Network Working Group S. Venaas
Internet-Draft UNINETT
Intended status: Informational February 12, 2008
Expires: August 15, 2008
Multicast Ping Protocol
draft-ietf-mboned-ssmping-03
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 15, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
The Multicast Ping Protocol specified in this document allows for
checking whether an endpoint can receive multicast, both Source-
Specific Multicast (SSM) and Any-Source Multicast (ASM). It can also
be used to obtain additional multicast related information like
multicast tree setup time etc. This protocol is based on an
implementation of tools called ssmping and asmping.
Venaas Expires August 15, 2008 [Page 1]
Internet-Draft Multicast Ping Protocol February 2008
Requirements Language
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 [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol specification . . . . . . . . . . . . . . . . . . . . 4
3.1. Option format . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Defined Options . . . . . . . . . . . . . . . . . . . . . 6
4. Packet Format . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Message types and options . . . . . . . . . . . . . . . . . . 10
6. Client Behaviour . . . . . . . . . . . . . . . . . . . . . . . 10
7. Server Behaviour . . . . . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 16
Venaas Expires August 15, 2008 [Page 2]
Internet-Draft Multicast Ping Protocol February 2008
1. Introduction
The Multicast Ping Protocol specified in this document allows for
checking multicast connectivity. In addition to checking reception
of multicast (SSM or ASM), the protocol can provide related
information like multicast tree setup time, the number of hops the
packets have traveled, as well as packet delay and loss. This
functionality resembles, in part, the ICMP Echo Request/Reply
mechanism, but uses UDP (RFC 768 [2] and RFC 2460 [3]) and requires
both a client and a server implementing this protocol.
The protocol here specified is based on the actual implementation of
the ssmping and asmping tools [5] which are widely used by the
Internet community to conduct multicast connectivity tests.
2. Architecture
Before describing the protocol in detail, we provide a brief overview
of how the protocol may be used and what information it may provide.
The typical protocol usage is as follows: A server runs continuously
to serve requests from clients. A client can test the multicast
reception from this server, provided it knows a unicast address of
the server. It will then send a unicast message to the server asking
for a group to use. Optionally the user may have requested a
specific group or scope, in which case the client will ask for a
group matching the user's request. The server will respond with a
group to use, or an error if no group is available. Next, for ASM,
the client joins an ASM group G, while for SSM it joins a channel
(S,G). Here G is the group specified by the server, and S is the
unicast address used to reach the server.
After joining the channel, the client unicasts multicast ping
requests to the server. The requests are sent using UDP with
destination port set to the standardised multicast ping port [TBD].
The requests are sent periodically, e.g., once per second, to the
server. The requests contain a sequence number, and typically a
timestamp. The requests are echoed back by the server, except the
server may add a few options. For each request, the server sends two
replies. One reply is unicast to the source IP address and source
UDP port of the request, while another is multicast back to requested
multicast group G and the source UDP port of the request. Both the
replies are sent from the same port from which the request was
received. The server should specify the TTL used for both the
unicast and multicast messages (we recommend at least 64) and
includes a TTL option for the client to compute the number of hops.
The client should leave the channel/group when it has finished its
measurements.
Venaas Expires August 15, 2008 [Page 3]
Internet-Draft Multicast Ping Protocol February 2008
By use of this protocol, a client can obtain information about
several multicast delivery characteristics. First, by receiving
unicast replies, it can verify that the server is receiving the
unicast requests, is operational and responding. Hence, provided
that the client receives unicast replies, a failure to receive
multicast indicates either a multicast problem or a multicast
administrative restriction. If it does receive multicast, it knows
not only that it can receive; it may also estimate the amount of time
it took to establish the multicast tree (at least if it is in the
range of seconds), whether there are packet drops, and the length and
variation of Round Trip Times (RTT). For unicast, the RTT is the
time from when the unicast request is sent to when the reply is
received. The measured multicast RTT also references the client's
unicast request. By use of the TTL option specifying the TTL of the
replies when they are originated, the client can also determine the
number of router hops it is from the source. Since similar
information is obtained in the unicast replies, the host may compare
its multicast and unicast results and is able to check for
differences in the number of hops, RTT, etc. The number of multicast
hops and changes in the number of hops over time, may also reveal
details about the multicast tree and multicast tree changes. E.g.,
with PIM-SM one may be able to tell whether the forwarding is on a
shared or source-specific tree and when an eventual switch occurs.
