Protocol information
RFC 661
| Document | Type |
RFC
- Unknown
(November 1974)
Updated by RFC 694
|
|
|---|---|---|---|
| Authors | |||
| Last updated | 2013-03-02 | ||
| RFC stream | Legacy stream | ||
| Formats | |||
| IESG | Responsible AD | (None) | |
| Send notices to | (None) |
RFC 661
Network Working Group J. Postel
Request for Comments: 661 SRI-ARC
NIC: 31203 November 1974
Protocol Information
This file contains information on the various protocols in the ARPA
Network. An effort will be made to keep the information current, but
this depends on the cooperation of the users of this file to convey
any information about protocol developments, or corrections to this
information to Jon Postel at SRI-ARC.
This is a compendium of all the protocol related activity and most of
this activity is with experimental protocols, for those protocols,
which are official standards the designation "[Official]" will be
appended to the name.
Much of the documentation of protocols appears as Requests for
Comments (RFCs) and many of these are available online. When a
document is accessible online, a pointer to that source will be
given. Also note that recent RFCs are online at Office-1 in
directory <NETINFO> with names of the form RFCnnn.TXT where nnn is
replaced by the RFC number.
This file is online as:
Pathname: [SRI-ARC] <POSTEL> PROTOCOL-INFORMATION.TXT
and also [SRI-ARC] <POSTEL> PROTOCOL-INFORMATION.NLS
IMP-IMP
surface
Contact:
McKenzie, Alex. (MCKENZIE@BBN)
Documents:
Heart, F. et. Al. "The Interface Message Processor for the
ARPA Computer Network," AFIPS Conference Proceedings,
36:551-567, SJCC 1970.
People:
John McQuillan (MCQUILLAN@BBN)
Postel [Page 1]
RFC 661 November 1974
Schedule:
Recent developments:
satellite
Contact:
Randy Rettberg (RETTEBERG@BBN)
Documents:
People:
Kahn, Robert. (Kahn@ISI)
Schedule:
Recent developments:
IMP-HOST
IMP-Host [Official]
Contact:
McKenzie, A. (McKenzie@BBN)
Documents:
"Specification for the Interconnection of a Host and an
IMP," BBN Report 1822, Revised March 1974.
McQuillan, J. "Host Alive/Dead Logic," BBN Memorandum to
Technical Liaisons, 18-July-74.
Burchfiel, J. "Ready Line Philosophy and Implementation,"
NIC 30872, RFC 642, 5-July-74.
Walden, D. "Some Changes to the IMP and the IMP/HOST
Interface," RFC 660, 23-Oct-74.
[Office-1 <NETINFO> RFC660.TXT
People:
McKenzie (MCKENZIE@BBN)
Postel [Page 2]
RFC 661 November 1974
Walden (WALDEN@BBN)
Postel (POSTEL@SRI-ARC)
Burchfiel (BURCHFIEL@BBN)
McQuillan (MCQUILLAN@BBN)
Schedule:
Recent developments:
The "link number" filed has been extended from 8 to 12 bits
and renamed the "message identification" field. Message
type 6 now is used to indicate a reason for a type 7
(destination dead) message. (See BBN1822).
There has been some recent changes to the Ready line
interpretation by the IMP for deciding the alive/dead status
of a host.
Important changes to the IMP and IMP/HOST interface
announced in RFC 660 23-Oct-74.
HOST-HOST
ncp - standard host-to-host [Official]
Contact:
Postel, Jon. (POSTEL@SRI-ARC)
Documents:
McKenzie, A. "Host/Host Protocol for the ARPA Network," NIC
8246. Jan 1972.
Postel, J. "Assigned Link Numbers," RFC604, NIC21186, 26-
Dec-73.
People:
Postel, Jon. (POSTEL@SRI-ARC)
McKenzie, Alex. (MCKENZIE@BBN)
Schedule:
Postel [Page 3]
RFC 661 November 1974
Recent developments:
ncp - standard host-to-host [Experimental]
Contact:
Postel, Jon. (POSTEL@SRI-ARC)
Documents:
McKenzie, A. "Host/Host Protocol for the ARPA Network," NICE
3246. Jan 1972.
Postel, J. "Assigned Link Numbers," RFC604, NIC22186, 26-
Dec-73.
Burchfiel, et. Al. "Tip-Tenex Reliability Improvements" RFC
636 NIC 30490 June 1974.
People:
Postel, Jon. (POSTEL@SRI-ARC)
McKenzie, Alex. (MCKENZIE@BBN)
Burchfiel, Jerry (BURCHFIEL@BBN)
Walden, Dave (WALDEN@BBN)
Schedule:
Recent developments:
The BBN TIP and TENEX groups have specified and are
implementing additional protocol commands with the intention
of providing better reliability and survivability over
system malfunctions. The additional protocol commands are
for cleaning up partly closed connections and
resynchronizing the allocation values on open connections.
(See RFC 636).
tcp - Transmission Control Protocol
Contact:
Cerf, Vint. (CERF@ISI)
Postel [Page 4]
RFC 661 November 1974
Documents:
Cert, V. and R. Kahn. "A Protocol for Packet Network
Intercommunication," IEEE Transactions on Communication Vol
COM-22 No 5, May 1974.
[parc-maxc] <cerf> TCPSPEC3.NLS
Mader, E. "A Protocol Experiment," RFC 700, NIC 31020.
[ISI] <CERF> TCP-CHANGES.
People:
Cerf at SU-DSL
Tomlinson at BBN
Kirstein at London
Postel at SRI-ARC
Schedule:
Some experiments now running. Implementation of full protocol
to begin by 15-Oct-74.
Recent developments:
Specification completed August 4th, but some work still in
progress on handling of single message conversations. A new
sequencing scheme (proposed by Tomlinson) may be utilized. The
addressing field is now used as 4-bit format, 4-bit network, 16
bit TCP, and 24 bit process&port. Crocker has suggested a 64-
bit path address to be parsed and reformatted by the gateways
along the route. There is reluctance to experiment with too
many things at one though.
