DTCP: Dynamic Tasking Control Protocol
draft-kala-dtcp-01
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| Authors | Sumit kala , David Cavuto | ||
| Last updated | 2017-06-25 (Latest revision 2017-06-21) | ||
| Replaces | draft-cavuto-dtcp | ||
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draft-kala-dtcp-01
IP Performance Metrics Group Sumit. Kala
Internet-Draft Juniper Networks
Intended status: Standards Track David. Cavuto
Expires: December 21, 2017 ATT
June 21, 2017
DTCP: Dynamic Tasking Control Protocol
draft-kala-dtcp-01
Abstract
Dynamic Tasking Control Protocol is a message-based interface by
which an authorized client may connect to a server -- usually a
network element (NE) or security policy enforcement point (PEP) --
and issue dynamic requests for data. These tasking requests contain,
among other parameters, packet matching criteria that may apply to
certain packets flowing through that network element. The primary
intent of the tasking request is to instruct that network element to
send copies of packets matching those criteria to a destination
(usually via tunneling) for further inspection or other action. The
protocol contains a security architecture to address client or server
spoofing as well as replay prevention. The protocol assumes that
multiple clients may simultaneously control a single server.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 21, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Operational Modes . . . . . . . . . . . . . . . . . . . . 4
1.2. Performance Considerations . . . . . . . . . . . . . . . . 4
1.3. Conventions used in this document . . . . . . . . . . . . 5
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Client . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Control Source . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Content Destination . . . . . . . . . . . . . . . . . . . 5
2.5. Criteria . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview of Operation . . . . . . . . . . . . . . . . . . . . 6
3.1. Request-Response Paradigm . . . . . . . . . . . . . . . . 6
3.2. Asynchronous Notifications . . . . . . . . . . . . . . . . 7
3.3. Data Delivery Mechanism . . . . . . . . . . . . . . . . . 8
4. Security Model . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. No Information Exposure . . . . . . . . . . . . . . . . . 9
4.2. Independence of Control Sources . . . . . . . . . . . . . 9
4.3. Control Source to Content Destination Access Control . . . 9
4.4. Per-Message Security Mechanisms . . . . . . . . . . . . . 9
4.4.1. Sequence Number . . . . . . . . . . . . . . . . . . . 9
4.4.1.1. Sequence Number Negative Window . . . . . . . . . 10
4.4.2. Hashing Message Authentication Code (HMAC) . . . . . . 11
5. Application-Layer Message Formats . . . . . . . . . . . . . . 12
5.1. Request General Format . . . . . . . . . . . . . . . . . . 13
5.2. Response General Format . . . . . . . . . . . . . . . . . 13
5.3. Notification General Format . . . . . . . . . . . . . . . 13
5.4. Add Request . . . . . . . . . . . . . . . . . . . . . . . 14
5.4.1. Criteria Timeouts . . . . . . . . . . . . . . . . . . 15
5.5. Add Response . . . . . . . . . . . . . . . . . . . . . . . 16
5.6. Delete Request . . . . . . . . . . . . . . . . . . . . . . 17
5.7. Delete Response . . . . . . . . . . . . . . . . . . . . . 18
5.8. Refresh Request . . . . . . . . . . . . . . . . . . . . . 19
5.9. Refresh Response . . . . . . . . . . . . . . . . . . . . . 20
5.10. List Request . . . . . . . . . . . . . . . . . . . . . . . 21
5.11. List Response . . . . . . . . . . . . . . . . . . . . . . 21
5.12. NoOp Request . . . . . . . . . . . . . . . . . . . . . . . 23
5.13. NoOp Response . . . . . . . . . . . . . . . . . . . . . . 24
5.14. Restart Notification . . . . . . . . . . . . . . . . . . . 24
5.15. Rollover Notification . . . . . . . . . . . . . . . . . . 24
5.16. NoOp Notification . . . . . . . . . . . . . . . . . . . . 24
5.17. Timeout Notification . . . . . . . . . . . . . . . . . . . 25
5.18. Congestion Notification . . . . . . . . . . . . . . . . . 25
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5.19. CongestionDelete Notification . . . . . . . . . . . . . . 26
5.20. DuplicatesDropped Notification . . . . . . . . . . . . . . 26
6. Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . 27
6.1. Special treatment of response to List request . . . . . . 27
6.2. Error or Exception Conditions . . . . . . . . . . . . . . 29
6.3. Extensions in ABNF . . . . . . . . . . . . . . . . . . . . 30
6.4. Current Version . . . . . . . . . . . . . . . . . . . . . 30
6.5. No specific port . . . . . . . . . . . . . . . . . . . . . 30
6.6. Unimplemented Protocol Methods and Parameters . . . . . . 31
6.7. Version Mismatches . . . . . . . . . . . . . . . . . . . . 31
6.7.1. DTCP Client version exceeds DTCP Server version . . . 32
6.7.2. DTCP Server version exceeds DTCP Client version . . . 32
7. Message Payload Examples . . . . . . . . . . . . . . . . . . . 32
7.1. Successful ADD Request and Response Payload . . . . . . . 33
7.2. Unsuccessful DELETE Request and Response Payload . . . . . 33
8. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 34
9. Security Considerations . . . . . . . . . . . . . . . . . . . 40
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
11. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 41
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Appendix A. Prior Implementation . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 42
1. Introduction
The Dynamic Tasking Control Protocol (DTCP) is a mechanism used to
dynamically control network elements in the course of performing a
security or other analysis on a transient network event.
Network Security personnel typically have little visibility into the
very networks they are monitoring. Routers and switches have awkward
mechanisms such as port mirroring and cFlowd to enable personnel some
meager view into the traffic flowing through a device.
However, when a security incident does happen to be detected, the
security analysis staff struggles to gain more insight as to the
actual content of the incident, via inference from these tools. This
is a time-consuming and cumbersome task.
cFlowd [9] and other aggregation mechanisms provide only session-
level statistics about the event, and fail to provide any view into
the actual packet data. In contrast, wholesale backhauling of port-
mirrored data is often cumbersome (and expensive) to set up, since it
requires pre-provisioned free bandwidth on wide-area links, and often
additional network hardware to implement.
The intent of DTCP is to provide a simple mechanism by which a third-
party device can interact with a network element or security policy-
enforcement-point (PEP) that normally processes packetized network
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data, and in that interaction cause the PEP to take some action
(usually copy) on a defined subset of that packet data to be
forwarded for further inspection and analysis.
packet +---+ packet
data ->---|NE |--->- data
+---+
^ |
| |
DTCP ----+ +---> copy of selected packet data
Figure 1 - DTCP interacting with a network element.
The Network Element (NE) or PEP may be a firewall or proxy server, or
some other non-security-specific network element, such as a router or
a switch. This is illustrated in Figure 1.
1.1. Operational Modes
The primary operation in DTCP is the specification of the filter
criteria used to select or filter packets. DTCP is designed to work
in an IPv4 environment, and accordingly all selection criteria are
chosen from IPv4 and higher-layer protocol definitions. Note that
current DTCP syntax is limited to L3 and L4, but could be expanded to
higher layers. Basic filter criteria definitions have semantic (if
not syntactic) similarity to well-known router access-control lists
(ACLs) or firewall rulesets.
The primary operational mode of DTCP is the "copy" mode, whereby the
controlled network element forwards the packet towards its intended
destination, and also makes a copy of that packet, which it forwards
towards a preconfigured collection and analysis center. In this
mode, the original packet flow is not interrupted. DTCP makes no
provisions for the potential performance impact on the network
element when performing this function; obviously a negligible impact
is most desirable.
DTCP also supports optional modes for purely redirecting the packet
data (instead of making a copy of it), as well as blocking packet
data. These modes, if implemented, can provide additional
functionality for network security personnel, who may have decided
that particular traffic is disallowed on the network and wishes to
interrupt the selected flow of traffic.
Of critical distinction to DTCP is the basic paradigm that DTCP does
NOT involve a "reprovisioning" or "reconfiguration" of the controlled
device. DTCP is by its very nature transient; controlled devices
should not attempt to maintain DTCP state in a non-volatile storage
system.
1.2. Performance Considerations
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It is envisioned that the controlling side of DTCP will be
implemented by both human-interactive systems and automated systems.
Since controlled Network Element MUST be able to respond to automated
requests at a potentially high rate (due to floods or other attacks),
the protocol implies a high performance requirement during the
"criteria specification" phase of the interaction. In particular,
the response time of the Network Element to respond to the DTCP
request to monitor data is of considerable importance, as the traffic
intended to be monitored may be short-lived.
While concrete performance requirements are outside the scope of this
document, implementers are urged to focus performance on this part of
the client-server interaction.
