Network Working Group N. Leymann
Internet Draft C. Heidemann
Intended Category: Informational Deutsche Telekom AG
M. Zhang
Huawei
M. Wasserman
Painless Security
Expires: January 7, 2016 July 6, 2015
GRE Tunnel Bonding
draft-zhang-gre-tunnel-bonding-00.txt
Abstract
It is an emerging demand to provide redundancy and load-sharing
across wired and cellular links from a single service provider so
that one customer is provided with "Hybrid Access" to the bonding of
multiple heterogeneous connections.
In this document, GRE (Generic Routing Encapsulation) Tunnel Bonding
is specified as an enabling approach for Hybrid Access. In GRE Tunnel
Bonding, GRE tunnels per network connections are set up and bonded
together to form a single GRE tunnel for a subscriber. Compared with
each composing connection, the bonding connection promises increased
access capacity and improved reliability.
Status of this Memo
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Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Acronyms and Terminology . . . . . . . . . . . . . . . . . . . 4
3. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Control Plane . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Traffic Classification and Distribution . . . . . . . . . . 7
4.4. Traffic Recombination . . . . . . . . . . . . . . . . . . . 7
4.5. Bypassing . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.6. Measurement . . . . . . . . . . . . . . . . . . . . . . . . 8
4.7. Policy Control Considerations . . . . . . . . . . . . . . . 9
5. Control Protocol Specification (Control Plane) . . . . . . . . 9
5.1. GRE Tunnel Setup Request . . . . . . . . . . . . . . . . . 11
5.1.1. Client Identification Name . . . . . . . . . . . . . . 11
5.1.2. Session ID . . . . . . . . . . . . . . . . . . . . . . 12
5.1.3. DSL Synchronization Rate . . . . . . . . . . . . . . . 13
5.2. GRE Tunnel Setup Accept . . . . . . . . . . . . . . . . . . 13
5.2.1. H IPv4 Address . . . . . . . . . . . . . . . . . . . . 14
5.2.1. H IPv6 Address . . . . . . . . . . . . . . . . . . . . 14
5.2.3. Session ID . . . . . . . . . . . . . . . . . . . . . . 15
5.2.4. RTT Difference Threshold . . . . . . . . . . . . . . . 15
5.2.5. Bypass Bandwidth Check Interval . . . . . . . . . . . . 15
5.2.6. Active Hello Interval . . . . . . . . . . . . . . . . . 16
5.2.7. Hello Retry Times . . . . . . . . . . . . . . . . . . . 16
5.2.8. Idle Timeout . . . . . . . . . . . . . . . . . . . . . 17
5.2.9. Bonding Key Value . . . . . . . . . . . . . . . . . . . 18
5.2.10. SOAP DSL Upstream Bandwidth . . . . . . . . . . . . . 19
5.2.11. SOAP DSL Downstream Bandwidth . . . . . . . . . . . . 19
5.2.12. RTT Difference Threshold Violation . . . . . . . . . . 20
5.2.13. RTT Difference Threshold Compliance . . . . . . . . . 20
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5.2.14. Idle Hello Interval . . . . . . . . . . . . . . . . . 21
5.2.15. No Traffic Monitored Interval . . . . . . . . . . . . 21
5.3. GRE Tunnel Setup Deny . . . . . . . . . . . . . . . . . . . 22
5.3.1. Error Code . . . . . . . . . . . . . . . . . . . . . . 22
5.4. GRE Tunnel Hello . . . . . . . . . . . . . . . . . . . . . 23
5.4.1. Timestamp . . . . . . . . . . . . . . . . . . . . . . . 23
5.4.2. IPv6 Prefix Assigned by HAG . . . . . . . . . . . . . . 24
5.5. GRE Tunnel Tear Down . . . . . . . . . . . . . . . . . . . 24
5.6. GRE Tunnel Notify . . . . . . . . . . . . . . . . . . . . . 24
5.6.1. Bypass Traffic Rate . . . . . . . . . . . . . . . . . . 25
5.6.2. Filter List Package . . . . . . . . . . . . . . . . . . 25
5.6.3. Switching to DSL Tunnel . . . . . . . . . . . . . . . . 28
5.6.4. Overflowing to LTE Tunnel . . . . . . . . . . . . . . . 28
5.6.5. DSL Link Failure . . . . . . . . . . . . . . . . . . . 29
5.6.6. LTE Link Failure . . . . . . . . . . . . . . . . . . . 29
5.6.7. IPv6 Prefix Assigned to Host . . . . . . . . . . . . . 29
5.6.8. Diagnostic Start: Bonding Tunnel . . . . . . . . . . . 30
5.6.9. Diagnostic Start: DSL Tunnel . . . . . . . . . . . . . 30
5.6.10. Diagnostic Start: LTE Tunnel . . . . . . . . . . . . . 31
5.6.11. Diagnostic End . . . . . . . . . . . . . . . . . . . . 31
5.6.12. Filter List Package ACK . . . . . . . . . . . . . . . 32
5.6.13. Switching to Active Hello State . . . . . . . . . . . 32
5.6.14. Switching to Idle Hello State . . . . . . . . . . . . 33
5.6.15. Tunnel Verification . . . . . . . . . . . . . . . . . 33
6. Tunnel Protocol Operation (Data Plane) . . . . . . . . . . . . 34
6.1. The GRE Header . . . . . . . . . . . . . . . . . . . . . . 35
6.2. Automatic Setup of GRE Tunnels . . . . . . . . . . . . . . 36
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 37
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 37
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
9.1. Normative References . . . . . . . . . . . . . . . . . . . 37
9.2. Informative References . . . . . . . . . . . . . . . . . . 37
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
Operators used to provide subscribers with separate access to their
fixed broadband networks and mobile networks. It becomes desirable to
bond the fixed and wireless networks together to offer customers with
increased access capacity and improved reliability. Solutions that
support Hybrid Access to fixed and wireless networks are required.
In this document, Hybrid Access focuses on the use case that DSL
(Digital Subscriber Line) connection and LTE (Long Term Evolution)
connection are bonded together to form a bonding connection. When the
traffic volume exceeds the bandwidth of the DSL connection, the
excess amount can be offloaded to the LTE connection. Hybrid Customer
Premises Equipment (HCPE) is the equipment at the customer side
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initiating the DSL and LTE connections. Hybrid Access Gateway (HAG)
is the network function resides in the provider's networks to
terminate the bonded connections. Note that if there are more than
two connections need to be bonded, the GRE Tunnel Bonding mechanism
can support as well. However, it's out the scope of this document.
This document bases the solution on GRE (Generic Routing
Encapsulation) since GRE is widely supported in both fixed and mobile
networks. GRE tunnels are set up per those heterogeneous connections
(DSL+LTE) between HCPE and HAG. All these GRE tunnels are further
bonded together to form a logical GRE tunnel for the customer. HCPE
conceals the composing GRE tunnels from users and users simply treat
the logical GRE tunnel as a single IP link. This provides an overlay:
user IP packets (inner IP) is encapsulated with GRE which is in turn
carried over IP (outer IP).