(28-Oct-74) A file indicating some of the changes in the
specifications since the 4-Aug-74 document is now available as
[ISI] <CERF> TCP-CHANGES. The areas of change are "Initial
Sequence Number", "Socket definition", "Additional user System
Calls", "Packet format", and "Discussion of opening and closing
(SYN,REL)".
(23-NOV-74) Specifications for test implementation are now said
to be ready on 1-DEC-74, and an implementation completed by 1-
FEB-74.
Postel [Page 5]
RFC 661 November 1974
nvp - Network Voice Protocol
Contact:
Cohen, Danny. (COHEN@ISI)
Documents:
The current specification is in an online file at isi in the
directory voice as nvp.lst.
Pathname = [isi] <voice> nvp.lst
People:
Recent developments:
New specification document available (10-Oct-74).
"Specifications for the Network Voice Protocol (NVP)" NSC
Note 43
packet radio
Contact:
Kahn, Robert. (KAHN@ISI)
Documents:
People:
Schedule:
Recent developments:
Network Debugging Protocol
Contact:
Eric Mader (Mader@BBN)
Documents:
Mader, E. "Network Debugging Protocol," NIC 30873, RFC 643,
July-74.
People:
Postel [Page 6]
RFC 661 November 1974
Schedule:
Recent Developments:
This is a protocol for a PDP-11 cross-network debugger.
HOST-FRONTEND
Host-Front End
Contact:
Michael Padlipsky (MAP@CASE-10)
Documents:
Padlipsky, M. "A Proposed Protocol for Connecting Host
Computers to ARPA-Like Networks via Front-End Processors,"
RFC 647, NIC 31117, 12-Nov-74.
[Office-1] <NETINFO>RFC647.TXT
People:
Padlipsky at MITRE Washington (MAP@CASE-10)
Postel at SRI-ARC (POSTEL@SRI-ARC)
McConnell at Illiac (JOHN@I4-TENEX)
Schedule:
Recent developments:
This is a suggested simple protocol for connecting to host
to front end computers, which are in turn connected to the
network.
PROCESS-PROCESS
ICP - Initial Connection Protocol [Official]
Contact:
Postel, Jon. [POSTEL@SRI-ARC)
Postel [Page 7]
Internet-Draft AURA Metrics & Methods January 2018
"discoverable" hosts or routers. Parallel subpaths contained
within clouds cannot be discovered. The assessment methods only
discover hosts or routers on the path that decrement TTL or Hop
Count, or cooperate with interrogation protocols. The presence of
tunnels and nested tunnels further complicate assessment by hiding
hops.
Hop: Although the [RFC2330] definition was a link-host pair, only
hosts are discoverable or have the capability to cooperate with
interrogation protocols where link information may be exposed.
The refined definition of Route metrics begins in the sections that
follow.
2. Scope
The purpose of this memo is to add new route metrics and methods of
measurement to the existing set of IPPM metrics.
The scope is to define route metrics that can identify the path taken
by a packet or a flow traversing the Internet between any two hosts.
<@@@@ or only hosts communicating at the IP layer? We would have to
re-define the Src and Dst Parameters and Host Identity if we
generalize beyond IP. Should we include MPLS and the capabilities of
[RFC8029], with explicit multipath identification (section 6.2.6)? >
Also, to specify a framework for active methods of measurement which
use the techniques described in [PT] at a minimum, and a framework
for hybrid active-passive methods of measurement, such as the Hybrid
Type I method [RFC7799] described in
[I-D.ietf-ippm-ioam-data](intended only for single administrative
domains), which do not rely on ICMP and provide a protocol for
explicit interrogation of nodes on a path. Combinations of active
methods and hybrid active-passive methods are also in-scope.
Further, this memo provides additional analysis of the round-trip
delay measurements made possible by the methods, in an effort to
discover more details about the path, such as the link technology in
use.
This memo updates Section 5 of [RFC2330] in the areas of path-related
terminology and path description, primarily to include the
possibility of parallel subpaths between a given Source and
Destination address pair (possibly resulting from Equal Cost Multi-
Path (ECMP) and Unequal Cost Multi-Path (UCMP) technologies).
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There are several simple non-goals of this memo. There is no attempt
to assess the reverse path from any host on the path to the host
attempting the path measurement. The reverse path contribution to
delay will be that experienced by ICMP packets (in active methods),
and may be different from UDP or TCP packets. Also, the round trip
delay will include an unknown contribution of processing time at the
host that generates the ICMP response. Therefore, the ICMP-based
active methods are not supposed to yield accurate, reproducible
estimations of the round-trip delay that UDP or TCP packets will
experience.
3. Route Metric Terms and Definitions
This section sets requirements for the following components to
support the Route Metric:
Note: the definitions concentrate on the IP-layer, but can be
extended to other layers, and follow agreements on the scope.
Host Identity For hosts communicating at the IP-layer, the globally
routable IP address(es) which the host uses when communicating
with other hosts under normal or error conditions. The Host
Identity revealed (and its connection to a Host Name through
reverse DNS) determines whether interfaces to parallel links can
be associated with a single host, or appear to be unique hosts.
Discoverable Host For hosts communicating at the IP-layer,
compliance with Section 3.2.2.4 of [RFC1122] when discarding a
packet due to TTL or Hop Limit Exceeded condition, MUST result in
sending the corresponding Time Exceeded message (containing a form
of host identity) to the source. This requirement is also
consistent with section 5.3.1 of [RFC1812] for routers.
Cooperating Host Hosts MUST respond to direct queries for their host
identity as part of a previously agreed and established
interrogation protocol. Hosts SHOULD also provide information
such as arrival/departure interface identification, arrival
timestamp, and any relevant information about the host or specific
link which delivered the query to the host.
Hop A Hop MUST contain a Host Identity, and MAY contain arrival and/
or departure interface identification.
3.1. Formal Name
Type-P-Route-Ensemble-Method-Variant, abbreviated as Route Ensemble.
