Optimizing AIX 7 network performance: Part 1, Network overview - Monitoring the hardware
About this series
Part 1 of this three-part series on AIX networking provides a networking
overview and discusses the tools that help you monitor your hardware.
Part 2 covers tuning the Network File System (NFS) with monitoring
utilities, such as
nfsstat and nmon, and it also goes over how to tune with nfso. Part 3 shows you how to monitor network packets and how to use netstat for this purpose. You'll learn how to tune your network subsystem using the no utility. This series also expounds on various best practices of network I/O performance tuning.Introduction
The first thing that usually comes to mind when a system administrator
hears that there might be some network contention issues is to run
netstat. netstat, the equivalent of using vmstat or iostat for your memory reports, is a quick way to get an overview of how your network is configured. Unlike vmstat or iostat,
the defaults usually do not give you as much information as you
probably would like. You need to understand the correct usage of netstat and how best to utilize it when monitoring your system.netstat is really not a monitoring tool in the sense of vmstat and iostat.
You can use other tools more suitable (discussed later in the article)
to help monitor your network subsystem. At the same time, you can't
really start to monitor unless you have a thorough understanding of the
various components related to network performance. These components
include your network adapters, your switches and routers, and how you
are using virtualization on your host logical partitions. If you
determine you are indeed having a network bottleneck, fixing the problem
might actually lay outside of your immediate host machine. There is
little you can do if the network switch is improperly configured on the
other end. Of course, you might be able to point the network team in the
right direction. You should also spend time gathering overall
information about your network. How are you going to be able to
understand how to troubleshoot your network devices unless you really
understand your network? In this article, you'll look at specific AIX
network tracing tools, such as netpmon, and how they can help you isolate your bottlenecks.
Finally, no matter which subsystem you are looking to tune, you must
think of systems tuning as an ongoing process. As stated before, the
best time to start monitoring your systems is at the beginning, before
you have any problems and users aren't screaming. You must have a
baseline of network performance so that you know what the system looks
like when it is behaving normally. Finally, when making changes, be
careful to make changes only one at a time so that you can really assess
the impact of your change.
This section provides an overview of the network as it relates to AIX 7
and covers the physical aspects of the network (device drives and
adapters), the AIX networking stack, and how to make some changes to
your adapter.
Understanding the network subsystem, as it relates to AIX, is not an
easy undertaking. When examining the CPU and memory bottlenecks, there
are far fewer areas that you need to examine from a hardware and
software aspect. Disk I/O tuning is more complex, as there are many more
issues that impact performance, particularly during the architectural
and build-out of your systems. In this respect, tuning your network is
probably most like tuning your disk I/O, which is actually not too
surprising, as they both relate to I/O. Let's start.
Figure 1 illustrates the AIX Transmission Control Protocol/Internet Protocol (TCP/IP) layers.
Figure 1. The AIX TCP/IP layers
Figure 1 illustrates that there is more to network monitoring than running
netstat and
looking for collisions. From the application layer through the media
layer, there are areas that need to be configured, monitored, and tuned.
At this point, you should notice some similarities between this
illustration and the Open Systems Interconnection Basic Reference Model
(OSI Model). The OSI Model has seven layers (bottom to top):- Physical
- Data-link
- Network
- Transport
- Session
- Presentation
- Application
Perhaps the most important concept to understand is that on the host
machine each layer communicates with its corresponding layer on the
remote machine. The actual application programs transmit data using
either User Datagram Protocol (UDP) or Transmission Control Protocol
(TCP) transport layer protocols. They receive the data from whatever
application you are using and divide them into packets. The packets
themselves differ, depending on whether it is a UDP or TCP packet.