Provided that the server sends the unicast and multicast replies
nearly simultaneously, the client may also be able to measure the
difference in one way delay for unicast and multicast on the path
from server to client, and also differences in delay. Servers may
optionally specify a timestamp. This may be useful since the unicast
and multicast replies can not be sent simultaneously (the delay
depending on the host's operating system and load).
3. Protocol specification
There are four different message types. There are Echo Request and
Echo Reply messages used for the actual measurements; there is an
Init message that SHOULD be used to initialise a ping session and
negotiate which group to use; and finally a Server Response message
that is mainly used in response to the Init message. The messages
MUST always be in network byte order. UDP checksums MUST always be
used.
The messages share a common format: one octet specifying the message
type, followed by a number of options in TLV (Type, Length and Value)
format. This makes the protocol easily extendible. The Init message
generally contains some prefix options asking the server for a group
from one of the specified prefixes. The server responds with a
Server Response message that contains the group address to use, or
Venaas Expires August 15, 2008 [Page 4]
Internet-Draft Multicast Ping Protocol February 2008
possibly prefix options describing what multicast groups the server
may be able to provide. For an Echo Request the client generally
includes a number of options, and a server may simply echo the
content back (only changing the message type), without inspecting the
options. However, the server SHOULD add a TTL option, and there are
other options that a server implementation MAY support, e.g., the
client may ask for certain information or a specific behaviour from
the server. The Echo Replies (one unicast and one multicast) MUST
first contain the exact options from the request (in the same order),
and then, immediately following, any options appended by the server.
A server MUST NOT process unknown options, but they MUST still be
included in the Echo Reply. A client MUST ignore any unknown
options.
This document defines a number of different options. Some options do
not require processing by servers and are simply returned unmodified
in the reply. There are, however, other client options that the
server may care about, and also server options that may be requested
by a client. Unless otherwise specified, an option MUST NOT be used
multiple times in the same message.
3.1. Option format
All options are TLVs formatted as specified below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (2 octets) specifies the option. The different options are
defined below.
Length (2 octets) specifies the length of the value field. Depending
on the option type, it can be from 0 to 65535.
Value. The value must always be of the specified length. See the
respective option definitions for possible values. If the length is
0, the value field is not included.
Venaas Expires August 15, 2008 [Page 5]
Internet-Draft Multicast Ping Protocol February 2008
3.2. Defined Options
Version, type 0. Length MUST be 1. This option MUST always be
included in all messages, and the value MUST be set to 2 (in
decimal). Note that there are older implementations of ssmping that
only partly follow this specification. They can be regarded as
version 1 and do not use this option.
Client ID, type 1. Length MUST be non-zero. A client SHOULD always
include this option in all messages (both Init and Request). The
client may use any value it likes to be able to detect whether a
reply is a reply to its Init/Request or not. A server should treat
this as opaque data, and simply leave it unchanged in the reply (both
Server Response and Reply). The value might be a process ID, perhaps
process ID combined with an IP address because it may receive
multicast responses to queries from other clients. It is left to the
client implementor how to make use of this option.
Sequence number, type 2. Length MUST be 4. A client MUST always
include this in Request messages and MUST NOT include it in Init
messages. A server replying to a Request message MUST copy it into
the Reply (or Server Response message on error). This contains a 32
bit sequence number. The values would typically start at 1 and
increase by one for each request in a sequence.