1.3. Conventions used in this document
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].
2. Definitions
The following sections define terms that have special significance
within the DTCP context.
2.1. Server
The DTCP Server is the PEP or network element that controls the data
of interest. The DTCP Server will be controlled in turn via DTCP.
The Server is responsible for maintaining state of DTCP Client
Requests, and forwarding data accordingly. Usually the DTCP Server
will be implemented on a firewall or router (or an accessory device
attached to one). The Server generally Responds to Requests, and can
also initiate Asynchronous Notifications. One Server generally
services more than one Client.
2.2. Client
The DTCP Client is an arbitrary host that initiates Requests to the
Server via DTCP.
2.3. Control Source
A Control Source is the instantiation of one DTCP Client, with
respect to a given Server. Each Control Source is preconfigured and
pre-authorized on a given Server to be able to interact with it via
DTCP. Control Sources may also receive Asynchronous Notifications.
There may be many Control Sources configured on a given Server. A
Control Source MUST NOT be identified by IP address; rather, Control
Sources are identified by user-configured character strings.
2.4. Content Destination
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A Content Destination is the recipient of the extracted data, once it
is forwarded by the server. Content Destinations are also
preconfigured on the server. A Content Destination MUST NOT be
identified by IP address; rather, Content Destinations are identified
by user-configured character strings.
2.5. Criteria
The Criteria is the list of matching conditions under which a packet
is selected and acted upon by the server. Criteria are specified in
requests from the client to the server, which maintains a list of
active criteria for each client.
3. Overview of Operation
This section describes the basic interaction between the DTCP
elements, as well as the protocol message flows.
3.1. Request-Response Paradigm
The basic model for DTCP is a request-response message exchange
paradigm, where the server waits for messages on a specific UDP port
from authorized Control Sources. When a request message arrives, the
server processes the request, performs the necessary internal state
change as per the request, and then sends a reply message.
Note that although DTCP is specified as a message-based protocol, it
is designed and specified here to operate via single UDP/IP packets,
for performance reasons. While it is certainly possible for DTCP to
be operated over TCP/IP for reliable connections, such use is
unexplored as yet, and any implementation-specific decisions made are
unspecified herein. This document is written assuming that UDP will
be used as the Layer-4 transport mechanism.
A DTCP Server MUST allocate at least ONE IP address and ONE UDP port
for inbound connections from clients. Each DTCP Client MUST be
statically configured with at least ONE IP address and ONE UDP port
representing the server.
There is no mechanism defined that ensures proper configuration
between DTCP Clients and servers for requests and responses.
In general, each request and each reply are a single UDP message,
contained within a single IP packet. Since IP packets may be
fragmented during delivery, each DTCP endpoint MUST be capable of IP
fragment reassembly.
An IP packet containing a DTCP Request message from a client to a
server MUST have the following attributes properly set:
1. Destination IP Address MUST equal an IP address of a DTCP Server;
2. IP Protocol MUST equal 17 (UDP);
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3. Destination UDP Port MUST equal a UDP port being listened on by
the respective DTCP Server.
The DTCP Server MUST NOT rely on the source IP address or source UDP
port of inbound request packets for any identification or
authentication of the message.
An IP packet containing a DTCP Reply message from a server to a
client MUST have the following attributes properly set:
1. Source IP Address MUST equal the Destination IP Address of the IP
packet containing the Request;
2. Destination IP address MUST equal the Source IP Address of the IP
packet containing the Request;
3. IP Protocol MUST equal 17 (UDP);
4. Destination UDP port MUST equal the Source UDP port of the UDP
message containing the Request;
5. Source UDP port MUST equal the Destination UDP port of the UDP
message containing the Request.
There is no specific UDP port registered for DTCP; rather, each DTCP
Server SHOULD permit the user to configure the port or set of ports
on which it will listen for inbound DTCP requests. Additionally, a
DTCP Server MAY choose to implement address or other filters on the
source of inbound client requests; however, this is optional and
implementation specific. (Recall that clients are identified by
strings, NOT IP addresses.)
3.2. Asynchronous Notifications
Notifications are sent out by the DTCP Server to a set of statically
preconfigured DTCP Clients who wish to receive notifications of
asynchronous events. Such messages are sent to IP addresses that
have been preconfigured therein.
A DTCP Client MAY provide a mechanism for accepting and processing
Notifications. The DTCP Server MUST be preconfigured with an IP
address and UDP port for each DTCP Client that wishes to receive
Notifications.
There is no mechanism defined that ensures proper configuration
between DTCP Clients and servers for Notifications.
An IP packet containing a DTCP Notification message from a server to
a client MUST have the following attributes properly set:
1. Destination IP address MUST equal the configured DTCP Client IP
address;
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2. IP Protocol MUST equal 17 (UDP);
3. Destination UDP port MUST equal the configured DTCP Client UDP
port.
A future enhancement to this document may be to provide a mechanism
for clients to dynamically self-register for notifications.
A DTCP Server SHOULD include a configuration parameter for each
configured Control Source to indicate the Notification Version for
that Control Source. If such a parameter is configured for a given
Control Source, all Asynchronous Notifications sent from the DTCP
Server to that Control Source MUST precisely match the Notification
Version configured for that Control Source. Additionally, if such a
parameter is configured for a given Control Source, the DTCP Server
MUST NOT send Asynchronous Notifications to that Control Source that
do not exist in the DTCP specification indicated for that Control
Source. Finally, the DTCP Server MUST ensure that Asynchronous
Notifications whose formats have been modified in newer versions of
DTCP are properly formatted to meet the older DTCP specification
version indicated for that Control Source.
Note that in general the DTCP Server SHOULD accept requests from a
DTCP Client using a DTCP Version other than that specified in the
Notification Version for that client.
If the DTCP Server is unable to meet these requirements, upon
receiving a request from a DTCP Client with a mismatching version, it
MUST return a a "505 DTCP Version not supported" error message *using
the highest version supported by the DTCP Server*, and discontinue
processing of that request.
It is recommended, however, that the DTCP Server reject such a state
at configuration time rather than at run time.
3.3. Data Delivery Mechanism
Since the original packet IP header is not originally addressed to
the intended Content Destination, each DTCP Server implementation
MUST provide a mechanism for delivery of redirected data packets to
appropriate Content Destinations. This explicitly includes IP
checksums and IP TTL, as well as any higher-layer headers -- which
SHOULD NOT be altered once captured -- but may not include MAC or
lower-layer checksums.
DTCP explicitly does not specify the mechanism of data delivery to
the Content Destination. Such a delivery mechanism is
implementation- specific, and is outside the scope of this document.
As an example, Servers could utilize such technologies as VLAN
tagging or IP tunneling to deliver entire unaltered data packets to
Content Destinations.
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4. Security Model
Since DTCP is, by design, a security protocol, it is imperative that
it be resistant to malicious use.
4.1. No Information Exposure
DTCP was designed with the explicit paradigm that only information
intentionally available to a given Control Source is ever exposed to
that Control Source. For example: the existence of other Control
Sources, or Content Destinations to which it has no access MUST NOT
be exposed to a given Control Source, e.g. via notifications or
error messages. Also, the server MUST NOT respond to any message
that fails its security checks. This basic paradigm MUST be upheld
in DTCP Server implementations.
4.2. Independence of Control Sources
DTCP may be implemented on network elements providing service to
different customers. If each customer is allowed access to the DTCP
Server, they MUST NOT be aware that another customer is using the
DTCP Server. More specifically, neither customer's use (or misuse)
of the DTCP Server can affect the other customer's use of it.
Limits on service-affecting actions that may be taken by a DTCP
Client are outside the scope of this document.
4.3. Control Source to Content Destination Access Control
A DTCP Server SHOULD provide a mechanism by which each configured
Control Source is granted access to one or more Content Destinations.
4.4. Per-Message Security Mechanisms
The primary motivation behind the per-message security mechanisms is
to provide both message integrity as well as source authenticity.
Additionally, providing insulation against replay-type attacks is
also a motivation, though secondary.
DTCP currently provides no mechanism for confidentiality. If
confidentiality is required, it is recommended that DTCP messages be
sent via a secure transport.
Note: Authentication failures, defined as a failure of these per-
message security mechanisms, MUST NOT be reported to the DTCP Client.
They SHOULD be logged on the DTCP server, and possibly acted upon by
administration staff.
4.4.1. Sequence Number
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Every message initiated by a DTCP Client MUST contain a sequence
number. The request sequence number is an unsigned 64-bit whole
number chosen arbitrarily by the client and maintained by the server
persistently for each Control Source. All requests from a given
Control Source MUST contain a monotonically-increasing sequence
number. The sequence number for each successive request may
increment by no more than 256. The stored last-valid sequence number
shall only be updated upon receipt of a valid, authentic message.
