ICNRG S. Mastorakis
Internet-Draft UCLA
Intended status: Experimental J. Gibson
Expires: February 27, 2017 I. Moiseenko
R. Droms
D. Oran
Cisco Systems
August 26, 2016
ICN Ping Protocol
draft-mastorakis-icnrg-icnping-00
Abstract
This document presents the design of an ICN Ping protocol. This
includes the operations both on the client and the forwarder side.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Background on IP-Based Ping Operation . . . . . . . . . . . . 2
3. Ping Functionality Challenges and Opportunities in ICN . . . 3
4. ICN Ping Echo Packet Formats . . . . . . . . . . . . . . . . 5
4.1. ICN Ping Echo Request Packet Format . . . . . . . . . . . 5
4.2. Ping Echo Reply Packet Format . . . . . . . . . . . . . . 8
5. Forwarder Handling . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix A. Ping Client Application (Consumer) Operation . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
Determining data plane reachability to a destination and taking
coarse performance measurements of round trip time are fundamental
facilities for network administration and troubleshooting. In IP,
where routing and forwarding are based on IP addresses, ICMP echo and
ICMP echo response are the protocol mechanisms used for this purpose,
generally exercised through the familiar ping utility. In ICN, where
routing and forwarding are based on name prefixes, the ability to
determine reachability of names is required.
This document proposes protocol mechanisms for a ping equivalent in
ICN networks. A non-normative appendix suggests useful properties
for an ICN ping client application, analogous to IP ping, that
originates echo requests and process echo replies.
1.1. 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 [RFC2119].
2. Background on IP-Based Ping Operation
In IP-based ping, an IP address is specified, either directly, or via
translation of a domain name through DNS. The ping client
application sends a number of ICMP Echo Request packets with the
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specified IP address as the IP destination address and an IP address
from the client's host as the IP source address.
An ICMP Echo Request is forwarded across the network based on its
destination IP address. If it eventually reaches the destination,
the destination responds by sending back an ICMP Echo Reply packet to
the IP source address from the ICMP Echo Request.
If an ICMP Echo Request does not reach the destination or the Echo
reply is lost, the ping client times out. Any ICMP error messages,
such as "no route to destination", generated by the ICMP Echo Request
message are returned to the client and reported.
3. Ping Functionality Challenges and Opportunities in ICN
In ICN protocols (e.g., NDN and CCNx), the communication paradigm is
based exclusively on named objects. An Interest is forwarded across
the network based on its name. Eventually, it retrieves a content
object either from a producer application or some forwarder's Content
Store (CS).
IP-based ping was built as an add-on on top of an already existing
network architecture. In ICN, we have the opportunity to incorporate
diagnostic mechanisms directly in the network layer protocol, and
hopefully provide more powerful diagnostic capability than can be
realized through the layered ICMP Echo approach.
An ICN network differs from an IP network in at least 4 important
ways:
o IP identifies interfaces to an IP network with a fixed-length
number, and delivers IP packets to one or more interfaces. ICN
identifies units of data in the network with a variable length
name consisting of a list of components.
o An IP-based network depends on the IP packets having source IP
addresses that are used as the destination address for replies.
On the other hand, ICN Interests do not have source addresses and
they are forwarded based on names, which do not refer to a unique
end-point. Data packets follow the reverse path of the Interests
based on hop-by-hop state created during Interest forwarding.
o An IP network supports multi-path, single destination, stateless
packet forwarding and delivery via unicast, a limited form of
multi-destination selected delivery with anycast, and group-based
multi-destination delivery via multicast. In contrast, ICN
supports multi-path and multi-destination stateful Interest
forwarding and multi-destination data delivery to units of named
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data. This single forwarding semantic subsumes the functions of
unicast, anycast, and multicast. As a result, consecutive (or
retransmitted) ICN Interest messages may be forwarded through an
ICN network along different paths, and may be forwarded to
different data sources (e.g., end-node applications, in-network
storage) holding a copy of the requested unit of data. This can
lead to a significant variance in round-trip times, which might
not be desirable in the case of a network troubleshooting
mechanism like ping.
o In the case of multiple Interests with the same name arriving at a
forwarder, a number of Interests may be aggregated in a common
Pending Interest Table (PIT) entry. Depending on the lifetime of
a PIT entry, the round-trip time an Interest-Data exchange might
significantly vary (e.g., it might be shorter than the full round-
trip time to reach the original content producer). To this end,
the round-trip time experienced by consumers might also vary.
