| Dispatch Working Group | C. Eckel |
| Internet-Draft | T. Kristensen |
| Intended status: Informational | M.K. Thompson |
| Expires: May 03, 2012 | G.A. Sandbakken |
| E. McLeod | |
| Cisco | |
| October 31, 2011 |
Revision of the Binary Floor Control Protocol (BFCP) for use over an unreliable transport
draft-sandbakken-dispatch-bfcp-udp-03
This draft describes how to extend the Binary Floor Control Protocol (BFCP) for use over an unreliable transport. It details the differences from the BFCP protocol definition document and the Session Description Protocol (SDP) format specified for BFCP streams.
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- Drafts is at http://datatracker.ietf.org/drafts/current/.
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 May 03, 2012.
Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.
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 extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
This draft describes how to extend the BFCP protocol to support unreliable transport. Minor changes to the transaction model are introduced in that all requests now have an appropriate response to complete the transaction. The requests are sent with a retransmit timer associated with the response to achieve reliability.
This extension does not change the semantics of BFCP. It permits UDP as an alternate transport. Existing implementations, in the spirit of the approach detailed in earlier versions of this draft (see Appendix Appendix A), have demonstrated the approach to be feasible. Initial compatibility among implementations has been achieved at previous interoperability events. The purpose of this draft is to formalize and publish the extension from the standard specification to facilitate complete interoperability between implementations.
The content of this draft relates to the BFCP protocol specification [RFC4582] and the SDP format for describing BFCP streams [RFC4583]. This draft is written with the goal of identifying the extensions associated with adding support for UDP as an alternate transport to an existing BFCP implementation.
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 [RFC2119].
In existing video conferencing deployments, BFCP is used to manage the floor for the content sharing associated with the conference. For peer to peer scenarios, including business to business conferences and point to point conferences in general, it is frequently the case that one or both endpoints exists behind a NAT/firewall. BFCP roles are negotiated in the offer/answer exchange as specified in [RFC4583], resulting in one endpoint being responsible for opening the TCP connection used for the BFCP communication.
+---------+
| Network |
+---------+
+-----+ / \ +-----+
| NAT |/ \| NAT |
+-----+ +-----+
+----+ / \ +----+
|BFCP|/ \|BFCP|
| UA | | UA |
+----+ +----+
The communication session between the video conferencing endpoints typically consists of a number of RTP over UDP media streams, for audio and video, and a BFCP connection for floor control. Existing deployments are most common in, but not limited to, enterprise networks. In existing deployments, NAT/firewall traversal for the RTP streams works using ICE and/or other methods, including those described in [I-D.ietf-mmusic-media-path-middleboxes].
When enhancing an existing SIP based video conferencing deployment with support for content sharing, the BFCP connection often poses a problem. The reasons for this fall into two general classes. First, there may be a strong preference for UDP based signaling in general. On high capacity endpoints (e.g. PSTN gateways or SIP/H.323 interworking gateways), TCP can suffer from head of line blocking, and it uses many kernel buffers. Network operators view UDP as a way to avoid both of these. Second, establishment and traversal of the TCP connection involving ephemeral ports, as is typically the case with BFCP over TCP, can be problematic, as described in Appendix A of [I-D.ietf-mmusic-ice-tcp]. A broad study of NAT behavior and peer-to-peer TCP establishment for a comprehensive set of TCP NAT traversal techniques over a wide range of commercial NAT products concluded it was not possible to establish a TCP connection in 11% of the cases [IMC05]. The results are worse when focusing on enterprise NATs. A study of hole punching as a NAT traversal technique across a wide variety of deployed NATs reported consistently higher success rates when using UDP than when using TCP [P2PNAT].
To overcome the problems with establishing TCP flows between BFCP entities, this draft defines UDP as an alternate transport for BFCP, leveraging the same mechanisms in place for the RTP over UDP media streams for the BFCP communication. When using UDP as the transport, it is RECOMMENDED to follow the guidelines provided in [RFC5405]. NAT traversal for BFCP over UDP entities is discussed in more detail in Section 6.
The authors view this extension as an admittedly non-ideal, but pragmatic, solution to an existing deployment challenge.