A reply message to a valid request MUST contain the identical
sequence number as the associated request.
Other than as specified below in "Sequence Number Negative Window",
repetition of the last sequence number, or an invalid (non-
monotonically-increasing) sequence number, in an otherwise-valid
message MUST result in the message being dropped and a security
violation being logged, except when the sequence number wraps over
zero due to bit-field-length constraints.
Rollover of the sequence number shall only be permitted when the MSB
of the current sequence number is all-ones; otherwise this shall be
considered a security violation. A rollover of the sequence number
shall cause both an asynchronous notification message to be sent to
any configured static address(es) for the respective Control Source
as well as a log message to be generated.
It is suggested that clients do whatever possible to persistently
store the current sequence number as there is no DTCP method by which
to reset the current sequence number.
DTCP Servers SHOULD provide some mechanism for manually resetting the
sequence number for a given client.
Additionally, DTCP Servers SHOULD implement a Negative Window feature
as specified in the following section.
4.4.1.1. Sequence Number Negative Window
Under high load, a multithreaded DTCP client may send multiple
requests (with properly incrementing sequence numbers) to the DTCP
Server without waiting for each reply to come back individually.
Because packets may be reordered through the network, they may arrive
at the DTCP Server out of order.
For example, the DTCP client may send:
1. Request 1 (Seq = 1)
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2. Request 2 (Seq = 2)
3. Request 3 (Seq = 3)
But due to network reordering, the DTCP Server may receive:
1. Request 1 (Seq = 1)
2. Request 3 (Seq = 3)
3. Request 2 (INVALID)
Unfortunately, the specification of the sequence number above will
make Request 2 invalid, because once Request 3 is processed, the
stored sequence number in the DTCP Server for that Client has been
incremented to 3.
Therefore to correct this problem, the DTCP Server SHOULD include a
"negative" window as well as the required "positive" window for
sequence numbers, and keep track of received sequence numbers within
that negative window. However, in order to maintain the replay-
protection afforded by the sequence number in the first place, any
DTCP Server implementing a negative window MUST also implement
tracking of particular sequence numbers received within the union of
both windows, and MUST NOT respond to any requests containing a
sequence number already received.
If the received sequence number is in the negative window, the DTCP
Server would simply store that sequence number as seen from that
particular DTCP Client and process the packet. If the sequence
number of the packet is in the positive window, the new positive and
negative window would begin and end at this packet's sequence number
respectively with the window sizes remaining the same. So a DTCP
packet with sequence number within the negative window but that has
not been seen (or anywhere within the positive window) is valid.
4.4.2. Hashing Message Authentication Code (HMAC)
A DTCP Server MUST store a statically-provisioned secret key for each
configured client. This key is manually shared with each DTCP
Client. Each request and response message MUST contain, as the last
entry, a parameter called Authentication-Info, whose value is the
HMAC algorithm specified in [RFC2104] of the rest of the message
payload (including the sequence number) generated using a SHA-1 [3]
digest and the secret key. This digest is expressed in hexadecimal
notation ([0-9a-f]), using 40 UTF-8 [4] characters to express the
160-bit SHA-1 hash.
Original Message: text
Secret Key: K
HMAC: hash = SHA1HMAC(K, text)
New Message: text + "Authentication-Info: " + hash
Figure 2 - Generating the message HMAC from the original message.
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The shared secret key MUST NOT be sent in any DTCP message.
The precise algorithm, excerpted here from RFC-2104 for reference
purposes (using SHA-1 as the hashing function H and byte length B=64)
is as follows:
We define two fixed and different strings ipad and opad as follows
(the 'i' and 'o' are mnemonics for inner and outer):
ipad = the byte 0x36 repeated B times
opad = the byte 0x5C repeated B times.
To compute HMAC over the data `text' we perform
H(K XOR opad, H(K XOR ipad, text))
5. Application-Layer Message Formats
In general, the best source for the message formats is the Formal
Syntax specified below. The following prose is provided for
informational purposes and implementation guidelines. Where apparent
syntactic conflicts exist, the Formal Syntax is defined to be
correct.
DTCP messages are formatted in human-readable CRLF-delimited UTF-8
text format, using a mechanism similar to HTTP [RFC1945] or SIP
[RFC3261]. Each message begins with an initial "command" line,
followed by an optional series of parameter-value lines. Each token
in the command line as well as each option line is separated by one
or more white space characters. The entire message MUST end with two
CRLFs.
The final token in any line MAY have whitespace before its
terminating CRLF, but is not so required, and is not so reflected in
the ABNF. DTCP servers SHOULD ignore extra whitespace between the
final token and the terminating CRLF, but MUST return a Syntax Error
otherwise.
Parameter names are specified in mixed case, but MUST be matched
regardless of case.
Control characters or other unprintable characters in the parameter
value may be indicated by a backslash (\) followed by precisely three
digits indicating the UTF-8 value for the character, possibly
including leading zeros. The backslash notation may be used to
express any character, including whitespace. Backslash notation is
explicitly forbidden from being interpreted as either an inter-token
delimiter or an inter-parameter delimiter.
DTCP Clients and server MUST NOT rely upon the order of parameters
within the DTCP message, since it is not guaranteed (other than the
final "Authentication-Info" parameter as noted below).
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Every DTCP message MUST contain the "Authentication-Info" parameter,
and it MUST be the final parameter in the message. Any parameters in
any DTCP message following the Authentication-Info parameter MUST be
disregarded.
If a parameter appears multiple times, the behavior is undefined and
not guaranteed; however, if a parameter does show up multiple times,
the endpoint SHOULD take the value of the first occurrence and
disregard any successive occurrences.
5.1. Request General Format
Each client-to-server message in DTCP begins with a single request
command line with the following format:
<command> <protocol-version-specifier> CRLF
The command line is followed by one or more parameter-value pairs,
comprising the message body. The message is terminated by two CRLFs.
A DTCP request MUST contain the Sequence Number and the Control
Source ID parameters.
5.2. Response General Format
Each server-to-client response message in DTCP shall begin with a
single response line with the following format:
<protocol-version-specifier> <response-code> <response-text> CRLF
where the response-code is a three-digit numeric value, and the
response-text is an arbitrary-length text string intended to be
human-readable. The response line is followed by one or more
parameter-value pairs comprising the message body. The message is
terminated by two CRLFs.
Responses to successful requests MUST contain the response-code "200"
and the response-text "OK".
A DTCP response MUST contain the Sequence Number parameter. A DTCP
response MUST also contain the Timestamp parameter.
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5.3. Notification General Format
Each server-to-client notification message in the control protocol
shall begin with a single response line with the following format:
<protocol-version-specifier> <response-code> <response-text> CRLF
where the response-code is a three-digit numeric value, and the
response-text is an arbitrary-length text string intended to be
human-readable. The response line is followed by one or more
parameter-value pairs comprising the message body. The message is
terminated by two CRLFs.
A DTCP notification message MUST contain the Timestamp parameter.
5.4. Add Request
The Add request specifies a new filter criteria to be merged with the
existing tasking list for a given Control Source and Content
Destination (regardless of order added). Any missing parameters in
the request will inferred to be a wildcard or "don't care". The Add
request MAY be accompanied by one or more of the following required
filter criterion parameters:
1. Source IP address, range or IP + bitmask, or wildcard
2. Destination IP address, range, or IP + bitmask, or wildcard
3. IP Protocol or range, or wildcard
4. Source Layer-4 Port or range, or wildcard (parameter only
meaningful when IP protocol range includes protocols 6 or 17)
5. Destination Layer-4 Port or range, or wildcard (parameter only
meaningful when IP protocol range includes 6 or 17)
6. ICMP Type or range, or wildcard (parameter only meaningful when
IP protocol range includes protocol 1)
7. ICMP Code or range, or wildcard (parameter only meaningful when
IP protocol range includes protocol 1)
A wildcard in a given field implies that any value will match it
(i.e. "don't care").
Additionally, the Add request MUST contain one or more of the
following parameters:
1. Timeout specified in seconds idle (maximum one day)
2. Timeout specified in seconds total (maximum one day)
3. Timeout specified in packets (maximum 64 bits)
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4. Timeout specified in bytes (maximum 64 bits)
5. Flag: Static, which indicates that this criterion will never
timeout and persist until explicitly deleted. All other timeouts
shall be ignored if a STATIC flag is present.
Additionally, the Add request may contain one or more of the
following parameters:
1. Relative Priority (unsigned integer, minimum value 1) (optional,
defaults to 1)
2. Flag: Send Timeout Async (optional), which will cause the server
to send a Asynchronous Notification when the criterion times out
for any reason.