Client Timestamp, type 3. Length MUST be 8 bytes. A client SHOULD
include this in Request messages and MUST NOT include it in Init
messages. A server replying to a Request message MUST copy it into
the Reply. The timestamp specifies the time when the Request message
is sent. The first 4 bytes specify the number of seconds since the
Epoch (beginning of the year 1970). The next 4 bytes specify the
number of microseconds since the last second since the Epoch.
Multicast group, type 4. Length MUST be greater than 1. It MAY be
used in Server Response messages to tell the client what group to use
in subsequent Request messages. It MUST be used in Request messages
to tell the server what group address to respond to (this group would
typically be previously obtained in a Server Response message). It
MUST be used in Reply messages (copied from the Request message). It
MUST NOT be used in Init messages. The format of the option value is
as below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | Multicast group address... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .... |
Venaas Expires August 15, 2008 [Page 6]
Internet-Draft Multicast Ping Protocol February 2008
The address family is a value 0-65535 as assigned by IANA for
Internet Address Families [4]. This is followed by the group
address. Length of the option value will be 6 for IPv4, and 18 for
IPv6.
Option Request Option, type 5. Length MUST be greater than 1. This
option MAY be used in client messages (Init and Request messages). A
server MUST NOT send this option, except that if it is present in a
Request message, the server MUST include it in a reply (Reply
message) to the Request. This option contains a list of option types
for options that the client is requesting from the server. Support
for this option is optional for both clients and servers. The length
of this option will be a non-zero even number, since it contains one
or more option types that are two octets each. The format of the
option value is as below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ..... |
This option might be used by the client to ask the server to include
options like Timestamp or Server Information. A client MAY request
Server Information in Init messages; it MUST NOT request it in other
messages. A client MAY request a Timestamp in Request messages; it
MUST NOT request it in other messages.
Server Information, type 6. Length MUST be non-zero. It MAY be used
in Server Response messages and MUST NOT be used in other messages.
Support for this option is optional. A server supporting this option
SHOULD add it in Server Response messages if and only if requested by
the client. The value is a UTF-8 string that might contain vendor
and version information for the server implementation. It may also
contain information on which options the server supports. An
interactive client MAY support this option, and SHOULD then allow a
user to request this string and display it.
Type 7, Reserved. This option code value was used by early
implementations for an option that is now deprecated. This option
should no longer be used. Clients MUST not use this option. Servers
MUST treat it as an unknown option (not process it if received, but
if received in a Request message, it MUST be echoed back in the Reply
message).
Type 8, Reserved. This option code value was used by early
Venaas Expires August 15, 2008 [Page 7]
Internet-Draft Multicast Ping Protocol February 2008
implementations for an option that is now deprecated. This option
should no longer be used. Clients MUST not use this option. Servers
MUST treat it as an unknown option (not process it if received, but
if received in a Request message, it MUST be echoed back in the Reply
message).
TTL, type 9. Length MUST be 1. This option contains a single octet
specifying the TTL of a Reply message. Every time a server sends a
unicast or multicast Reply message, it SHOULD include this option
specifying the TTL. This is used by clients to determine the number
of hops the messages have traversed. It MUST NOT be used in other
messages. A server SHOULD specify this option if it knows what the
TTL of the Reply will be. In general the server can specify a
specific TTL to the host stack. Note that the TTL is not necessarily
the same for unicast and multicast.
Multicast prefix, type 10. Length MUST be greater than 2. It MAY be
used in Init messages to request a group within the prefix(es), it
MAY be used in Server Response messages to tell the client what
prefix(es) it may try to obtain a group from. It MUST NOT be used in
Request/Reply messages. Note that this option MAY be included
multiple times to specify multiple prefixes.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | Prefix Length |Partial address|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .... |
The address family is a value 0-65535 as assigned by IANA for
Internet Address Families [4]. This is followed by a prefix length
(0-32 for IPv4, 0-128 for IPv6), and finally a group address. The
group address need only contain enough octets to cover the prefix
length bits (e.g., there need be no group address if the prefix
length is 0, the group address would have to be 3 octets long if the
prefix length is 17-24). Any bits past the prefix length MUST be
ignored. For IPv4 the option value length will be 3-7, while for
IPv6 3-19.