The design of the GRE Tunnel Bonding exhibits how the function blocks
of Hybrid Access are realized, such as traffic classification,
distribution, recombination, measurement of the connection, etc.
Although the industry might develop more solutions for Hybrid Access
besides GRE Tunnel Bonding, the function blocks need to be realized
are common and the mapping out of the function blocks here is
referential to other potential solutions.
2. Acronyms and Terminology
GRE: Generic Routing Encapsulation
DSL: Digital Subscriber Line
LTE: Long Term Evolution
Hybrid Access: The bonding of multiple access connections based on
heterogeneous technologies (e.g., DSL and LTE).
HCPE: Hybrid Customer Premises Equipment (CPE). A CPE enhanced to
support the simultaneous use of both fixed broadband and 3GPP access
connections.
HAG: Hybrid Access Gateway. A logical function in the operator
network implementing a bonding mechanism for customer access
services.
C: The endpoint of the bonding connection at the HCPE.
E: The endpoint of the LTE connection resides in HCPE.
D: The endpoint of the DSL connection resides in HCPE
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H: The endpoint of the bonding connection at HAG. Usually, this is
also used as the endpoint for each heterogeneous connection.
CIR: Committed Information Rate [RFC2698]
RTT: Round Trip Time
FQDN: A Fully Qualified Domain Name (FQDN) is a domain name that
includes all higher level domains relevant to the entity named.
[RFC1594]
DSCP: The six-bit codepoint (DSCP) of the Differentiated Services
Field (DS Field) in the IPv4 and IPv6 Headers [RFC2724].
BRAS: Broadband Remote Access Server
PGW: Packet Data Network Gateway. In the Long Term Evolution (LTE)
architecture for the Evolved Packet Core (EPC), the PGW acts as an
anchor for user plane mobility.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Use Case
+-+ +-+
| +--------- Bonding Connection -------+ |
| | | |
| | +-+ | |
|C| |E+------ LTE Connection -------+H|
| | +-+ | |
| | +-+ | |
| | |D+------ DSL Connection -------+ |
+-+ +-+ +-+
\________/
HCPE HAG
Figure 3.1: Offloading from DSL to LTE, increased access capacity
For a Service Provider who owns heterogeneous networks, such as fixed
and mobile, customers wish to use its networks simultaneously with
increased access capacity rather than just uses a single network. As
shown by the reference model in Figure 3.1, the customer expects the
whole bandwidth of the bonding connection equals the sum of the
bandwidth of the DSL connection and the LTE connection between HCPE
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and HAG. In other words, when the traffic volume exceeds the
bandwidth of the DSL connection, the excess amount may be offloaded
to the LTE connection.
Most common implementation balance the load among multiple paths.
However, the use case described here is about per-packet offloading
rather than per-flow load-balance. For the per-flow load-balance, the
maximum bandwidth that may be used by a flow actually equals to the
bandwidth of the connection selected. The GRE Tunnel Bonding
mechanism is able to support the use case that requires per-flow
traffic classification and distribution though it's out the scope of
this document.
Use cases with more than two connections between HCPE and HAG is out
the scope of this document. However, the GRE Tunnel Bonding mechanism
can well support those use cases.
4. Overview
In this document, the widely supported GRE is chosen as the tunneling
technique. With the newly defined control protocol, GRE tunnels are
setup on top of the DSL and LTE connections which are ended at D and
H or E and H. These tunnels are bonded together to form a single
logical bonding GRE tunnel whose endpoint IP addresses are C and H.
Customers uses this logical tunnel without knowing the composing GRE
tunnels.
4.1. Control Plane
A clean-slate control protocol is designed to manage the GRE tunnels
that are setup per heterogeneous connections between HCPE and HAG.
The goal is to design a compact control plane for Hybrid Access only
instead of reusing existing control planes.
In order to measure the performance of connections, control packets
need co-route the same path with data packets. Therefore, a GRE
Channel is opened for the purpose of data plane forwarding of control
plane packets. The GRE header as specified in [RFC2890] is being
used. The GRE Protocol Type (tbd1) is used to identify this GRE
Channel. A family of control messages are encapsulated with GRE
header and carried over this channel. Attributes, formatted in Type-
Length-Value style, are further defined and included in each control
message.
With the newly defined control plane, the GRE tunnels between HCPE
and HAG can be established, managed and released without the
involvement of man-power of operators.
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4.2. Data Plane
With the new defined control plane, GRE tunnels can be automatically
setup per heterogeneous connections between HCPE and HAG. For the use
case depict in Section 3, there are the GRE tunnel ended at the DSL
WAN interfaces (shorted as DSL GRE tunnel) and the GRE tunnel ended
at the LTE WAN interfaces (shorted as LTE GRE tunnel). Each tunnel
may carry user's IP packets as payload, which forms a typical IP-in-
IP overlay. These tunnels are bonded together to offer a single
access point to customers.
The GRE header per [RFC2890] is used to encapsulate data packets. The
Protocol Type is 0x0800, which indicates the inner header is an IP
header. For per-packet offloading use case, the Key field is used as
a clear-text password. The Sequence Number field is used to maintain
the sequence of packets transported in all GRE tunnels as a single
flow between a pair of HCPE and HAG.
For the per-flow traffic classification and distribution, the Key
field will be used as the demultiplexer for flows. The
Acknowledgement field as specified in [RFC2637] will be used to
achieve a low-level congestion and flow control.
4.3. Traffic Classification and Distribution
For the offloading use case, the coloring mechanism specified in
[RFC2698] is being used to classify customer's IP packets, both
upstream and downstream, into the DSL GRE tunnel or LTE GRE tunnel.
Packets colored as green will be distributed into the DSL GRE tunnel
and packets colored as yellow will be distributed into the LTE GRE
tunnel. For the scenario that requires more than two GRE tunnels,
multiple levels of token buckets might be realized. For example, the
packets classified as not to be distributed to DSL may be further
colored as either to be distributed to LTE or distributed to WiFi.
The implementation detail is out the scope of this document.
The Committed Information Rate (CIR) of the coloring mechanism is set
to the total DSL WAN bandwidth minus the bypassing DSL bandwidth (See
Section 4.4.). The total DSL WAN bandwidth MAY be configured, MAY be
got from the SOAP server and MAY be timely detected and reported by
using ANCP [RFC6320].
Besides the per-packet offloading use case, the GRE Tunnel Bonding
mechanism is also applicable to per-flow classification and
distribution.
