17-TCP Acceleration Option

TCP Acceleration Option
NetPerformer® System Reference

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Published Date: April 2011
Document # 1609
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Contents
Chapter 1: NetPerformer Support of TCP Acceleration. . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1. 1 About the NetPerformer TCP Acceleration Option . . . . . . . . . . . . . . . . . . 1-2

1.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1. 2 Problems with TCP/IP in a Satellite Environment . . . . . . . . . . . . . . . . . . . 1-3

1.2.1 Bit Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.2 Latency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.3 Asymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1. 3 Other Considerations and Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1.3.1 Transparency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3.2 Backward Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3.3 Network Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3.4 Network Scalability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1. 4 NetPerformer Solutions to TCP/IP over Satellite . . . . . . . . . . . . . . . . . . . . 1-7

1.4.1 TCP Spoofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
1.4.2 Window Scaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
1.4.3 Timestamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
1.4.4 Selective Negative Acknowledgment (SNACK) . . . . . . . . . . . . . 1-9
1.4.5 Congestion Avoidance and Control . . . . . . . . . . . . . . . . . . . . . 1-10
1.4.6 Fast Checksum Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
1. 5 Availability on NetPerformer Products . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
Chapter 2: Configuring TCP Acceleration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2. 1 Before You Configure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.1.1 Is the TCP Acceleration option already Installed? . . . . . . . . . . . 2-3
2. 2 TCP Acceleration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.2.1 TCP acceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.2.2 TCP congestion control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2. 3 Configuration Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.1 Console Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.3.2 LAN Port. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.3.3 WAN Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.3.4 PPPoE Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
2.3.5 PVC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
2.3.6 SVC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2. 4 Monitoring TCP Acceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
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Chapter 3: Application Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3. 1 Connecting to a Remote Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index-1
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NetPerformer Support of TCP Acceleration
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TCP Acceleration Options
1.1 About the NetPerformer TCP Acceleration Option

The NetPerformer TCP Acceleration Option permits higher performance on satellite links,
extending the feasibility of the TCP/IP protocol to satellite applications. It is offered on
the SDM-9220 and SDM-9230 as a licensed software option in NetPerformer version
10.2.x and above.
NOTE: The TCP Acceleration option is not available on the NetPerformer VoIP Gate-
way product (SDM-9230GW).
Some features of TCP acceleration congestion control are also available as non-
configurable features on all NetPerformer base products running V10.2, and can be used
on terrestrial networks. Refer to Table 1-1.
1.1.1 Overview
Satellite communications provide an easy and flexible way to globally extend the
enterprise network. TCP/IP via satellite can take advantage of an instant communications
infrastructure to almost anywhere in the world.
The NetPerformer TCP Acceleration Option handles the obvious problems associated
with using TCP/IP, a protocol that was optimized to run on terrestrial networks, in a
satellite environment:
• Link latency: A satellite network is necessarily comprised of high-delay prod-
ucts, and satellite link bandwidth is not efficiently utilized
• High error rate: The potentially higher bit error rate of a satellite results in poor
TCP/IP performance
• Asymmetry: Satellite links often operate in an asymmetric mode where they
receive at a higher data rate than they transmit. The low-rate uplink easily
becomes congested.
NOTE: These inherent problems are discussed further on “Problems with TCP/IP in a
Satellite Environment” on page 1-3.
The reduced efficiency and Quality of Service (QoS) of the typical satellite link is largely
overcome when the TCP Acceleration Option is installed on all NetPerformer units that
act as a gateway to the satellite network with a MODULATOR satellite connection.
NOTE: The NetPerformer unit may be installed in front of a satellite modem or

another router.
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1.2 Problems with TCP/IP in a Satellite Environment
1.2.1 Bit Errors

Most networking protocols were designed for use in a terrestrial environment where the
Bit Error Rate (BER) is extremely low (typically less than 10-10). On a satellite link,
the raw BER is typically much higher (10-2 to 10-6).
Forward Error Correction (FEC) can be used to reduce the BER to an acceptable level.
However, the benefit of a lower BER comes at the price of increased complexity and
reduced channel capacity. The trade-off factor is equal to the code rate used.
Rather than trying to make the satellite link look like a terrestrial link from a BER
perspective, the NetPerformer solution involves enhancing the TCP/IP protocol to
operate effectively in an environment with a high BER. Turn to “NetPerformer Solutions
to TCP/IP over Satellite” on page 1-7 for further information.
1.2.2 Latency
Latency in a terrestrial environment is typically very low. For example, the
prorogation time across the North American continent is approximately 30 ms. Latency to
and from a geo-stationary satellite is much higher: approximately 260 ms each way.
• This means that the Round Trip Time (RTT) via satellite is 520 ms, even exclud-
ing any coding delays or terrestrial-based latencies.
• The large discrepancy between terrestrial and satellite RTTs is the main reason
why networks cannot be extended to satellite applications efficiently.
• Short of changing orbital parameters, nothing can be done to reduce the RTT.
Protocol enhancement is required to accommodate latency.
On a satellite link, actual throughput is a function of the window size divided by the RTT.
As the RTT increases the throughput decreases, and the link experiences higher bandwidth
delays. To avoid reduced throughput on links with increased bandwidth delays, TCP
applications can:
• Increase the window size. Turn to “Window Scaling” on page 1-9.
• Use a larger buffer for the connections. This buffer is directly related to the
window size.
1.2.3 Asymmetry
Unlike terrestrial networks, satellite links often operate in asymmetric mode, receiving
segments at a higher transmission rate than they transmit. This is due to two main
factors:
• Satellite terminals, especially portable or mobile stations, are often uplink power
limited.
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These stations have a ceiling on their uplink transmit capability, but can receive
as many signals on the downlink as the application requires.
• In some cases, the asymmetry of satellite links may simply reflect an asymmetry
in the actual data flow between locations.
For example, many Web servers send out vast quantities of information in
response to relatively short requests.
Because of these factors, it is not uncommon for the ratio of downlink to uplink capacity
to reach 100 to 1, or even higher.
Uplink/downlink asymmetry is not the ideal environment for the self-clocking mechanism
of TCP (see “Latency” on page 1-3):
• Most TCP segments received over the high rate downlink are responded to with
an ACK, which is sent over the low rate uplink.
• The low rate link may become congested with ACKs.
• Flow control starts up, reducing the amount of traffic that can be sent over the
high rate downlink even though it is not congested itself.
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1.3 Other Considerations and Requirements