3. Action (optional), which specifies whether the packet stream
identified by the criterion will be a) copied to the Content
Destination and also forwarded to its original intended
destination ("Copy"), b) copied but not forwarded ("Redirect"),
or c) not copied and not forwarded ("Block"). By default, Action
is "Copy".
Finally, the Add request MUST contain the following control protocol
parameters:
1. Control Source Identifier
2. Content Destination Identifier
3. Sequence number (MUST be monotonically increasing for each
request from a given Control Source)
4. HMAC authenticator (MUST span message payload, plus secret key)
Although not explicitly expressed in the request, the DTCP Server
MUST maintain the date/time of each filter criterion successfully
added. This time is the local DTCP Server time, either maintained
independently by the server or synchronized via NTP.
5.4.1. Criteria Timeouts
Timeouts are required for each filter criterion added. These
timeouts may be specified in any of four formats: seconds-idle,
seconds-total, bytes, or packets. Any combination of these four
timeouts may be used in a filter criterion as long as at least one is
used.
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Once a criterion is added, the timeouts will begin decrementing as
appropriate. Only the timeouts that are specified in the request
will be used for timing-out that criterion. When any active timeout
is decremented to zero, the DTCP Server will automatically delete the
filter criterion. For each Control Source, if enabled, when a
criterion times-out and is deleted, timeout notifications will be
sent to any statically-configured Notification Destination(s)
associated with that Control Source.
A criterion may be added as STATIC. Any such criterion shall persist
in the active state unless and until explicitly deleted or deleted
due to congestion, provided the DTCP Server maintains its normal
operational state. (See section 5.18 Congestion Notification for
more information on congestion and timeouts.)
If all timeout values are zero and the criterion is not marked
STATIC, the DTCP Server MUST return Error 433 (Improper Timeout
Specification) and the criterion must not be added. For STATIC
criteria, the DTCP Server MUST ignore the all timeout values.
If the server fails, STATIC rules may be lost. Any Control Source
that uses STATIC criteria SHOULD attempt to ensure that such criteria
are still up and active following any maintenance or failure event on
the server.
5.5. Add Response
The response to a successful Add request will consist of the
following parameters:
Criteria ID
The Criteria ID will be persistent for the duration of that request,
until it is removed explicitly by the client, or is removed
implicitly by either timeout or some failure of the DTCP Server. The
Criteria ID MUST uniquely identify that particular filter criterion
for that particular Control Source (and be agnostic to the Content
Destination).
DTCP Servers MUST ensure that generated Criteria ID are unique for
all currently-active requests for a given Control Source.
Ideally, the Criteria ID SHOULD be globally unique across Control
Sources, but this is not strictly required (since all requests will
always be from a particular Control Source).
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DTCP Servers SHOULD provide unique Criteria IDs for new requests,
even if old ones have been deleted resulting in a fragmented ID
space. This prevents race conditions that can cause inconsistent
behavior e.g., a criterion specified in an Add request gets the same
Criterion Id as a recently deleted criterion (deleted due to
timeout), and before the delete notification could reach the Control
Source, it sends out an explicit delete request for the old
criterion, which when received by the DTCP Server would delete the
recently added criterion, which is clearly undesirable.
This response MUST also include the following parameters:
1. Timestamp
2. Sequence number (MUST match the sequence number for the request)
3. HMAC authenticator (MUST span message payload, plus secret key)
Responses to unsuccessful Add requests may take any of the following
forms:
o Syntax Error
o Improper Filter Criterion Specification
o Unknown Destination Identifier
o Invalid Timeout Specification
o Improper Authentication (logged, but never sent to client)
o Invalid Sequence Number (logged, but never sent to client)
o Unknown Control Source Identifier (logged, but never sent to
client)
5.6. Delete Request
The Delete request removes a particular filter criterion (or
optionally all filter criteria) for the particular Control Source.
The Delete request MUST take precisely one of the following
parameters:
o Criteria ID or list of ranges of Criteria IDs
o Content Destination Identifier
Additionally, the Delete request may contain one or more of the
following parameters:
o Flag: Static, which indicates that criteria added as STATIC should
be deleted as well. (optional) If this flag is omitted, STATIC
criteria MUST NOT be deleted.
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If a single Criteria ID or list of ranges Criteria IDs is specified,
the respective criterion/criteria is/are removed from the list of
filter conditions that apply for that Control Source.
If a Content Destination Identifier is specified, all criteria are
removed from the list of filter conditions to that particular Content
Destination for that Control Source, except for STATIC criteria
--unless the STATIC flag is specified. (Note that any other criteria
specified by any other Control Sources MUST remain unaffected.)
Additionally, the Delete request MUST contain the following
parameters:
o Control Source Identifier
o Sequence number (MUST be monotonically increasing for each request
from a given Control Source)
o HMAC authenticator (MUST span message payload, plus secret key)
5.7. Delete Response
The response to a successful Delete will consist of the following
parameter:
o Number of Criteria Deleted
This parameter is an integer specifying the total number of filter
criteria that were actually deleted. The number will be precisely 1
if a single, valid Criteria ID is supplied in the Delete request. If
multiple valid Criteria IDs are supplied, the number of criteria
actually deleted will be returned.
If any individual Criteria ID is invalid, the entire response will
return an error and no action shall be taken by the server for any
supplied Criteria ID. If a Content Destination Identifier is
supplied, the number of criteria deleted shall be equal to the total
number of active filter criteria from the requesting Control Source
to that particular Content Destination. If no such criteria exist,
the DTCP Server will return a successful delete response (with
criteria deleted parameter set to zero).
When a range is specified, any existing criteria matching the
Criteria ID in that range (inclusive) will be deleted and the true
number of criteria deleted (including possibly zero) will be
returned.
Trying to delete a STATIC criterion without the STATIC flag in the
Delete request will result in that criterion NOT being deleted. Such
a deletion attempt will return a success (non-error) response,
including the actual number of criteria deleted (which may be zero).
This response MUST also include the following parameters:
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o Timestamp
o Sequence number (MUST match the sequence number for the request)
o HMAC authenticator (MUST span message payload, plus secret key)
Responses to unsuccessful Delete requests may take any of the
following forms:
o Syntax Error
o Unknown Criteria ID
o Unknown Destination Identifier
o Improper Authentication (logged, but never sent to client)
o Invalid Sequence Number (logged, but never sent to client)
o Unknown Control Source Identifier (logged, but never sent to
client)
5.8. Refresh Request
The Refresh request updates the timeout for a particular filter
criterion or set of filter criteria (or optionally all filter
criteria) for the particular Control Source assigned to a particular
Content Destination. This is used to maintain active criteria that
are in danger of timing-out based on the original Add request. The
updated timeout will replace the current remaining timeout, NOT be
added to it. The Refresh request MUST take precisely one of the
following parameters:
o Criteria ID or list of ranges of Criteria IDs
o Content Destination Identifier
Additionally, the Refresh request MUST contain one or more of the
following parameters:
o Timeout specified in seconds total
o Timeout specified in seconds idle
o Timeout specified in packets
o Timeout specified in bytes
(Note that a Refresh request MUST NOT be used to make an existing
filter criterion STATIC. A criterion MUST be added explicitly as
STATIC in its original Add.)
Finally, the Refresh request MUST contain the following parameters:
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o Control Source Identifier
o Sequence number (MUST be monotonically increasing for each request
from a given Control Source)
o HMAC authenticator (MUST span message payload, plus secret key)
5.9. Refresh Response
The response to a successful Refresh will consist of the following
parameters:
o Number of Criteria Refreshed
This parameter is an integer specifying the total number of filter
criteria that were actually updated. The number will be precisely 1
if a single, valid Criteria ID is supplied. If multiple valid
Criteria ID are supplied, the number of criteria updated will be
returned, and that will equal the number of supplied Criteria IDs.
If any Criteria ID is invalid, the entire response will return an
error and no action shall be taken by the server for any supplied
Criteria ID. If a Content Destination Identifier is supplied, the
number of criteria updated shall be equal to the total number of
active filter criteria from the requesting Control Source to that
particular Content Destination, including zero (which will NOT return
an error).
This response MUST also include the following parameters:
o Timestamp
o Sequence number (MUST match the sequence number for the request)
o HMAC authenticator (MUST span message payload, plus secret key)
Responses to unsuccessful Refresh requests may take any of the
following forms:
o Syntax Error
o Invalid Timeout Specification
o Unknown Criteria ID
o Unknown Destination Identifier
o Improper Authentication (logged, but never sent to client)
o Invalid Sequence Number (logged, but never sent to client)
o Unknown Control Source Identifier (logged, but never sent to
client)
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5.10. List Request
The List request makes no change on the DTCP Server, but returns a
list of all criteria that a particular Control Source has added. The
Control Source may request this list on the basis of Content
Destination, Criteria ID, or overall (for that particular Control
Source). The List request takes the following parameters:
o Content Destination Identifier (optional)
o Criteria ID or List of ranges of Criteria IDs (optional)
o Flag: Statistics / Criteria / All
If neither of the optional parameters is included, the server MUST
reply with the full set of criteria associated with that Control
Source.