In selecting the approach of defining UDP as an alternate transport for BFCP, several alternatives were considered and explored to some degree. Each of these is discussed briefly in the following subsections. In summary, while these alternatives work in a number of scenarios, they are not sufficient, in and of themselves, to address the use case targeted by this draft.
ICE TCP [I-D.ietf-mmusic-ice-tcp] extends ICE to TCP based media, including the ability to offer a mix of TCP and UDP based candidates for a single stream. ICE TCP has, in general, a lower success probability for enabling TCP connectivity without a relay if both of the hosts are behind a NAT (see Appendix A of [I-D.ietf-mmusic-ice-tcp]) than enabling UDP connectivity in the same scenarios. The happens because many of the currently deployed NATs in video conferencing networks do not support the flow of TCP hand shake packets seen in case of TCP simultaneous-open, either because they do not allow incoming TCP SYN packets from an address to which a SYN packet has been sent to recently, or because they do not properly process the subsequent SYNACK. Implementing various techniques advocated for candidate collection in [I-D.ietf-mmusic-ice-tcp] should increase the success probability, but many of these techniques require support from some network elements (e.g., from the NATs). Such support is not common in enterprise firewalls and NATs.
Teredo [RFC4380] enables nodes located behind one or more IPv4 NATs to obtain IPv6 connectivity by tunneling packets over UDP. Teredo extensions [RFC6081] provide additional capabilities to Teredo, including support for more types of NATs and support for more efficient communication.
As defined, Teredo could be used to make BFCP work for the video conferencing use cases addressed in this draft. However, running the service requires the help of "Teredo servers" and "Teredo relays" [RFC4380]. These servers and relays generally do not exist in the existing video conferencing deployments. It also requires IPv6 awareness on the endpoints. It should also be noted that ICMP6, as used with Teredo to complete an initial protocol exchange and confirm that the appropriate NAT bindings have been set up, is not a conventional feature of IPv4 or even IPv6, and some currently deployed IPv6 firewalls discard ICMP messages. As these networks continue to evolve and tackle the transaction to IPv6, Teredo servers and relays may be deployed, making Teredo available as a suitable alternative to BFCP over UDP.
GUT [I-D.manner-tsvwg-gut] attempts to facilitate tunneling over UDP by encapsulating the native transport protocol and its payload (in general the whole IP payload) within a UDP packet destined to the well-known port GUT_P. Unfortunately, it requires user-space TCP, for which there is not a readily available implementation, and creating one is a large project in itself. This draft has expired and its future is still not clear as it has not yet been adopted by a working group.
Universal Plug and Play Internet Gateway Devices (UPnP IGD) sit on the edge of the network, providing connectivity to the Internet for computers internal to the LAN, but do not allow Internet devices to connect to computers on the internal LAN. IGDs enable a computer on an internal LAN to create port mappings on their NAT, through which hosts on the Internet can send data that will be forwarded to the computer on the internal LAN. IGDs may be self-contained hardware devices or may be software components provided within an operating system.
In considering UPnP IGD, several issues exist. Not all NATs support UPnP, and many that do support it are configured with it turned off by default. NATs are often multilayered, and UPnP does not work well with such NATs. For example, a typical DSL modems acts as a NAT, and the user plugs in a wireless access point behind that, which adds another layer NAT. The client can discover the first layer of NAT using multicast but it is harder to figure out how to discover and control NATs in the next layer up.
The NAT Port Mapping Protocol (NAT PMP) allows a computer in a private network (behind a NAT router) to automatically configure the router to allow parties outside the private network to contact it. NAT PMP runs over UDP. It essentially automates the process of port forwarding. Included in the protocol is a method for retrieving the public IP address of a NAT gateway, thus allowing a client to make this public IP address and port number known to peers that may wish to communicate with it.
Many NATs do not support PMP. In those that do support it, it has similar issues with negotiation of multilayer NATs as UPnP. Video conferencing is used extensively in enterprise networks, and NAT PMP is not generally available in enterprise-class routers.
This section details the difference from [RFC4582], the base protocol specification of BFCP, required for use over an unreliable transport. The section numbers to which differences apply are indicated in parentheses in the titles of the sub-sections below.
