For users with private DS3-based network links between sites, for the case
where 2 or more of these DS3's are to be bundled together in a multi-link PPP
connection, Cisco will not support this configuration due to insufficient 7200
cpu resources, so packet-by-packet load sharing must be used
What about the case of the strong coder who decides that networking is more
interesting as a life's work, moves into networking, will not consider
employment where coding is even a remote possibility, and will successfully
land another networking job elsewhere if management even brings up the
at some point, but if the subject of
coding comes up, many will move on.
-Original Message-
From: Randy Bush [mailto:ra...@psg.com]
Sent: Monday, February 27, 2012 6:23 PM
To: Holmes,David A
Cc: North American Network Operators' Group
Subject: Re: Programmers with network engineering skills
Bush
Cc: Holmes,David A; North American Network Operators' Group
Subject: Re: Programmers with network engineering skills
a real programmer can be productive in networking tools in a matter of a
month or two. i have seen it multiple times.
a networker can become a useful real progammer in a year
The problem with using engineering as a model is that computer science
networking theory is based upon mathematical logic and formal mathematics (for
instance Finite State Machines, Turing Machines), and operates on what are
essentially robotic automatons running in real time. Engineering as I
With telcos increasingly implementing Metro Ethernet Forum (MEF) networks, I
have found that telco technicians tasked with maintaining and operating these
carrier Ethernet networks appear to disregard common high availability
practices. For instance, after diagnosing a routing protocol neighbor
I have found that -5dB or -10dB attenuators must be used on the send or receive
strands between Cisco LX connected switches at relatively short distances of
1 km over standard singlemode fiber.
Other Vendors' SFPs rated up to 25 km do not need attenuators at distances 1
km.
-Original
Check out Arista's white papers on low-latency networking, the use of merchant
silicon, and queueing theory applied to serialization delay.
-Original Message-
From: James Braunegg [mailto:james.braun...@micron21.com]
Sent: Thursday, January 26, 2012 5:28 PM
To: Eddie Parra; Rodrick Brown
In the 2002-2003 time frame I worked for a company that colo'd strategic
business servers in various telco facilities (big names, some that are still in
business today), but these telco's had no problem with closing down the colo
and giving 6 months notice to all tenants, with very little
If I am not mistaken the IETF efforts to standardize the TRILL spec, and IEEE
efforts to standardize the DCB spec will provide the desired features to
Ethernet: lossless delivery, QoS, and bringing an IS-IS layer 3 model to layer
2. I think Cisco has a pre TRILL/DCB standards feature set called
The max limit for 100 base FX (100 Mbps Ethernet) is around 6600 feet. Many
campus ductbank systems built in the 1990s when 10 and 100 Mbps Ethernet were
the commodity speeds (before GiGE) used 62.5/125 MM fiber to connect buildings.
It is not unusual to see long MM runs on campus facilities
From time to time some have posted questions asking if BGP load balancers such
as the old Routescience Pathcontrol device are still around, and if not what
have others found to replace that function. I have used the Routescience
device with much success 10 years ago when it first came on the
For this very reason I have advocated using longest prefix BGP routing for some
years now, and checking periodically for the expected path, as it became
obvious from investigating traceroutes that traffic was not being routed as
intended using AS prepends.
-Original Message-
From:
My concern is whether or not consolidating border router and firewall functions
in the same device violates, if not explicitly, then the spirit of the defense
in depth Internet edge design principle. Here is a link to a Department of
Homeland Security document where this is discussed (for
Some firewall vendors are proposing to collapse all Internet edge functions
into a single device (border router, firewall, IPS, caching engine, proxy,
etc.). A general Internet edge design principle has been the defense in depth
concept. Is anyone collapsing all Internet edge functions into one
Personally, I have worked in places where I have performed all of the skills
below (router/switch/Unix/Linux/AD/firewall/proxy/web admin/sendmail admin,
etc.), and also in places where just router/switch/architect layer 1-3 skills
were the primary focus. I prefer the latter, and find this to be
What I have seen lately with telco's building and operating Metro Ethernet
Forum (MEF) based Ethernet networks is that relatively inexperienced telco
staff are in charge of configuring and operating the networks, where telco
operational staff are unaware of layer 2 Ethernet network nuances,
For fixed 3G sites where 3G is used as a backup to wireline access, this has
been found to be an acceptable solution, although round trip latency is quite
high. My understanding is that the wireless and wireline backbone networks
interconnect/peer in the eastern Texas area, meaning that a
Formal construction contract bids use the Construction Specification Institute
(CSI) format. There are 2 versions, I am familiar with and use the 1998
version. The 1998 CSI format is broken up into 16 divisions (mechanical, civil,
electrical, architectural, etc.). Electrical, where network
This is a perfect example of why it is crucial that inbound route filters be
scrupulously maintained in upstream BGP providers. Who knows who is out there.