Session ID, type 11. Length MUST be non-zero. A server MAY include
this in Server Response and Reply messages. If a client receives
this option in a message, the client MUST echo the Session ID option
in subsequent Reply messages, with the exact same value, until the
next message is received from the server. If the next message from
the server has no Session ID or a new Session ID value, the client
should do the same, either not use the Session ID, or use the new
value. The Session ID may help the server in keeping track of
Venaas Expires August 15, 2008 [Page 8]
Internet-Draft Multicast Ping Protocol February 2008
clients and possibly manage client state. It is left to the server
implementer to decide whether it is useful and how to make use of it.
Server Timestamp, type 12. Length MUST be 8 bytes. A server
supporting this option, SHOULD include it in Reply messages, if
requested by the client. The timestamp specifies the time when the
Reply message is sent. The first 4 bytes specify the number of
seconds since the Epoch (beginning of the year 1970). The next 4
bytes specify the number of microseconds since the last second since
the Epoch.
4. Packet Format
The format of all messages is a one octet message type, directly
followed by a variable number of options.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Option |
+-+-+-+-+-+-+-+-+ . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option |
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.
.
.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option |
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
There are four message types defined. Type 81 (the character Q in
ASCII) specifies an Echo Request (Query). Type 65 (the character A
in ASCII) specifies an Echo Response (Answer). Type 73 (the
character I in ASCII) is an Init message, and type 83 (the character
S in ACII) is a Server Response message.
The options directly follow the type octet and are not aligned in any
way (no spacing or padding), i.e., options might start at any octet
Venaas Expires August 15, 2008 [Page 9]
Internet-Draft Multicast Ping Protocol February 2008
boundary. The option format is specified above.
5. Message types and options
For the readers convenience we provide the matrix below, showing what
options can go in what messages.
Option / Message Type | Init | Server Response | Request | Reply |
-----------------------------------------------------------------+
Version (0) | MUST | ECHO | MUST | ECHO |
Client ID (1) |SHOULD| ECHO | SHOULD | ECHO |
Sequence number (2) | NOT | ECHO | MUST | ECHO |
Client Timestamp (3) | NOT | NOT | SHOULD | ECHO |
Multicast group (4) | NOT | MAY | MUST | ECHO |
Option Request (5) | MAY | NOT | MAY | ECHO |
Server Information (6)| NOT | RQ | NOT | NOT |
Reserved (7) | NOT | NOT | NOT | ECHO |
Reserved (8) | NOT | NOT | NOT | ECHO |
TTL (9) | NOT | NOT | NOT |SHOULD |
Multicast prefix (10) | MAY | MAY | NOT | NOT |
Session ID (11) | NOT | MAY | ECHO | MAY |
Server Timestamp (12) | NOT | NOT | NOT | RQ |
NOT means that the option MUST NOT be included. ECHO for a server
means that if the option is specified by the client, then the server
MUST echo the option back in the response, with the exact same option
value. ECHO for a client means that it MUST echo the option it got
in the last message from the server in any subsequent messages it
sends. RQ means that the server SHOULD include the option in the
response, when requested by the client using the Option Request
option.
6. Client Behaviour
We will consider how a typical interactive client using the above
protocol would behave. A client need only require a user to specify
the unicast address of the server. It can then send an Init message
with a prefix option containing the desired address family and zero
prefix length. The server is then free to decide which group it
should return. A client may also allow a user to specify a group
address(es) or prefix(es) (for IPv6, the user may only be required to
specify a scope or an RP address, from which the client can construct
the desired prefix, possibly embedded-RP). From this the client can
specify one or more prefix options in an Init message to tell the
server which address it would prefer. If the user specifies a group
address, that can be encoded as a prefix of maximal length (e.g. 32
Venaas Expires August 15, 2008 [Page 10]
Internet-Draft Multicast Ping Protocol February 2008
for IPv4). The prefix options are in prioritised order, i.e., the
client should put the most preferred prefix first.