Note that Type-P depends heavily on the chosen method and variant.
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3.2. Parameters
This section lists the REQUIRED input factors to specify a Route
metric.
o Src, the IP address of a host
o Dst, the IP address of a host
o i, the TTL or Hop Limit of a packet sent from the host at Src to
the host at Dst.
o MaxHops, the maximum value of i used, (i=1,2,3,...MaxHops).
o T0, a time (start of measurement interval)
o Tf, a time (end of measurement interval)
o T, the host time of a packet as measured at MP(Src), meaning
Measurement Point at the Source.
o Ta, the host time of a reply packet's *arrival* as measured at
MP(Src), assigned to packets that arrive within a "reasonable"
time (see parameter below).
o Tmax, a maximum waiting time for reply packets to return to the
source, set sufficiently long to disambiguate packets with long
delays from packets that are discarded (lost), thus the
distribution of delay is not truncated.
o F, the number of different flows simulated by the method and
variant.
o flow, the stream of packets with the same n-tuple of designated
header fields that (when held constant) results in identical
treatment in a multi-path decision (such as that taken in load
balancing).
o Type-P, the complete description of the packets for which this
assessment applies (including the flow-defining fields).
3.3. Metric Definitions
This section defines the REQUIRED measurement components of the Route
metrics (unless otherwise indicated):
M, the total number of packets sent between T0 and Tf.
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N, the smallest value of i needed for a packet to be received at Dst
(sent between T0 and Tf).
Nmax, the largest value of i needed for a packet to be received at
Dst (sent between T0 and Tf). Nmax may be equal to N.
Next, define a *singleton* definition for a Hop on the path, with
sufficient indexes to identify all Hops identified in a measurement
interval.
A Hop, designated h(i,j), the IP address and/or identity of one of j
Discoverable Hosts (or Cooperating Hosts) that are i hops away from
the host with IP address = Src during the measurement interval, T0 to
Tf. As defined above, a Hop singleton measurement MUST contain a
Host Identity, hid(i,j), and MAY contain one or more of the following
attributes:
o a(i,j) Arrival Interface ID
o d(i,j) Departure Interface ID
o t(i,j) Arrival Timestamp (where t(i,j) is ideally supplied by the
hop, or approximated from the sending time of the packet that
revealed the hop)
o Measurements of Round Trip Delay (for each packet that reveals the
same Host Identity and attributes, but not timestamp of course,
see next section)
Now that Host Identities and related information can be positioned
according to their distance from the host with address Src in hops,
we introduce two forms of Routes:
A Route Ensemble is defined as the combination of all routes
traversed by different flows from the host at Src address to the host
at Dst address. The route traversed by each flow (with addresses Src
and Dst, and other fields which constitute flow criteria) is a member
of the ensemble and called a Member Route.
Using h(i,j) and components and parameters, further define:
A Member Route is an ordered graph {h(1,j), ... h(Nj, j)} in the
context of a single flow, where h(i-1, j) and h(i, j) are by 1 hop
away from each other and Nj=Dst is the minimum TTL value needed by
the packet on Member Route j to reach Dst. Member Routes must be
unique. This uniqueness requires that any two Member routes j and k
that are part of the same Route Ensemble differ either in terms of
minimum hop count Nj and Nk to reach the destination Dst, or, in the
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case of identical hop count Nj=Nk, they have at least one distinct
hop: h(i,j) != h(i, k) for at least one i (i=1..Nj).
The Route Ensemble from Src to Dst, during the measurement interval
T0 to Tf, is the aggregate of all m distinct Member Routes discovered
between the two hosts with Src and Dst addresses. More formally,
with the host having address Src omitted:
Route Ensemble = {
{h(1,1), h(2,1), h(3,1), ... h(N1,1)=Dst},
{h(1,2), h(2,2), h(3,2),..., h(N2,2)=Dst},
...
{h(1,m), h(2,m), h(3,m), ....h(Nm,m)=Dst}
}
where the following conditions apply: i <= Nj <= Nmax (j=1..m)
Note that some h(i,j) may be empty (null) in the case that systems do
not reply (not discoverable, or not cooperating).
h(i-1,j) and h(i,j) are the Hops on the same Member Route one hop
away from each other.
Hop h(i,j) may be identical with h(k,l) for i!=k and j!=l ; which
means there may be portions shared among different Member Routes
(parts of various routes may overlap).
3.4. Related Round-Trip Delay and Loss Definitions
RTD(i,j,T) is defined as a singleton of the [RFC2681] Round-trip
Delay between the host with IP address = Src and the host at Hop
h(i,j) at time T.
RTL(i,j,T) is defined as a singleton of the [RFC6673] Round-trip Loss
between the host with IP address = Src and the host at Hop h(i,j) at
time T.
3.5. Discussion
Depending on the way that Host Identity is revealed, it may be
difficult to determine parallel subpaths between the same pair of
hosts (i.e. multiple parallel links). It is easier to detect
parallel subpaths involving different hosts.
o If a pair of discovered hosts identify two different IP addresses,
then they will appear to be different hosts.
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o If a pair of discovered hosts identify two different IP addresses,
and the IP addresses resolve to the same host name (in the DNS),
then they will appear to be the same hosts.
o If a discovered host always replies using the same IP address,
regardless of the interface a packet arrives on, then multiple
parallel links cannot be detected at the IP layer.
o If parallel links between routers are aggregated below the IP
layer, In other words, all links share the same pair of IP
addresses, then the existence of these parallel links can't be
detected at IP layer.
Section 9.2 of [RFC2330] describes Temporal Composition of metrics,
and introduces the possibility of a relationship between earlier
measurement results and the results for measurement at the current
time (for a given metric). If this topic is investigated further,
there may be some value in establishing a Temporal Composition
relationship for Route Metrics. However, this relationship does not
represent a forecast of future route conditions in any way.