4.4. Traffic Recombination
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The recombination function at the receiver provides the in-order
delivery of customers' traffic. As specified in [RFC2890], the
receiver maintains a small amount of reordering buffer and order the
data packets in this buffer by the Sequence Number field of the GRE
header. For the offloading use case, all bonded GRE tunnels use the
same Key value. All packets carried on these bonded GRE tunnels go
into a single reordering buffer.
For the per-flow classification and distribution, Sequence Numbers
are set per Key values at the sender. Buffers per Key values are
maintained at the receiver. In addition, the Acknowledge Number field
can be introduced in order to achieve a low level congestion and flow
control [RFC2637]. As stated in [RFC2637], retransmissions are not
performed by the tunnel peers.
4.5. Bypassing
Service Providers need some types of services not delivered by the
bonding of GRE tunnels. For example, Service Providers do not expect
the real-time IPTV to be carried by the LTE GRE tunnel. It's required
that these kind of services bypass the GRE Tunnel Bonding and use
just the raw DSL bandwidth. In this way, the do not subject to the
traffic classification and distribution specified as above. There are
two kinds of bypassing:
o Fully bypassing: The raw DSL connection used for bypassing is not
controlled by HAG. It may or may not go through HAG.
o Partial bypassing: HAG controls the raw DSL connection used for
bypassing. The raw DSL connection goes through HAG
For either of the bypassing, HAG notifies the the service types that
need to bypass the bonded GRE tunnels using the Filter List Package
attribute as specified in Section 5.6.2. HCPE and HAG need set aside
the DSL bandwidth for bypassing. The available DSL bandwidth for the
GRE Tunnel Bonding equals to the total DSL bandwidth minus the
bypassing bandwidth.
4.6. Measurement
Since control packets co-route the same path with data packets. The
real performance of the data paths (e.g., the GRE tunnels) can be
measured. The GRE Tunnel Hello messages specified in Section 5.3 are
used to carry the timestamp information and the Round Trip Time (RTT)
value can therefore be calculated based on the timestamp.
Besides the end to end delay of the GRE tunnels, HCPE and HAG need
also measure the capacity of the tunnels. For example, for the fully
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bypassing, HCPE is REQUIRED to timely measure the downstream
bypassing bandwidth and report it to HAG (See Section 5.6.1.).
4.7. Policy Control Considerations
Operators and customers may input policies into the GRE Tunnel
Bonding. These policies will be interpreted into parameters or
actions that impact the traffic classification, distribution,
combination, measurement and bypassing.
Operators and customers may offer the service types that need to
bypass the bonded GRE tunnels. These service types will be delivered
from HAG to HCPE and HCPE will stick to raw DSL interfaces to
transmit traffic of these service types.
Since the GRE tunnels are setup on top of heterogeneous DSL and LTE
connections, if the difference of the transmission delays of these
connections exceeds a given threshold for a certain period, HCPE and
HAG should be able to stop the offloading behavior and fallback to a
traditional transmission mode, where the LTE GRE tunnel is disabled
while all traffic is transmitted over the DSL GRE tunnel. Operators
are allowed to defined this threshold and period.
Operators may determine the maximum allowed size (See
MAX_PERFLOW_BUFFER in [RFC2890]) of the buffer for reordering. They
may also define the maximum time (See OUTOFORDER_TIMER in [RFC2890])
that a packet can stay in the buffer for reordering. These parameters
impact the traffic recombination.
Operators may specify the interval for sending Hello messages and the
retry times for HCPE or HAG to send out Hello messages before it
declare the failure of a connection.
5. Control Protocol Specification (Control Plane)
Control messages are used to establish, maintain, measure and tear
down GRE tunnels between the HCPE and HAG. Also, the control plane
undertakes the responsibility to bond tunnels and convey traffic
policies.
For the purpose of measurement, control messages need to be delivered
as GRE encapsulated packets and delivered as co-route with data plane
packets. The new GRE Protocol Type [tbd1] is allocated for this
purpose and the standard GRE header as per [RFC2890] is used. The
format of the GRE header is as follows:
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
C (Bit 0)
Checksum Present. Set to zero (0).
K (Bit 2)
Key Present. Set to one (1).
S (Bit 3)
Sequence Number Present. Set to zero (0).
Protocol Type (2 octets)
Set to [tbd1].
Key
The Key field is used as a security feature, functioning as a 32-
bit clear-text password. Also, the Key field is used as a
demultiplexer for GRE tunnels at the HAG. This value of the Key is
generated by HAG and informed to HCPE. (See Section 5.2.9.)
The general format of the entire control message is as follows:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| |1|0| Reserved0 | Ver | Protocol Type = tbd1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MsgType| Rsvd1 | |
+-+-+-+-+-+-+-+-+ Attributes +
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MsgType (4 bits)
Message Type. The control message family contains the following 6
types of control messages:
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Control Message Family Type
========================== =========
GRE Tunnel Setup Request 1
GRE Tunnel Setup Accept 2
GRE Tunnel Setup Deny 3
GRE Tunnel Hello 4
GRE Tunnel Tear Down 5
GRE Tunnel Notify 6
Reserved 0,7-15
Rsvd1 (4 bits)
Reserved1. These bits MUST be set to zero.
Attributes
The Attributes field includes the attributes that need to be
carried in the control message. Each Attribute has the following
format.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Value ~ (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type (1 octet)
The Attribute Type specifies the type of the attribute.
Attribute Length (2 octets)
Attribute Length indicates the length of the Attribute Value.
Attribute Value (variable)
The Attribute Value includes the value of the attribute.
All control messages are sent in network order (high order octets
first). Since the Protocol Type carried in the GRE header for the
control message is tbd1, the receiver will determine to consume it
locally rather than further forwarding.
5.1. GRE Tunnel Setup Request
HCPE uses the GRE Tunnel Setup Request message to request HAG to
establish GRE tunnels. It is sent out from HCPE's LTE and DSL WAN
interfaces separately. Attributes that need be to included in this
message are defined in Section 5.1.1 through Section 5.1.3.
5.1.1. Client Identification Name
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Operator uses the Client Identification Name (CIN) to identify the
HCPE. The HCPE sends the CIN to HAG for authentication and
authorization as specified in [TS23.401]. It's REUIRED that the GRE
Tunnel Setup Request message sent out from the LTE WAN interface
contains the CIN attribute while the GRE Tunnel Setup Request message
sent out from the DSL WAN interface does not contain this attribute.
The CIN attribute has the following format:
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Client Identification Name (40 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
CIN, set to 3.
Attribute Length
Set to 40.
Client Identification Name
This is a 40 bytes ANSI string value set by the operator. It's
used as the identification of HCPE in the operator's network.