Generally speaking, UDP is faster, while TCP is more secure. There are
many tunable parameters to look at—you'll get to these parameters during
subsequent phases of the series. You might want to start to familiarize
yourself with the
no command,
which is the utility designed to make the majority of your network
changes. From a hardware perspective, it is critical that you understand
the components that need to be configured appropriately to optimize
performance. Though you might work together with the network teams that
manage your switches and routers, it is unlikely that you will be
configuring them (unless you are a small shop or a one-person IT
department). The most important component you will be working with is
your network adapter. Gigabit Ethernet is now the standard network
interface, although 10Gbit network cards and infrastructure is becoming
more accessible.Maximum Transfer Unit
Maximum Transfer Unit (MTU) is defined as the largest packet that can be
sent over a network. The size depends on the type of network. For
example, 16-bit token ring has a default MTU size of 17914, while Fiber
Distributed Data Interface (FDDI) has a default size of 4352. Ethernet
has a default size of 1500 (9000 with jumbo frames enabled). Larger
packets require less packet transfers, which result in higher bandwidth
utilization on your system. In particular, using jumbo frames allows for
an entire 8KB NFS block to be exchanged in a single packet, which can
significantly improve performance. An exception to this is if your
application prefers smaller packets, and this includes web applications
on the Internet, since most Internet connections do not support jumbo
frames. If you are using a Gigabit Ethernet, you can use a jumbo frames
option. To support the use of jumbo frames, it's important to note that
your switch must also be configured, accordingly.
To change to jumbo frames, use this fastpath:
# smit devices.
Then go to Communication>Ethernet>Adapter>Change/show characteristics of an Ethernet adapter. Try to change the transmit jumbo frames option from "No" to "Yes" (see Listing 1).
Listing 1. Characteristics of an Ethernet adapter screen
Change / show characteristics of an Ethernet adapter
Change / Show Characteristics of an Ethernet Adapter
Type or select values in entry fields.
Press Enter AFTER making all desired changes.
[Entry Fields]
Ethernet Adapter ent0
Description Virtual I/O Ethernet Adapter (l-lan)
Status Available
Location
Enable ALTERNATE ETHERNET address no +
ALTERNATE ETHERNET address [0x000000000000] +
Minimum Tiny Buffers [512] +#
Maximum Tiny Buffers [2048] +#
Minimum Small Buffers [512] +#
Maximum Small Buffers [2048] +#
Maximum Medium Buffers [128] +#
Maximum Medium Buffers [256] +#
Minimum Large Buffers [24] +#
Maximum Large Buffers [64] +#
Minimum Huge Buffers [24] +#
Maximum Huge Buffers [64] +#
Transmit Copy Buffers [32] +#
Transmit Copy Buffer Size [65536] +#
Trace Debug Enable no +
Checksum Offload Enable yes +
I/O memory entitlement reserved for device 0
Apply change to DATABASE only no +
Where is the jumbo frames option? In this case, you cannot make the
change. The reason for this is because you are only using the Virtual
I/O Ethernet on this system—this topic is discussed in more detail
later.
On a system where you have direct access to the network hardware, check the system using Listing 2.
Listing 2. Checking the system
Change / show characteristics of an Ethernet adapter
Type or select values in entry fields.
Press Enter AFTER making all desired changes.
[Entry Fields]
Ethernet Adapter ent1
Description 10/100/1000 Base-TX P>
Status Available
Location 1j-08
RX descriptor queue size [1024] +#
TX descriptor queue size [1024] +#
Software transmit queue size [8192] +#
Transmit jumbo frames yes +
Enable hardware TX TCP resegmentation yes +
Enable hardware transmit and receive checksum yes +
Media speed Auto_Negotiation +
Enable ALTERNATE ETHERNET address no +
ALTERNATE ETHERNET address [0x000000000000] +
Apply change to DATABASE only no +
F1=Help F2=Refresh F3=Cancel F4=List
F5=Reset F6=Command F7=Edit F8=Image
F9=Shell F10=Exit Enter=Do
You have now changed the field to support jumbo frames.
Most modern network switches and environments can take advantage of
auto-negotiation to provide the best speed, especially as full-duplex
network switches have become the standard. However, you force a
particular configuration if the auto-negotiation fails to configure a
speed that you know your network switch is capable of supporting.
