPPoE Relay AVP
56
PPPoE Relay Response Capability AVP
57
PPPoE Relay Forward Capability AVP
58
Extended Vendor ID AVP
59
Message Digest
60
Router ID
61
Assigned Control Connection ID
62
Pseudowire Capabilities List
63
Local Session ID
64
Remote Session ID
65
Assigned Cookie
66
Remote End ID
67
Application Code
68
Pseudowire Type
69
L2-Specific Sublayer
70
Data Sequencing
71
Circuit Status
72
Preferred Language
73
Control Message Authentication Nonce
74
Tx Connect Speed
75
Rx Connect Speed
76
Failover Capability
77
Tunnel Recovery
78
Suggested Control Sequence
79
Failover Session State
80
Multicast Capability
81
New Outgoing Sessions
82
New Outgoing Sessions Acknowledgement
83
Withdraw Outgoing Sessions
84
Multicast Packets Priority
85
Frame-Relay Header Length
86
ATM Maximum Concatenated Cells AVP
87
OAM Emulation Required AVP
88
ATM Alarm Status AVP
Also, see ATM Alarm Status AVP Values below
89
Attachment Group Identifier
90
Local End Identifier
91
Interface Maximum Transmission Unit
92
FCS Retention
93
Tunnel Switching Aggregator ID AVP
94
Maximum Receive Unit (MRU) AVP
95
Maximum Reassembled Receive Unit (MRRU) AVP
96
VCCV Capability AVP
97
Connect Speed Update AVP
98
Connect Speed Update Enable AVP
99
TDM Pseudowire AVP
100
RTP AVP
101
PW Switching Point AVP
102
S-BFD Target Discriminator ID
103
ECN Capability
104-65535
Unassigned
Message Type AVP (Attribute Type 0) Values
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
Control Connection Management
0
(reserved)
1
(SCCRQ) Start-Control-Connection-Request
2
(SCCRP) Start-Control-Connection-Reply
3
(SCCCN) Start-Control-Connection-Connected
4
(StopCCN) Stop-Control-Connection-Notification
5
(reserved)
6
(HELLO) Hello
20
(ACK) Explicit Acknowledgement
Call Management
7
(OCRQ) Outgoing-Call-Request
8
(OCRP) Outgoing-Call-Reply
9
(OCCN) Outgoing-Call-Connected
10
(ICRQ) Incoming-Call-Request
11
(ICRP) Incoming-Call-Reply
12
(ICCN) Incoming-Call-Connected
13
(reserved)
14
(CDN) Call-Disconnect-Notify
Link Status
15
(WEN) WAN-Error-Notify
16
(SLI) Set-Link-Info
17
(MDMST) Modem Status
PPPoE Relay
18
(SRRQ) Service Relay Request Message
19
(SRRP) Service Relay Reply Message
Multicast Management
23
(MSRQ) Multicast-Session-Request
24
(MSRP) Multicast-Session-Response
25
(MSE) Multicast-Session-Establishment
26
(MSI) Multicast-Session-Information
27
(MSEN) Multicast-Session-End-Notify
Failover Management
21
(FSQ) Failover Session Query
22
(FSR) Failover Session Response
Access Line Information Attributes
28
(CSUN) Connect-Speed-Update-Notification
29
(CSURQ) Connect-Speed-Update-Request
Result Code AVP (Attribute Type 1) Values
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
Result Code values for the StopCCN message
0
Reserved
1
General request to clear control connection
2
General error--Error Code indicates the problem
3
Control channel already exists
4
Requester is not authorized to establish a control channel
5
The protocol version of the requester is not
supported
Error Code indicates highest version supported
6
Requester is being shut down
7
Finite State Machine error
8
Control connection due to mismatching CCDS value
Result Code values for the CDN message
0
Reserved
1
Call/Session disconnected due to loss of carrier
2
Call/Session disconnected for the reason indicated
in error code
3
Call/Session disconnected for administrative reasons
4
Call/Session failed due to lack of appropriate facilities
being available (temporary condition)
5
Call/Session failed due to lack of appropriate facilities being
available (permanent condition)
6
Invalid destination
7
Call failed due to no carrier detected
8
Call failed due to detection of a busy signal
9
Call failed due to lack of a dial tone
10
Call was not established within time allotted by LAC
11
Call was connected but no appropriate framing was
detected
12
Disconnecting call due to mismatching SDS value
13
Session not established due to losing tie breaker (L2TPv3)
14
Session not established due to unsupported PW type (L2TPv3)
15
Session not established, sequencing required without valid
L2-Specific Sublayer (L2TPv3).