Additionally, the List request MUST contain the following parameters:
o Control Source Identifier
o Sequence number (MUST be monotonically increasing for each request
from a given Control Source)
o HMAC authenticator (MUST span message payload, plus secret key)
5.11. List Response
The response to a successful List will consist of a formatted list --
essentially a table -- of filter criteria and related parameters.
Fields will be included and excluded depending on the presence and
the value of Stats/Criteria/All entry in the request as noted in
square brackets [] following the value listed below. Each entry in
the List list shall contain the following fields as specified in the
original criteria:
o Control Source Identifier
o Control Source IP Address
o Content Destination Identifier
o Criteria ID
o Date/Time added
o Specified Source IP address, range or IP + bitmask , or wildcard
[Criteria]
o Specified Destination IP address, range, or IP + bitmask, or
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wildcard [Criteria]
o IP Protocol or range, or wildcard [Criteria]
o Source Layer-4 Port or range, or wildcard (parameter only
meaningful when IP protocol range includes protocols 6 or 17)
[Criteria]
o Destination Layer-4 Port or range, or wildcard (parameter only
meaningful when IP protocol range includes 6 or 17) [Criteria]
o ICMP Type or range, or wildcard (parameter only meaningful when IP
protocol range includes protocol 1) [Criteria]
o ICMP Code or range, or wildcard (parameter only meaningful when IP
protocol range includes protocol 1) [Criteria]
o Timeout specified in seconds total [Criteria]
o Timeout specified in seconds idle [Criteria]
o Timeout specified in packets [Criteria]
o Timeout specified in bytes [Criteria]
The List list shall also contain the following statistical
information based on each criterion:
o An ordinal counter to specify the position of this entry in the
context of the list
o An integer specifying the total number of entries in the list
o Timeout remaining in seconds total [Stats]
o Timeout remaining in seconds idle [Stats]
o Timeout remaining in packets [Stats]
o Timeout remaining in bytes [Stats]
o An indication if the timeout is STATIC
o Last 10-second average bandwidth, in bits/second [Stats]
o Total number of packets that have matched this Criteria [Stats]
o Total number of bytes that have matched this Criteria [Stats]
o Total times this rule has been Refreshed [Stats]
o Date/Time of last Refresh [Stats]
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This response MUST also include the following parameters:
o Timestamp
o Sequence number (MUST match the sequence number for the request)
o HMAC authenticator (MUST span message payload, plus secret key)
Responses to unsuccessful List requests may take any of the following
forms:
o Syntax Error
o Unknown Destination Identifier
o Unknown Criteria ID
o Improper Authentication (logged, but never sent to client)
o Invalid Sequence Number (logged, but never sent to client)
o Unknown Control Source Identifier (logged, but never sent to
client)
Important Note: the response to the List message, in particular all
entries in the generated table, SHOULD be internally consistent and
atomic, regardless of the activity in progress at the time of and
during the course of transmission of the message. The data SHOULD
represent a snapshot of the relevant information at the quantum in
time that the List message is processed.
5.12. NoOp Request
This request takes no action on the server whatsoever, other than
returning a successful response. The sole purpose of this command is
to verify the end-to-end application-layer connectivity between a
Control Source and the DTCP Server. The NoOp request may contain the
following parameter:
o Flag: SendAsync
See 5.13 NoOp Response for a description of the SendAsync flag.
Additionally, the NoOp request MUST contain the following parameters:
o Control Source Identifier
o Sequence number (MUST be monotonically increasing for each request
from a given Control Source)
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o HMAC authenticator (MUST span message payload, plus secret key)
5.13. NoOp Response
The response to a successful NoOp will consist of a successful
response message indicator, and contain the following parameters:
o Timestamp
o Sequence number (MUST match the sequence number for the request)
o HMAC authenticator (MUST span message payload, plus secret key)
If the SendAsync parameter is specified in the NoOp request, the
server shall cause an asynchronous notification message to be sent to
any configured notification destinations for that particular Control
Source.
5.14. Restart Notification
The Restart notification shall be sent from the server to any
configured notification-recipient when the system experiences a
failure such that all the filter criteria are lost. The Restart
notification shall contain the following parameters:
o Restart Reason, a text string indicating the reason for the
restart, if known
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
5.15. Rollover Notification
The Rollover notification shall be sent from the server to any
configured notification-recipient when the server experiences a
sequence-number rollover. The Rollover notification shall contain
the following parameters:
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
5.16. NoOp Notification
The NoOp notification shall be sent from the server to any configured
notification-recipient when the DTCP Server receives a NoOp message
with the SendAsync parameter present. The NoOp notification shall
contain the following parameters:
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
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5.17. Timeout Notification
The Timeout notification shall be sent from the server to the
appropriate notification-recipient(s) when the server times out a
filter criterion on any one of its configured timeout parameters and
the criterion contains a SendTimeoutAsync parameter.
The Timeout notification shall contain the following parameters:
o Criteria ID, to indicate the particular criteria that has timed
out
o Timeout specified in seconds total [omit if unconfigured]
o Timeout remaining in seconds total [omit if unconfigured]
o Timeout specified in seconds idle [omit if unconfigured]
o Timeout remaining in seconds idle [omit if unconfigured]
o Timeout specified in packets [omit if unconfigured]
o Timeout remaining in packets [omit if unconfigured]
o Timeout specified in bytes [omit if unconfigured]
o Timeout remaining in bytes [omit if unconfigured]
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
5.18. Congestion Notification
The Congestion notification shall be sent from the server to any
configured notification-recipient when the total 10-second average
data rate (in bits/second) summed over all active filter criteria to
a configured Content Destination exceeds the configured soft limit
for that destination. The Congestion notification shall contain the
following parameters:
o Content Destination ID, to indicate the particular destination
experiencing excessive bandwidth
o Current total 10-second average Bandwidth, in bits/second
o Configured SoftLimit Threshold, in bits/second
o Configured HardLimit Threshold, in bits/second
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o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
Note that since multiple Control Sources may be responsible for this
overload, this Notification MUST be sent to all configured Control
Sources that have currently-active filter criteria to this particular
Content Destination.
5.19. CongestionDelete Notification
The CongestionDelete notification shall be sent from the server to
any configured notification-recipient when the total 10-second
average data rate (in bits/second) summed over all active filter
criteria to a configured Content Destination exceeds the configured
hard limit for that destination, causing the DTCP Server to begin
purging filter criteria. The CongestionDelete notification shall
contain the following parameters:
o Content Destination ID
o List of Criteria ID purged
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
CongestionDelete messages MUST be specifically and uniquely sent to
all configured notification-recipients for the Control Sources to
which they apply. To be clear: a given Control Source notification-
recipient MUST only receive CongestionDelete messages containing
Criteria ID created by that Control Source.
5.20. DuplicatesDropped Notification
The DuplicatesDropped notification shall be sent from the server to
any configured notification-recipient when capacity has been exceeded
in such a way as to cause packets matching criteria added by the
corresponding Control Source to be dropped. This notification will
be sent periodically as long as packets continue to be dropped. The
DuplicatesDropped notification shall contain the following
parameters:
o Content Destination ID
o Applicable CriteriaID pertaining to Dropped Packets
o Total Number of Dropped Packets
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o Sum of Bytes contained in Dropped Packets
o Timestamp
o HMAC authenticator (MUST span message payload, plus secret key)
DuplicatesDropped messages MUST be specifically and uniquely sent to
all configured notification-recipients for the Control Sources to
which they apply.
6. Miscellaneous
6.1. Special treatment of response to List request
The List request inherently provides unique functionality with
respect to the messaging architecture of DTCP. All other requests
result in reasonably terse replies, which can be encapsulated in, at
worst, a few IP packets.