The
lsattr command
gives you the information that you need. The en prefix displays your
driver parameters, while the ent prefix displays your hardware
parameters. Let's display your hardware parameters (see Listing 3).Listing 3. Displaying the hardware parameters
testsys:/home/test>lsattr -El ent0 alt_addr 0x000000000000 Alternate Ethernet Address Truechksum_offload yes Checksum Offload Enable True copy_buffs 32 Transmit Copy Buffers True copy_bytes 65536 Transmit Copy Buffer Size True desired_mapmem 0 I/O memory entitlement reserved for device False max_buf_huge 64 Maximum Huge Buffers True max_buf_large 64 Maximum Large Buffers True max_buf_medium 256 Maximum Medium Buffers True max_buf_small 2048 Maximum Small Buffers True max_buf_tiny 2048 Maximum Tiny Buffers True min_buf_huge 24 Minimum Huge Buffers True min_buf_large 24 Minimum Large Buffers True min_buf_medium 128 Minimum Medium Buffers True min_buf_small 512 Minimum Small Buffers True min_buf_tiny 512 Minimum Tiny Buffers True trace_debug no Trace Debug Enable True use_alt_addr no Enable Alternate Ethernet Address True
In this case, your interface is set as auto-negotiate.
You
should also check your firmware levels to make sure they are up to
date. We've seen many network problems fixed when updating to the latest
levels of firmware. The
lscfg command gives you the firmware information (see Listing 4).Listing 4. Using the
lscfg command for firmware information
testsys:/home/test >lscfg -vp | grep -p ETHERNET
4 X 1GB ETHERNET: Record Name.................VINI
Flag Field..................XXET
Hardware Location Code......U78C0.001.DBJ3229-P2-C8
Customer Card ID Number.....2BC4
Serial Number...............YL10D9360034
CCIN Extender...............1
Product Specific.(VZ).......04
FRU Number..................46K5965
Part Number.................46K6484
Product Specific.(HE).......0001
Product Specific.(CT).......30910008
Product Specific.(HW).......0001
Product Specific.(B3).......000000000001
Product Specific.(B4).......00
Product Specific.(B7).......000000000000000000000000
Product Specific.(B1).......00215EEB40C0002000215EEB40E00020
Version.....................ipzSeries
Physical Location: U78C0.001.DBJ3229-P2-C8
4 X 1GB ETHERNET:
Record Name.................VINI
Flag Field..................XXET
Hardware Location Code......U78C0.001.DBJ3226-P2-C8
Customer Card ID Number.....2BC4
Serial Number...............YL10D9360085
CCIN Extender...............1
Product Specific.(VZ).......04
FRU Number..................46K5965
Part Number.................46K6484
Product Specific.(HE).......0001
Product Specific.(CT).......30910008
Product Specific.(HW).......0001
Product Specific.(B3).......000000000001
Product Specific.(B4).......00
Product Specific.(B7).......000000000000000000000000
Product Specific.(B1).......00215EEB4680002000215EEB46A00020
Version.....................ipzSeries
Physical Location: U78C0.001.DBJ3226-P2-C8
4 X 1GB ETHERNET:
Record Name.................VINI
Flag Field..................XXET
Hardware Location Code......U78C0.001.DBJ3227-P2-C8
Customer Card ID Number.....2BC4
Serial Number...............YL10D9360028
CCIN Extender...............1
Product Specific.(VZ).......04
FRU Number..................46K5965
Part Number.................46K6484
Product Specific.(HE).......0001
Product Specific.(CT).......30910008
Product Specific.(HW).......0001
Product Specific.(B3).......000000000001
Product Specific.(B4).......00
Product Specific.(B7).......000000000000000000000000
Product Specific.(B1).......00215EEB4140002000215EEB41600020
Version.....................ipzSeries
Physical Location: U78C0.001.DBJ3227-P2-C8
See the Resources section at the end of the article for a link to the most current release information for your adapter.