Fourth paragraph change:
Before seventh paragraph (page 9), insert:
The figure below should replace Figure 5: COMMON-HEADER 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ver |I| Res | Primitive | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Conference ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transaction ID | User ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following text precedes "Reserved" on page 15:
The Reserved field changes name to Res due to limited space in the ASCII graphic in Figure 2. In the description of the Reserved field "the 5 bits" is changed to "the 4 bits".
The description of Transaction ID should have the final clause deleted with the reference to Section 8 remaining. The value used for server-initiated transactions MUST be non-zero when BFCP is used over unreliable transports, and this qualification shall be described in the updated Section 8.
The values below should be appended to the end of Table 1: BFCP primitives.
| Value | Primitive | Direction |
|---|---|---|
| 14 | FloorRequestStatusAck | P -> S ; Ch -> S |
| 15 | ErrorAck | P -> S ; Ch -> S |
| 16 | FloorStatusAck | P -> S ; Ch -> S |
| 17 | Goodbye | P -> S ; Ch -> S ; |
| P <- S ; Ch <- S | ||
| 18 | GoodbyeAck | P -> S ; Ch -> S ; |
| P <- S ; Ch <- S |
The value below should be appended to the end of Table 5: Error Code meaning.
| Value | Meaning |
|---|---|
| 10 | Unable to parse message |
| 11 | Use DTLS |
This new subsection specifies the normative ABNF for the new primitive, FloorRequestStatusAck.
FloorRequestStatusAck = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
This new subsection specifies the normative ABNF for the new primitive, ErrorAck.
ErrorAck = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
This new subsection specifies the normative ABNF for the new primitive, FloorStatusAck.
FloorStatusAck = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
This new subsection specifies the normative ABNF for the new primitive, Goodbye.
Goodbye = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
This new subsection specifies the normative ABNF for the new primitive, GoodbyeAck.
GoodbyeAck = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
An additional behavior is recommended for entities participating in communication over an unreliable transport that either wish to leave or are asked to leave an established BFCP connection, as detailed in the revised section introduction text below.
BFCP entities may elect to exchange BFCP messages using TCP connections. TCP provides an in-order reliable delivery of a stream of bytes. Consequently, message framing is implemented in the application layer. BFCP implements application-layer framing using TLV-encoded attributes.
A client MUST NOT use more than one TCP connection to communicate with a given floor control server within a conference. Nevertheless, if the same physical box handles different clients (e.g. a floor chair and a floor participant), which are identified by different User IDs, a separate connection per client is allowed.
If a BFCP entity (a client or a floor control server) receives data that cannot be parsed, the entity MUST close the TCP connection, and the connection SHOULD be reestablished. Similarly, if a TCP connection cannot deliver a BFCP message and times out, the TCP connection SHOULD be reestablished.
The way connection reestablishment is handled depends on how the client obtains information to contact the floor control server. Once the TCP connection is reestablished, the client MAY resend those messages for which it did not get a response from the floor control server.
If a floor control server detects that the TCP connection towards one of the floor participants is lost, it is up to the local policy of the floor control server what to do with the pending floor requests of the floor participant. In any case, it is RECOMMENDED that the floor control server keep the floor requests (i.e., that it does not cancel them) while the TCP connection is reestablished.
To maintain backwards compatibility with older implementations of [RFC4583], BFCP entities MUST interpret the graceful close of their TCP connection from their associated participant as an implicit Goodbye message.
BFCP entities may elect to exchange BFCP messages using UDP datagrams. UDP is an unreliable transport where neither delivery nor order is assured. Each BFCP UDP datagram MUST contain exactly one BFCP message. In the event the size of a BFCP message exceeds the MTU size, the BFCP message will be fragmented at the IP layer. Considerations related to fragmentation are covered in Section 4.9.3. The message format for exchange of BFCP in UDP datagrams is the same as for a TCP stream above.
Clients MUST announce their presence to the floor control server by transmission of a Hello message. This Hello message MUST be responded to with a HelloAck message and only upon receipt can the client consider the floor control service as present and available.