-Original Message-
From: McCall, Gabriel [mailto:gabriel.mcc...@thyssenkrupp.com]
Sent: Tuesday, November 01, 2011 7:29 PM
To:
Looking at the link referenced below, the route optimization method mentioned
appears to be very similar to the old Routescience or Sockeye BGP optimization
products.
-Original Message-
From: Jay Nakamura [mailto:zeusda...@gmail.com]
Sent: Thursday, October 20, 2011 1:54 PM
To: bas
Cc:
I used Pathcontrol with great success, moving bandwidth from one provider to
another at a very granular level. It beat the Netflow/CAIDA tools manual
approach hands down. I don't understand the performance issue, though, and this
is not the first time performance has been raised as an issue.
ESX does support link aggregation, if by that is meant more than one Ethernet
switch-to-ESX bundle, acting as a single logical pipe, and with stacked TOR
switch configurations the bundles Ethernet links can connect to different TOR
switches for redundancy. Nexus 1000V is better for network
I think this shows the need for an Internet-wide multicast implementation.
Although I can recall working on a product that delivered satellite multicast
streams (with each multicast group corresponding to individual TV stations) to
telco CO's. This enabled the telco to implement multicast at
Way too many players ... means that the telecom marketplace is good for the
consumer, with competition keeping prices low. Many network users feel that
prices are still way too high, particularly for high speed circuits and dark
fiber, areas in which Level 3 and Global Crossing have
EXFO purchased the BRIX active management system a couple of years ago. BRIX
can be used to determine basic rtt, packet loss, jitter, and also contains a
suite of application tests such as ftp, various voice codecs, etc.
-Original Message-
From: Dustin Swinford
Talari management apparently has experience at the old Routescience BGP
load-balancer startup, so this warrants a closer look. Has anyone used their
products?
One of the best active measurement products is the BRIX monitoring
system, now owned by EXFO. Active measurement systems have the
capability of sending out emulated application probes (for instance
G.711 calls), or alternatively simple ping tests to gather round trip
times (RTT), jitter, and
1 GiGE switches at a minimum; some vendors (e.g., arista) have low cost
48 port 1000/1 switches. Cisco's UCS system uses 8 10 GiGE uplinks
where the servers (running a hypervisor kernel) plug into a chassis
backplane with 2 10 GiGE connectors each, that mux 10 GiGE and 4/8/16
GiG FC over the
Sometimes it is a hard sell, but the factor most overlooked when
designing high speed networks is that of designing for low latency.
Bandwidth and over/under subscription are only part of the network
design. Low latency networks (regional RTTs of 1-5 milliseconds; campus
RTTs in the sub
Some use AS prepends, not for traffic engineering, as ISPs often
override AS prepends with private peering (communities/local pref
settings), but for the simple purpose of making advertised prefixes
stand out amongst a welter of BGP routes.
-Original Message-
From: Greg Whynott
We've been looking at Cisco's Unified Computing System (UCS) blade
server, which appears to have great potential. Very fast, and eliminates
almost all top-of-rack copper cabling from servers to top-of-rack
switch. Custom-built for VMWare optimization, but other virtualization
OS's will run also
EXFO also sells the BRIX SLA verifier, which calculates RTT, packet
loss, and jitter for various applications running on top of the link
layer.
-Original Message-
From: Tim Jackson [mailto:jackson@gmail.com]
Sent: Wednesday, October 27, 2010 6:54 PM
To: Diogo Montagner
Cc:
With the assumption that you will have a wired backhaul to your HQ over
which the retail access-layer devices connect to commerce servers, make
sure that the wireless carrier's gateways to their wired network (where
the wired backhaul is connected to) are geographically well-dispersed
such that
Modern telephone pole aerial fiber uses all dialectric self-supporting
(ADSS) technology, where the self-supporting component consists
primarily of aramid yarn, the same material used for bullet-proof vests.
This makes for an extremely light weight, almost indestructible fiber
bundle. My guess is
For business purposes such as fixed wireless access for small branch
offices, it would seem that Wi-Max is superior to current GSM and CDMA
proprietary networks in that the upload/download speeds are symmetric.
It appears that GSM and CDMA networks are based on the asymmetric low
upload
We use Cisco 3750 L3 switches for Metro Ethernet connectivity. The 3750
SFPs can run at wire speed up to 1 GiGE. The 3750s are very reliable,
and have good, follow-the-sun technical support in case of problems.
Some caveats:
1. only the ME version supports MPLS, in case you want to overlay an
The ability to manage bandwidth over multiple ISP links each of which
may charge variable rates per Mb, and also be billed by the 95th
percentile billing method, is the main justification for a device like
the Routescience product. In my experience ROI is captured in a
relatively short time.