These differences introduce new challenges, new opportunities and new
requirements in the design of an ICN ping protocol. Following this
communication model, a ping client should be able to express ping
echo requests with some name prefix and receive responses.
Our goals are the following:
o Test the reachability and the operation of an ICN forwarder.
o Test the reachability of an application (in the sense of whether
Interests for a prefix that it serves can be forwarded to it) and
discover the forwarder with local connectivity to (an instance of)
the application.
o Test whether a specific named object is cached in some on-path CS,
and, if so, return the corresponding forwarder.
o Perform some simple network performance measurements.
To this end, a ping name can represent:
o An administrative name that has been assigned to a forwarder.
o A name that includes an application's namespace as a prefix.
o A named object that might reside in some in-network storage.
In order to provide stable and reliable diagnostics, it is desirable
that the packet encoding of a ping echo request enables the
forwarders to distinguish a ping from a normal Interest, while also
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allowing for forwarding behavior to be as similar as possible to that
of an Interest packet. In the same way, the encoding of a ping echo
reply should allow for forwarder processing similar to that used for
data packets.
The ping protocol should also enable relatively stable round-trip
time measurements. To this end, it is important to have a mechanism
to steer consecutive ping echo requests for the same name towards a
common path.
It is also important, in the case of ping echo requests for the same
name from different sources, to have a mechanism to avoid aggregating
those requests in the PIT. To this end, we need some encoding in the
ping echo requests to make each request for a common name unique, and
hence avoid PIT aggregation and further enabling the exact matching
of a response with a particular ping packet.
4. ICN Ping Echo Packet Formats
Based on the goals mentioned in the previous section, we propose two
types of ping packets, an echo request and an echo reply packet type.
Both these packets follow the CCNx packet format [CCNMessages], where
messages exist within outermost containments (packets).
4.1. ICN Ping Echo Request Packet Format
The format of the ping echo request packet is presented below:
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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
+---------------+---------------+---------------+---------------+
| | | |
| Version | EchoRequest | PacketLength |
| | | |
+---------------+---------------+---------------+---------------+
| | | | |
| HopLimit | Reserved | Flags | HeaderLength |
| | | | |
+---------------+---------------+---------------+---------------+
/ /
/ PathSteering TLV /
/ /
+---------------+---------------+---------------+---------------+
| |
| Echo Request Message TLVs |
| |
+---------------+---------------+---------------+---------------+
Echo Request Packet Format
The existing packet header fields have similar functionality to the
header fields of a CCNx Interest packet. The value of the packet
type field is Echo Request. The exact numeric value of this field
type is to be determined.
Compared to the typical format of a CCNx packet header [CCNMessages],
there is a new optional fixed header TLV added to the packet header:
o A PathSteering hop-by-hop header TLV, which is constructed hop-by-
hop in the echo reply and included in the echo request to steer
consecutive echo requests expressed by a ping client towards a
common forwarding path. An example of such a scheme is presented
in [LIPSIN].
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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
+---------------+---------------+---------------+---------------+
| | |
| PathSteering_Type | PathSteering_Length |
| | |
+---------------+---------------+---------------+---------------+
| |
| PathSteering_Value |
| |
+---------------+---------------+---------------+---------------+
PathSteering TLV
The message of an echo request is presented below:
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
+---------------+---------------+---------------+---------------+
| | |
| MessageType = 1 | MessageLength |
| | |
+---------------+---------------+---------------+---------------+
| |
| Name TLV |
| |
+---------------+---------------+---------------+---------------+
Echo Request Message Format
The echo request message is of type Interest in order to leverage the
Interest forwarding behavior provided by the network. The Name TLV
has the structure described in [CCNMessages]. The name consists of
the prefix that we would like to ping appended with a nonce typed
name component as its last component. The value of this TLV will be
a 64-bit nonce. The purpose of the nonce is to avoid Interest
aggregation and allow client matching of replies with requests. As
described below, the nonce is ignored for CS checking.