If the client receives a Server Response message containing a group
address it can start sending Request messages, see the next
paragraph. If there is no group address option, it would typically
exit with an error message. The server may have included some prefix
options in the Server Response. The client may use this to provide
the user some feedback on what prefixes or scopes are available.
Assuming the client got a group address in a Server Response it can
start pinging. Before it does that it should let the user know which
group is being used. Normally, a client should send at most one ping
request per second. When sending ping Requests the client must
always specifiy the group option. If the last message from the
server contained a Session ID, then it must also include that with
the same value. Typically it would receive a Session ID in a Server
Response together with the group address, and then the ID would stay
the same during the entire ping sequence. However, if for instance
the server process is restarted, it may still be possible to continue
pinging but the Session ID may be changed by the server. Hence a
client implementation must always use the last Session ID it
received, and not necessarily the one from the Server Response
message. If a client receives a Server Response message in response
to a Request message (that is, a Server Response message containing a
sequence number), this means there is an error and it should stop
sending Requests. This may for instance happen after server restart.
The client may have an option for the user to obtain server
information. If the user asks for server information, the client can
send an Init message with no prefix options, but with an Option
Request Option, requesting the server to return a Server Information
option. The server will return server information if supported, and
it may also return a list of prefixes it supports. It will however
not return a group address. The client may also try to obtain only a
list of prefixes by sending an Init message with no prefixes and not
requesting any specific options.
Note that a client may pick a multicast group and send Request
messages without first going through the Init - Server Response
negotiation. If this is supported by the server and the server is
okay with the group used, the server can then send Reply messages as
usual. If the server is not okay, it will send a Server Response
telling the client to stop and possibly pick a new group.
Venaas Expires August 15, 2008 [Page 11]
Internet-Draft Multicast Ping Protocol February 2008
7. Server Behaviour
We will consider how a typical server using the above protocol would
behave. First we consider how to respond to Init messages. If the
Init message contains prefix options, the server should look at them
in order and see if it can assign a multicast address in the given
range. The server would be configured, possibly have a default,
specifying which groups it can offer. It may have a large pool just
picking a group at random, possibly choose a group based on hashing
of the clients IP address or identifier, or just use a fixed group.
It is left to the server to decide whether it should allow the same
address to be used simultaneously by multiple clients. If the server
finds a suitable group address, it returns this in a group option in
a Server Response message. The server may additionally include a
Session ID. This may help the server if it is to keep some state,
for instance for making sure the client uses the group it got
assigned. A good Session ID would be a random byte string that is
hard to predict. If the server cannot find a suitable group address,
or if there were no prefixes in the Init message, it may send a
Server Response message containing prefix options listing what
prefixes may be available to the client. Finally, if the Init
message requests the Server Information option, it should include
that.
When the server receives a Request message, it may first check that
the group address and Session ID (if provided) are valid. If the
server is satisfied it will send a unicast Reply message back to the
client, and also a multicast Reply message to the group address. The
Reply messages contain the exact options and in the same order, as in
the Request, and after that the server adds a TTL option and
additional options if needed. E.g., it may add a timestamp if
requested by the client. If the server is not happy with the Request
(bad group address or Session ID, request is too large etc), it may
send a Server Response message asking the client to stop. This
Server Response must echo the sequence number from the Request. This
Server Response may contain which prefixes the client can try to
request addresses from. The unicast and multicast Reply messages
have identical UDP payload apart from possibly TTL and timestamp
option values.