16
Finite state machine error or timeout.
17
FR PVC was deleted permanently (no longer provisioned)
18
FR PVC has been INACTIVE for an extended period of time
19
Mismatched FR Header Length
20
HDLC Link was deleted permanently (no longer provisioned)
21
HDLC Link has been INACTIVE for an extended period of time
22
Session not established due to other LCCE can not support
the OAM Cell Emulation
23
Mismatching interface MTU
24
Attempt to connect to non-existent forwarder
25
Attempt to connect to unauthorized forwarder
26
Loop Detected
27
Attachment Circuit bound to different PE
28
Attachment Circuit bound to different remote Attachment
Circuit
29
Unassigned
30
Return code to indicate connection was refused because of
TDM PW parameters. The error code indicates the problem.
31
Sequencing not supported
Result Code values for the MSEN message
0
Reserved
1
No multicast traffic for the group
2
Session terminated for the reason indicated in the error code
3
No more receivers
4
No more receivers (filter-mode change)
General Error Codes
0
No general error
1
No control connection exists yet for this LAC-LNS pair
2
Length is wrong
3
One of the field values was out of range or
reserved field was non-zero
4
Insufficient resources to handle this operation now
5
The Session ID is invalid in this context
6
A generic vendor-specific error occurred in the LAC
7
Try another. If LAC is aware of other possible LNS
destinations, it should try one of them. This can be
used to guide an LAC based on LNS policy, for instance,
the existence of multilink PPP bundles.
8
Session or tunnel was shutdown due to receipt of an
unknown AVP with the M-bit set (see section 4.2). The Error
Message SHOULD contain the attribute of the offending AVP in
(human readable) text form.
9
Try another directed. If an LAC or LNS is aware of other
possible destinations, it should inform the initiator of the
control connection or session. The Error Message MUST contain
a comma-separated list of addresses from which the initiator
may choose. If the L2TP data channel runs over IPv4, then
this would be a comma-separated list of IP addresses in the
canonical dotted-decimal format (e.g., "192.0.2.1, 192.0.2.2,
192.0.2.3") in the UTF-8 charset using the Default
Language . If there are no servers for the LAC or
LNS to suggest, then Error Code 7 should be used. For IPv4,
the delimiter between addresses MUST be precisely a single
comma and a single space. For IPv6, each literal address MUST
be enclosed in "[" and "]" characters, following the encoding
described in .
10
Next hop unreachable. This identifies an error condition
explicitly in the multi-TSA environment.
11
Next hop busy. This identifies an error condition
explicitly in the multi-TSA environment.
12
TSA busy. This identifies an error condition
explicitly in the multi-TSA environment.
TDM PW Specific error codes, to be used with 30 result code for the CDN message
0
Reserved
1
Bit Rate values disagree.
2
Different trunk types in the case of trunk-specific CESoPSN
with CAS.
3
Requested payload size too big or too small.
4
RTP header cannot be generated.
5
Requested timestamp clock frequency cannot be generated.
Proxy Authen Type AVP (Attribute Type 29) Values
First Come First Served
0
Reserved
1
Textual username/password exchange
2
PPP CHAP
3
PPP PAP
4
No Authentication
5
Microsoft CHAP Version 1 (MSCHAPv1)
6
Reserved
7
EAP
Service Category AVP (Attribute Type 42) Flag Field
Specification Required
Carlos Pignataro (primary), Ignacio Goyret (secondary)
The Attribute Value field is a 16-bit field.
0x0001
S-bit (real-time)
PPP Disconnect Cause Code (Attribute Type 46) Values
0-32767
IESG Approval
32768-65279
First Come First Served
65280-65535
Reserved for Private or Experimental Use
Global Errors
0
No information available
1
Administrative disconnect.
2
Link Control Protocol (LCP) renegotiation at
LNS disabled; LNS expects proxy LCP information,
LAC did not send it.
3
Normal Disconnection, LCP Terminate-Request sent.
Valid Direction values are:
1: LCP Terminate-Request sent by peer
2: LCP Terminate-Request sent by local
4
Compulsory encryption required by a PPP peer was
refused by the other.
Valid Direction values are:
1: Required by local; refused by peer
2: Required by peer; refused by local
LCP Errors
5
FSM (Finite State Machine) Timeout error.
(PPP event "TO-".)
6
No recognizable LCP packets were received.
7
LCP failure: Magic Number error; link possibly
looped back.
8
LCP link failure: Echo Request timeout.
9
Peer has unexpected Endpoint-Discriminator for
existing Multilink PPP (MP) bundle.