A number of considerations affect what methods can be used to improve TCP/lP
performance over satellite links in a viable way. The NetPerformer solution meets all of
these requirements:
• “Transparency” on page 1-5
• “Backward Compatibility” on page 1-5
• “Network Efficiency” on page 1-5
• “Network Scalability” on page 1-6
1.3.1 Transparency
The NetPerformer TCP Acceleration Option is a transparent solution. A protocol
enhancement is considered transparent if it:
• Has no negative impact on performance or connections
• Does not require special procedures to obtain the desired improvement, and can
be used without the end user’s knowledge
• Does not compromise the integrity of the protocol or its features. For example, a
protocol that guarantees end-to-end reliability must continue to provide end-to-
end reliability under enhancement.
1.3.2 Backward Compatibility

The NetPerformer TCP Acceleration Option is backward compatible. Backward
compatibility requires that:
• The protocol enhancement can work with existing Internet and intranet infra-
structures.
There is no need to change or upgrade your applications to accommodate
the enhancement.
• The enhancement is application independent.
There is no need to standardize the applications that are used across your
organization in order to optimize network extension via satellite. Your current
applications will continue to work, even if they include parameters that affect
performance in some way.
1.3.3 Network Efficiency

Satellite links are typically more expensive than terrestrial links. This cost factor is offset
somewhat by the ability of satellite links to provide instant infrastructure. Nevertheless,
network efficiency is of primary concern:
• The satellite link must be used as efficiently as possible
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• The protocol enhancement should correct aspects of the protocol that result in
inefficient use of the satellite link.
Improved satellite network efficiency is the main advantage of the NetPerformer TCP
Acceleration Option.
1.3.4 Network Scalability

The NetPerformer TCP Acceleration Option provides a scalable approach to TCP/IP
performance improvement. Through scalability, it is able to:
• Support high transmission rates
• Accommodate a large number of users.
The NetPerformer approach is able to satisfy both short-term needs and projected growth
in network size and performance demands.
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1.4 NetPerformer Solutions to TCP/IP over Satellite

The NetPerformer TCP Acceleration Option includes the following enhancements that
provide a solution to the problems, considerations and requirements discussed earlier
(“Problems with TCP/IP in a Satellite Environment” on page 1-3 to “Network Scalability”
on page 1-6):
• “TCP Spoofing” on page 1-7
• “Window Scaling” on page 1-9
• “Timestamp” on page 1-9
• “Selective Negative Acknowledgment (SNACK)” on page 1-9
• “Congestion Avoidance and Control” on page 1-10
• “Fast Checksum Calculation” on page 1-11.
NOTE: Some of these solutions are available on all NetPerformer products that run
V10.2, without requiring a software license. See “Availability on NetPer-
former Products” on page 1-12.
1.4.1 TCP Spoofing

With TCP spoofing, TCP end-to-end connections are broken virtually.
NOTE: The link remains intact at the physical level as a composite of three connec-
tions, rather than a single point-to-point connection.
The NetPerformer unit that breaks the connection takes responsibility for delivering
the data to its proper destination. This resolves the delays that result from high latency
(see “Latency” on page 1-3) and the congestion problems associated with asymmetry (see
“Asymmetry” on page 1-3). In this approach:
• A NetPerformer gateway at the outskirts of the satellite portion of the network
examines the content of all TCP headers in segments received from the source
node. Refer to Figure 1-1.
• This NetPerformer sends spoofed ACKs back to the source node, and takes
responsibility for delivering these ACKs successfully.
• It deletes the real ACKs it receives from the satellite destination. This prevents
any confusion on the part of the source node.
NOTE: In NetPerformer V10.2 a maximum of 300 connections can be spoofed,
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depending on the type of license installed (the license can be scaled to the
size of your application, and may support a lower maximum number of con-
nections). Any additional connections will use end-to-end TCP, which is the
same as routing the traffic with TCP Acceleration disabled.
Through TCP spoofing, the NetPerformer approach:

• Overcomes the effects of the slow start algorithm that is used for TCP conges-
tion control
• Still requires “Window Scaling” on page 1-9, described in the next section, to
overcome the window size limitations that result from latency.
Satellite
Gateway
SDM-9230 Satellite dish
1. End-to-end TCP: no spoofing by the NetPerformer gateway

No gateway intervention
Data
ACK
2. TCP Spoofing: NetPerformer gateway intervenes