5.1.2. Session ID
This Session ID is generated by HAG when the LTE GRE Tunnel Setup
Request message is received and then notifies the Session ID to HCPE
through the LTE GRE Tunnel Setup Accept message. For those WAN
interfaces that need to be bonded together, the HCPE MUST use the
same Session ID. The HCPE MUST carry the Session ID attribute in each
DSL GRE Tunnel Setup Request message. For the first time that the LTE
GRE Tunnel Setup Request message is sent to the HAG, the Session ID
attribute need not be included. However, if the LTE GRE Tunnel fails
and HCPE tries to revive it, the LTE GRE Tunnel Setup Request message
MUST include the Session ID attribute.
The Session ID attribute has the following format:
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+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Session ID (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Session ID, set to 4.
Attribute Length
Set to 4.
Session ID
This is a 4 bytes ANSI string value generated by the HAG. It's
used as the identification of bonded GRE Tunnels.
5.1.3. DSL Synchronization Rate
HCPE uses the DSL Synchronization Rate to notify HAG about the
downstream bandwidth of the DSL link. The DSL GRE Tunnel Setup
Request message MUST include the DSL Synchronization Rate attribute.
The LTE GRE Tunnel Setup Request message SHOULD NOT include this
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| DSL Synchronization Rate (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
DSL Synchronization Rate, set to 7.
Attribute Length
Set to 4.
DSL Synchronization Rate
This is a unsigned integer with the unit of kbps.
5.2. GRE Tunnel Setup Accept
HAG uses the GRE Tunnel Setup Accept message as the response to the
GRE Tunnel Setup Request message. This message indicates the
permission of the tunnel establishment and carries parameters of the
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GRE tunnels. Attributes that need be to included in this message are
defined in Section 5.2.1 through Section 5.2.13.
5.2.1. H IPv4 Address
HAG uses the H IPv4 Address attribute to inform HCPE the H IPv4
address. HCPE uses the H IPv4 address as the endpoint IPv4 address of
the GRE tunnels. The LTE GRE Tunnel Setup Accept message MUST include
the H IPv4 Address attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| H IPv4 Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
H IPv4 Address, set to 1.
Attribute Length
Set to 4.
H IPv4 Address
Set to the pre-configured IPv4 address which is used as the
endpoint IP address of GRE tunnels by HAG.
5.2.1. H IPv6 Address
HAG uses the H IPv6 Address attribute to inform HCPE the H IPv6
address. HCPE uses the H IPv6 address as the endpoint IPv6 address of
the GRE tunnels. The LTE GRE Tunnel Setup Accept message MUST include
the H IPv6 Address attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| H IPv4 Address (16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
H IPv6 Address, set to 1.
Attribute Length
Set to 16.
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H IPv6 Address
Set to the pre-configured IPv6 address which is used as the
endpoint IP address of GRE tunnels by HAG.
5.2.3. Session ID
The LTE GRE Tunnel Setup Accept message MUST include Session ID
attribute as defined in Section 5.1.2.
5.2.4. RTT Difference Threshold
HAG uses the RTT Difference Threshold to attribute to inform HCPE the
acceptable threshold of RTT difference between the DSL link and the
LTE link. If the measured RTT difference exceeds this threshold
SHOULD stop offloading traffic to the LTE GRE tunnel. The LTE GRE
Tunnel Setup Accept message MUST include the RTT Difference Threshold
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| RTT Difference Threshold (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
RTT Difference Threshold, set to 9.
Attribute Length
Set to 4.
RTT Difference Threshold
A unsigned integer with the unit of millisecond. This value can be
chosen in the range 0 through 1000.
5.2.5. Bypass Bandwidth Check Interval
HAG uses the Bypass Bandwidth Check Interval attribute to inform HCPE
the interval that the bypass bandwidth should be checked. HCPE should
check the bypass bandwidth of the DSL WAN interface in each time
period as indicates by this interval. The LTE GRE Tunnel Setup Accept
message MUST include the Bypass Bandwidth Check Interval attribute.
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+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Bypass Bandwidth Check Interval (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Bypass Bandwidth Check Interval, set to 10.
Attribute Length
Set to 4.
Bypass Bandwidth Check Interval
A unsigned integer with the unit of second. This value can be
chosen in the range 0 through 300.
5.2.6. Active Hello Interval
HAG uses the Active Hello Interval attribute to inform HCPE the pre-
configured interval for sending out GRE Tunnel Hellos. HCPE should
send out GRE Tunnel Hellos via both the DSL and LTE WAN interfaces in
each time period as indicates by this interval. The LTE GRE Tunnel
Setup Accept message MUST include the Active Hello Interval
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Active Hello Interval (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Active Hello Interval, set to 14.
Attribute Length
Set to 4.
Active Hello Interval
A unsigned integer with the unit of second. This value can be
chosen in the range 0 through 100.
5.2.7. Hello Retry Times
HAG uses the Hello Retry Times attribute to inform HCPE the retry
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times for sending GRE Tunnel Hellos. If the HCPE does not receive any
acknowledgement to the GRE Tunnel Hellos from the HAG over a GRE
Tunnel after it tries the times specified in this attribute, the HCPE
will declare the failure this GRE Tunnel. The LTE GRE Tunnel Setup
Accept message MUST include the Hello Retry Times attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Hello Retry Times (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Hello Retry Times, set to 15.
Attribute Length
Set to 4.
Hello Retry Times
A unsigned integer number which takes value in the range 3 through
10.
5.2.8. Idle Timeout
HAG uses the Idle Timeout attribute to inform HCPE the pre-configured
timeout value to terminate the DSL GRE tunnel. When an LTE GRE Tunnel
failure is detected, all traffic will be sent over the DSL GRE
tunnel. If the failure of the LTE GRE tunnel lasts longer than the
Idle Timeout, the traffic will be sent over the raw DSL rather the
tunnel over it, and the DSL GRE tunnel SHOULD be terminated. The LTE
Tunnel Setup Accept message MUST include the Idle Timeout attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Idle Timeout (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Idle Timeout, set to 16.
Attribute Length
Set to 4.
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Idle Timeout
A unsigned integer number with the unit of second. It takes value
in the range 0 through 172,800 with the granularity of 60. The
default value is 1,440 (24 hours). The value 0 indicates the idle
timer never expires.
5.2.9. Bonding Key Value
HAG uses the Bonding Key Value attribute to inform HCPE the number
which is to be used as the Key of the GRE header for each tunneled
control messages. The Bonding Key Value is generated by HAG and used
for the purpose of demultiplexing. HAG is REQUIRED to distinguish the
GRE tunnels from the Bonding Key Value. Different tunnels MUST use
different Bonding Key Values. HAG SHOULD identify the GRE tunnels by
their source IP addresses which are carried in the outer IP header.
Since the CIN attribute is carried in the GRE Tunnel Setup Request
sent on the LTE GRE tunnel only, HAG can figure out the source IP
address used for the LTE GRE tunnel from the message carrying the CIN
attribute. Similarly, HAG can figure out the source IP address used
for the DSL GRE tunnel from the message carrying the DSL
Synchronization Rate attribute.