When a route assessment employs packets at the IP layer (for
example), the reality of flow assignment to parallel subpaths
involves layers above IP. Thus, the measured Route Ensemble is
applicable to IP and higher layers (as described in the methodology's
packet of Type-P and flow parameters).
@@@@ Editor's Note: There is an opportunity to investigate and
discuss the RFC 2330 notion of equal treatment for a class of
packets, "...very useful to know if a given Internet component treats
equally a class C of different types of packets", as it applies to
Route measurements. Knowledge of "class C" parameters on a path
potentially reduces the number of flows required for a given method.
3.6. Reporting the Metric
@@@@ to be provided
4. Route Assessment Methodologies
There are two classes of methods described in this section, active
methods relying on the reaction to TTL or Hop Limit Exceeded
condition to discover hosts on a path, and Hybrid active-passive
methods that involve direct interrogation of cooperating hosts
(usually within a single domain). Description of these methods
follow.
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@@@@ Editor's Note: We need to incorporate description of Type-P
packets (with the flow parameters) used in each method below.
4.1. Active Methodologies
We have chosen to describe the method based on that employed in
current open source tools, thereby providing a practical framework
for further advanced techniques to be included as method variants.
This method is applicable to use across multiple administrative
domains.
Paris-traceroute [PT] provides some measure of protection from path
variation generated by ECMP load balancing, and it ensures traceroute
packets will follow the same path in 98% of cases according to
[SCAMPER]. If it is necessary to find every path possible between
two hosts, Paris-traceroute provides "exhaustive" mode while scamper
provides "tracelb" (stands for traceroute load balance).
The Type-P of packets used could be ICMP (as ones in the original
traceroute), UDP and TCP. The later are used when a particular
characteristic is needed to verify, such as filtering or traffic
shaping on specific ports (i.e., services).
The advanced route assessment methods used in Paris-traceroute [PT]
keep the critical fields constant for every packet to maintain the
appearance of the same flow. Since route assessment can be conducted
using TCP, UDP or ICMP packets, this method REQUIRES the Diffserv
field, the protocol number, IP source and destination addresses, and
the port settings for TCP or UDP kept constant. For ICMP probes, the
method additionally REQUIRES the type, code, and ICMP checksum
constant; which take the same position in the header of an IP packet,
e.g., bytes 20 to 23 when the header IP has no options.
Maintaining a constant checksum in ICMP is most challenging because
the ICMP Sequence Number is part of the calculation. The advanced
traceroute method requires calculations using the IP Sequence Number
Field and the Identifier Field, yielding a constant ICMP checksum in
successive packets. For an example of calculations to maintain a
constant checksum, see Appendix A of [RFC7820], where revision of a
timestamp field is complemented by modifying the 2 octet checksum
complement field (these fields take the roles of the ICMP Sequence
Number Identifier Fields, respectively).
For TCP and UDP packets, the checksum must also be kept constant.
Therefore, the first four bytes of UDP (or TCP) data field are
modified to compensate for fields that change from packet to packet.
Note: other variants of advanced traceroute are planned be described.
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Finally, the return path is also important to check. Taking into
account that it is an ICMP time exceeded (during transit) packet, the
source and destination IP are constant for every reply. Then, we
should consider the fields in the first 32 bits of the protocol on
the top of IP: the type and code of ICMP packet, and its checksum.
Again, to maintain the ICMP checksum constant for the returning
packets, we need to consider the whole ICMP message. It contains the
IP header of the discarded packet plus the first 8 bytes of the IP
payload; that is some of the fields of TCP header, the UDP header
plus four data bytes, the ICMP header plus four bytes. Therefore,
for UDP case the data field is used to maintain the ICMP checksum
constant in the returning packet. For the ICMP case, the identifier
and sequence fields of the sent ICMP probe are manipulated to be
constant. The TCP case presents no problem because its first eight
bytes will be the same for every packet probe.
Formally, to maintain the same flow in the measurements to a certain
hop, the Type-P-Route-Ensemble-Method-Variant packets should be[PT]:
o TCP case: Fields Src, Dst, port-Src, port_Dst, and Diffserv Field
should be the same.
o UDP case: Fields Src, Dst, port-Src, port-Dst, and Diffserv Field
should be the same, the UDP-checksum should change to maintain
constant the IP checksum of the ICMP time exceeded reply. Then,
the data length should be fixed, and the data field is used to
fixing it (consider that ICMP checksum uses its data field, which
contains the original IP header plus 8 bytes of UDP, where TTL, IP
identification, IP checksum, and UDP checksum changes).
o ICMP case: The Data field should compensate variations on TTL, IP
identification, and IP checksum for every packet.
Then, the way to identify different hops and attempts of the same
flow is:
o TCP case: The IP identification field.
o UDP case: The IP identification field.
o ICMP case: The IP identification field, and ICMP Sequence number.
4.2. Hybrid Methodologies
The Hybrid Type I methods provide an alternative method for Route
Member assessment. As mentioned in the Scope section,
[I-D.ietf-ippm-ioam-data] provides a possible set of data fields that
would support route identification.
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In general, nodes in the measured domain would be equipped with
specific abilities:
1. The ingress node adds one or more fields to the measurement
packets, and identifies to other nodes in the domain that a route
assessment will be conducted using one or more specific packets.
The packets typically originate from a host outside the domain,
and constitute normal traffic on the domain.
2. Each node visited by the specific packet within in the domain
identifies itself in a data field of the packet (the field has
been added for this purpose).
3. When a measurement packet reaches the edge node of the domain,
the edge node adds its identity to the list, removes all the
identities from the packet, forwards the packet onward, and
communicates the ordered list of node identities to the intended
receiver.
In addition to node identity, nodes may also identify the ingress and
egress interfaces utilized by the tracing packet, the time of day
when the packet was processed, and other generic data (as described
in section 4 of [I-D.ietf-ippm-ioam-data]).