Data
d ACK Data
Spoofe
Gateway intervention
Real ACK ACK

suppresed
Figure 1-1: NetPerformer Spoofing of TCP Traffic
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1.4.2 Window Scaling

Actual TCP performance depends on both the transfer rate and the RTT, together referred
to as the bandwidth delay. In other words, the bandwidth delay measures the amount of
traffic that would “fill the pipe”.
In high-delay applications such as a satellite link, the size of the window required to fill
the pipe can be so high that the 16-bit Window field of the TCP header is too small to hold
its value. To circumvent this problem the NetPerformer uses window scaling, an extension
of the TCP protocol that was introduced in RFC-1323.
• Allows window sizes larger than 216

• Expands the definition of the TCP window to 32 bits
• Scales the 32-bit value to fit the 16-bit Window field of the TCP header.
1.4.3 Timestamp
TCP timeouts and retransmissions depend on the measured Round Trip Time (RTT).
However, the RTT must be ignored when packets have been sent more than once.
It is often difficult to get a correct RTT measurement in a noisy environment such as
satellite. To circumvent this problem the NetPerformer uses the timestamp option, an
extension of the TCP protocol that was introduced in RFC-1323.
• The timestamp option permits accurate RTT measurement for practically every
ACK that passes through the gateway.
1.4.4 Selective Negative Acknowledgment (SNACK)

As mentioned in “Bit Errors” on page 1-3, a satellite link has a significantly higher error
rate than its terrestrial equivalent. As a result, a larger proportion of transmitted segments
are discarded.
TCP uses timeouts to determine when to retransmit a discarded segment. This works
satisfactorily when the error rate is fairly low, but can significantly degrade performance
when the error rate is high.
TCP has a cumulative acknowledgment scheme in which received segments are
acknowledged only if they are at the left edge of the receive window. If a segment is lost,
the sender must either:
• Wait one full round trip time to find out what happened to the lost segment
• Retransmit segments that may have been received correctly.
If many segments are lost from a single window of data, the TCP protocol can lose its
ACK-based clock. This reduces overall throughput, with sometimes catastrophic results.
The NetPerformer uses an extension of the TCP protocol, Selective Negative
Acknowledgment (SNACK -- see Note below), to counter the effects of the TCP
cumulative acknowledgment scheme. SNACK is a bandwidth-efficient error recovery
mechanism that reduces retransmission time and can convey a lot of information using a
small number of bits.
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NOTE: Introduced in the Consultative Committee for Space Data Sys-

tems (CCSDS) “Blue Book” on Space Communications Proto-
col Specification (SCPS) - Transport Protocol, 714.0-B-1, May
1999.
Rather than notifying the sender about all segments that were received successfully, when
SNACK is invoked the receiver provides the sender with:
• A list of missing segments that require retransmission
• The sequence number of the segment up to which no segments were lost.
As a result:
• The sender does not need to retransmit segments that have already been success-
fully delivered to the receiver
• Missing segments are retransmitted immediately, accelerating overall perform-
ance.
The SNACK capability comes with the NetPerformer V10.2 base product and is
always available for negotiation, even if TCP Acceleration is not enabled or no
software license is entered. Outside of a TCP Acceleration application, SNACK can be
useful for:
• Improved speed of the NetPerformer user interface
• Rapid display of real-time statistics
• Faster file downloads
• Faster Telnet access to the console.
1.4.5 Congestion Avoidance and Control

Traffic congestion occurs when several connections are trying to transmit at the same time
through their corresponding window. This can result in a higher occurrence of
retransmissions, which further congest the connections.
The congestion avoidance and control scheme is an extension of the TCP protocol that
controls window size to avoid these unwanted retransmissions. This scheme includes
algorithms that manage the following extended TCP features:
• From RFC 2581, TCP Congestion Control, April 1999:
- Slow start
- Congestion avoidance
- Fast retransmit
- Fast recovery.
• From a later research paper:
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- Fair share
- Dynamic right-sizing.
These features can be useful for terrestrial and satellite networks alike. For example, Fast
Retransmit permits higher speeds:
• If a unit receives 3 identical ACKs after a segment has not been received, it will
retransmit automatically.
• If a hole in the segment stream is detected, it can send immediately.
NOTE: Fast Retransmit comes with the NetPerformer V10.2 base product and is
always enabled. Fast Retransmit is beneficial for all products, and can
improve performance of the NetPerformer FTP transmitter.
Fair share and dynamic right-sizing control buffer management in terrestrial and satellite
networks. With these algorithms, both the RTT and the available bandwidth are considered
in the buffer size decision, which determines the window size. The fair share algorithm
ensures that all connections get a fair share of the bandwidth, and redistributes any unused
bandwidth to connections that need it the most.
NOTE: TCP Congestion Control is always enabled on the NetPerformer base

product. It is a separately configured feature on a SDM-9220 or SDM-
9230 that has been installed with the TCP Acceleration licensed software
option. On these products, TCP congestion control is enabled by default, but
can be disabled if the TCP acceleration parameter has been set to YES. Refer
to “TCP acceleration” on page 2-4.
1.4.6 Fast Checksum Calculation

Following RFC-1071, the NetPerformer employs a routine that calculates all checksums
using 32 bits instead of 16 bits. In addition, it is able to perform incremental updates,
rather than having to recalculate the checksum of the entire segment. This approach
speeds up checksum calculation and improves overall processing speed.
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1.5 Availability on NetPerformer Products