As described in Section 8, each request sent by a floor participant or chair shall form a client transaction that expects an acknowledgement message back from the floor control server within a retransmission window. Concordantly, messages sent by the floor control server that are not transaction-completing (e.g. FloorStatus announcements as part of a FloorQuery subscription) are server-initiated transactions that require acknowledgement messages from the floor participant and chair entities to which they were sent.
If a BFCP entity receives data that cannot be parsed, the receiving participant MAY send an Error message with parameter value 10 indicating receipt of a malformed message. If the message can be parsed to the extent that it is able to discern that it was a response to an outstanding request transaction, the client MAY discard the message and await retransmission. BFCP entities receiving an Error message with value 10 SHOULD acknowledge the error and act accordingly.
Transaction ID values are non-sequential and entities are at liberty to select values at random. Entities MUST only have at most one outstanding request transaction at any one time. Implicit subscriptions, such as FloorRequest messages that have multiple responses as the floor control server processes intermediate states until Granted or Denied terminal states attained, can be characterized by a client-initiated request transaction whose acknowledgement is implied by the first FloorRequestStatus response from the floor control server. The subsequent changes in state for the request are new transactions whose Transaction ID is determined by the floor control server and whose receipt by the client participant shall be acknowledged with a FloorRequestStatusAck message. [Editorial note: would it be more straightforward to have all FloorRequestStatus messages acknowledged with a FloorRequestStatusAck message?]
By restricting entities to having at most one pending transaction open, both the out-of-order receipt of messages as well as the possibility for congestion are mitigated. Additional details regarding congestion control are provided in Section 4.9.2.1. A server-initiated request (e.g. a FloorStatus with an update from the floor control server) received by a participant before the initial FloorRequestStatus message that closes the client-initiated transaction that was instigated by the FloorRequest MUST be treated as superseding the information conveyed in any delinquent response. As the floor control server cannot send a second update to the implicit floor status subscription until the first is acknowledged, ordinality is maintained.
BFCP may be characterized to generate "low data-volume" traffic, per the classification in [RFC5405]. Nevertheless is it necessary to ensure suitable and necessary congestion control mechanisms are used for BFCP over UDP. As described in previous paragraph every entity - client or server - is only allowed to send one request at a time, and await the acknowledging response. This way at most one datagram is sent per RTT given the message is not lost during transmission. In case the message is lost, the request retransmission timer T1 specified in Section 4.14 will fire and the message is retransmitted up to three times. The default initial interval is set to 500ms and the interval is doubled after each retransmission attempt, this is identical to the specification of the T1 timer in SIP as described in Section 17.1.1.2 of [RFC3261].
If a BFCP entity receives an ICMP port unreachable message mid-conversation, the entity SHOULD treat the conversation as closed (e.g. an implicit Goodbye message from the peer) and behave accordingly. The entity MAY attempt to re-establish the conversation afresh. The new connection will appear as a wholly new floor participant, chair or floor control server with all state previously held about that participant lost.
Note: This is because the peer entities cannot rely on IP and port tuple to uniquely identify the participant, nor would extending Hello to include an attribute that advertised what the entity previously was assigned as a User ID be acceptable due to session hijacking.
In deployments where NAT appliances, firewalls or other such devices are present and affecting port reachability for each entity, one possibility is to utilize the peer connectivity checks, relay use and NAT pinhole maintenance mechanisms defined in ICE [RFC5245].
Large messages become a concern when using BFCP if the overall size of a single BFCP message exceeds that representable within the 16-bit Payload Length field of the COMMON-HEADER. When using UDP, there is the added concern that a single BFCP message can be fragmented at the IP layer if its overall size exceeds the MTU threshold of the network.
The target use cases for BFCP via UDP typically involve relatively small BFCP messages. Combining that with the goal of minimizing differences to the standard BFCP specification, BFCP entities SHOULD ensure that their messages are smaller than the recommended MTU size of 1300 bytes when encoded to minimize the likelihood of fragmentation in route to their peer entity.