4.3. Combining Different Methods
In principle, there are advantages if the entity conducting Route
measurements can utilize both forms of advanced methods (active and
hybrid), and combine the results. For example, if there are hosts
involved in the path that qualify as Cooperating Hosts, but not as
Discoverable Hosts, then a more complete view of hops on the path is
possible when a hybrid method (or interrogation protocol) is applied
and the results are combined with the active method results collected
across all other domains.
In order to combine the results of active and hybrid/interrogation
methods, the network hosts that are part of a domain supporting an
interrogation protocol have the following attributes:
1. Hosts at the ingress to the domain SHOULD be both Discoverable
and Cooperating, and SHOULD reveal the same Host Identity in
response to both active and hybrid methods.
2. Any Hosts within the domain that are both Discoverable and
Cooperating SHOULD reveal the same Host Identity in response to
both active and hybrid methods.
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3. Hosts at the egress to the domain SHOULD be both Discoverable and
Cooperating, and SHOULD reveal the same Host Identity in response
to both active and hybrid methods.
When Hosts follow these requirements, it becomes a simple matter to
match single domain measurements with the overlapping results from a
multidomain measurement.
In practice, Internet users do not typically have the ability to
utilize the OAM capabilities of networks that their packets traverse,
so the results from a remote domain supporting an interrogation
protocol would not normally be accessible. However, a network
operator could combine interrogation results from their access domain
with other measurements revealing the path outside their domain.
5. Background on Round-Trip Delay Measurement Goals
The aim of this method is to use packet probes to unveil the paths
between any two end-hosts of the network. Moreover, information
derived from RTD measurements might be meaningful to identify:
1. Intercontinental submarine links
2. Satellite communications
3. Congestion
4. Inter-domain paths
This categorization is widely accepted in the literature and among
operators alike, and it can be trusted with empirical data and
several sources as ground of truth (e.g., [RTTSub] [bdrmap][IDCong]).
The first two categories correspond to the physical distance
dependency on Round Trip Delay (RTD) while the last one binds RTD
with queueing delay on routers. Due to the significant contribution
of propagation delay in long distance hops, RTD will be at least
100ms on transatlantic hops, depending on the geolocation of the
vantage points. Moreover, RTD is typically greater than 480ms when
two hops are connected using geostationary satellite technology
(i.e., their orbit is at 36000km). Detecting congestion with latency
implies deeper mathematical understanding since network traffic load
is not stationary. Nonetheless, as the first approach, a link seems
to be congested if after sending several traceroute probes, it is
possible to detect congestion observing different statistics
parameters (e.g., see [IDCong]).
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6. Tools to Measure Delays in the Internet
Internet routing is complex because it depends on the policies of
thousands Autonomous Systems (AS). While most of the routers perform
load balancing on flows using Equal Cost Multiple Path (ECMP), a few
still divide the workload through packet-based techniques. The
former scenario is defined according to [RFC2991] while the latter
generates a round-robin scheme to deliver every new outgoing packet.
ECMP keeps flow state in the router to ensure every packet of a flow
is delivered by the same path, and this avoids increasing the packet
delay variation and possibly producing overwhelming packet reordering
in TCP flows.
Taking into account that Internet protocol was designed under the
"end-to-end" principle, the IP payload and its header do not provide
any information about the routes or path necessary to reach some
destination. For this reason, the well-known tool traceroute was
developed to gather the IP addresses of each hop along a path using
the ICMP protocol [RFC0792]. Besides, traceroute adds the measured
RTD from each hop. However, the growing complexity of the Internet
makes it more challenging to develop accurate traceroute
implementation. For instance, the early traceroute tools would be
inaccurate in the current network, mainly because they were not
designed to retain flow state. However, evolved traceroute tools,
such as Paris-traceroute [PT] [MLB] and Scamper [SCAMPER], expect to
encounter ECMP and achieve more accurate results when they do.
Paris-traceroute-like tools operate in the following way: every
packet should follow the same path because the sensitive fields of
the header are controlled to appear as the same flow. This means
that source and destination IP addresses, source and destination port
numbers are the same in every packet. Additionally, Differentiated
Services Code Point (DSCP), checksum and ICMP code should remain
constant since they may affect the path selection.
Today's traceroute tools can send either UDP, TCP or ICMP packet
probes. Since ICMP header does not include transport layer
information, there are no fields for source and destination port
numbers. For this reason, these tools keep constant ICMP type, code,
and checksum fields to generate a kind of flow. However, the
checksum may vary in every packet, therefore when probes use ICMP
packets, ICMP Identifier and Sequence Number are manipulated to
maintain constant checksum in every packet. On the other hand, when
UDP probes are generated, the expected variation in the checksum of
each packet is again compensated by manipulating the payload.
Paris-traceroute allows its users to measure RTD in every hop of the
path for a particular flow. Furthermore, either Paris-traceroute or
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Scamper is capable of unveiling the many available paths between a
source and destination (which are visible to this method). This task
is accomplished by repeating complete traceroute measurements with
different flow parameters for each measurement. The Framework for IP
Performance Metrics (IPPM) ([RFC2330] updated by[RFC7312]) has the
flexibility to require that the round-trip delay measurement
[RFC2681] uses packets with the constraints to assure that all
packets in a single measurement appear as the same flow. This
flexibility covers ICMP, UDP, and TCP. The accompanying methodology
of [RFC2681] needs to be expanded to report the sequential hop
identifiers along with RTD measurements, but no new metric definition
is needed.
7. RTD Measurements Statistics
Several articles have shown that network traffic presents a self-
similar nature [SSNT] [MLRM] which is accountable for filling the
queues of the routers. Moreover, router queues are designed to
handle traffic bursts, which is one of the most remarkable features
of self-similarity. Naturally, while queue length increases, the
delay to traverse the queue increases as well and leads to an
increase on RTD. Due to traffic bursts generate short-term overflow
on buffers (spiky patterns), every RTD only depicts the queueing
status on the instant when that packet probe was in transit. For
this reason, several RTD measurements during a time window could
begin to describe the random behavior of latency. Loss must also be
accounted for in the methodology.