The various enhancements to the TCP protocol and its processing methods are available
on NetPerformer products running V10.2, as follows:
NetPerformer Requires
Enhancement Configurable?
Products License?
TCP Spoofing SDM-9220 and YES NO

SDM-9230 only
Window Scaling All V10.2 prod- NO NO

ucts
Timestamp All V10.2 prod- NO NO

ucts
SNACK All V10.2 prod- NO NO

ucts
Congestion Avoidance All V10.2 prod- NO YES (with soft-

and Control ucts ware license only,
when TCP Accel-
eration is
enabled)
Fast Checksum Calcu- All V10.2 prod- NO NO

lation ucts
Table 1Availability of TCP Protocol Enhancements in NetPerformer V10.2
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2
Configuring TCP Acceleration
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2.1 Before You Configure

The TCP Acceleration option includes a Software Licensing Agreement, which can be
found in the product package.
You must agree to the terms and conditions of this agreement before loading the software.
Each NetPerformer unit that serves as a gateway in the TCP Acceleration application
requires a separate software license.
The TCP Acceleration option can be loaded on a NetPerformer SDM-9220 or SDM-9230
only.
The TCP Acceleration software must be activated on the NetPerformer unit (an
SDM-9220 or SDM-9230 only) before you can configure and use any TCP
Acceleration features. This requires entering the TCP Acceleration Software License to
the License Profile.
NOTE: A specific License Profile is valid for a single NetPerformer unit only.
To prepare for TCP Acceleration configuration you must first:

• Install the NetPerformer SDM-9220 or SDM-9230 unit according to the instruc-
tions given in the Hardware Installation Guide for the particular product,
which is available on the NetPerformer Documentation CD (Part No. 161-
0692-001).
• Install and activate the TCP Acceleration Option software license, following the
procedure provided in the Software Licensing chapter of the Software Instal-
lation and Licensing fascicle of this document series.
A bundled license, including both the SkyPerformer and TCP Acceleration
options, is also available for the NetPerformer base product or a gateway product
installed with the PowerCell Option. Both parts of this bundled license are
installed at the same time.
• At any time, you can reset the unit configuration to its factory defaults: enter FS
at the command prompt. The TCP Acceleration Option is reset along with all
other areas of the configuration, and all previously defined values are lost.
When you execute the FS command, the NetPerformer unit clears its License
Profile and sets the TCP Acceleration parameter on all ports, PVCs and SVCs to
NO. You must:
- Re-enter the TCP Acceleration Option software license, and
- Change the TCP acceleration parameter on all ports, PVCs and SVCs
involved in the application to YES (see next section).
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2.1.1 Is the TCP Acceleration option already Installed?

To determine whether a NetPerformer unit is already installed with the TCP Acceleration
licensed software option, execute any of the following commands:
• Display Parameters (DP)
• Display Version (DV)
• Display Alarms (DA).
These commands include information on any optional software that has already been
installed on the unit. The message TCP acceleration license (AAAA-BBBB-
CCCCCCCC-DDDD) enabled on this unit indicates the software license number. The
following line indicates the maximum number of accelerated connections available on the
unit.
DP example: SDM-9230>DP
with TCP DISPLAY PARAMETERS
Acceleration Item (BRIDGE/CALLER ID/CLASS/CUSTOM/FILTER/GLOBAL/HUNT/IP/IPX/MAP/
enabled PHONE/
PORT/PU/PPPOE/PPPUSER/PVC/REDUNDANCY/SCHEDULE/SLOT/USER/VLAN,
def:REDUNDANCY) ? ALL
Wait for <ENTER> after each screen (NO/YES,def:YES) ? NO
NetPerformer SDM-9230 vX.X.X Memotec Inc. (c) 2004
Signaling Engine vX.X.X Memotec Inc. (c) 2004
Console connected on port CSL
TCP acceleration license (AAAA-BBBB-CCCCCCCC-DDDD) enabled on this
unit
Number of accelerated connections: XXX
...
DV example: SDM-9230>DV
with TCP DISPLAY VERSION
Acceleration SDM-9230 vX.X.X Memotec Inc. (c) 2004
enabled Signaling Engine vX.X.X Memotec Inc. (c) 2004
DSP code version: X.X.X
unit
DA example: SDM-9230>DA
with TCP DISPLAY ALARMS
Acceleration SDM-9230 vX.X.X Memotec Inc. (c) 2004
enabled Signaling Engine vX.X.X Memotec Inc. (c) 2004
DSP code version: X.X.X
unit
...
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2.2 TCP Acceleration Parameters

Only two parameters are required, but they recur in many areas of the unit configuration.
2.2.1 TCP acceleration

Console SNMP Text-based Config
TCP acceleration ifwanTcpAcceleration [ifwan] TcpAcceleration

iflanTcpAcceleration [iflan] TcpAcceleration
pvcTcpAcceleration [pvc] TcpAcceleration
atmpvcTcpAcceleration [atmpvc] TcpAcceleration
atmsvcTcpAcceleration [atmsvc] TcpAcceleration
pppoeTcpAcceleration [pppoe] TcpAcceleration
Table 2-1: TCP acceleration parameters