However, the List request will generate an arbitrary amount of reply
data, since it could contain all requests that are still active, up
to the limit of the device. This section specifically describes how
responses to the List request are sent.
a) The full reply to the List request MAY consist of multiple
packets. Each packet will contain a single "Response" element;
therefore, each packet will have a single Status-Line and a single
trailer (Authentication-Info) terminated by 2xCRLF. A UDP packet MUST
NOT contain more than ONE "Response" element.
b) A "Response" element in each packet shall contain zero or more
"List-Resp-Entry" elements (in "List-Resp-Parameters"). Each filter
criteria is encoded into a single "List-Resp-Entry" element. The
sequence number MUST be identical for all "Response" elements in a
multi-packet reply.
c) Each "List-Resp-Entry" element MUST contain the following two
elements: "Criteria-Num" and "Criteria-Count". "Criteria-Num" MUST
be valued as an enumeration starting with 1 (one) and incrementing by
one for each "List-Resp-Entry" sent. "Criteria-Count" SHOULD be set
to the total number of matching Criteria in the given particular LIST
response (see below for potential exceptions).
d) Therefore, a full reply to the List request shall consist of as
many "List-Resp-Entry" elements as necessary to fully transmit the
List, divided into multiple packets as described above.
e) DTCP Servers SHOULD ensure that each "List-Resp-Entry" element is
not divided across multiple IP packets.
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f) DTCP Clients can use the simple test (Criteria-Num==Criteria-
Count) to determine if they've received the last packet in the
series. However, in order to ensure that all packets were received
(and, respectively, all List-Resp-Entry elements), the DTCP Client
MUST traverse through the list of Criteria-Count to ensure it's
complete from 1 to XX where XX==Criteria-Num==Criteria-Count.
g) At the UDP layer, all packets in the response MUST contain
identical UDP port numbers. DTCP Clients SHOULD maintain their
socket open until either all expected Response messages are received,
or a timeout occurs.
h) If the List request matches no criteria, but does not supply
invalid Criteria-IDs, the "Response" element will contain zero "List-
Resp-Entry" elements.
i) DTCP Servers MAY simplify their implementation by only including a
single "List-Resp-Entry" element in each "Response" element (and
therefore in each packet).
j) DTCP Servers MAY simplify their implementation by transmitting the
"Criteria-Count" element in each List-Resp-Entry element as ZERO (0)
until the final element is sent, whereupon it is set to the proper
value.
A List response that matches 3 criteria may look as follows:
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=============== First UDP packet
DTCP header
Seq: A
criteria-id: x ; this is the first List-Resp-Entry element
...
criteria-num: 1
criteria-count: 3
criteria-id: y ; this is the second List-Resp-Entry element
...
criteria-num: 2
criteria-count: 3
HMAC
================
=============== Second UDP packet
DTCP header
Seq: A
criteria-id: z ; this is the third List-Resp-Entry element
...
criteria-num: 3
criteria-count: 3
HMAC
================
If the list request matches no criteria, it will look as follows:
=============== First UDP packet
DTCP header
Seq: B
HMAC
================
6.2. Error or Exception Conditions
Errors in DTCP requests are reported in response messages via any
Response-Code other than "200" (OK). When such error or exception
condition exists, the server SHOULD attempt to indicate the precise
nature of the error or exception using the Error-Parameters element.
This behavior, though helpful, is not strictly required by the
protocol.
For example, if a Delete request contained a specific Criteria-ID not
currently active in the server, the response error message MUST begin
with a 431 - Unknown Criteria ID response line. The server SHOULD
also add the Criteria-ID parameter indicating the unknown Criteria
ID.
Again, note that authentication failures MUST NOT be reported in
response messages; they MUST be silently dropped.
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The DTCP Server MUST attempt to provide the most specific error
message to report the specific error or exception condition. When
the request message meets any of the following conditions, if no such
specific error message exists, the server MAY return a 400 (Bad
Request) error:
o Missing required fields
o Parse failure
o Parameters beyond range
In these cases, the server SHOULD include the specific line from the
request that caused the condition using the Error-Parameters element.
6.3. Extensions in ABNF
Extension placeholders are provided in the formal syntax for the
definition of future methods, parameters, and response-codes.
Vendors SHOULD NOT define implementation-specific extensions; rather,
such extensions SHOULD be brought to the DTCP working group for
inclusion into the protocol, to ensure interoperability.
However, in order to provide faster extensions to the protocol, the
"X-" extension parameter construct has been borrowed from other
protocols, including SIP and SMTP.
The DTCP Server or the DTCP Client MAY include an arbitrary
parameter-value pair, as long as the parameter is preceded by the
character string "X-", and all other parameter-value conventions are
followed.
The sender of such extension parameters MUST NOT rely on the
recipient correctly processing those values.
The recipient of such extension parameters MAY process the values as
appropriate upon receipt, but MUST discard without error those
extension parameters that it does not recognize.
6.4. Current Version
The current version string for this release of the DTCP protocol is:
DTCP/0.7
6.5. No specific port
While it is common practice to register and/or publish a TCP or UDP
port for applications that define them as a layer-4 transport, DTCP
has no specific UDP ports predefined. This is intended both to allow
flexibility for implementers and users, as well as to make it more
difficulty to detect DTCP messages on untrusted networks.
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6.6. Unimplemented Protocol Methods and Parameters
Some DTCP Server vendors have indicated their interest in supporting
a subset of the functionality specified here, due to their position
in the security space. Additionally, some constructs (arbitrary
lists, in particular) add complexity to implementations that may not
require that complexity.
To address this need, rather than adding complexity by changing the
grammar to indicate optional sections, specific error messages have
been added to indicate to the client that the server cannot process
the request in its current format. Depending on the request, the
client might be able to reformat that request into one that the
server implementation is able to process.
In order to be compliant with this protocol, the following rules
apply:
a) If a vendor chooses not to implement one or more DTCP Methods,
when responding to a request containing one of the unsupported
methods, the DTCP Server MUST send a "501 Not Implemented" Response
error message, and discontinue processing of that request.
b) If a vendor chooses not to implement a list element, when
responding to a request containing such a list, the DTCP Server MUST
send a "501 Not Implemented" Response error message, and discontinue
processing of that request.
c) If a vendor chooses not to implement one or more specific
parameters or parameter value options in a request, the DTCP Server
MUST send a "501 Not Implemented" Response error message, and
discontinue processing of that request.
d) The DTCP Server SHOULD include the method, parameter, or value
which caused the "501 Not Implemented" error to be sent, within the
error response message (to be consistent with 6.4 above)
e) The DTCP Server SHOULD support prior versions of DTCP. However, if
the vendor chooses not to implement prior versions of the protocol,
the DTCP Server MUST send a "505 DTCP Version not supported" error
message, and discontinue processing of that request.
The onus is on the client to determine if it can reformat the message
to make it acceptable to the particular DTCP Server implementation.
6.7. Version Mismatches
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The intent of this section is to clarify any ambiguity arising from
mismatches between DTCP versions supported by the DTCP Client and the
DTCP Server. In practice is has been observed that unintended
consequences have arisen by leaving the implementation vague, so it
was decided that clarifing at least a set of reccomendations, if not
rising to the level of requirements, will help guide DTCP
implementations and help ensure interoperability.
Two possible cases of mismatch exist: when the client exceeds the
server version, and when the server exceeds the client version. They
are handled separately, but the motivation in each case is to permit
maximum compatibility.
In this case, versions are compared numerically, with a single digit
after decimal point. For example: 0.4 is greater than 0.2, 1.9 is
greater than 1.4, and 3.1 is greater than 2.9
6.7.1. DTCP Client version exceeds DTCP Server version
If the DTCP Client attempts to make a request to a DTCP Server using
a DTCP version greater than that supported by the DTCP Server, the
DTCP Server MUST return a "505 DTCP Version not supported" error
message using the GREATEST DTCP version supported by the DTCP Server,
and discontinue processing of that request. It has not way of
knowing what new parameters might exist in a newer version of the
protocol and simply has to abandon processing altogether.
In this case, the onus is on the DTCP Client to revert to an older
version of the protocol specification to talk with this DTCP Server
to ensure that its request is properly handled.
6.7.2. DTCP Server version exceeds DTCP Client version
It is expected that a given DTCP Server will support a range of DTCP
protocol specification versions, for interoperability purposes.
If the DTCP Server receives a request from a DTCP Server using a DTCP
version lesser than the most current version supported by the DTCP
Server, the server SHOULD attempt to process that response using the
semantics of the earlier specification, and MUST reply using the
precise DTCP version included in the request.
If the DTCP server is unable to do this, the DTCP Server MUST return
a "505 DTCP Version not supported" error message using the LEAST DTCP
version supported by the DTCP Server, and discontinue processing of
that request
Asynchronous Notifications sent to a client using an earlier version
are addressed in Section 3.2 (Asynchronous Notifications).
7. Message Payload Examples
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Note: These are only examples of message payloads, and are not
intended to illustrate the full breadth of the protocol. Also,
please note that the Authentication-Info shown are correct if each
line is terminated with CRLF as specified and the key "secret" is
used. (Terminating CRLFs are not shown.)