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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
+---------------+---------------+---------------+---------------+
| | |
| Nonce_Type | Nonce_Length = 8 |
| | |
+---------------+---------------+---------------+---------------+
| |
| |
| |
| Nonce_Value |
| |
| |
+---------------+---------------+---------------+---------------+
Nonce Typed Name Component TLV
4.2. Ping Echo Reply Packet Format
The format of a ping echo reply packet is presented below:
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
+---------------+---------------+---------------+---------------+
| | | |
| Version | EchoReply | PacketLength |
| | | |
+---------------+---------------+---------------+---------------+
| | | |
| Reserved | Flags | HeaderLength |
| | | |
+---------------+---------------+---------------+---------------+
| |
| PathSteering TLV |
| |
+---------------+---------------+---------------+---------------+
| |
| Echo Reply Message TLVs |
| |
+---------------+---------------+---------------+---------------+
Echo Reply Packet Format
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The header of an echo reply consists of the header fields of a CCNx
Content Object and a hop-by-hop PathSteering TLV. The value of the
packet type field is Echo Reply. The exact numeric value of this
field type is to be determined. The PathSteering header TLV is as
defined for the echo request packet.
A ping echo reply message is of type Content Object, contains a Name
TLV (name of the corresponding echo request), a PayloadType TLV and
an ExpiryTime TLV with a value of 0 to indicate that echo replies
must not be cached by the network.
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
+---------------+---------------+---------------+---------------+
| | |
| MessageType = 2 | MessageLength |
| | |
+---------------+---------------+---------------+---------------+
| |
| Name TLV |
| |
+---------------+---------------+---------------+---------------+
| |
| PayloadType TLV |
| |
+---------------+---------------+---------------+---------------+
| |
| ExpiryTime TLV |
| |
+---------------+---------------+---------------+---------------+
Echo Reply Message Format
The PayloadType TLV is presented below. It is of type
T_PAYLOADTYPE_DATA, and the data schema consists of 2 TLVs: 1) the
name of the sender of this reply (with the same structure as a CCNx
Name TLV), 2) the sender's signature of their own name (with the same
structure as a CCNx ValidationPayload TLV), 3) a TLV with return
codes to indicate what led to the generation of this reply (i.e.,
existence of a local application, a CS hit or a match with a
forwarder's administrative name as specified in Section 5).
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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
+---------------+---------------+---------------+---------------+
| | |
| T_PAYLOADTYPE_DATA | Length |
| | |
+---------------+---------------+---------------+---------------+
/ /
/ Sender's Name TLV /
/ /
+---------------+---------------+---------------+---------------+
/ /
/ Sender's Signature TLV /
/ /
+---------------+---------------+---------------+---------------+
/ /
/ Echo Reply Code TLV /
/ /
+---------------+---------------+---------------+---------------+
Echo Reply Message Format
The goal of including the name of the sender in the echo reply is to
enable the user to reach this entity directly to ask for further
management/administrative information using generic Interest-Data
exchanges after a successful verification of the sender's name.
The structure of the Echo Reply Code TLV is presented below (16-bit
value). The potential values are the following:
o 1: Indicates that the target name matched the administrative name
of a forwarder.
o 2: Indicates that the target name matched a prefix served by an
application.
o 3: Indicates that the target name matched the name of an object in
a forwarder's CS.
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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
+---------------+---------------+---------------+---------------+
| | |
| Echo_Reply_Code_Type | Echo_Reply_Code_Length = 2 |
| | |
+---------------+---------------+---------------+---------------+
| |
| Echo_Reply_Code_Value |
+---------------+---------------+---------------+---------------+
Echo Reply Code TLV
5. Forwarder Handling
When a forwarder receives an echo request, it will first extract the
message's base name (i.e., the request name with the Nonce name
component excluded).
In some cases, the forwarder will originate an echo reply, sending
the reply downstream through the face on which the echo request was
received. An echo reply will include the forwarder's own name and
signature, and, the appropriate echo reply code based on the
condition that triggered the reply generation. It will also include
a path steering TLV, initially a null value (since the echo reply
originator does not forward the request and, thus, does not make a
path choice).
The forwarder generates an echo reply in the following cases:
o Assuming that a forwarder has been given one or more
administrative names, the echo request base name exactly matches
any of the forwarder's administrative name(s).
o The echo request's base name exactly matches the name of a
content-object residing in the forwarder's CS (unless the ping
client application has chosen not to receive replies due to CS
hits as specified in Appendix A).
o The echo request base name matches (in a Longest Prefix Match
manner) a FIB entry with an outgoing face referring to a local
application.