Expand the section to mandate support for DTLS when transport over UDP is used such that it reads as follows:
The final clause of the introduction to section 8 should be read as:
The final clause of this section should be read as:
New section:
T1 is a timer that schedules retransmission of a request until an appropriate response is received or until the maximum number of retransmissions have occurred. The timer doubles on each re-transmit, failing after three unacknowledged transmission attempts.
If a valid response is not received for a client- or server-initiated transaction, the implementation MUST consider the BFCP association as failed. Implementations SHOULD follow the reestablishment procedure described in section 6 (e.g. initiate a new offer/answer [RFC3264] exchange). Alternatively, they MAY continue without BFCP and therefore not be participant in any floor control actions.
T2 is a timer that, when fires, signals that the BFCP entity can release knowledge of the transaction against which it is running. It is started upon the first transmission of the response to a request and is the only mechanism by which that response is released by the BFCP entity. Any subsequent retransmissions of the same request can be responded to by replaying the cached response, whilst that value is retained until the timer has fired.
T2 shall be set such that it encompasses all legal retransmissions per T1 plus a factor to accommodate network latency between BFCP entities.
The table below defines the different timers required when BFCP entities communicate over an unreliable transport.
| Timer | Description | Value/s |
|---|---|---|
| T1 | Initial request retransmission timer | 0.5s |
| T2 | Response retransmission timer | 10s |
The default value for T1 is 500 ms, this is an estimate of the RTT for completing the transaction. T1 MAY be chosen larger, and this is RECOMMENDED if it is known in advance that the RTT is larger. Regardless of the value of T1, the exponential backoffs on retransmissions described in Section 4.14 MUST be used.
The first sentence of the second paragraph should be read as:
Change each instance of "TLS" to "TLS/DTLS", and each instance of "TCP" to "TCP/UDP".
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
Prepend the sentence below at the start of this subsection:
The sentence below shall appear as a new subsection:
The sentence below shall appear as a new subsection:
The sentence below shall appear as a new subsection:
Change each instance of "TLS" to "TLS/DTLS", and each instance of "TCP" to "TCP/UDP".
This section instructs the IANA to register the following new values for the BFCP primitive subregistry.
| Value | Primitive | Reference |
|---|---|---|
| 14 | FloorRequestStatusAck | RFC 4582bis |
| 15 | ErrorAck | RFC 4582bis |
| 16 | FloorStatusAck | RFC 4582bis |
| 17 | Goodbye | RFC 4582bis |
| 18 | GoodbyeAck | RFC 4582bis |
This section instructs the IANA to register the following new values for the BFCP Error Code subregistry.
| Value | Meaning | Reference |
|---|---|---|
| 10 | Unable to parse message | RFC 4582bis |
| 11 | Use DTLS | RFC 4582bis |
With reference to Section 4.1, the following figures show representative call-flows for requesting and releasing a floor, and obtaining status information about a floor when BFCP is deployed over an unreliable transport. The figures here show a loss-less interaction.
Editorial Note: A future version of this draft will show an example with lost packets due to unreliable transport, as well as examples on usage of DTLS and STUN in call the setup phase.
Floor Participant Floor Control
Server
|(1) FloorRequest |
|Transaction ID: 123 |
|User ID: 234 |
|FLOOR-ID: 543 |
|---------------------------------------------->|
| |
|(2) FloorRequestStatus |
|Transaction ID: 123 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| OVERALL-REQUEST-STATUS |
| Request Status: Pending |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
|<----------------------------------------------|
| |
|(3) FloorRequestStatus |
|Transaction ID: 4098 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| OVERALL-REQUEST-STATUS |
| Request Status: Accepted |
| Queue Position: 1st |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
|<----------------------------------------------|
| |
|(4) FloorRequestStatusAck |
|Transaction ID: 4098 |
|User ID: 234 |
|---------------------------------------------->|
| |
|(5) FloorRequestStatus |
|Transaction ID: 4130 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| OVERALL-REQUEST-STATUS |
| Request Status: Granted |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
|<----------------------------------------------|
| |
|(6) FloorRequestStatusAck |
|Transaction ID: 4130 |
|User ID: 234 |
|---------------------------------------------->|
| |
|(7) FloorRelease |
|Transaction ID: 154 |
|User ID: 234 |
|FLOOR-REQUEST-ID: 789 |
|---------------------------------------------->|
| |
|(8) FloorRequestStatus |
|Transaction ID: 154 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| OVERALL-REQUEST-STATUS |
| Request Status: Released |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
|<----------------------------------------------|
Note that in Figure 8, the FloorRequestStatus message from the floor control server to the floor participant is a transaction-closing message as a response to the client-initiated transaction with Transaction ID 154. It does not and SHOULD NOT be followed by a FloorRequestStatusAck message from the floor participant to the floor control server.
