Thursday, December 31, 2009

Gus Dus Biography

Former President of Indonesia to 4 Abdurrahman Wahid, often called Gus Dur (born in Jombang, East Java, September 7, 1940, and died in Jakarta, December 30, 2009 at age 69 years).

He is a Muslim of Indonesian kiai and political leader who became president of Indonesia from 1999 to 2001. He succeeded President BJ Habibie after elected by the People's Consultative Assembly (MPR) 1999 election results.

Implementation of government assisted the National Unity Cabinet. Abdurrahman Wahid's presidency begins October 20, 1999 and ended after transmitted through the Special Session of the Assembly in 2001.

Right July 23, 2001, his leadership was replaced by Megawati Sukarnoputri after the mandate was revoked by the Assembly.

Abdurrahman Wahid is the former chairman of Tanfidziyah (executive body) NT NU and founder of the National Awakening Party (PKB).

Gus Dur was born on the 4th and 8th month of Islamic calendar year 1940 in the village of Denanyar, Jombang, East Java, from pair Wahid Hasyim and Solichah.

There is a belief that he was born on August 4, but the calendar used to mark the day of birth is the Islamic calendar, which means he was born on 4 Sha'ban, equal to September 7, 1940.

He was born with the name of Abdurrahman Addakhil. "Addakhil" means "The Conqueror". The word "Addakhil" is not well known, and changed the name of "Wahid", and then better known as Gus Dur calls.

"Gus" is a typical boarding school honor calls to a child kiai means "brother" or "mas".

Gus Dur is the first son of six children. Wahid was born from a very respectable family in the Muslim community of East Java. Grandfather from his father is KH Hasyim Asyari, founder of Nahdlatul Ulama (NU), while the maternal grandfather, KH Bisri Syansuri is the first boarding school teacher who teaches classes on women.

Father Gus Dur, the KH Wahid Hasyim, was involved in the nationalist movement and became Minister of Religious Affairs in 1949. Her mother, Mrs. Hj. Sholehah is the daughter of the founder of Pesantren Denanyar Jombang.

Gus Dur has openly stated that he had blood Tionghoa. He claimed descent from Tan Kim Han who is married to Tan A Lok, siblings Raden Patah (Tan Eng Hwa), founder of the Sultanate of Demak.

A Lok Tan and Tan Eng Hwa is a son of Princess Campa, daughter of a concubine China Raden Brawijaya V.

Tan Kim Han himself and based on studies of a French researcher, Louis-Charles Damais, identified as Sheik Abdul al-Shini Qodir the grave was found in the area Trowulan, East Java.

In 1944, Wahid moved from Jombang to Jakarta, where his father was elected as Chairman I Masyumi Party of Indonesia (Masyumi), an organization that stands with the support of the Japanese army occupied Indonesia.

After the declaration of Independence of Indonesia on August 17, 1945, Wahid returned to Jombang and remained there during the war of independence against the Dutch Indonesia.

At the end of 1949, Wahid moved to Jakarta, and his father was appointed as Minister of Religious Affairs. Abdurrahman Wahid studied in Jakarta, went to primary school before moving to KRIS SD Matraman Perwari. Wahid was also taught to read non-Muslim books, magazines, and newspapers by his father to expand his knowledge.

Wahid continued to live in Jakarta with his family although his father was not a minister of religion in 1952. In April 1953, Wahid's father died from a car accident.

Wahid continued education and in 1954, he entered the Junior Secondary School. In that year, he did not take the class. His mother then sent Gus Dur to Yogyakarta to continue his education. In 1957, after graduating from junior high, Wahid moved to Magelang to start education in pesantren Tegalrejo Muslims. He developed a reputation as a gifted student, completing the pesantren in two years (instead of four years). In 1959, Wahid moved to Tambakberas Pesantren in Jombang. There, while continuing his own education, Abdurrahman Wahid also received his first job as a teacher and later as head of the madrassa schools. Gus Dur is also employed as a journalist magazines like Horizon and Culture Magazine Jaya.

Overseas Education

In 1963, Wahid received a scholarship from the Ministry of Religious Affairs to study at Al Azhar University in Cairo, Egypt. He went to Egypt in November 1963.

Although he was proficient in Arabic, Wahid was told by the university that he had to take remedial classes before studying Islam and Arabic. Unable to provide proof that he has the ability Arabic, Wahid was forced to take remedial classes.