Though the series focuses on tuning in subsequent parts, you might want
to start to familiarize yourself with the memory management facility of
network subsystems. What you need to know at this point is that it
relates to data structures called mbufs. These are used to store kernel
data for incoming and outbound traffic. The buffer sizes themselves can
range from 32 to 16384 bytes. They are created by making allocation
requests to the Virtual Memory Manager (VMM). In an SMP box, each memory
pool is split evenly for every processor. The monitoring section below
shows you how to view mbufs. An important concept to note is that
processors cannot borrow from the memory pool outside of its own
processor.
Two other concepts you should be familiar with are virtual Ethernet and shared Ethernet.
- Virtual Ethernet: Virtual Ethernet allows for inter-partition- and IP-based communications between logical partitions on the same frame. This is done by the use of a virtual I/O switch. The Ethernet adapters themselves are created and configured using the HMC. If you recall, you tried to change an adapter earlier that was configured with virtual Ethernet.
- Shared Ethernet: Shared Ethernet allows for the use of Virtual I/O servers (VIOs), where several host machines can actually share one physical network adapter. Typically, this is used in environments that do not require substantial network bandwidth.
While the scope of this series is not on virtualization, you should
understand that if you are using virtualization, there might be other
reasons for your bottleneck outside of what you are doing on your host
machine. While virtualization is a wonderful thing, be careful not to
share too many adapters from your VIO server, or you might pay a large
network I/O penalty. Keep in mind as well that with workload partitions
(WPAR), the network configuration of the host environment is used and
shared by each partition; you cannot configure WPAR network performance
individually. Using appropriate monitoring tools should inform you if
you have a problem.
In addition, application performance can be affected fundamental
services, such as domain name service (DNS) used to resolve hostnames
and Internet addresses.
Monitoring
This section provides an overview of general network monitoring commands
and specific AIX 7 tools available to you. Some of the tools allow you
to troubleshoot a performance problem quickly while others capture data
for historical trending and analysis.
Let's get back to the old standby,
netstat, which displays overall network statistics. Probably one of the most common commands you type in is netstat -in (see Listing 5).Listing 5. Using
netstat with the -in optionl488pp065_pub[/tmp] > netstat -in Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll en1 1500 link#2 66.da.93.d1.6b.18 70136750 0 336237 0 0 en1 1500 10.153 10.153.20.65 70136750 0 336237 0 0 en0 1500 link#3 66.da.93.d1.6b.17 202571785 0 79277 0 0 en0 1500 172.29.128 172.29.148.225 202571785 0 79277 0 0 lo0 16896 link#1 778719 0 778718 0 0 lo0 16896 127 127.0.0.1 778719 0 778718 0 0 lo0 16896 ::1%1 778719 0 778718 0 0
Here is what it means:
- Name: Interface name.
- MTU: Interface Maximum Transfer Unit size.
- Network: The actual network address that the interface connects to.
- Address: Mac and IP address.
- Ipkts: The total amount of packets received by the interface.
- Ierrs: The amount of errors reported back from the interface.
- Opkts: The amount of packets transmitted from the interface.
- Oerrs: The amount of error packets transmitted from the interface.
- Coll: The amount of collisions on the adapter. If you are using Ethernet, you won't see anything here.
Another handy
netstat flag is the -m option.