10
Peer has unexpected MRRU for existing MP bundle.
11
Peer has unexpected Short-Sequence-Number option
for existing MP bundle.
12
Compulsory call-back required by a PPP peer was
refused by the other.
Valid Direction values are:
1: Required by local; refused by peer
2: Required by peer; refused by local
Authentication Errors
13
FSM Timeout error.
14
Peer has unexpected authenticated name for
existing MP bundle.
15
PPP authentication failure: Authentication protocol
unacceptable.
Valid Direction values are:
1: All local authentication protocols were
rejected by the peer.
2: All authentication protocols requested by peer
were unacceptable or unimplemented locally.
16
PPP authentication failure: Authentication failed
(bad name, password, or secret).
Valid Direction values are:
1: Authentication of peer identity by local system.
2: Authentication of local identity by peer system.
Network Control Protocol (NCP) Errors
17
FSM Timeout error.
18
No NCPs available (all disabled or rejected); no NCPs
went to Opened state. (Control Protocol Number may be
zero only if neither peer has enabled NCPs.)
19
NCP failure: failed to converge on acceptable addresses.
Valid Direction values are:
1: Too many Configure-Naks received from peer.
2: Too many Configure-Naks sent to peer.
20
NCP failure: user not permitted to use any addresses.
Valid Direction values are:
1: Local link address not acceptable to peer.
2: Remote link address not acceptable to local system.
21-32767
Unassigned (by IESG Approval)
32768-65279
Unassigned (First Come First Served)
65280-65535
Private or Experimental Use
ATM Alarm Status AVP (Attribute Type 88) Values
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
Circuit Status Reason values for the SLI message
0
Reserved
1
No alarm or alarm cleared (default for Active Status)
2
Unspecified or unknown Alarm Received (default for
Inactive Status)
3
ATM Circuit received F1 Alarm on ingress LCCE
4
ATM Circuit received F2 Alarm on ingress LCCE
5
ATM Circuit received F3 Alarm on ingress LCCE
6
ATM Circuit received F4 Alarm on ingress LCCE
7
ATM Circuit received F5 Alarm on ingress LCCE
8
ATM Circuit down due to ATM Port shutdown on Peer LCCE
9
ATM Circuit down due to loop-back timeout on ingress LCCE
General ATM Alarm failures
0
Reserved
1
No Alarm type specified (default)
2
Alarm Indication Signal (AIS)
3
Remote Defect Indicator (RDI)
4
Loss of Signal (LOS)
5
Loss of pointer (LOP)
6
Loss of framer (LOF)
7
loopback cells (LB)
8
Continuity Check (CC)
VCCV Capability AVP (Attribute Type 96) Values
IETF Review
Bit numbering: In this sub-registry, the most significant (high order) bit
is labeled Bit 7, and the least significant (low order) bit is labeled Bit 0,
see parenthetical "Value".
L2TPv3 Control Channel (CC) Types
0
L2-Specific Sublayer with V-bit set
1
Reserved
2
Reserved
3
Reserved
4
Reserved
5
Reserved
6
Reserved
7
Reserved
L2TPv3 Connectivity Verification (CV) Types
0
ICMP Ping
1
Reserved
2
BFD IP/UDP-encapsulated, for PW Fault Detection only
3
BFD IP/UDP-encapsulated, for PW Fault Detection and
AC/PW Fault Status Signaling
4
BFD PW-ACH-encapsulated, for PW Fault Detection only
5
BFD PW-ACH-encapsulated, for PW Fault Detection and
AC/PW Fault Status Signaling
6
S-BFD IP/UDP-encapsulated, for PW Fault Detection only
7
S-BFD L2SS-encapsulated, for PW Fault Detection only
Bearer Field definition
Standards Action
The Bearer field is used by the Bearer Capabilities and Bearer Type
AVPs. It is a 32-bit bit field, with current defined bit values of:
0x00000001
D-bit (Digital access requested)
0x00000002
A-bit (Analogue access requested)
0x00000004
B-bit (ATM Bearer support)
Framing Field definition
Standards Action
The Framing field is used by the Framing Capabilities and Framing Type
AVPs. It is a 32-bit bit field, with current defined bit values of:
0x00000001
S-bit (synchronous framing)
0x00000002
A-bit (asyncronous framing)
Leading Bits of the L2TP AVP Header
Standards Action
There are six bits at the beginning of the L2TP AVP header.
L2TPv2 and L2TPv3 share a common registry for the definitions
of the six leading bits.