To understand the ongoing process, examining the quartiles provides a
non-parametric way of analysis. Quartiles are defined by five
values: minimum RTD (m), RTD value of the 25% of the Empirical
Cumulative Distribution Function (ECDF) (Q1), the median value (Q2),
the RTD value of the 75% of the ECDF (Q3) and the maximum RTD (M).
Congestion can be inferred when RTD measurements are spread apart,
and consequently, the Inter-Quartile Range (IQR), the distance
between Q3 and Q1, increases its value.
This procedure requires to compute quartile values "on the fly" using
the algorithm presented in [P2].
This procedure allow us to update the quartiles value whenever a new
measurement arrives, which is radically different from classic
methods of computing quartiles because they need to use the whole
dataset to compute the values. This way of calculus provides savings
in memory and computing time.
To sum up, the proposed measurement procedure consists in performing
traceroutes several times to obtain samples of the RTD in every hop
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from a path, during a time window (W) and compute the quantiles for
every hop. This could be done for a single path flow or for every
detected path flow.
Even though a particular hop may be understood as the amount of hops
away from the source, a more detailed classification could be used.
For example, a possible classification may be identify ICMP Time
Exceeded packets coming from the same routers to those who have the
same hop distance, IP address of the router which is replying and TTL
value of the received ICMP packet.
Thus, the proposed methodology is based on this algorithm:
================================================================
1 input: W (window time of the measurement)
2 i_t (time between two measurements)
3 E (True: exhaustive, False: a single path)
4 Dst (destination IP address)
5 output: Qs (quartiles for every hop and alt in the path(s) to Dst)
----------------------------------------------------------------
6 T <? start_timer(W)
7 while T is not finished do:
8 | start_timer(i_t)
9 | RTD(hop,alt) = advanced-traceroute(Dst,E)
10 | for each hop and alt in RTD do:
11 | | Qs[Dst,hop,alt] <? ComputeQs(RTD(hop,alt))
12 | done
13 | wait until i_t timer is expired
14 done
15 return (Qs)
================================================================
In line 9 the advance-traceroute could be either Paris-traceroute or
Scamper, which will use "exhaustive" mode or "tracelb" option if E is
set True, respectively. The procedure returns a list of tuples
(m,Q1,Q2,Q3,M) for each intermediate hop in the path towards the Dst.
Additionally, it could also return path variations using "alt"
variable.
8. Conclusions
Combining the method proposed in Section 4 and statistics in
Section 7, we can measure the performance of paths interconnecting
two endpoints in Internet, and attempt the categorization of link
types and congestion presence based on RTD.
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RFC 661 November 1974
Documents:
Postel, J. "Official Initial Connection Protocol," NIC 7101
11-June-71.
Wolfe, S. [no title] RFC 202 NIC 7155 26-July-71.
Postel, J. "Official Telnet-Logger Initial Connection
Protocol," NIC 7103 15-June-71.
People:
Postel at Sri-arc
Schedule:
Recent developments:
Telnet
Old Telnet
Contact:
Postel, Jon. (POSTEL@SRI-ARC)
Documents:
Postel, J. "Telnet Protocol," RFC 318 3-April-72.
People:
Schedule:
Recent developments:
New Telnet [Official]
Contact:
Postel at SRI-ARC
Documents:
NIC 18639 "TELNET Protocol Specifications" AUG 73
NIC 1864C "Telnet Option Specification" Aug 73
Postel [Page 8]
RFC 661 November 1974
Telnet Options
NIC 15389 "Binary Transmission"
NIC 15390 "Echo"
NIC 15391 "Reconnection"
NIC 15392 "Suppress Go Ahead Option"
NIC 15393 "Approximate Message Size Negotiation"
NIC 31154 "Status" RFC 65125-Oct-74.
[Office] <NETINFO>RFC651.TXT
NIC 16236 "Timing Mark"
NIC 19859 "Remote Controlled Transmission and
Echoing" 1-Nov-73.
NIC 20196 "Output Line Width" 13-Nov-73.
NIC 20197 "Output Page Size" 13-Nov-73.
NIC 31155 "Output Carriage Return Disposition" RFC
652 25-Oct-74.
[Office-1] <NETINFO>RFC652.TXT
NIC 31157 "Output Horizontal Tab Disposition" RFC
654 25-Oct-74.
[Office-1] <NETINFO>RFC653.TXT
NIC 31156 "Output Horizontal Tab Stops" RFC 653
25-Oct-74.
[Office-1] <NETINFO>RFC653.TXT
NIC31157 "Output Form Feed Disposition" RFC 655
25-Oct-74.
[Office-1] <NETINFO>RFC655.TXT
NIC 31159 "Output Vertical Tab Stops" RFC 656 25-
Oct-74.
Postel [Page 9]
RFC 661 November 1974
[Office-1] <NETINFO>RFC656.TXT
NIC 31160 "Output Vertical Tab Disposition" RFC 657
25-Oct-74
[Office-1] <NETINFO>RFC657.TXT
NIC 31161 "Output Line Feed Disposition" RFC 658
25-Oct-74.
[Office-1] <NETINFO>RFC658.TXT
NIC 16239 "Extended Options List"
People:
Jon Postel at Sri-Arc (POSTEL@SRI-ARC)
Alex McKenzie at BBN (MCKENZIE@BBN)
Doug Dodds at BBN (DODDS@BBN)
Dave Crocker at UCLA-NMC (DCROCKER@ISI)
Kurt Barthelmess at UCSD (BOWLES@ISI)
Schedule:
All Hosts were to have been running the new Telnet (both
user and server) by 1 January 1974.
Recent developments:
A significant number of server systems now have new
telnet implementations. (See RFC 702).
Note: the server program is to be available on socket
23 decimal (27 octal).
The Status Option has been revised to take advantage of
the subcommand feature and to reduce the amount of data
transmitted to report the option status.
Seven new options have been defined to allow control of
the format effectors Carriage Return, Line Feed, Form
Feed, Horizontal Tab, and Vertical Tab.