Abdurrahman Wahid began to enjoy living in Egypt in 1964, watching the European and American films, and also watch the football. Wahid was also involved with the Indonesian Student Association and became the association's magazine journalist.

At the end of the year, he successfully passed the remedial class was Arab. When he began his studies in Islam and Arabic in 1965, Wahid was disappointed. He has studied many of the materials provided and refuse to learn the methods used by the university.

In Egypt, Wahid was employed at the Embassy of Indonesia. By the time he worked, Movement event occurred 30 September 1965. Major General Suharto in Jakarta to handle the situation and the efforts made to eradicate communism.

As part of these efforts, the Indonesian Embassy in Egypt was ordered to conduct investigation on university students and provide reports on their political stance. This command is given to Wahid, who was assigned to write a report

But it can be said Wahid failed in Egypt. He did not agree with the method of education and work after the G 30 S / PKI which distracted him.

In 1966 he was told that he had to repeat. Wahid's tertiary education be saved through scholarship at the University of Baghdad. Wahid then was later moved to Iraq and enjoying his new environment.

Although he failed at first, Wahid quickly learned. He also continued his involvement in the Indonesian Students Association and also wrote the association's magazine.

After completing his education at the University of Baghdad in 1970, Wahid went to Holland to continue his education. Wahid wants to study at the University of Leiden, but was disappointed that his education at the University of Baghdad is less recognized. From the Netherlands, Wahid went to Germany and France before returning to Indonesia in 1971.

Early Career

Wahid returned to Jakarta and expect he will go abroad again to study at McGill University in Canada. It's kept himself busy by joining the Institute for Research, Education and Economic and Social Information (LP3ES), an organization comprised of Muslim intellectuals and progressive social democrats.

LP3ES then founded a magazine called Prisma, and Wahid became one of the main contributors to the magazine. In addition to working as a contributor LP3ES, Wahid was also around the pesantren and madrasah throughout Java.

At that time, boarding schools struggling to get funding from the government by adopting the government curriculum. Wahid was concerned that the conditions for the traditional values of the fade due to boarding school this change.

Wahid was also concerned with the poverty he saw the pesantren. At the same time when they persuaded the government boarding schools to adopt curricula, the government is also encouraging pesantren as agents of change and assist the government in the economic development of Indonesia. Wahid decided to drop plans for overseas studies in favor of developing the pesantren.

Abdurrahman Wahid then continued his career as a journalist, and writes for Tempo magazine and newspaper Kompas. The article was well received, and he began to develop a reputation as a social commentator.

With the popularity of that, he was invited to give lectures and seminars, forcing him to travel back and forth between Jakarta and Jombang, where Wahid lived with his family.

Despite having a successful career at that time, Gus Dur was still found it hard to live only from one source of livelihood, and he worked to earn additional income by selling peanuts and delivering ice to be used in her businesses Es Lilin.

In 1974 Wahid was an additional job as a teacher in Jombang in Pesantren Tambakberas, and soon developed a personal reputation. One year later, Wahid add jobs to become teachers Kitab Al Hikam.

In 1977, joined the University of Wahid Hasyim Asyari as Dean of the Faculty of Islamic practice and belief. Once again, Wahid was his job and the universities that want to Wahid to teach additional subjects such as pedagogy, Islamic Shari'a and missiology.

But the excess lead to resentment by some universities, and Wahid was blocked for teaching these subjects. While undertaking all these, Wahid was also addressed during Ramadan at the Muslim community in Jombang

NU
Zahid's family background and then quickly become meaningless. He will be asked to play an active role in running the NU. This ran contrary to the aspirations of Gus Dur in a public intellectual, and he had twice rejected offers to join the Religious Advisory Council of NU.
However, Wahid finally joined the board after his grandfather, Bisri Syansuri, gave him a third bid. Since taking this job, Wahid also choose to move from Jombang to Jakarta and stayed in the capital. As a member of the Religious Advisory Council, Wahid himself as a reformer to lead NU.
At Dur ituGus also got his first political experience. In legislative elections in 1982, Wahid was campaigning for the United Development Party (PPP), an Islamic party that was formed as a result of a merger of four Islamic parties, including NU.
Wahid said that the government interfere with the PPP campaign by arresting people like him. However, Wahid always managed to escape because they have relationships with important people, among them the General Benny Moerdani.