-
From: Antonio Querubin [mailto:t...@lava.net]
Sent: Monday, January 04, 2010 12:13 PM
To: Holmes,David A
Cc: Brandon Galbraith; nanog@nanog.org
Subject: RE: Experiences with Comcast Ethernet/Transit service
On Mon, 4 Jan 2010, Holmes,David A wrote:
I do not know of Comcast's Ethernet services
Running fiber in the sewers can lead to many very expensive problems for
homeowners. This is so because some municipalities consider the lateral
sewer line running from the main sewer line in the street to the
homeowners' house the responsibility of the homeowner. If the lateral
should get blocked
Most purpose-built routing appliances use ternary content addressable memory
(TCAM) in order to accomplish deterministic, hardware-based, longest-prefix
lookups in large routing tables, such as a full Internet BGP feed. TCAM is used
to replace software-based table lookup algorithms which have
BGP load-balancing appliances such as the old Routescience Pathcontrol
provided a deterministic end-to-end solution by measuring the RTTs of
the second and third packets of the TCP 3-way handshake between the
commercial web site and user destination networks. A full BGP feed was
required from each
An additional requirement often overlooked by Metro Ethernet architects
is to ensure that layer 3 multicast stateful protocols are implemented
in the carrier equipment. In order to ensure that PIM (S,G) stateful
packets are not flooded out all ports in customers'
geographically-dispersed switches,
This says more about current ADSL technology not really being
broadband than it does about South Africa's telecommunications
infrastructure. Doing the arithmetic, my Southern California ATT
384/1.5 ADSL connection would take approximately 23 hours to transmit 32
Gb (4 GB x 8) with the 384 Kbps
The time should be measured in seconds for your BGP advertised prefixes
to propagate to most of the Internet. It may take longer for some
isolated ISP's to receive the routes. If you use the longest prefix
method to advertise to your preferred ISP, a convergence to the backup
ISP (where shorter
Cisco recommends both cards for access-layer use, principally as wiring
closet aggregation for desktop users. Cisco recommends 65xx or 67xx line
cards for backbone (read deterministic) connections, which means that
only 65xx devices with sup720s, or older switch fabric modules can be
used for
Another approach to collecting buffer utilization is to infer such
utilization from other variables. Active measurement of round trip times
(RTT), packet loss, and jitter on a link-by-link basis is a reliable way
of inferring interface queuing which leads to packet loss. A link that
runs with good
In my opinion the Sup32 platform has some limitations when the
technology is considered for high data rate, deterministic carrier
customer-facing scenarios. Cisco sells the Sup32 as a wiring closet
aggregation switch the main purpose of which is to connect desktop users
to central core switches.
It seems intuitive, but according to basic queuing theory splitting up a
single channel into N fixed smaller channels makes the response time
(T), N times worse, where T= (queuing + transmission time).
-Original Message-
From: Rod Beck [mailto:rod.b...@hiberniaatlantic.com]
Sent:
We use the BRIX active measurement system (BRIX now owned by EXFO) which
gathers round trip time, packet loss, and jitter randomly every minute
24x7x365 for our major backbone links to calculate SLAs. Network
Availability can be measured empirically using BRIX calculated values
of packet loss, and
In a layer 3 switch I consider unicast flooding due to an L2 cam table timeout
a design defect. To test vendors' L3 switches for this defect we have used a
traffic generator to send 50-100 Mbps of pings to a device that does not reply
to the pings, where the L3 switch was routing from one vlan
Some things to remember about the MSFC2s when designing a deterministic
network:
Without the switch fabric module, the 6509 only has a 32 Gbps
contention-based BUS as a backplane. Also I believe only classic line
cards work without the switch fabric module. Classic line cards share
hardware port
We have just implemented Avocent console and power concentrators.
Console servers are reachable via a highly customizable web interface.
The Avocent software can also be virtualized on VMWare. Console
connectivity can be provisioned to first try SSH via the IP network, and
automatically failover
But I recollect that FORE ATM equipment using LAN Emulation (LANE) used
a broadcast and unknown server (BUS) to establish a point-to-point ATM
PVC for each broadcast and multicast receiver on a LAN segment. As well
as being inherently unscalable (I think the BUS ran on an ASX1000 cpu),
this scheme
From the network operators' standpoint, designing a network that
operates at 50% utilization (without using ponderous QoS schemes)
assumes that there is no random queuing behavior in the network that can
result in dropped packets and large variations in packet arrival jitter.