If none of the conditions to reply to the echo request are met, the
forwarder will attempt to forward the echo request upstream based on
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the path steering value (if present) the results of the FIB LPM
lookup and PIT creation (based on the name including the nonce typed
name component). If no valid next-hop is found, an InterestReturn is
sent downstream (as with a failed attempt to forward an ordinary
Interest).
A received echo reply will be matched to an existing PIT entry as
usual. On the reverse path, the path steering TLV of an echo reply
will be updated by each forwarder to encode its next-hop choice.
When included in subsequent echo requests, this path steering TLV
will allow the forwarders to steer the requests along the same path.
6. Security Considerations
To avoid reflection attacks, where a compromised forwarder includes
in the reply the name of a victim forwarder to redirect the future
administrative traffic towards the victim, the forwarder that
generates a reply has to sign the name included in the payload. In
this way, the client is able to verify that the included name is
legitimate and refers to the forwarder that generated the reply.
Alternatively, the forwarder can include in the reply payload their
routable prefix(es) encoded as a signed NDN Link Object [SNAMP].
7. Acknowledgements
The authors would like to thank Mark Stapp for the fruitful
discussion on the objectives of ICN ping protocol.
8. References
8.1. Normative References
[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>.
8.2. Informative References
[CCNMessages]
Mosko, M., Solis, I., and C. Wood, "CCNx Messages in TLV
Format.", 2016, <https://tools.ietf.org/html/draft-irtf-
icnrg-ccnxmessages-03>.
[LIPSIN] Jokela, P. and et al, "LIPSIN: line speed publish/
subscribe inter-networking, ACM SIGCOMM Computer
Communication Review 39.4: 195-206", 2009.
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[SNAMP] Afanasyev, A. and et al, "SNAMP: Secure namespace mapping
to scale NDN forwarding, IEEE Conference on Computer
Communications Workshops (INFOCOM WKSHPS)", 2015.
Appendix A. Ping Client Application (Consumer) Operation
This section is an informative appendix regarding the proposed ping
client operation.
The ping client application is responsible for generating echo
requests for prefixes provided by users.
When generating a series of echo requests for a specific name, the
first echo request will typically not include a PathSteering TLV,
since no TLV value is known. After an echo reply containing a
PathSteering TLV is received, each subsequent echo request can
include the received path steering value in the PathSteering header
TLV to drive the requests towards a common path as part of checking
the network performance. To discover more paths, a client can omit
the path steering TLV in future requests. Moreover, for each new
ping echo request, the client has to generate a new nonce and record
the time that the request was expressed. It will also set the
lifetime of an echo request, which will have semantics similar to the
lifetime of an Interest.
Moreover, the client application might like not to receive echo
replies due to CS hits. A mechanism to achieve that would be to use
a Content Object Hash Restriction TLV with a value of 0 in the
payload of an echo request message.
When it receives an echo reply, the client would typically match the
reply to a sent request and compute the round-trip time of the
request. It should parse the PathSteering value and decode the
reply's payload to parse the the sender's name and signature. The
client should verify that both the received message and the
forwarder's name have been signed by the key of the forwarder, whose
name is included in the payload of the reply (by fetching this
forwarder's public key and verifying the contained signature). The
client can also decode the Echo Reply Code TLV to understand the
condition that triggered the generation of the reply.
In the case that an echo reply is not received for a request within a
certain time interval (lifetime of the request), the client should
time-out and send a new request with a new nonce value up to some
maximum number of requests to be sent specified by the user.
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Authors' Addresses
Spyridon Mastorakis
UCLA
Los Angeles, CA
US
Email: mastorakis@cs.ucla.edu
Jim Gibson
Cisco Systems
Cambridge, MA
US
Email: gibson@cisco.com
Ilya Moiseenko
Cisco Systems
Cambridge, MA
US
Email: iliamo@mailbox.org
Ralph Droms
Cisco Systems
Cambridge, MA
US
Email: rdroms.ietf@gmail.com
Dave Oran
Cisco Systems
Cambridge, MA
US
Email: daveoran@orandom.net
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