Election 1999 and the MPR

In June 1999, PKB participate in the legislative election arena. PKB won 12 percent of the vote, while the PDI-P won with 33 percent of the vote Raihan.
With the victory party, Megawati will win the election expected in the MPR president. However, the PDI-P does not have a full majority, thus forming an alliance with PKB.
In July, Amien Rais forming the Central Axis, a coalition of Islamic parties. Central Axis then began nominated Gus Dur as a third candidate in the presidential elections, and the commitment of PKB to the PDI-P began to change.
On October 7, 1999, Amien and Central Axis officially declared candidate Abdurrahman Wahid as president. On October 19, 1999, the Assembly rejected Habibie's accountability speech, and Habibie had to withdraw from the presidential election.
A few moments later Akbar Tanjung, Golkar Party Chairman and Chairman of the House declared that Golkar would support Gus Dur. On October 20, 1999, the Assembly re-assembled and began to elect a new president. Abdurrahman Wahid and Indonesia was elected as President of the 4th with 373 votes, while Megawati won only 313 votes.
Not happy because their candidates failed to win the election, Megawati supporters raged, Gus Dur and Megawati must realize that the elected vice president.
Once convinced, General Wiranto, to not participate in the election of vice-president and make the PKB supports Megawati, Gus Dur had managed to convince Megawati to participate.
On October 21, 1999 participate in the election of Megawati's vice president and defeated Hamzah Haz of the PPP



Friday, December 04, 2009

Dispelling LTE Myth

Myth 1: LTE is Data only

Reality: LTE supports voice and efficient support of voice was one of the key considerations in designing LTE. The voice solution for LTE is IMS VoIP and it is fully specified.

The 3GPP solution for voice over LTE is a combination of multiple efforts:

  • The work in Rel 7 to optimize IMS signalling and VoIP encoding so it would be as good or better than CS voice in terms of quality and efficiency,
  • The work in Rel 8 to develop a radio and core network evolution optimized for the transfer of packet data.
  • The work in Rel-7 to add the IMS emergency call requirements and to adapt it to regulatory requirements in LTE and GPRS in Rel-9.
  • The work in Rel-8 to add the always-on IP connectivity requirements in LTE

A key consideration to recognize is that under LTE, voice is just one of many potential media streams that can be communicated. A packet based network and VoIP allows this flexibility while still providing efficient use of radio and network resources.

However, 3GPP recognizes that adoption of both LTE and IMS will not occur overnight. For this reason 3GPP provided a transition solution for voice called CS Fallback. This allows a LTE device to drop back to the legacy 3G or 2G network if IMS VoIP capabilities are not supported. This is viewed as an interim solution to ease the transition to IMS and VoIP.

Myth 2: SMS isn’t supported over LTE

Reality: LTE and EPS will support a rich variety of messaging applications and also SMS is supported over LTE. The solution is twofold, covering both the full IMS case and a transition solution for those networks that do not support IMS.

SMS over IP was fully specified 3GPP Rel 7. It depends on IMS and it is intended to provide compatibility between the existing cellular legacy and the implementations with more elaborate messaging capabilities via SMS and IMS interworking..

For environments without IMS a transition solution was specified. This is called SMS over SGs (previously called the misleading name: SMS over CS). It is a hybrid approach that allows the transmission of native SMS from CS infrastructure over the LTE radio network. SMS over SGs was specified as part of Rel 8. SMS over SGs provides SMS service for mobiles in LTE and since it requires also CS domain infrastructure for the SMS transmission, it is intended to be a transition solution.

Myth 3: IMS isn’t ready for prime time

Reality: IMS has been around a long time. It was first developed as part of Rel 5 in 2002. It is based on IETF protocols such as SIP and SDP that are very mature. These technologies have been embraced by the industry as the signalling mechanism for multimedia applications.

In Rel 7 an effort was made to optimize IMS and the supporting protocols to ensure that voice and other media were supported as efficiently as in circuit switched networks.

IMS is fully specified and mature. The difficulties in rolling out IMS are not due to the protocols or the specifications. The consideration point is not only technical aspects but also shifting the whole industry paradigm from CS services to a truly IP-based environment, i.e. service migration, policies, interoperability and deployment plan included. However, these complexities must be addressed if the idea is to truly provide a richer service environment. This work is ongoing in many forums outside of 3GPP (e.g. Rich Communication Suite).