This flag allows you to view the Kernel malloc statistics; the mbuf
memory requests, including the size of the buffers, the amount in use
and the failures by CPU (see Listing 6).Listing 6. netstat with
-m optionl488pp065_pub[/tmp] > netstat -m Kernel malloc statistics: ******* CPU 0 ******* By size inuse calls failed delayed free hiwat freed 64 566 2015884 0 7 266 5240 0 128 5890 1830085 0 175 158 2620 0 256 5781 651987 0 295 2875 5240 500 512 8000 181192188 0 972 56 6550 0 1024 3165 1889042 0 792 35 2620 0 2048 1071 3387085 0 520 23 3930 0 4096 2056 2775 0 83 5 1310 0 8192 6 260 0 3 163 327 0 16384 256 413 0 62 0 163 0 32768 55 274 0 23 4 81 0 65536 117 175 0 76 0 81 0 131072 4 5 0 0 102 204 0 ******* CPU 1 ******* By size inuse calls failed delayed free hiwat freed 64 46 226765 0 0 146 5240 0 128 58 152657 0 2 134 2620 0 256 51 70035 0 2 301 5240 0 512 78 46458768 0 4 66 6550 0 1024 62 171426 0 12 30 2620 0 2048 23 3669503 0 5 25 3930 0 4096 1 891 0 4 9 1310 0 8192 1 567 0 3 306 327 0 16384 0 12 0 5 2 163 0 32768 2 17 0 3 7 81 0 65536 0 11 0 6 0 81 0 131072 0 1 0 0 20 40 0 ******* CPU 2 ******* By size inuse calls failed delayed free hiwat freed 64 21 1295 0 1 43 5240 0 128 9 781 0 0 23 2620 0 256 9 1226 0 0 39 5240 0 512 81 36991563 0 10 55 6550 0 1024 27 1241 0 15 33 2620 0 2048 5 3286 0 0 23 3930 0 4096 0 52 0 1 5 1310 0 8192 0 1 0 1 0 327 0 32768 0 1 0 1 1 81 0 131072 0 0 0 0 16 32 0 ******* CPU 3 ******* By size inuse calls failed delayed free hiwat freed 64 42 1224 0 2 86 5240 0 128 15 1195 0 13 401 2620 0 256 12 2607 0 82 1316 5240 0 512 83 36405229 0 222 1733 6550 0 1024 32 1220 0 14 32 2620 0 2048 23 4549 0 260 507 3930 0 4096 1 42 0 3 3 1310 0 8192 0 58 0 7 21 327 0 16384 0 128 0 19 121 163 0 32768 2 29 0 7 22 81 0 65536 0 47 0 24 47 81 0 131072 0 0 0 0 102 204 0
The
-m option is
particularly useful because it shows the network performance statistics
in relation to individual CPUs. When monitoring and managing the
performance with LPAR and WPAR environments, the ability to correlate
your CPU resources and the network resources can give you valuable
information about the correct allocation and distribution of network
resources.
For Ethernet, you can use the
entstat command to display device-driver statistics. This provides a plethora of information (seeListing 7).Listing 7. Using the
entstat command to display device driver statistics
l488pp065_pub[/tmp] > entstat -d ent0
-------------------------------------------------------------
ETHERNET STATISTICS (ent0) :
Device Type: Virtual I/O Ethernet Adapter (l-lan)
Hardware Address: 66:da:93:d1:6b:17
Elapsed Time: 16 days 1 hours 48 minutes 7 seconds
Transmit Statistics: Receive Statistics:
-------------------- -------------------
Packets: 79636 Packets: 203054741
Bytes: 15868037 Bytes: 30905882351
Interrupts: 0 Interrupts: 201058047
Transmit Errors: 0 Receive Errors: 0
Packets Dropped: 0 Packets Dropped: 0
Bad Packets: 0
Max Packets on S/W Transmit Queue: 0
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0
Broadcast Packets: 5 Broadcast Packets: 203036730
Multicast Packets: 6171 Multicast Packets: 215
No Carrier Sense: 0 CRC Errors: 0
DMA Underrun: 0 DMA Overrun: 0
Lost CTS Errors: 0 Alignment Errors: 0
Max Collision Errors: 0 No Resource Errors: 0
Late Collision Errors: 0 Receive Collision Errors: 0
Deferred: 0 Packet Too Short Errors: 0
SQE Test: 0 Packet Too Long Errors: 0
Timeout Errors: 0 Packets Discarded by Adapter: 0
Single Collision Count: 0 Receiver Start Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 0
General Statistics:
-------------------
No mbuf Errors: 0
Adapter Reset Count: 0
Adapter Data Rate: 20000
Driver Flags: Up Broadcast Running
Simplex 64BitSupport ChecksumOffload