Set this parameter to YES to enable the TCP Acceleration scheme on this element (port,
channel, PVC or SVC). This option is available only on a SDM-9220 or SDM-9230
installed with the TCP Acceleration licensed software option.
When TCP acceleration is set to YES, the connection can take advantage of TCP
acceleration control and TCP spoofing, and can be configured for TCP congestion control.
Set this parameter to NO to disable TCP Acceleration.
NOTE: TCP acceleration will enhance overall performance even if it is enabled on

only one side of the connection. However, if you want to use TCP accelera-
tion, it is preferable to set the TCP acceleration parameter to YES on both
sides of the connection.
Values: NO, YES

Default: NO
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2.2.2 TCP congestion control

Console SNMP Text-based Config
TCP congestion control ifwanTcpCongestion- [ifwan]

Control TcpCongestionControl
iflanTcpCongestion-Con- [iflan]
trol TcpCongestionControl
pvcTcpCongestion-Con- [pvc]
trol TcpCongestionControl
atmpvcTcpCongestion- [atmpvc] TcpCongestion-
Control Control
atmsvcTcpCongestion- [atmsvc]
Control TcpCongestionControl
pppoeTcpCongestion- [pppoe] TcpCongestion-
Control Control
Table 2-2: TCP congestion control parameters
NOTE: This parameter appears at the NetPerformer console only if the TCP accelera-
tion parameter has been set to YES. It is configurable only on a SDM-9220
or SDM-9230 installed with the TCP Acceleration licensed software
option. On other NetPerformer products, congestion control is always
enabled, to improve throughput and reduce the number of retransmissions.
• Set TCP congestion control to YES to implement TCP congestion control on this
element (port, channel, PVC or SVC). When TCP congestion control is imple-
mented, the congestion avoidance and control mechanisms are activated (refer to
“Congestion Avoidance and Control” on page 1-10).
YES is the default value of the TCP congestion control parameter, and the
preferred setting for a satellite link.
• Set TCP congestion control to NO to disable all congestion avoidance and control
mechanisms on this element. In this case, the NetPerformer will always use the
full window advertised by the remote unit.
NOTE: TCP congestion control is not configurable for a PVC set to FRF.8, ATM-
MULTIPLEX, MULTIPLEX or TRANSP mode.
Values: NO, YES

Default: YES
Memotec Inc. 2-5

2.3 Configuration Procedures

TCP Acceleration can be implemented on the following NetPerformer elements:
• CSL port: PPP protocol
• LAN port: Ethernet protocol
• WAN port: PVCR or PPP protocol
• PPPoE port: PPP protocol over an Ethernet port
• PVC: PVCR or RFC1490 mode
• ATM PVC: ATMPPP, ATMPVCR or RFC1483 mode
• ATM SVC: ATMPPP, ATMPVCR or RFC1483 mode.
NOTE: Each NetPerformer element that you would like to include in TCP Accelera-
tion must be configured separately for this feature.
Unit ID>
(main prompt)
Setup (SE)
Port (PO) PPPoE PVC (PV) Slot (SL) SVC (SV)
PVCR RFC1490 ATMPPP. . . ATMPPP ATMPVCR RFC1483
CSL ETH # Channel #
PPP PVCR PPP PVCR PPP
Figure 2-1: TCP Acceleration Configuration Commands in the CLI Tree
2.3.1 Console Port

The console port must be set to the PPP protocol.
To configure the console port (CSL) for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  PORT 
CSL
2. Set the Protocol parameter to PPP
2-6 Memotec Inc.

3. Set the TCP acceleration parameter to YES

4. Change the other parameters from their default values, if desired.
SDM-9230>SE
SETUP
Item (BRIDGE/CALLER ID/CLASS/CUSTOM/FILTER/GLOBAL/HUNT/IP/IPX/MAP/
PHONE/
def:PORT) ? PORT
Port number (ETH1/ETH2/CSL/1,def:ETH1) ? CSL
PORT CSL> Protocol (def:CONSOLE) ? PPP
PORT CSL> Format (def:ASYNC) ?
PORT CSL> Interface.............................AUTO
PORT CSL> Reception flow control (def:NONE) ?
...
PORT CSL> IP multicast active (def:NO) ?
PORT CSL> NAT enable (def:NO) ?
PORT CSL> TCP acceleration (def:NO) ? YES
PORT CSL> TCP congestion control (def:YES) ?
PORT CSL> Filter (def:ALL) ?
2.3.2 LAN Port

To configure the LAN port for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  PORT 
ETH
On a NetPerformer product with two Ethernet ports, enter either of the following:
• SE  PORT  ETH1
• SE  PORT  ETH2
SDM-9230>SE
SETUP
PHONE/
def:PORT) ? PORT
Port number (ETH1/ETH2/CSL/1,def:CSL) ? ETH1
PORT ETH 1> Protocol (def:ETH AUTO) ?
PORT ETH 1> Link integrity (def:YES) ?
PORT ETH 1> LAN speed (mbps) (def:AUTO) ?
...
PORT ETH 1> IP multicast 4 (def:000.000.000.000) ?
PORT ETH 1> NAT enable (def:NO) ?
PORT ETH 1> TCP acceleration (def:NO) ? YES
PORT ETH 1> TCP congestion control (def:YES) ?
PORT ETH 1> VLAN enable (def:NO) ?
...
Memotec Inc. 2-7