7.1. Successful ADD Request and Response Payload
Following is an example of the UDP payload for an Add request:
ADD DTCP/0.6
Source-Address: 192.168.10.4
Dest-Address: 10.1.1.1-10.1.1.10
Protocol: 6,17
Dest-Port: 53
Timeout-Idle: 600
Action: Copy
Priority: 2
Flags: SendAsync
Cdest-ID: cdst_b
Csource-ID: csrc_a
Seq: 3827443
Authentication-Info: 28eb606458ba46160d7a59da48763020f5aef9f5
Following is the UDP payload of one potential successful response to
that Add request:
DTCP/0.6 200 OK
Criteria-ID: 38224
Seq: 3827443
Timestamp: 2005-01-01 12:01:01.111
Authentication-Info: 38099d03fcb5b12a849b36f9bdccc757303fafd0
7.2. Unsuccessful DELETE Request and Response Payload
Following is an example of the UDP payload for an Delete request:
DELETE DTCP/0.6
Criteria-ID: 55331
Csource-ID: csrc_d
Flags: Static
Seq: 2655371
Authentication-Info: 6af62247a2b59a2a06e0ca08ec5a80a644e2cd67
Following is the UDP payload of one potential unsuccessful response
to that Delete request:
DTCP/0.6 431 Unknown Criteria ID
Criteria-ID: 55331
Seq: 2655371
Timestamp: 2005-02-02 12:02:02.222
Authentication-Info: 5de4552e98832c2d2c3a9ffa8a2958c967b4e1e8
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This delete request was unsuccessful because the Criteria ID supplied
did not exist. Note that the error-causing parameter is included
within the reply to assist in debugging.
8. Formal Syntax
All of the mechanisms specified in this document are described in
both prose and an Augmented Backus-Naur Form (ABNF) defined in RFC
4234 [7]. Section 6.1 of RFC 4234 defines a set of core rules that
are used by this specification, and not repeated here. Implementers
need to be familiar with the notation and content of RFC 4234 in
order to understand this specification. Certain basic rules are in
uppercase, such as SP, LWS, HTAB, CRLF, DIGIT, ALPHA, etc.
Note that while much of this syntax is taken from the Session
Initiation Protocol (SIP), some of its constructs have been
simplified for this application here. Where appropriate, these
digressions have been noted with comments.
The following core definitions appear throughout the formal syntax:
COL = *(WSP) ":" *(WSP) ; used in parameter-value pair
NPCHAR = "\" 3DIGIT ; used to express ctrl-chars
DSTRING = *(VCHAR / NPCHAR) ; no embedded whitespace
WC = "*" ; wildcard character for matching
NOT = "!" ; invert character for matching
N64BITNUM = 1*20DIGIT
N32BITNUM = 1*10DIGIT
N16BITNUM = 1*5DIGIT
N8BITNUM = 1*3DIGIT
DAYSEC = 1*5DIGIT
IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
TEXT = 1*(1*(VCHAR) WSP) ; includes whitespace
DTCP-Time = 4DIGIT "-" 2DIGIT "-" 2DIGIT SP 2DIGIT ":"
2DIGIT ":" 2DIGIT "." 3DIGIT
; This is ISO date/time: YYYY-MM-DD sp HH:MM:SS.TTT
Additionally, the following definitions are excerpted from RFC 3986
[8]:
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IPv6address = 6( h16 ":" ) ls32
/ "::" 5( h16 ":" ) ls32
/ [ h16 ] "::" 4( h16 ":" ) ls32
/ [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
/ [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
/ [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32
/ [ *4( h16 ":" ) h16 ] "::" ls32
/ [ *5( h16 ":" ) h16 ] "::" h16
/ [ *6( h16 ":" ) h16 ] "::"
ls32 = ( h16 ":" h16 ) / IPv4address
; least-significant 32 bits of address
h16 = 1*4HEXDIG
; 16 bits of address represented in hexadecimal
Here begins the formal syntax:
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DTCP-Message = Request / Response / Notification
Request = Request-Line
( Add-Req-Parameters
/ Delete-Req-Parameters
/ Refresh-Req-Parameters
/ List-Req-Parameters
/ Noop-Req-Parameters)
*(extension-parameter)
Csource-ID
Seq
Authentication-Info
CRLF
Response = Status-Line
( ( Add-Resp-Parameters
/ Delete-Resp-Parameters
/ Refresh-Resp-Parameters
/ List-Resp-Parameters
/ Noop-Resp-Parameters) / Error-Parameters )
*(extension-parameter)
Timestamp
Seq ; note absence of Csource-ID
Authentication-Info
CRLF
Notification = Status-Line
( Restart-Notif-Parameters
/ Rollover-Notif-Parameters
/ Noop-Notif-Parameters
/ Timeout-Notif-Parameters
/ Congestion-Notif-Parameters
/ CongDel-Notif-Parameters )
*(extension-parameter)
Timestamp
Authentication-Info ; note absence of Seq
CRLF
DTCP-Version = "DTCP" "/" 1*DIGIT "." 1*DIGIT
Status-Line = DTCP-Version SP Status-Code SP Reason-Phrase CRLF
Request-Line = Method SP DTCP-Version CRLF
Method = "ADD" / "DELETE" / "REFRESH" / "LIST" / "NOOP"
/ extension-method
extension-method = DSTRING
Status-Code = Provisional
/ Success
/ Redirection
/ Request-Failure
/ Server-Failure
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/ Global-Failure
/ extension-code
Reason-Phrase = TEXT ; differs from SIP
extension-code = 3DIGIT
Provisional = "130" ; Sequence Number Rollover (Notif)
/ "131" ; NoOp Notification (Notif)
Success = "200" ; OK
Redirection = "390" ; Criterion Timeout Delete (Notif)
Request-Failure = "400" ; Bad Request
/ "430" ; Unknown Content Destination
/ "431" ; Unknown Criteria ID
/ "432" ; Improper Filter Specification
/ "433" ; Improper Timeout Specification
/ "497" ; Invalid Authentication
; (never sent to client)
/ "498" ; Invalid Sequence Number
; (never sent to client)
/ "499" ; Unknown Control Source Identifier
; (never sent to client)
Server-Failure = "500" ; Server Internal Error
/ "501" ; Not Implemented
/ "505" ; DTCP Version not supported
/ "550" ; Max Criteria Limit Exceeded
/ "551" ; Max Content Destination Exceeded
/ "580" ; Congestion (Notif)
/ "598" ; Duplicate Packets Dropped (Notif)
/ "599" ; Server Restart (Notif)
Global-Failure = "680" ; Criterion Congestion Delete (Notif)
Error-Parameters = Cdest-ID
/ Criteria-ID
/ Filter-Block
/ Timeout-Block
Add-Req-Parameters = Filter-Block Timeout-Block [Action]
Option-Block [Flags] Cdest-ID
Filter-Block = *(Filter-Element)
Timeout-Block = *(Timeout-Element)
TRemaining-Block = *(TRemaining-Element)
Option-Block = *(Option-Element)
Timeout-Required-Block = 1*(Timeout-Element)
TRemaining-Required-Block = 1*(TRemaining-Element)
Filter-Element = Source-Address
/ Dest-Address
/ Protocol
/ Source-Port
/ Dest-Port
/ ICMP-Type
/ ICMP-Code
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Timeout-Element = Timeout-Idle
/ Timeout-Total
/ Timeout-Packets
/ Timeout-Bytes
TRemaining-Element = Remaining-Idle
/ Remaining-Total
/ Remaining-Packets
/ Remaining-Bytes
Option-Element = Priority
Add-Resp-Parameters = Criteria-ID
Delete-Req-Parameters = ( (Criteria-ID / Criteria-ID-Filter)
Cdest-ID ) [Flags]
Delete-Resp-Parameters = Criteria-Count
Refresh-Req-Parameters = ( (Criteria-ID / Criteria-ID-Filter)
Cdest-ID ) Timeout-Required-Block
Refresh-Resp-Parameters = Criteria-Count
List-Req-Parameters = [ ( (Criteria-ID / Criteria-ID-Filter)
Cdest-ID ) ] [Flags]
List-Resp-Parameters = *(List-Resp-Entry CRLF)
List-Resp-Entry = Criteria-Count Criteria-Num Main-List
[Criteria-List] [Stats-List]
Main-List = Csource-ID Csource-Address Cdest-ID
Criteria-ID Timestamp
Criteria-List = *(Filter-Element) *(Timeout-Element) [Flags]
Stats-List = TRemaining-Block Stats-Block
Stats-Block = Average-Bandwidth Matching-Packets
Matching-Bytes Num-Refresh Last-Refresh
Noop-Req-Parameters = [Flags]
Noop-Resp-Parameters = [] ; no parameters