The specific method used to generate this number is up to
implementations. The Pseudo Random Number Generator defined in ANSI
X9.31 Appendix A.2.4 is RECOMMENDED. Both the LTE GRE Tunnel Setup
Accept message and the DSL GRE Tunnel Setup Accept message MUST
include the Bonding Key Value attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Bonding Key Value (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Bonding Key Value, set to 20.
Attribute Length
Set to 4.
Bonding Key Value
A 32-bit number generated by the HAG. It's REQUIRED that different
tunnels are allocated with different Key values. The HAG MAY set
aside a few bits (e.g., the highest 4 bits) in the Key field as
the demultiplexer for the tunnels while other bits are filled in
with a value generated by a random number generator.
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5.2.10. SOAP DSL Upstream Bandwidth
HAG obtains the upstream bandwidth of the DSL link from the SOAP
server and uses the SOAP DSL Upstream Bandwidth attribute to inform
HCPE. The HCPE uses this informed upstream bandwidth as the Committed
Information Rate for the DSL link [RFC2698]. The DSL GRE Tunnel Setup
Accept message MUST include the SOAP DSL Upstream Bandwidth
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| SOAP DSL Upstream Bandwidth (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
SOAP DSL Upstream Bandwidth, set to 22.
Attribute Length
Set to 4.
SOAP DSL Upstream Bandwidth
A unsigned integer with the unit of kbps.
5.2.11. SOAP DSL Downstream Bandwidth
HAG obtains the downstream bandwidth of the DSL link from the SOAP
server and uses the SOAP DSL Downstream Bandwidth attribute to inform
HCPE. The HCPE uses this informed downstream bandwidth as the base in
calculating of the bypassing bandwidth. The DSL GRE Tunnel Setup
Accept message MUST include the SOAP DSL Downstream Bandwidth
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| SOAP DSL Downstream Bandwidth (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
SOAP DSL Downstream Bandwidth, set to 23.
Attribute Length
Set to 4.
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SOAP DSL Downstream Bandwidth
A unsigned integer with the unit of kbps.
5.2.12. RTT Difference Threshold Violation
HAG uses the RTT Difference Threshold Violation attribute to inform
HCPE the times of the measurements that the RTT Difference Threshold
(See Section 5.2.4.) is continuously detected to be violated. If RTT
Difference Threshold is continuously detected to be violated more
than this informed times, the HCPE MUST stop using the LTE GRE
tunnel. The LTE GRE Tunnel Setup Accept message MUST include the RTT
Difference Threshold Violation attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| RTT Diff Threshold Violation (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
RTT Difference Threshold Violation, set to 24.
Attribute Length
Set to 4.
RTT Difference Threshold Violation
A unsigned integer which takes from the range 1 through 25.
5.2.13. RTT Difference Threshold Compliance
HAG uses the RTT Difference Threshold Compliance attribute to inform
HCPE the times of the measurements that the RTT Difference Threshold
(See Section 5.2.4.) is continuously detected to be compliant. If the
RTT Difference Threshold is continuously detected to be compliant
more than this informed times, the HCPE MAY resume the LTE GRE
tunnel. The LTE GRE Tunnel Setup Accept message MUST include the RTT
Difference Threshold Compliance attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| RTT Diff Threshold Compliance (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
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Attribute Type
RTT Diff Threshold Compliance, set to 25.
Attribute Length
Set to 4.
RTT Diff Threshold Compliance
A unsigned integer which takes from the range 1 through 25.
5.2.14. Idle Hello Interval
HAG uses the Idle Hello Interval attribute to inform HCPE the pre-
configured interval for sending out GRE Tunnel Hellos when the
customer is detected to be idle. HCPE SHOULD begin to send out GRE
Tunnel Hellos via both the DSL and LTE WAN interfaces in each time
period as indicates by this interval, if the bonding tunnels have
seen no traffic longer than the "No Traffic Monitored Interval" (See
Section 5.2.15.). The LTE GRE Tunnel Setup Accept message MUST
include the Idle Hello Interval attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Idle Hello Interval (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Idle Hello Interval, set to 31.
Attribute Length
Set to 4.
Idle Hello Interval
A unsigned integer with the unit of second. This value can be
chosen in the range 100 through 86,400 (24 hours) with the
granularity of 100. The default value is 1800 (30 minutes).
5.2.15. No Traffic Monitored Interval
HAG uses the No Traffic Monitored Interval attribute to inform HCPE
the pre-configured interval for switching the GRE Tunnel Hello mode.
If traffic is detected on the bonding GRE tunnels before this
informed interval expires, the HCPE SHOULD switch to Active Hello
Interval. The LTE GRE Tunnel Setup Accept message MUST include the No
Traffic Monitored Interval attribute.
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+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| No Traffic Monitored Interval (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
No Traffic Monitored Interval, set to 32.
Attribute Length
Set to 4.
No Traffic Monitored Interval
A unsigned integer with the unit of second. This value can be
chosen in the range 30 through 86,400 (24 hours). The default
value is 60.
5.3. GRE Tunnel Setup Deny
HAG MUST sends the GRE Tunnel Setup Deny message to HCPE if the GRE
tunnel setup request from this HCPE is denied. The HCPE MUST
terminate the GRE tunnel setup process as soon as it receives the GRE
Tunnel Setup Deny message.
5.3.1. Error Code
HAG uses the Error Code attribute to inform HCPE the error code. The
error code depicts the reason why the GRE tunnel setup request is
denied. Both the LTE GRE Tunnel Setup Deny message and the DSL GRE
Tunnel Setup Deny message MUST include the Error Code attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Error Code (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Error Code, set to 17.
Attribute Length
Set to 4.
Error Code
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A unsigned integer. The list of the codes are listed as follows.
1: HAG is not reachable via LTE during GRE tunnel setup request.
2: HAG is not reachable via DSL during GRE tunnel setup request.
3: LTE GRE tunnel to the HAG fails.
4: DSL GRE tunnel to the HAG fails.
5: The given DSL User ID is not allowed to use GRE tunnel bonding
service.
6: The given User Alias (TOID)/User ID (GUID) is not allowed to
use GRE tunnel bonding service.
7: LTE and DSL User IDs mismatching.
8: HAG denies the GRE tunnel setup request since a bonding session
with the same User ID already exists.
9: HAG denies the GRE tunnel setup request since the user's CIN is
not permitted.
10: HAG terminates a GRE tunnel bonding session for maintenance
reasons.
11: There is a communication error between the HAG and SOAP server
during the LTE tunnel setup request.
12: There is a communication error between the HAG and SOAP server
during the DSL tunnel setup request.
5.4. GRE Tunnel Hello
After the GRE tunnel is established, the HCPE begins to periodically
send out GRE Tunnel Hello messages while the HAG acknowledges by
returning the GRE Tunnel Hello messages back to HCPE, until the
tunnel is terminated.