Postel [Page 10]
RFC 661 November 1974
FTP
Old File Transfer
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
McKenzie, A. "File Transfer Protocol," NIC 14333, RFC 454,
16-Feb-73.
People:
Schedule:
Recent developments:
New File Transfer
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
Neigus, N. "File Transfer Protocol," NIC 17759 RFC 542 12-
July-73.
Postel, J. "Revised FTP Reply codes," NIC 30843 RFC 640 5-
June-74.
People:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Nancy Neigus at BBN (NEIGUS@BBN)
Ken Pogran at MIT-Multics (Pogran.CompNet@MIT-Multics)
Wayne Hathaway at NASA AMES (Hathaway@AMES-67)
Mark Krilanovich at UCSB (Krilanovich@UCSB-MOD75)
Kurt Barthelmess at UCSD (BOWLES@ISI)
Schedule:
Postel [Page 11]
RFC 661 November 1974
Recent developments:
Pathnames
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
Crocker, D. "Network Standard Data Specification Syntax,"
RFC 645, NIC 30899, Jul-74.
People:
Dave Crocker at UCLA-NMC (DCROCKER@ISI)
Schedule:
Recent developments:
File Access Protocol
Contact:
John Day (Day. CAC@MIT-Multics)
Documents:
Day, J. "Memo to FTP Group: File Access Protocol," RFC 520,
NIC 16819, 25-Jun-73
People:
Ken Pogran (Pogran.CompNet@MIT-Multics)
Schedule:
Recent developments:
Mail
Current Mail
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Postel [Page 12]
RFC 661 November 1974
Documents:
page 26 of RFC 454 (see old file transfer).
Bhushan, A. "Standardizing Network Mail Headers," NIC 18516,
RFC 561, 5-Sep-73
Sussman, J. "FTP Error Code Usage for More Reliable Mail
Service," RFC 630, NIC 30874, RFC 644, 22-July-74.
People:
Julie Sussman at bbn (SUSSMAN@BBN)
Bob Thomas at bbn (BTHOMAS@BBN)
Schedule:
Recent developments:
Concern over the authentication of the author of network
messages has led to the concept of an authorized mail
sending process (see RFC 644).
Proposed Mail
Contact:
Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
White, J. "A Proposed Mail Protocol," NIC 17140, RFC 524,
13-Jun-73.
Crocker, D. "Thoughts on the Mail Protocol Proposed in RFC
524," NIC 17644, RFC 539, 7-July-73.
White, J. "Response to Critiques of the Proposed Mail
Protocol," NIC 17993, RFC 555, 27-July-73.
People:
Jim White at SRI-ARC (WHITE@SRI-ARC)
Postel at Sri-ARC (POSTEL@SIR-ARC)
Schedule:
Postel [Page 13]
RFC 661 November 1974
Recent developments:
RJE - Remote Job Entry
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
Bressler, B. "Remote Job Entry Protocol," RFC 407, NIC
12112, 16-Oct-72
Krilanovich, M. "Announcement of RJS at UCSB," RFC 436, NIC
13700, 10-Jan-73.
People:
Schedule:
Recent developments:
RJS - CCNs Remote Job Service
Contact:
Robert Braden at UCLA-CCN (BRADEN@UCLA-CCN)
Documents:
Braden, R. "Interim NETRJS Specification," RFC 18@ nic
July-71.
Braden, R. "Update on NETRJS," RFC 599, NIC 20854, 13-Dec-
73.
People:
Robert Braden (BRADEN@UCLA-CCN)
Steve Wolfe (WOLFE@UCLAL-CCN)
Schedule:
Recent developments:
Postel [Page 14]
RFC 661 November 1974
Graphics
Contact:
Robert Sproull (SPROULL@PARC-MAXC)
Documents:
Sproull, R, and E. Thomas. "A Networks Graphics Protocol,"
NIC 24308, 16-Aug-74.
People:
Robert Sproull (SPROULL@PARC-MAXC)
Elaine Thomas (Thomas@MIT-Multics)
James Michener at MIT-DMS (JCM@MIT-DMS)
Schedule:
Recent developments:
New document available from Robert Sproull.
Data Reconfiguration Service
Contact:
Jon Postel at SRI-ARC (POSTEL@SRI-ARC)
Documents:
Anderson, B. "Status Report on Proposed Data Reconfiguration
Service," NIC 6715, RFC 138, 28-April-71.
Feah, "Data Reconfiguration Service at UCSB," RFC 437, NIC
13701, 30-June-74.
People:
Schedule:
Recent developments:
Postel [Page 15]
RFC 661 November 1974
RSEXEC
Contact:
Thomas, Bob. (BTHOMAS@BBN)
Documents:
People:
Schedule:
Recent developments:
Line Processor Protocol
Contact:
Don Andrews at SRI-ARC (ANDREWS@SRI-ARC)
Documents:
[SRI-ARC] <hardy>1pprot.nls
[SRI-ARC] <hardy>prot.txt
People:
Martin Hardy at SRI-ARC (HARDY@SRI-ARC)
Don Andrews at Sri-ARC (ANDREWS@SRI-ARC)
Schedule:
Recent developments:
PROGRAMS
Neted - Network Standard Editor [Official]
Contact:
Michael Padlipsky (MAP@CASE-10)
Documents:
Padlipsky, M. "NETED: A Common Editor for the ARPA Network,"
RFC 569, NIC 18972, 15-Oct-73.
Postel [Page 16]
RFC 661 November 1974
People:
Padlipsky at MITRE (MAP@CASE-10)
Postel at SRI-ARC (POSTEL@SRI-ARC0
Hathaway at AMES (HATHAWAY@AMES-67)
Schedule:
Recent developments:
NATIONAL SOFTWARE WORKS
The National Software Works is developing a set of protocols for its
use of the ARPA Network, other uses of these protocols is encouraged.