Floor Participant Floor Control
Server
|(1) FloorQuery |
|Transaction ID: 257 |
|User ID: 234 |
|FLOOR-ID: 543 |
|---------------------------------------------->|
| |
|(2) FloorStatus |
|Transaction ID: 257 |
|User ID: 234 |
|FLOOR-ID:543 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 764 |
| OVERALL-REQUEST-STATUS |
| Request Status: Accepted |
| Queue Position: 1st |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 124 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| OVERALL-REQUEST-STATUS |
| Request Status: Accepted |
| Queue Position: 2nd |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
|<----------------------------------------------|
| |
|(3) FloorStatus |
|Transaction ID: 4319 |
|User ID: 234 |
|FLOOR-ID:543 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 764 |
| OVERALL-REQUEST-STATUS |
| Request Status: Granted |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 124 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| OVERALL-REQUEST-STATUS |
| Request Status: Accepted |
| Queue Position: 1st |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
|<----------------------------------------------|
| |
|(4) FloorStatusAck |
|Transaction ID: 4319 |
|User ID: 234 |
|---------------------------------------------->|
| |
|(5) FloorStatus |
|Transaction ID: 4392 |
|User ID: 234 |
|FLOOR-ID:543 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| OVERALL-REQUEST-STATUS |
| Request Status: Granted |
| FLOOR-REQUEST-STATUS |
| Floor ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
|<----------------------------------------------|
| |
|(6) FloorStatusAck |
|Transaction ID: 4392 |
|User ID: 234 |
|---------------------------------------------->|
This section details revisions to [RFC4583], the SDP format for specifying BFCP streams. The section number to which updates apply are indicated in parentheses in the titles of the sub-sections below.
The section shall be re-written to remove reference to the exclusivity of TCP as a transport for BFCP streams.
In last paragraph, change "When TLS is used, once the underlaying TCP connection is established" to "When TLS is used with TCP, once the underlying connection is established".
Append to the first paragraph, "Furthermore, when using DTLS over UDP, considerations for its use with RTP and RTCP are presented in [RFC5763]. The requirements for the offer/answer exchange, as listed in Section 5 of that document, MUST be followed."
This section should be renamed now that there are more values to register in the SDP parameters registry, with the following added to the table:
| Value | Reference |
|---|---|
| UDP/BFCP | RFC 4583bis |
| UDP/TLS/BFCP | RFC 4583bis |
One of the key benefits when using UDP for BFCP communication is the ability to leverage the existing NAT traversal infrastructure and strategies deployed to facilitate transport of the media associated with the video conferencing sessions. Depending on the given deployment, this infrastructure typically includes some subset of ICE [RFC5245].
In order to facilitate the initial establishment of NAT bindings, and to maintain those bindings once established, BFCP over UDP entities are RECOMMENDED to use STUN [RFC5389] for keep-alives, as described for SIP [RFC5626]. This results in each BFCP entity sending a packet, both to open the pinhole and to learn what IP/port the NAT assigned for the binding.
In order to facilitate traversal of BFCP packets through NATs, BFCP over UDP entities are RECOMMENDED to use symmetric ports for sending and receiving BFCP packets, as recommended for RTP/RTCP [RFC4961].
This draft reflects a work in progress, with at least the following items to be documented and/or revised:
We acknowledge substantial contributions to one or more previous versions of this draft from Trond G. Andersen, Alfred E. Heggestad, Gonzalo Camarillo, Roni Even, Lorenzo Miniero, Joerg Ott, Hadriel Kaplan, Dan Wing, Cullen Jennings, David Benham, and Alan Ford.