DataRateSet
Virtual I/O Ethernet Adapter (l-lan) Specific Statistics:
---------------------------------------------------------
RQ Length: 4481
Trunk Adapter: False
Filter MCast Mode: False
Filters: 255
Enabled: 1 Queued: 0 Overflow: 0
LAN State: Operational
Hypervisor Send Failures: 0
Receiver Failures: 0
Send Errors: 0
Hypervisor Receive Failures: 0
Invalid VLAN ID Packets: 0
ILLAN Attributes: 0000000000003002 [0000000000003002]
Port VLAN ID: 2
VLAN Tag IDs: None
Switch ID: ETHERNET0
Hypervisor Information
Virtual Memory
Total (KB) 79
I/O Memory
VRM Minimum (KB) 100
VRM Desired (KB) 100
DMA Max Min (KB) 128
Transmit Information
Transmit Buffers
Buffer Size 65536
Buffers 32
History
No Buffers 0
Virtual Memory
Collisions are largely a thing of the past with modern network switches,
but look for transmit errors and make sure they are not increasing too
fast. You need to learn to troubleshoot collision and error problems
before you even begin to think about tuning. Alternatively, you can use
netstat -v, which provides similar information.
Let's look at
netpmon. netpmon provides
information on CPU usage as it relates to the network, and it also
includes data about the network device driver I/O, Internet socket
calls, and other various statistics. Similar to its other trace
brethren, tprof andfilemon, it starts a trace and runs in the background until you stop it with the trcstop command. We like netpmon because
it really gives you a detailed overview of network activity and also
captures data for trending and analysis (though it is not as useful as nmon for this purpose). Here you'll use a trace buffer size of two million bytes (see Listing 8).Listing 8. netpmom with
-T optionl488pp065_pub[/tmp] > netpmon -T 2000000 -o /tmp/net.out Run trcstop command to signal end of trace. Sun Aug 15 04:58:06 2010 System: AIX 7.1 Node: l488pp065_pub Machine: 00F604884C00
Listing 9. Stopping netpmom
l488pp065_pub[/tmp] > trcstop[netpmon: Reporting started] 23675650 Missed Entries found [netpmon: Reporting completed] [ 4 traced cpus ] [ 0.091 secs total preempt time ] [netpmon: 43.388 secs in measured interval]
Listing 10. Sample output
Sun Aug 15 04:58:06 2010System: AIX 7.1 Node: l488pp065_pub Machine: 00F604884C00
========================================================================
Process CPU Usage Statistics:
-----------------------------
Network
Process (top 20) PID CPU Time CPU % CPU %
----------------------------------------------------------
netpmon 12976354 41.7559 24.072 0.000
netpmon 14155800 32.1352 18.526 0.000
inetd 14155804 29.3093 16.897 0.000
xmtopas 14155834 29.2385 16.856 0.000
xmtopas 14155830 29.2381 16.856 0.000
xmtopas 14155822 28.9899 16.713 0.000
xmtopas 14155816 28.9433 16.686 0.000
xmtopas 14155826 28.9390 16.683 0.000
xmtopas 14155828 28.9308 16.679 0.000
inetd 14155824 28.9287 16.677 0.000
xmtopas 14155820 28.9227 16.674 0.000
xmtopas 14155814 28.9158 16.670 0.000
inetd 14155866 23.7606 13.698 0.000
inetd 14155864 23.7131 13.671 0.000
xmtopas 14155846 19.0223 10.966 0.000
inetd 14155848 19.0083 10.958 0.000
inetd 9371742 18.8547 10.870 0.000
inetd 9371658 16.5665 9.551 0.000
inetd 9371886 16.4571 9.488 0.000
xmtopas 9371888 16.4094 9.460 0.000
----------------------------------------------------------
Total (all processes) 838.3315 483.300 0.000
Idle time 78.8376 45.450
========================================================================
First Level Interrupt Handler CPU Usage Statistics:
---------------------------------------------------
Network
FLIH CPU Time CPU % CPU %
----------------------------------------------------------
data page fault 255.0988 147.065 0.000
UNKNOWN 17.9673 10.358 0.000
PPC decrementer 2.7282 1.573 0.000