0
Mandatory Bit, "M-bit"
1
Hidden Bit, "H-bit"
2
Reserved
3
Reserved
4
Reserved
5
Reserved
Leading Bits of the L2TP Message Header
Standards Action
There are 12 bits at the beginning of the L2TP Message Header.
L2TPv2 and L2TPv3 share a common registry for the definitions
of the 12 leading bits.
0
Message Type, "T-bit"
1
Length Field is Present, "L-bit"
2
Reserved
3
Reserved
4
Sequence Numbers Present, "S-bit"
5
Reserved
6
Offset Field is Present
7
Priority Bit, "P-bit"
8
B (Fragmentation) bit
9
E (Fragmentation) bit
10
Reserved
11
Reserved
L2TPv3 Pseudowire Types
Carlos Pignataro (primary), Ignacio Goyret (secondary)
The Pseudowire Type (PW Type, Section 5.4) is a two-octet value used
in the Pseudowire Type AVP and Pseudowire Capabilities List AVP defined in
Section 5.4.3. There are no specific pseudowire types assigned within this
document. Each pseudowire-specific document must allocate its own PW types
from IANA as necessary.
0-32767
Expert Review
32768-65535
First Come First Served
0x0001
Frame Relay DLCI Pseudowire Type
0x0002
ATM AAL5 SDU VCC transport
0x0003
ATM Cell transparent Port Mode
0x0004
Ethernet VLAN Pseudowire Type
0x0005
Ethernet Pseudowire Type
0x0006
HDLC Pseudowire Type
0x0009
ATM Cell transport VCC Mode
0x000A
ATM Cell transport VPC Mode
0x000B
Unassigned
0x000C
MPEG-TS Payload Type (MPTPW)
"Data-Over-Cable
Service Interface Specifications: Downstream External PHY Interface
Specification CM-SP-DEPI-I01-050805", DOCSIS, August 2005
0x000D
Packet Streaming Protocol (PSPPW)
"Data-Over-Cable
Service Interface Specifications: Downstream External PHY Interface
Specification CM-SP-DEPI-I01-050805", DOCSIS, August 2005
0x000E-0x0010
Unassigned
0x0011
Structure-agnostic E1 circuit
0x0012
Structure-agnostic T1 (DS1) circuit
0x0013
Structure-agnostic E3 circuit
0x0014
Structure-agnostic T3 (DS3) circuit
0x0015
CESoPSN basic mode
0x0016
Unassigned
0x0017
CESoPSN TDM with CAS
Circuit Status Bits
IETF Review
The Circuit Status field is a 16 bit mask, with the two high order
bits assigned.
9
S (Standby) bit
10
E (Local PSN-facing PW (egress) Tx Fault) bit
11
I (Local PSN-facing PW (ingress) Rx Fault) bit
12
T (Local AC (egress) Tx Fault) bit
13
R (Local AC (ingress) Rx Fault) bit
14
N (New) bit [use deprecated]
15
A (Active) bit
Default L2-Specific Sublayer bits
The Default L2 Specific Sublayer contains 8 bits in the low-order
portion of the header. Reserved bits may be assigned by IETF
Review .
0
V (VCCV) bit
1
S (Sequence) bit
2
B (Fragmentation) bit
3
E (Fragmentation) bit
4
Reserved
5
Reserved
6
Reserved
7
Reserved
L2-Specific Sublayer Type
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
The L2-Specific Sublayer Type is a 2 octet unsigned integer.
Additional values may be assigned by Expert Review .
0
No L2-Specific Sublayer
1
Default L2-Specific Sublayer present
2
ATM-Specific Sublayer present
3
MPT-Specific Sublayer
"Data-Over-Cable
Service Interface Specifications: Downstream External PHY Interface
Specification CM-SP-DEPI-I01-050805", DOCSIS, August 2005
4
PSP-Specific Sublayer
"Data-Over-Cable
Service Interface Specifications: Downstream External PHY Interface
Specification CM-SP-DEPI-I01-050805", DOCSIS, August 2005
Data Sequencing Level
Expert Review
Carlos Pignataro (primary), Ignacio Goyret (secondary)
The Data Sequencing Level is a 2 octet unsigned integer
Additional values may be assigned by Expert Review .
0
No incoming data packets require sequencing.
1
Only non-IP data packets require sequencing.
2
All incoming data packets require sequencing.
ATM-Specific Sublayer bits
IETF Review
0
V (VCCV) bit
1
S (Sequence) bit
2
B (Fragmentation) bit
3
E (Fragmentation) bit
4
T (Transport type) bit
5
G (EFCI) bit
6
C (CLP) bit
7
U (Command/Response) bit