Note that the server may receive Request messages with no prior Init
message. This may happen when the server restarts or if a client
sends a Request with no prior Init message. The server may go ahead
and respond if it is okay with the group used. In the responses it
may add a Session ID which will then be in later requests from the
client. If the group is not okay, the server sends back a Server
Response. The Response is just as if it got an Init message with no
prefixes. If the server adds or modifies the SessionID in replies,
Venaas Expires August 15, 2008 [Page 12]
Internet-Draft Multicast Ping Protocol February 2008
it must use the exact same SessionID in the unicast and multicast
replies.
By default a server should perform rate limiting and for a given
client, respond to at most one Request message per second. A leaky
bucket algorithm is suggested, where the rate can be higher for a few
seconds, but the average rate should by default be limited to a
message per client per second.
8. Acknowledgements
The ssmping concept was proposed by Pavan Namburi, Kamil Sarac and
Kevin C. Almeroth in the paper SSM-Ping: A Ping Utility for Source
Specific Multicast, and also the Internet Draft
draft-sarac-mping-00.txt. Mickael Hoerdt has contributed with
several ideas. Alexander Gall, Nicholas Humfrey, Nick Lamb and Dave
Thaler have contributed in different ways to the implementation of
the ssmping tools at [5]. Many people in communities like TERENA,
Internet2 and the M6Bone have used early implementations of ssmping
and provided feedback that have influenced the current protocol.
Thanks to Kevin Almeroth, Toerless Eckert, Gorry Fairhurst, Liu Hui,
Bharat Joshi, Olav Kvittem, Hugo Santos, Kamil Sarac, Pekka Savola,
Trond Skjesol and Cao Wei for reviewing and providing feedback on
this draft. In particular Hugo, Gorry and Bharat have provided lots
of input on several revisions of the draft
9. IANA Considerations
IANA is requested to provide a UDP port number for use by this
protocol, and also to provide registries for message and option
types.
There should be a message types registry. Message types are in the
range 0-255. Message types 0-191 can be assigned referencing an RFC
(it may be Informational), while types 192-255 are freely available
for experimental, private or vendor specifc use.
There should also be an option type registry. Option types 0-49151
can be assigned referencing an RFC (it may be Informational), while
types 49152-65535 are freely available for experimental, private or
vendor specifc use.
10. Security Considerations
There are some security issues to consider. One is that a host may
Venaas Expires August 15, 2008 [Page 13]
Internet-Draft Multicast Ping Protocol February 2008
send a request with an IP source address of another host, and make an
arbitrary multicast ping server on the Internet send packets to this
other host. This behaviour is fairly harmless. The worst case is if
the host receiving the unicast replies also happen to be joined to
the multicast group used. In this case, there would be an
amplification effect where the host receives twice as many replies as
there are requests sent.
Servers should perform rate limiting, to guard against this function
being used as a DoS attack. By default, clients should send at most
one request per second, and servers should perform rate limiting if a
client sends more frequent requests. Server implementations should
provide administrative control of which client IP addresses to serve,
and may also allow certain clients to perform more rapid requests.
Implementors of applications/tools using this protocol should
consider the UDP guidelines [6], in particular if clients are to
send, or servers are to accept, requests at rates exceeding one per
second.
A client should use the client ID option to distinguish replies to
its own requests from replies that might be to other requests.
11. References
11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[3] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998.
[4] "IANA, Address Family Numbers",
<http://www.iana.org/assignments/address-family-numbers>.
11.2. Informative References
[5] "ssmping implementation",
<http://www.venaas.no/multicast/ssmping/>.
[6] Eggert, L. and G. Fairhurst, "UDP Usage Guidelines for
Application Designers", draft-ietf-tsvwg-udp-guidelines-05 (work
in progress), February 2008.
Venaas Expires August 15, 2008 [Page 14]
Internet-Draft Multicast Ping Protocol February 2008
Author's Address
Stig Venaas
UNINETT
Trondheim NO-7465
Norway
Email: venaas@uninett.no
Venaas Expires August 15, 2008 [Page 15]
Internet-Draft Multicast Ping Protocol February 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Venaas Expires August 15, 2008 [Page 16]