2.3.3 WAN Port

The serial port or digital channel must be set to the PVCR or PPP protocol.
To configure a built-in serial port for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  PORT
2. Select the Port number
3. Set the Protocol to PVCR or PPP
SDM-9230>SE
SETUP
PHONE/
def:PORT) ? PORT
Port number (ETH1/ETH2/CSL/1,def:ETH1) ? 1
PORT 1> Protocol (def:PVCR) ? PVCR
PORT 1> Interface...............................DTE-V35
PORT 1> Clocking mode (def:EXTERNAL) ?
...
PORT 1> IP multicast active (def:NO) ?
PORT 1> NAT enable (def:NO) ?
PORT 1> TCP acceleration (def:NO) ? YES
PORT 1> TCP congestion control (def:YES) ?
PORT 1> IPX RIP (def:DISABLE) ?
...
To configure a serial port on the Dual Serial interface card for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  SLOT
2. Select the Slot number
3. Select the Channel number
4. Set the Protocol to PVCR or PPP
To configure a digital data channel for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  SLOT
2. Select the Slot number
3. Enter LINK
4. Set the Status to ENABLE
5. Set the Signaling mode to NONE
6. Press <Esc>
7. Enter CHANNEL
2-8 Memotec Inc.

8. Select the Channel number

9. Set the Protocol parameter to PVCR or PPP
SDM-9230>SE
SETUP
PHONE/
def:PORT) ? SLOT
SLOT> Slot number (1,def:1) ? 1
Item (LINK/CHANNEL,def:LINK) ? CHANNEL
SLOT> Channel Number (101-124/ALL,def:101) ? 101
PORT 101> Protocol (def:OFF) ? PVCR
PORT 101> Timeslot (def:1) ?
PORT 101> Number of consecutive timeslots (1-24,def:1) ?
...
PORT 101> IP multicast active (def:NO) ?
PORT 101> NAT enable (def:NO) ?
PORT 101> TCP acceleration (def:NO) ? YES
PORT 101> TCP congestion control (def:YES) ?
PORT 101> IPX RIP (def:DISABLE) ?
...
2.3.4 PPPoE Port

To configure a PPPoE port for TCP Acceleration:
1. At the NetPerformer command line prompt, enter the menu sequence: SE  PPPOE
2. Select the PPPoE number
3. Set the Mode to CLIENT
4. Specify the LAN port
5. Define the following PPPOE parameters:
• AC Name
• Service Name
• PPP User
9230-1>SE
SETUP
PHONE/
Memotec Inc. 2-9

def:PORT) ? PPPOE
PPPoE number (1-32,def:1) ?
PPPoE 1> Mode (def:OFF) ? CLIENT
PPPoE 1> LAN port (def:ETH1) ? ETH2
PPPoE 1> AC Name (def:) ? ANK2-CTRLPSTDOL
PPPoE 1> Service Name (def:) ?
PPPoE 1> PPP User (def:NONE) ? 1
PPPoE 1> Silent (def:SEND REQUEST) ?
PPPoE 1> LCP timeout (seconds) (1-255,def:3) ?
PPPoE 1> LCP retries, 255 = forever (0-255,def:255) ?
PPPoE 1> Negotiate MRU (def:NO) ? YES
PPPoE 1> Proposed MRU (256-1492,def:1492) ?
PPPoE 1> Use MRU proposed by peer (def:NO) ? YES
PPPoE 1> Maximum accepted MRU from peer (256-1492,def:1492) ?
...
PPPoE 1> IP multicast active (def:NO) ?
PPPoE 1> NAT enable (def:NO) ?
PPPoE 1> TCP acceleration (def:NO) ? YES
PPPoE 1> TCP congestion control (def:YES) ?
PPPoE 1> Filter (def:ALL) ?
2.3.5 PVC
NOTE: A PVC on the NetPerformer base product must be set to PVCR or RFC1490
mode. On a product installed with the ATM licensed software option, the PVC
may also be set to ATMPPP, ATMPVCR or RFC1483 mode.
To configure a PVC for TCP Acceleration:

1. At the NetPerformer command line prompt, enter the menu sequence: SE  PVC
2. Select the PVC number
3. Set the Mode to PVCR, RFC1490, ATMPPP, ATMPVCR or RFC1483
NOTE: ATMPPP, ATMPVCR and RFC1483 are available with the ATM option only.

SDM-9230>SE
SETUP
PHONE/
def:PORT) ? PVC
PVC number (1-300,def:1) ?
2-10 Memotec Inc.

PVC 1> Mode (def:RFC1490) ?

PVC 1> Port (def:1) ?
PVC 1> DLCI address (0-1022,def:100) ?
PVC 1> Committed Information rate (4000-6144000,def:2048000) ?
PVC 1> Burst Information rate (4000-6144000,def:2048000) ?
PVC 1> Remote unit name (def:EST) ?
PVC 1> IP address (def:000.000.000.000) ?
PVC 1> Subnet mask (number of bits) (0-32,def:8) ?
{255.000.000.000}
PVC 1> NAT enable (def:NO) ?
PVC 1> TCP acceleration (def:NO) ? YES
PVC 1> TCP congestion control (def:YES) ?
PVC 1> Frame size (128-8192,def:1500) ?
2.3.6 SVC
NOTE: The SVC must be an ATM SVC set to ATMPPP, ATMPVCR or RFC1483
mode.
To configure an SVC for TCP Acceleration:

1. At the NetPerformer command line prompt, enter the menu sequence: SE  SVC
2. Select the SVC number
3. Set the Mode to ATMPPP, ATMPVCR or RFC1483
NOTE: ATMPPP, ATMPVCR and RFC1483 are available with the ATM licensed soft-
ware option only.