5.4.1. Timestamp
HAG uses the Timestamp attribute to inform HCPE the timestamp value
that is used for RTT calculation. Both the LTE GRE Tunnel Hello
message and DSL GRE Tunnel Hello message MUST include the Timestamp
attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Timestamp (8 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Timestamp, set to 5.
Attribute Length
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Set to 8.
Timestamp
The high-order 4 octets indicate a unsigned integer with the unit
of second; the low-order 4 octets indicate a unsigned integer with
the unit of millisecond.
5.4.2. IPv6 Prefix Assigned by HAG
HAG uses the IPv6 Prefix Assigned by HAG attribute to inform HCPE the
assigned IPv6 prefix. This IPv6 prefix is to be captured by the
Lawful Interception. Both the LTE GRE Tunnel Hello message and the
DSL GRE Tunnel Hello message MUST include the IPv6 Prefix Assigned by
HAG attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| IPv6 Prefix Assigned by HAG (16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
IPv6 Prefix Assigned by HAG, set to 13.
Attribute Length
Set to 17.
IPv6 Prefix Assigned by HAG
The highest-order 16 octets encode an IPv6 address. The lowest-
order one octet encodes the length of a network mask. These two
values are put together to represent an IPv6 prefix.
5.5. GRE Tunnel Tear Down
HAG can terminate a GRE tunnel by sending the GRE Tunnel Tear Down
message to the HCPE. The Error Code attribute as defined in Section
5.3.1 MUST be included in this message.
5.6. GRE Tunnel Notify
HCPE and HAG uses the GRE Tunnel Notify message to notify each other
about their status, the information for the bonding tunnels, the
actions need to be taken, etc.
Usually, the receiver just sends the received attributes back as the
acknowledgement for each GRE Tunnel Notify message. There is an
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exception for the Filter List Package. Since the size of the Filter
List Package attribute can be very large, a special attribute is
specified in Section 5.6.12 as the acknowledgement.
Attributes that need be to included in the GRE Tunnel Notify message
are defined in Section 5.6.1 through Section 5.6.15.
5.6.1. Bypass Traffic Rate
There are a few types of traffic that need to transmitted over the
raw DSL WAN interface rather than the bonding GRE tunnels. The HCPE
has to set aside a bypass bandwidth on the DSL WAN interface for
these kind of traffic types. Therefore, the available bandwidth of
the DSL GRE tunnel is the entire DSL WAN interface bandwidth minus
the occupied bypass bandwidth.
HCPE uses the Bypass Traffic Rate attribute to inform HAG the
downstream bypass bandwidth for the DSL WAN interface. The Bypass
Traffic Rate attribute will be included in the DSL GRE Tunnel Notify
message. HAG calculates the available downstream bandwidth for the
DSL GRE tunnel as the SOAP DSL Downstream Bandwidth minus this
informed bypass bandwidth. This available DSL bandwidth will be used
as the Committed Information Rate (CIR) of the coloring system
[RFC2698].
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Bypass Traffic Rate (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Bypass Traffic Rate, set to 6.
Attribute Length
Set to 4.
Bypass Traffic Rate
A unsigned integer with the unit of kbps.
5.6.2. Filter List Package
HAG uses the Filter List Package attribute to inform HCPE the service
types that need to bypass the bonding GRE tunnels. Each Filter List
Package carries a collection of Filter List TLVs and each such Filter
List TLV specifies a filter item. At the HCPE, a list of filter items
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is maintained. Also, HCPE need maintain an exception list of filter
items. For example, the packets carrying the control messages defined
in this document should be excluded from the filter list.
Incoming packets that match an filter item in the filter list while
not match any item in the exception list MUST be transmitted over the
raw DSL rather than the bonding GRE tunnels. Both the LTE GRE Tunnel
Notify message and GRE Tunnel Notify message MAY include the Filter
List Package attribute. The DSL GRE Tunnel Notify message is
preferred.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Filter List TLVs (variable) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Filter List Package, set to 8.
Attribute Length
The total length of the Filter List TLVs. The maximum length is
969 bytes.
Filter List TLVs
Each Filter List TLV has the following format.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Commit_Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet_Sum | Packet_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Enable | Description Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Description Value (0~4 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value (0~32 bytes) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Commit_Count
A unsigned integer which identifies the version of the Filter
List Package. HCPE will refresh its filter list, when a new
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Commit_Count is received.
Packet_Sum
If the Filter List Package attribute might make the control
message larger than the MTU, fragmentation is used. The
Packet_Sum indicates the total number of Filter List Packages.
Packet_ID
The fragmentation index of one of those multiple Filter List
Packages.
Type
The Type of the Filter List TLV. Currently used types are
described as follows.
Filter List TLVs Type
========================= ============
FQDN [RFC1594] 1
DSCP [RFC2724] 2
Destination Port 3
Destination IP 4
Destination IP&Port 5
Source Port 6
Source IP 7
Source IP&Port 8
Source Mac 9
Protocol 10
Source IP Range 11
Destination IP Range 12
Source IP Range&Port 13
Destination IP Range&Port 14
Reserved
Length
The length of the Filter List TLV. Commit_Count, Packet Sum,
Packet ID, Type and Length are excluded.
Enable
Whether the filter item defined in this Filter List TLV is
enabled. One means enabled and zero means disabled. Other
possible values are reserved.
Description Length
The length of the Description Value.
Description Value
A variable ASCII string that describes the Filter List TLV
(e.g., "FQDN").
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Value
A variable ASCII string that specify the value of the Filter
List TLV (e.g. "www.yahoo.com"). As an example, Type = 1 and
Value = "www.yahoo.com" means that packets whose FQDN field
equal "www.yahoo.com" match the filter item.
5.6.3. Switching to DSL Tunnel
If the RTT difference is continuously detected to violate the RTT
Difference Threshold (See Section 5.2.4.) more than the times
described by the RTT Difference Threshold Violation (See Section
5.2.12.), HCPE uses the Switching to DSL Tunnel attribute to inform
HAG to use the DSL GRE tunnel only. When HAG receives this attribute,
it MUST begin to transmit downstream traffic to this HCPE solely over
the DSL GRE tunnel. The DSL GRE Tunnel Notify message MAY include the
Switching to DSL Tunnel attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Switching to DSL Tunnel, set to 11.
Attribute Length
Set to 0.
5.6.4. Overflowing to LTE Tunnel
If the RTT difference is continuously detected to not violated the
RFF Difference Threshold (See Section 5.2.4.) more than the times
described by the RTT Difference Compliance (See Section 5.2.13), HCPE
uses the Overflowing to LTE Tunnel attribute to inform HAG that LTE
GRE tunnel can be used again. The DSL GRE Tunnel Notify message MAY
include the Overflowing to LTE Tunnel attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Overflowing to LTE Tunnel, set to 12.
Attribute Length
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Set to 0.