An active measurement
My understanding is that ATT uses an MPLS/VRF CE router facing the user
such that the resulting network connectivity is a private MPLS VPN. VZW
apparently requires the user to implement a GRE/IPSec configuration just
to reach their MPLS/VRF layer. The resulting user router config is thus
much
Wireless RF links have their drawbacks:
1. Current GHz Frequency technology places upper limit of 1 Gbps on
point-to-point links, and distance at 1 Gbps is limited. Commercial GiGE
radios are just now appearing, replacing 100 Mbps Ethernet and oc3 SONET
radios. Telco use of wireless links to
Take a look at the BRIX active measurement instrumentation product which is now
owned by EXFO. Many carriers use the BRIX probes to produce empirical data
representing SLA values such as jitter, packet loss and round trip times for
their network links. BRIX also has other more sophisticated
In cases where lengthy in-house DS3 demarc extensions must be run, we
have found it expedient to have the local telco provider (Qwest in
Scottsdale?) extend the demarc. That way the telco is responsible for
end-to-end CSU-to-CSU wiring diagnosis and repair.
-Original Message-
From: Jay
Important network design parameters to take into consideration when
planning SUP720 vs SUP32:
1. SUP720 has 720 Gb backplane (switchfabric) on supervisor card, and 32
Gb shared bus backplane.
2. SUP32 only has 32 Gb shared bus backplane
3. New Cisco line cards with dual 20 Gb connections to 720
Make sure that the new 10 GiGE line cards are not in your plans if you
choose the SUP32. This holds for some of the other copper and fiber line
cards where line card buffer capacity may be critical to effective
throughput. Some new line cards only connect to the 720 Gig backplane.
-Original
The Talari device appears to operate like the old Routescience
Pathcontrol BGP load balancer circa 2002 (Routescience is now owned by
Avaya I believe). Routescience was able to compile the best path to
Internet BGP prefixes so that a web site could connect to multiple 2nd
tier ISPs (for circuit
We use BRIX for SLA's by measuring round trip times, jitter, and packet
loss across all of our backbone links. In conjunction with a traffic
generator to add background traffic, and potentially invoke queueing on
interfaces, we have found that BRIX enables us to accurately predict the
behavior of
Arista claims to have the fastest 1/10 Gig 24 and 48 port 1RU switch,
with a backplane capacity guaranteeing 10 Gig full duplex line rate per
port.
Cisco's CEF is local only and functions to download the arp cache and
routing table into ASICs for hardware switching; but look at Cisco's
NSF/SSO
Haven't seen one. With the huge heat sink and serialization circuitry on
the X2, what advantage would a single strand connector bring? MRV may
have one if anyone does, though.
-Original Message-
From: Andrey Slastenov [mailto:a.slaste...@gmail.com]
Sent: Thursday, February 19, 2009 1:06
We use the BRIX active measurement instrumentation product to measure
round-trip, jitter, and packet loss SLA conformity.
-Original Message-
From: Saqib Ilyas [mailto:msa...@gmail.com]
Sent: Thursday, February 19, 2009 7:50 AM
To: nanog@nanog.org
Subject: Network SLA
Greetings
I am
I am in need of dark fiber in the Parker, Arizona area.
If anyone can help please contact me off list.
Thanks,
David
We're not a big verizon wireless customer, (we have been allocated a /25
for remote data access devices). We run multi-homed BGP with vw. vw says
that they must advertise 48 summarized prefixes to us, instead of just
the /25. The 48 prefixes are apparently advertised to all of the
de-aggregated
For large plants, the Sageon brand is excellent and for small scale, 48
VDC @ 30 amps the Argus brand is excellent. The Sageon units are
stand-alone. The Argus units are rm @ 19 and 23.
We use both.
David
-Original Message-
From: Frank Bulk [mailto:frnk...@iname.com]
Sent: Wednesday,
If an Industrial Ethernet switch is required it may be productive to
look at Ruggedcom products. Ruggedcom has a published upper operating
range of +85 C, which we have deployed in outside non-HVAC enclosures in
environments where the outside ambient temperature can reach +49 to +55
C for extended
I have used Solarwinds Wan Killer, but have yet to discover a method of
initiating round-trip traffic from a single generator, but Solarwinds
can stress a GiGE MAN link using a desktop PC with a GiGE card as the
generator.
-Original Message-
From: Stephens, Josh [mailto:[EMAIL PROTECTED]
The Metro Ethernet Forum (MEF) MEF10-1 ELAN multipoint-to-multipoint
specification says that multicast packets must be replicated out all
ports in the ELAN, except the ingress port. Some carriers have taken
this literally and built a virtual ELAN service emulating a 1990's style
hub in which all
If the switches are Cisco, then Cisco Works has a L2 STP forwarding path
graphical display which can be used in cases where the L3 path is a
logical abstraction overlaid on the underlying L2 topology.
-Original Message-
From: Larry Sheldon [mailto:[EMAIL PROTECTED]
Sent: Wednesday,
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