9360>SE
SETUP
PHONE/
PORT/PU/PPPOE/PPPUSER/PVC/REDUNDANCY/SCHEDULE/SLOT/SVC/USER/VLAN,
def:GLOBAL) ? SVC
SVC number (1-300,def:1) ?
SVC 1> Mode (def:OFF) ? ATMPVCR
SVC 1> SVC Destination address
(def:0000000000000000000000000000000000000000) ?
SVC 1> Local Address (def:00000000000000) ?
SVC 1> Type (def:DEDICATED) ?
SVC 1> Call Delay (1-255,def:5) ?
SVC 1> Call Retry Delay (1-255,def:10) ?
Memotec Inc. 2-11

SVC 1> Peak cell rate (PCR) (0-4679,def:1000) ?

SVC 1> Payload information rate is 384000 bps
SVC 1> Total information rate is 424000 bps
SVC 1> Remote unit name (def:) ?
SVC 1> Timeout (msec) (1000-30000,def:1000) ?
SVC 1> Number of retransmission retries (1-1000,def:100) ?
SVC 1> Compression (def:YES) ?
SVC 1> IP address (def:000.000.000.000) ?
SVC 1> Subnet mask (number of bits) (0-32,def:8) ?
{255.000.000.000}
SVC 1> IP RIP (def:V1) ?
SVC 1> IP RIP TX/RX (def:DUPLEX) ?
SVC 1> OSPF (def:DISABLE) ?
SVC 1> IP multicast active (def:NO) ?
SVC 1> NAT enable (def:NO) ?
SVC 1> TCP acceleration (def:NO) ? YES
SVC 1> TCP congestion control (def:YES) ?
SVC 1> IPX RIP (def:DISABLE) ?
SVC 1> IPX SAP (def:DISABLE) ?
SVC 1> IPX network number (def:00000000) ?
SVC 1> Filter (def:ALL) ?
SVC 1> Maximum number of voice channels (0-10000,def:10000) ?
SVC 1> Maximum Voice Channels If High Priority Data (0-
10000,def:10000) ?
SVC 1> Cell Packetization (def:YES) ?
2-12 Memotec Inc.

2.4 Monitoring TCP Acceleration

The following areas of the NetPerformer console command set provide information on
how TCP Acceleration is affecting your network:
• To view information about received and transmitted packets, use the IP option of
the Display Counters (DC) command. These statistics are not specifically related
to TCP Acceleration, but can they help you determine what is happening at the IP
layer.
• Take a traffic capture with the Start Capture (STC) and View Capture (VC) com-
mands. A port capture decodes the TCP/IP segments, which lets you trace the
connection.
Unit ID>
(main prompt)
Display Counters Start Capture

View Capture (VC)
(DC) (STC)
Figure 2-2: TCP Acceleration Statistics and Capture Commands in the CLI Tree
Memotec Inc. 2-13

2-14 Memotec Inc.

3
Application Example
Memotec Inc. 3-1

3.1 Connecting to a Remote Site

In the example below, the NetPerformer at the remote site (Kujuak) accesses the Internet
using a satellite link to the NetPerformer at the central site (Montreal).
Satellite
Kujuak Montreal Internet

10.0.1.1 10.0.1.2
10.0.0.1 Satellite Satellite NAT router

dish dish Firewall
PC-1 www.google.ca
10.0.0.2
Figure 3-1: TCP Acceleration Application Example
• Both WAN ports (Kujuak and Montreal WAN 1) are configured with the FR-
USER protocol
• An RFC1490 PVC is set up at each location, and TCP Acceleration is imple-
mented on each PVC
• TCP connections are automatically spoofed if they are sent or received at a con-
nection where TCP Acceleration is activated.
The configuration of the RFC1490 PVCs is as follows:
KUJUAK>SE
SETUP
PHONE/
def:PORT) ? PVC
PVC number (1-300,def:1) ? 1
PVC 1> Mode (def:RFC1490) ? RFC1490
PVC 1> Port (def:1) ? 1
PVC 1> DLCI address (0-1022,def:100) ? 100
PVC 1> Remote unit name (def:) ? MONTREAL
PVC 1> IP address (def:000.000.000.000) ? 10.0.1.1
PVC 1> Subnet mask (number of bits) (0-32,def:8) ? 24
...
PVC 1> BRG connection (def:NO) ? YES
3-2 Memotec Inc.

Application Example
...
PVC 1> Filter (def:ALL) ?
MONTREAL>SE
SETUP
PHONE/
def:PORT) ? PVC
PVC number (1-300,def:1) ? 1
PVC 1> Mode (def:RFC1490) ? RFC1490
PVC 1> Port (def:1) ? 1
PVC 1> DLCI address (0-1022,def:100) ? 100
PVC 1> Remote unit name (def:) ? KUJUAK
PVC 1> IP address (def:000.000.000.000) ? 10.0.1.2
PVC 1> Subnet mask (number of bits) (0-32,def:8) ? 24
...
PVC 1> BRG connection (def:NO) ? YES
...
PVC 1> Filter (def:ALL) ?
With this configuration, all TCP connections from PC-1 to the Internet are processed using
three real TCP connections. The intervening connections are entirely transparent to PC-1,
which the user perceives as being directly connected to the Internet site. In fact, the
NetPerformer units in Kujuak and Montreal spoof the connection twice.
PC-1 Kujuak Montreal Internet Site
SYN
Spoofed SYN
SYN ACK
Spoofed SYN
Spoofed SYN ACK Real

SYN ACK Real SYN ACK
Suppressed SYN ACK
Suppressed
Figure 3-2: Establishment of Connections using TCP Spoofing
Memotec Inc. 3-3

3-4 Memotec Inc.