The procedure call protocol is intended to facilitate the sharing of
resources in the network at the subroutine level. The procedure call
protocol will be used to split nls into a front end and back end
components. Procedure call protocol is also to be used in the nsw as
the basis for communication between the works manager, the tool
bearing hosts, and front desk procedure packages.
The documents cited below give a view of the Procedure Call Protocol
and its use.
Contact:
Jim White (WHITE@SRI-ARC)
Jon Postel (POSTEL@SIR-ARC)
Documents:
These documents are the second published version of the
Procedure Call Protocol and NSW protocol - PCP/NSW Version 2.
Version 2 is SUBSTANTIALLY different than Version 1; it and all
intermediate, informally distributed PCP/NSW documents are
obsoleted by this release.
The first document, PCP, is the place the interested ready
should start. It gives the required motivation for the use
Protocol and states the substance of the Protocol proper. The
ready may then, if he chooses, read the next three documents:
PIP, PSP, and PMP. The latter has the most to offer the casual
reader; the programmer faced with coding in the PCP environment
should ready all three. The next three documents - PCPFMT,
Postel [Page 17]
RFC 661 November 1974
PCPHST, and PCPFRK - are of interest only to the PCP
implementer. The next document - HOST - is a preliminary
thought about how the NSW might use the standard HOST-HOST
protocol NCP. The last four documents - EXEC, FILE, BATCH, and
LLDBUG - describe procedure packages needed to carry out NSW
functions, but such packages may well be useful in other
contexts.
Version 2 consists of the following documents. Each is
available online in two forms: as an NLS file and as a
formatted text file. The journal number (e.g., 24459) refers
to the former, of course and the pathname (e.g., [SRI-ARI]
<NLS> PCP.TXT) to the latter, accessible via FTP using
USER=ANONYMOUS and PASSWORD=GUEST (no account required).
Hardcopy is being forwarded by US Mail to all those who have
expressed an interest in PCP. If you don't receive a copy and
would like one of this and/or future releases, send a note to
that effect to WHITE@SRI-ARC:
PCP (24459,) "The Procedure Call Protocol"
This document describes the virtual programming
environment provided by PCP, and the inter-process
exchanges that implement it.
Pathname: [SRI-ARC] <NLS>PCP.TXT
PIP (24460,) "The Procedure Interface Package"
This document describes a packages that runs in the
setting provided by PCP and that serves as a procedure-
call-level interface to PCP proper. It includes
procedures for calling, resuming, interrupting, and
aborting remote procedures.
Pathname: [SRI-ARC] <NLS>PIP.TXT
PSP (24461,) "The PCP Support Packages"
This document describes a package that runs in the
setting provided by PCP and that augments PCP proper,
largely in the area of data store manipulation. It
includes procedures for obtaining access to groups of
remote procedures and data stores, manipulating remote
data stores, and creating temporary ones.
Pathname: [SRI-ARC] <NLS>PSP.TXT
Postel [Page 18]
RFC 661 November 1974
PMP (24462,) "The Process Management Package"
This document describes a package that runs in the
setting provided by PCP and that provides the necessary
tools for interconnecting two or more processes to form a
multi-process system (e.g., NSW). It includes procedures
for creating, deleting, logically and physically
interconnecting processes, and for allocating and
releasing processors.
Pathname: [SRI-ARC] <NLS>PMP.TXT
PCPFMT (24576,) "PCP Data Structure Formats"
This document defines formats for PCP data structures,
each of which is appropriate for one or more physical
channel types.
Pathname: [SRI-ARC] <NLS>POPFMT.TXT
PCPHST (24577,) "PCP ARPANET Inter-Host IPC Implementation"
This document defines an implementation, appropriate for
mediating communication between Tenex folks, of the IPC
primitives required by PCP.
Pathname: [SRI-ARC] <NLS.PCPHST.TXT
PCPFRK (24578,) "PCP Tenex Inter-Fork IPC Implementation"
This document defines an implementation, appropriate for
mediating communication between processes on different
hosts within the ARPANET, of the IPC primitives required
by PCP.
Pathname: [SRI-ARC] <NLS.PCPFRK.TXT
HOST (24581,) "NSW Host Protocol"
This document describes the host level protocol used in
the NSW. The protocol is a slightly constrained version
of the standard ARPANET host to host protocol. The
constraints affect the allocation, RFNM wait, and
retransmission policies.
Pathname: [SRI-ARC] <NLS>HOST.TXT
Postel [Page 19]
RFC 661 November 1974
EXEC (24580,) "The Executive Package"
This document describes a package that runs in the
setting provided by PCP. It includes procedures and data
stores for user identification, accounting, and usage
information.
Pathname: [SRI-ARC] <NLS> EXEC.TXT
FILE (24582,) "The File Package"
This document describes a package that runs in the
setting provided by PCP. It includes procedures and data
stores for opening, closing, and listing directories, for
creating, deleting, and renaming files, and for
transferring files and file elements between processes.
Pathname: [SRI-ARC] <NLS>FILE.TXT
BATCH (24583,) "The Batch Job Package"
This document describes a package that runs in the
setting provided by PCP. It includes procedures for
creating and deleting batch jobs, obtaining the status of
a batch job, and communicating with the operator of a
batch processing host. This package is implemented at
the host that provides the batch processing facility.
Pathname: [SRI-ARC] <NLS>BATCH.TXT
LLDBUG (24579,) "The Low-Level Debug Package"
This document describes a package that runs in the
setting provided by PCP. It includes procedures for a
remote process to debug at the assembly-language level,
any process known to the local process. The package
contains procedures for manipulating and searching the
process' address space, for manipulating and searching
its symbol tables, and for setting and removing
breakpoints from its address space. Its data stores hold
process characteristics and state information, and the
contents of program symbol tables.
Pathname: [SRI-ARC] <NLS>LLDBUG.TXT
People:
Postel [Page 20]
RFC 661 November 1974
Schedule:
A demonstration of the National Software Works concept is to
be performed in July 1975.
Recent developments:
The set of documents cited above is available.
Postel [Page 21]