5.6.5. DSL Link Failure
When HCPE detects the DSL WAN interface status is down, it MUST tear
down the DSL GRE tunnel. It informs HAG about the failure using the
DSL Link Failure attribute. HAG MUST tear down the DSL GRE tunnel
upon the DSL Link Failure attribute is received. The DSL Link Failure
attribute SHOULD be carried in the LTE GRE Tunnel Notify message.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Attribute Type
DSL Link Failure, set to 18.
Attribute Length
Set to 0.
5.6.6. LTE Link Failure
When HCPE detects the LTE WAN interface status is down, it MUST tear
down the LTE GRE tunnel. It informs HAG about the failure using the
LTE Link Failure attribute. HAG MUST tear down the LTE GRE tunnel
upon the LTE Link Failure attribute is received. The LTE Link Failure
attribute SHOULD be carried in the DSL GRE Tunnel Notify message.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
LTE Link Failure, set to 19.
Attribute Length
Set to 0.
5.6.7. IPv6 Prefix Assigned to Host
If HCPE changes the IPv6 prefix assigned to the host, it uses the
IPv6 Prefix Assigned to Host attribute to inform HAG. Both the LTE
GRE Tunnel Notify message and the DSL GRE Tunnel Notify message MAY
include the IPv6 Prefix Assigned to Host attribute.
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+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| IPv6 Prefix Assigned to Host (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
IPv6 Prefix Assigned to Host, set to 21.
Attribute Length
Set to 17.
IPv6 Prefix Assigned to Host
The highest-order 16 octets encode an IPv6 address. The lowest-
order one octet encodes the length of a network mask. These two
values are put together to represent an IPv6 prefix.
5.6.8. Diagnostic Start: Bonding Tunnel
HCPE uses the Diagnostic Start: Bonding Tunnel attribute to inform
HAG to switch to diagnostic mode to test the performance of the
entire bonding tunnel. The Diagnostic Start: Bonding Tunnel attribute
SHOULD be carried in the DSL GRE Tunnel Notify message.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Diagnostic Start: Bonding Tunnel, set to 26.
Attribute Length
Set to 0.
5.6.9. Diagnostic Start: DSL Tunnel
HCPE uses the Diagnostic Start: DSL Tunnel attribute to inform HAG to
switch to diagnostic mode to test the performance of the DSL GRE
tunnel. The Diagnostic Start: DSL Tunnel attribute SHOULD be carried
in the DSL GRE Tunnel Notify message.
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+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Diagnostic Start: DSL Tunnel, set to 27.
Attribute Length
Set to 0.
5.6.10. Diagnostic Start: LTE Tunnel
HCPE uses the Diagnostic Start: LTE Tunnel attribute to inform HAG to
switch to diagnostic mode to test the performance of the entire
bonding tunnel. The Diagnostic Start: LTE Tunnel attribute SHOULD be
carried in the DSL GRE Tunnel Notify message.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Diagnostic Start: LTE Tunnel, set to 18.
Attribute Length
Set to 0.
5.6.11. Diagnostic End
HCPE uses the Diagnostic End attribute to inform HAG to stop the
diagnostic mode. The Diagnostic End attribute SHOULD be carried in
the DSL GRE Tunnel Notify message.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Diagnostic End, set to 29.
Attribute Length
Set to 0.
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5.6.12. Filter List Package ACK
HCPE uses the Filter List Package ACK attribute to acknowledge the
Filter List Package sent by HAG. Both the LTE GRE Tunnel Notify
message and the DSL GRE Tunnel Notify message MAY include the Filter
List Package ACK attribute.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
| Filter List Package ACK (5 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
Attribute Type
Filter List Package ACK, set to 30.
Attribute Length
Set to 5.
Filter List Package ACK
The highest-order 4 octets are the Commit_Count as defined in
Section 5.6.2. The lowest-order 1 octet encodes the following
error codes:
0: The Filter List Package is acknowledged.
1: The Filter List Package is not acknowledged. The HCPE is a new
subscriber and has not ever received a Filter List Package. In
this case, HAG SHOULD tear down the bonding tunnels and force
the HCPE to re-establish the GRE Tunnels.
2: The Filter List Package is not acknowledged. The HCPE has
already got a valid Filter List Package. The filter list on the
HCPE will continue to be used while HAG need do nothing.
5.6.13. Switching to Active Hello State
If traffic is being sent/receive over the bonding GRE tunnels before
the "No Traffic Monitored Interval" expires (See Section 5.2.15.),
HCPE sends to HAG a GRE Tunnel Notify message containing the
Switching to Active Hello State attribute.
HAG will switch to active hello state and send HCPE a GRE Tunnel
Notify message carrying the Switching to Active Hello State attribute
as the ACK.
When HCPE receives the ACK, it will switch to active hello state,
start RTT detection and start sending GRE Tunnel Hello messages with
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the Active Hello Interval (See Section 5.2.6.).
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Switching to Active Hello State, set to 33.
Attribute Length
Set to 0.
5.6.14. Switching to Idle Hello State
HCPE initiates switching to idle hello state when the bonding of GRE
Tunnels is successfully established and the LTE GRE Tunnel Setup
Accept message carrying the Idle Hello Interval attribute (See
Section 5.2.14.) is received. HCPE sends to HAG a GRE Tunnel Notify
message containing the Switching to Idle Hello State attribute.
HAG will switch to idle hello state, clear RTT state and send HCPE a
GRE Tunnel Notify message carrying the Switching to Idle Hello State
attribute as the ACK.
When HCPE receives the ACK, it will switch to idle hello state, stop
RTT detection, clear RTT state as well and start sending GRE Tunnel
Hello messages with the Idle Hello Interval (See Section 5.2.14).
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Switching to Idle Hello State, set to 34.
Attribute Length
Set to 0.
5.6.15. Tunnel Verification
HAG uses the Tunnel Verification attribute to inform HCPE to verify
whether an existing LTE GRE tunnel is still functioning. The Tunnel
Verification attribute SHOULD be carried in the LTE GRE Tunnel Notify
message. It provides a mean to detect the tunnel faster than the GRE
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Tunnel Hello, especially when the LTE GRE tunnel is in the Idle Hello
state and it takes much longer time to detect this tunnel.
When HAG receives an LTE GRE Tunnel Setup Request and finds the
requested tunnel is conflicting with an existing tunnel, the HAG
initiates the Tunnel Verification. The HAG drops all conflicting LTE
GRE Tunnel Setup Request messages and send GRE Tunnel Notify messages
carrying the Tunnel Verification attribute until the verification
ends. HCPE MUST response to HAG same Tunnel Verification attribute as
the ACK if the tunnel is still functioning.
If the ACK of the Tunnel Verification attribute is received from the
HCPE, HAG judges that the existing tunnel is still functioning. An
LTE GRE Tunnel Deny message (with Error Code = 8) will be sent to the
HCPE. HCPE SHOULD terminate the GRE tunnel setup request process
immediately.