Restart-Notif-Parameters = Alert-Info
Rollover-Notif-Parameters = [] ; no parameters
Noop-Notif-Parameters = [] ; no parameters
Timeout-Notif-Parameters = Criteria-ID
/ Timeout-Required-Block
/ TRemaining-Required-Block
Congestion-Notif-Parameters = Cdest-ID Average-Bandwidth
Alert-Bandwidth Max-Bandwidth
CongDel-Notif-Parameters = Cdest-ID Criteria-ID-Filter
extension-parameter = "X-" DSTRING COL DSTRING CRLF
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Csource-ID = "Csource-ID" COL DSTRING CRLF
Seq = "Seq" COL N64BITNUM CRLF
Authentication-Info = "Authentication-Info" COL 40HEXDIG CRLF
ID-List = DSTRING *("," DSTRING)
Cdest-ID = "Cdest-ID" COL ID-List CRLF
Source-Address = "Source-Address" COL IPFilter CRLF
Dest-Address = "Dest-Address" COL IPFilter CRLF
Protocol = "Protocol" COL ProtFilter CRLF
Source-Port = "Source-Port" COL PortFilter CRLF
Dest-Port = "Dest-Port" COL PortFilter CRLF
ICMP-Type = "ICMP-Type" COL ICMPFilter CRLF
ICMP-Code = "ICMP-Code" COL ICMPFilter CRLF
Timeout-Idle = "Timeout-Idle" COL DAYSEC CRLF
Timeout-Total = "Timeout-Total" COL DAYSEC CRLF
Timeout-Packets = "Timeout-Packets" COL N32BITNUM CRLF
Timeout-Bytes = "Timeout-Bytes" COL N64BITNUM CRLF
Priority = "Priority" COL N8BITNUM CRLF
Criteria-ID = "Criteria-ID" COL N32BITNUM CRLF
Criteria-ID-Filter = "Criteria-ID" COL CritFilter CRLF
Criteria-Count = "Criteria-Count" COL N32BITNUM CRLF
Criteria-Num = "Criteria-Num" COL N32BITNUM CRLF
Csource-Address = "Csource-Address" COL (IPv4address /
IPv6address) CRLF
Timestamp = "Timestamp" COL DTCP-Time CRLF
Remaining-Idle = "Remaining-Idle" COL DAYSEC CRLF
Remaining-Total = "Remaining-Total" COL DAYSEC CRLF
Remaining-Packets = "Remaining-Packets" COL N32BITNUM CRLF
Remaining-Bytes = "Remaining-Bytes" COL N64BITNUM CRLF
Average-Bandwidth = "Average-Bandwidth" COL N64BITNUM CRLF
Matching-Packets = "Matching-Packets" COL N64BITNUM CRLF
Matching-Bytes = "Matching-Bytes" COL N64BITNUM CRLF
Num-Refresh = "Num-Refresh" COL N32BITNUM CRLF
Last-Refresh = "Last-Refresh" COL DTCP-Time CRLF
Alert-Info = "Alert-Info" COL TEXT CRLF
Alert-Bandwidth = "Alert-Bandwidth" COL N64BITNUM CRLF
Max-Bandwidth = "Max-Bandwidth" COL N64BITNUM CRLF
Action = "Action" COL ActionEntry CRLF
ActionEntry = "Copy"
/ "Block"
/ "Redirect"
/ extension-action
extension-action = DSTRING
Flags = "Flags" COL FlagEntry *("," FlagEntry) CRLF
FlagEntry = "Static"
/ "SendAsync"
/ "Stats"
/ "Criteria"
/ "Both"
IPFilter = [NOT] IPEntry *("," [WSP] [NOT] IPEntry)
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ProtFilter = [NOT] ProtEntry *("," [WSP] [NOT] ProtEntry)
PortFilter = [NOT] PortEntry *("," [WSP] [NOT] PortEntry)
ICMPFilter = [NOT] ICMPEntry *("," [WSP] [NOT] ICMPEntry)
CritFilter = [NOT] CritEntry *("," [WSP] [NOT] CritEntry)
IPEntry = IPv4Entry
/ IPv6Entry
IPv4Entry = IPv4address ; Single Entry
/ IPv4address "/" N8BITNUM ; Address/mask
/ IPv4address "-" IPv4address ; Range
/ IPv4address "-" WC ; Range to UBOUND
/ WC "-" IPv4address ; LBOUND to Range
/ WC ; Pure Wildcard
IPv6Entry = IPv6address ; Single Entry
/ IPv6address "/" N8BITNUM ; Address/mask
/ IPv6address "-" IPv6address ; Range
/ IPv6address "-" WC ; Range to UBOUND
/ WC "-" IPv6address ; LBOUND to Range
/ WC ; Pure Wildcard
PortEntry = N16BITNUM ; Single Entry
/ N16BITNUM "-" N16BITNUM ; Range
/ N16BITNUM "-" WC ; Range to UBOUND
/ WC "-" N16BITNUM ; LBOUND to Range
/ WC ; Pure Wildcard
ProtEntry = N8BITNUM ; Single Entry
/ N8BITNUM "-" N8BITNUM ; Range
/ N8BITNUM "-" WC ; Range to UBOUND
/ WC "-" N8BITNUM ; LBOUND to Range
/ WC ; Pure Wildcard
ICMPEntry = N8BITNUM ; Single Entry
/ N8BITNUM "-" N8BITNUM ; Range
/ N8BITNUM "-" WC ; Range to UBOUND
/ WC "-" N8BITNUM ; LBOUND to Range
/ WC ; Pure Wildcard
CritEntry = N64BITNUM ; Single Entry
/ N64BITNUM "-" N64BITNUM ; Range
/ N64BITNUM "-" WC ; Range to UBOUND
/ WC "-" N64BITNUM ; LBOUND to Range
/ WC ; Pure Wildcard
9. Security Considerations
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DTCP empowers network security personnel to monitor packet data
transitioning through a network element. As such, it is a powerful
protocol that can cause any network data to be redirected to a
arbitrary location for inspection. Consequently, it is of greatest
criticality that any DTCP Servers fully implement the security model
outlined in this draft. Failure to do so could result in malicious
individuals either obtaining unauthorized access to data or
interruption of data transmission.
10. IANA Considerations
This document has no actions for IANA.
11. Conclusions
This protocol has undergone extensive testing and several rounds of
refinements. The resulting protocol is highly effective at meeting
its goals of providing a real-time mechanism to inspect raw packets
containing security-related events traversing a network in real-time.
12. Acknowledgments
Thanks to all at AT&T and Juniper Networks who provided testing and
support for this experimental protocol
The authors would specifically like to thank Joju Chevookaran, and
Saravanan Deenadayalan from Juniper since they have not only worked
hard on the implementation, but also on the some of the enhancements
(specially VRF support, input/out interface filters etc).
Also, Rick Suntag, Michael Nanashko, and Michael St. Angelo from
AT&T all deserve special note for extensive testing as well as
excellent protocol definition suggestions and corrections.
13. References
[RFC1945] Berners-Lee, T., Fielding, R. and H. Frystyk, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945, DOI 10.17487/
RFC1945, May 1996, <http://www.rfc-editor.org/info/
rfc1945>.
[RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, DOI
10.17487/RFC2104, February 1997, <http://www.rfc-
editor.org/info/rfc2104>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, <http://www.rfc-editor.org/info/
rfc2119>.
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[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M. and E. Schooler,
"SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487
/RFC3261, June 2002, <http://www.rfc-editor.org/info/
rfc3261>.
[RFC5938] Morton, A. and M. Chiba, "Individual Session Control
Feature for the Two-Way Active Measurement Protocol
(TWAMP)", RFC 5938, DOI 10.17487/RFC5938, August 2010,
<http://www.rfc-editor.org/info/rfc5938>.
Appendix A. Prior Implementation
This document fully and accurately describes the operation of DTCP/
0.7 implementations. However, in development of this protocol, some
implementations with working versions of the protocol were released.
This appendix describes the differences between the DTCP/0.7 protocol
specification documented herein and the prior DTCP/0.5 and DTCP/0.6
protocol specifications.
Other than the changes documented in this appendix, the older
protocol specifications precisely follow DTCP/0.7 described herein.
This appendix is provided for backward-compatibility purposes only;
all new implementations should ignore this appendix.
A.1. Version Number
Authors' Addresses
Sumit Kala
Juniper Networks
Flat #202, Propulsive Pride Apartment, Doddakannelli Road
Bangalore, Karnataka 560035
INDIA
Phone: +91 8197477794
Email: sumitk@juniper.net
David Cavuto
ATT
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