Index
A See also Software license

Link latency 1-2
Application example 3-1
Asymmetry 1-2, 1-3
Availability
M
in areas of the configuration 2-6 Monitoring commands 2-13
of protocol enhancements 1-12
on NetPerformer products 2-2 N
NetPerformer solutions 1-7
B Network efficiency 1-5
Backward compatibility 1-5
Bit errors 1-3 O
Buffering 1-3
Bundled license License, bundled 2-2 Operational requirements 1-5
C P
Configuration Parameters 2-4
commands 2-6 PPPoE port configuration 2-9
preparing for 2-2 Product license 2-2
procedures 2-6 See also Software license
Congestion control 1-10 Protocol enhancement 1-3
Console port configuration 2-6 PVC configuration 2-10
example 3-2
D
Q
Dynamic right-sizing 1-11
Quality of Service 1-2
E
R
Error rate 1-2, 1-3
Example application 3-1 Requirements
installation 1-2
operational 1-5
F
Factory Setup command 2-2 S
Fair share 1-11
Fast checksum 1-11 Scalability 1-6
FS command 2-2 Slow start algorithm 1-8
SNACK 1-9
in non-satellite environment 1-10
I Software license 2-2
Installation requirements 1-2 agreement 2-2
Installation status 2-3 SVC configuration 2-11
L T
LAN port configuration 2-7 TCP acceleration parameter 2-4
Latency 1-3 TCP congestion control 2-5
License 2-2 TCP spoofing 1-7, 3-3
TCP Acceleration Options 1

TCP/IP
problems with satellite 1-3
Timestamp 1-9
Transparency 1-5
U
Uplink capacity 1-3
W
WAN port configuration 2-8
Window scaling 1-9
Window size 1-3
2 Memotec Inc.
TCP Acceleration Options 3
REACH FURTHER. OFFER MORE.
Contact Memotec:
tel.: +1-514-738-4781
e-mail: MemotecSupport@memotec.com
7755 Henri Bourassa Blvd. West

Montreal, Quebec | Canada H4S 1P7 www.memotec.com

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NetPerformer® System Reference

Any other trademarks are the property of their respective companies.

Copyright © 2011 Memotec Inc.

Chapter 1: NetPerformer Support of TCP Acceleration. . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1. 1 About the NetPerformer TCP Acceleration Option . . . . . . . . . . . . . . . . . . 1-2

1. 2 Problems with TCP/IP in a Satellite Environment . . . . . . . . . . . . . . . . . . . 1-3

1. 3 Other Considerations and Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1. 4 NetPerformer Solutions to TCP/IP over Satellite . . . . . . . . . . . . . . . . . . . . 1-7

1. 5 Availability on NetPerformer Products . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12

Chapter 2: Configuring TCP Acceleration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2. 1 Before You Configure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2. 2 TCP Acceleration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2. 3 Configuration Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2. 4 Monitoring TCP Acceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

3. 1 Connecting to a Remote Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Memotec Inc. 1-1

1.1 About the NetPerformer TCP Acceleration Option

NOTE: The NetPerformer unit may be installed in front of a satellite modem or

1-2 Memotec Inc.

1.2 Problems with TCP/IP in a Satellite Environment

1.2.1 Bit Errors

Memotec Inc. 1-3

1-4 Memotec Inc.

1.3 Other Considerations and Requirements

1.3.2 Backward Compatibility

1.3.3 Network Efficiency

Memotec Inc. 1-5

1.3.4 Network Scalability

1-6 Memotec Inc.

1.4 NetPerformer Solutions to TCP/IP over Satellite

1.4.1 TCP Spoofing

NOTE: In NetPerformer V10.2 a maximum of 300 connections can be spoofed,

Memotec Inc. 1-7

Through TCP spoofing, the NetPerformer approach:

SDM-9230 Satellite dish

1. End-to-end TCP: no spoofing by the NetPerformer gateway

2. TCP Spoofing: NetPerformer gateway intervenes

Real ACK ACK

Figure 1-1: NetPerformer Spoofing of TCP Traffic

1-8 Memotec Inc.

1.4.2 Window Scaling

• Allows window sizes larger than 216

1.4.4 Selective Negative Acknowledgment (SNACK)

Memotec Inc. 1-9

NOTE: Introduced in the Consultative Committee for Space Data Sys-

1.4.5 Congestion Avoidance and Control

1-10 Memotec Inc.

NOTE: TCP Congestion Control is always enabled on the NetPerformer base

1.4.6 Fast Checksum Calculation

Memotec Inc. 1-11

1.5 Availability on NetPerformer Products

TCP Spoofing SDM-9220 and YES NO

Window Scaling All V10.2 prod- NO NO

Timestamp All V10.2 prod- NO NO

SNACK All V10.2 prod- NO NO

Congestion Avoidance All V10.2 prod- NO YES (with soft-

Fast Checksum Calcu- All V10.2 prod- NO NO

Table 1Availability of TCP Protocol Enhancements in NetPerformer V10.2

1-12 Memotec Inc.