external device 0.0081 0.005 0.000
instruction page fault 0.0002 0.000 0.000
queued interrupt 0.0000 0.000 0.000
----------------------------------------------------------
Total (all FLIHs) 275.8026 159.001 0.000
========================================================================
TCP Socket Call Statistics (by Process):
----------------------------------------
------ Read ----- ----- Write -----
Process (top 20) PID Calls/s Bytes/s Calls/s Bytes/s
------------------------------------------------------------------------
sshd: 5636334 0.12 1888 0.53 37
nonstop_aix 3539136 0.05 9 0.05 0
java 4260046 0.05 9 0.05 0
------------------------------------------------------------------------
Total (all processes) 0.21 1907 0.62 37
========================================================================
Detailed TCP Socket Call Statistics (by Process):
-------------------------------------------------
PROCESS: sshd: PID: 5636334
reads: 5
As
you can see, there is little overall network I/O activity going on
during this time. The top section is most important, as it really helps
you get an understanding of what processes are consuming network I/O
time, and you can use the more detailed per-process output to obtain
more specific information.
lsattr (used
earlier to view the hardware parameters) is another command you will be
using frequently to display statistics on your interfaces. The
attributes that you see here are configured using either the chdev or no commands. Let's display your driver parameters (see Listing 11).Listing 11. Displaying the driver parameters using
lsattr
l488pp065_pub[/tmp] > lsattr -El en0alias4 IPv4 Alias including Subnet Mask True alias6 IPv6 Alias including Prefix Length True arp on Address Resolution Protocol (ARP) True authority Authorized Users True broadcast Broadcast Address True mtu 1500 Maximum IP Packet Size for This Device True netaddr 172.29.148.225 Internet Address True netaddr6 IPv6 Internet Address True netmask 255.255.192.0 Subnet Mask True prefixlen Prefix Length for IPv6 Internet Address True remmtu 576 Maximum IP Packet Size for REMOTE Networks True rfc1323 Enable/Disable TCP RFC 1323 Window Scaling True security none Security Level True state up Current Interface Status True tcp_mssdflt Set TCP Maximum Segment Size True tcp_nodelay Enable/Disable TCP_NODELAY Option True tcp_recvspace Set Socket Buffer Space for Receiving True tcp_sendspace Set Socket Buffer Space for Sending True
Finally, let's look at Figure 2.
Figure 2. nmon statistics
If you've been following the other series on AIX 7 (see Resources), you know we love
nmon and you should also, once you start using it. With nmon (type
in n after startup), you have a quick snapshot of everything going on
in your network, including adapter details, MTU, error counters and
collisions, and megabit rating.
Further, you also have the ability to capture data with
nmon.
Using the nmon analyzer, you can print out graphical reports directly
from Microsoft® Excel spreadsheets. See Resources for a link to an IBM
Wiki for the nmon manual or for downloads.
Summary
This article covered the relative importance of the network I/O
subsystem, and defined the AIX 7 network I/O layers and how it relates
to the OSI Model. You learned some best practices for network
configuration, changed your Ethernet settings to support jumbo frame,
and viewed interface hardware and driver data. You even examined the
monitoring tools available to you and captured data using
netpmon and nmon. In the next part of the series, you'll tune NFS, find out more about monitoring utilities, such as nfsstat and nmon, and discover how to tune with nfso.
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