If HAG does not receive a Tunnel Verification ACK message until up to
3 times (1 sending + 2 resending), it will regard the existing tunnel
as failed and the LTE GRE Tunnel Setup Request will be accepted.
+-+-+-+-+-+-+-+-+
|Attribute Type | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute Type
Tunnel Verification, set to 35.
Attribute Length
Set to 0.
6. Tunnel Protocol Operation (Data Plane)
GRE tunnels are set up over heterogeneous connections, such as LTE
and DSL, between HCPE and HAG. Users' IP (inner) packets are
encapsulated in GRE packets which in turn are carried over IP
(outer). The general structure of the packets is shown as below.
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+--------------------------------+
| Media Header |
+--------------------------------+
| Outer IP Header |
+--------------------------------+
| GRE Header |
+--------------------------------+
| Inner IP Packet |
+--------------------------------+
6.1. The GRE Header
The GRE header is first standardized in [RFC2874]. [RFC2890] adds the
optional key and sequence number fields which makes the whole GRE
header have the following format.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum (optional) | Reserved1 (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Checksum is not used in the GRE Tunnel Bonding, therefore the C
bit is set to zero.
The Key bit is set to one. For per-packet traffic distribution, the
Key field is used as a 32-bit random number. It is generated by the
HAG and notified to HCPE. Different from the Key filed used in
control packets, each bonding of GRE tunnels gets a single Key value.
HCPE MUST carry this number in each GRE header. For the per-flow
traffic classification and distribution, the Key field will be used
to identify the traffic flows.
The S bit is set to one and the sequence number is present for in-
order delivery as per [RFC2890].
For the per-flow traffic, the GRE header need also enable the
Acknowledgement Number field as used in PPTP [RFC2637]. The A bit
(Bit 8) is set to one to indicate this field is present in the GRE
header. This acknowledgement number and the sequence number field are
used to achieve a low-level congestion and flow control. Unless
explicitly pointed out, the acknowledgement number field is used as
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per [RFC2637]. The enhanced GRE header has the following format:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| |1|1| Rsvd0 |1| Rsvd1 | Ver | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Acknowledgement Number (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.2. Automatic Setup of GRE Tunnels
The HCPE gets the DSL WAN interface IP address (D) from BRAS via
PPPoE, and gets the LTE WAN interface IP address (E) through PDP from
PGW. The DNS resolution of HAG's domain name is requested via DSL/LTE
WAN interface. The DNS server will reply with the corresponding HAG
IP address (H) which MAY be pre-configured by operators.
After the interface IP addresses have been acquired, the HCPE starts
the following GRE Tunnel Bonding procedure. It's REQUIRED that the
HCPE first sets up the LTE GRE tunnel and then sets up the DSL GRE
tunnel.
The HCPE sends the GRE Tunnel Setup Request message to HAG via the
LTE WAN interface. The HAG, which receives the GRE Tunnel Setup
Request message, will initiate the Authentication and Authorization
procedure, as specified in [TS23.401], to check whether HCPE is being
trusted by the PGW.
If the Authentication and Authorization succeed, HAG will reply to
HCPE's LTE WAN interface with the GRE Tunnel Setup Accept message in
which a Session ID randomly generated by the HAG is carried.
Otherwise, the HAG MUST send to the HCPE's LTE WAN interface the GRE
Tunnel Setup Deny message and the HCPE MUST terminate the tunnel set
up process upon it receives the GRE Tunnel Setup Deny message.
After the LTE GRE tunnel is successfully set up, the HCPE will obtain
the C address over the tunnel from HAG through DHCP. After that, the
HCPE starts to set up the DSL GRE tunnel. It sends GRE Tunnel Setup
Request message with HAG's address as the destination IP of GRE via
the DSL WAN interface, carrying the aforementioned session ID
received from the HAG. The HAG, which receives the GRE Tunnel Setup
Request message, will initiate the Authentication and Authorization
procedure in order to check whether HCPE is trusted by the BRAS.
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If the Authentication and Authorization succeed, the HAG will reply
to the HCPE's DSL WAN interface with the GRE Tunnel Setup Accept
message. In this way, the two tunnels with the same Session ID can be
used to carry traffic from the same user. That is to say, the two
tunnels are "bonded" together. Otherwise, if the Authentication and
Authorization fail, the HAG MUST send to the HCPE's DSL WAN interface
the GRE Tunnel Setup Deny message. Meanwhile, it MUST send to the
HCPE's LTE WAN interface the GRE Tunnel Tear Down message. The HCPE
MUST terminate the tunnel set up process upon it receives the GRE
Tunnel Setup Deny message and MUST tear down the LTE GRE tunnel that
has been set up upon it receives the GRE Tunnel Tear Down Message.
7. Security Considerations
As a security feature, the Key field of the GRE header of the control
messages and the data packets for the per-packet traffic distribution
could be generated as a 32-bit clear-text password.
8. IANA Considerations
No IANA action is required in this document. RFC Editor: please
remove this section before publication.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2698] Heinanen, J. and R. Guerin, "A Two Rate Three Color
Marker", RFC 2698, September 1999.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
[TS23.401] "3GPP TS23.401, General Packet Radio Service (GPRS)
enhancements for Evolved Universal Terrestrial Radio Access
Network (E-UTRAN) access", September 2013.
9.2. Informative References
[RFC1594] Marine, A., Reynolds, J., and G. Malkin, "FYI on Questions
and Answers - Answers to Commonly asked "New Internet User"
Questions", RFC 1594, March 1994.
[RFC2724] Handelman, S., Stibler, S., Brownlee, N., and G. Ruth,
"RTFM: New Attributes for Traffic Flow Measurement", RFC
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2724, October 1999.
[RFC2637] Hamzeh, K., Pall, G., Verthein, W., Taarud, J., Little, W.,
and G. Zorn, "Point-to-Point Tunneling Protocol (PPTP)",
RFC 2637, July 1999.
[RFC6320] Wadhwa, S., Moisand, J., Haag, T., Voigt, N., and T.
Taylor, Ed., "Protocol for Access Node Control Mechanism in
Broadband Networks", RFC 6320, October 2011.
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Author's Addresses
Nicolai Leymann
Deutsche Telekom AG
Winterfeldtstrasse 21-27
Berlin 10781
Germany
Phone: +49-170-2275345
Email: n.leymann@telekom.de
Cornelius Heidemann
Deutsche Telekom AG
Heinrich-Hertz-Strasse 3-7
Darmstadt 64295
Germany
Phone: +4961515812721
Email: heidemannc@telekom.de
Mingui Zhang
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095 P.R. China
EMail: zhangmingui@huawei.com
Margaret Wasserman
Painless Security
EMail: mrw@painless-security.com
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