Myth 4: LTE doesn’t support emergency calls

Reality: VoIP support for emergency calls (including location support) is specified as part of Rel 9. This fulfils the last regulatory requirement separating VoIP from CS in 3GPP networks. A transition solution exists which is falling back to 3G/2G for completing emergency calls. This solution has existed since IMS was introduced (Rel 5).

However, to satisfy the situation of a fallback network not existing, this enhancement was completed in Rel 9. This allows the operator the option of supporting the regulatory requirements for LTE VoIP calls both for phones that can register for normal services and for those in limited service, including the USIM-less case.

Also the emergency call callback from the PSAP and its interaction with the possibly activated supplementary services is specified.

Legacy ServiceTransition SolutionEPS Solution
CS Voice CS Fallback (Rel 8) IMS VoIP (Rel 7)
SMS SMS over SGs (used to be called SMS over CS) (Rel 8) SMS over IP (Rel 7)
Supplementary Services CS Fallback (Rel 8) Multimedia Telephony (Rel 7)
Emergency Calls w Location Support CS Emergency Calls (Rel 5) IMS Emergency Calls w Location Support (Rel 9)

Wednesday, December 02, 2009

What is LTE

Introduction
LTE (Long Term Evolution) is the preferred development path of
GSM/W-CDMA/HSPA networks currently deployed, and an
option for evolution of CDMA networks. This essential evolution
will enable networks to offer the higher data throughput to mobile
terminals needed in order to deliver new and advanced mobile
broadband services.
The primary objectives of this network evolution are to provide
these services with a quality at least equivalent to what an end-user
can enjoy today using their fixed broadband access at home, and to
reduce operational expenses by means of introducing flat IP
architecture.

Why LTE
lthough 3G/3.5G technologies such as HSPA/EV-DO deliver
significantly higher bit rates than 2G technologies, they do not
fully satisfy the “wireless broadband” requirements of instant-on,
always-on and multi-megabit throughput. With LTE delivering
even higher peak throughput and much lower latency, mobile
operators (either 3GPP or 3GPP2 based) have a unique
opportunity to evolve their existing infrastructure to next-
generation wireless networks. These
networks will deliver their subscriber’s Quality of Experience
(QoE) expectations in terms of real-time services such as Voice
Over IP, Multi-User Gaming Over IP, High Definition Video On
Demand and Live TV. This will also continue to improve the
quality of delivery for all legacy applications (e-mail, internet
browsing, MMS, etc.)

The improved speed and low latency provided by LTE will offer a
much improved end-user experience for all corporate services:
• For applications where data throughput is important - faster e-
mail and file uploads, enhanced VPN connection, high-speed
internet, etc. and;
• For interactive applications where latency is crucial - IMS
based VoIP, mail and file synchronization with an on-line
server, peer-to-peer applications such as “NetMeeting”, SIP
multimedia services including video and voice conference
over IP, application sharing, etc.

In addition to typical corporate applications, we expect an
increased interest from the vertical markets where information
accuracy, reliability and immediacy are key: medical applications
where latency and high resolution imaging are highly important;
machine-to-machine communication where security and
immediacy are crucial; live network based navigation; etc.
The mass market will benefit from improvements delivered by LTE
for all person-to-person and internet community applications:
Push-to-See, improved quality for VoIP, photo and video
downloading / uploading for personal blogs, online gaming,
mobile social networks (such as YouTube, myspace), and “Second
life” type applications etc.
On top of those improvements, LTE will enable the introduction
of new services, such as High Definition Video (or HD TV) and
multi-user interactive gaming:
• HD TV requires between 10 to 20 Mbits/s bandwidth (18
Mbits/s for example with Blue Ray standard), which is higher
than current HSPA capabilities.
• Interactive multi-user gaming is extremely sensitive to latency:
the very low latency offered by LTE (less than 10ms versus
60ms with HSPA) is key for fighting games, car races, or any
action games involving a large number of simultaneous users.
In addition, the higher throughput offered will enable high-
resolution video games.
Lastly LTE will play a key role in the development of N-uple
services at home (IP TV, Internet, telephone, mobile…services
bundle). We are observing an increasing need for broadband
access at home and the same will apply to mobile services for two
main reasons. Firstly, as subscribers become used to higher speeds
at home, they will require the same quality of service when they are
mobile so as to benefit from a seamless experience. The second
reason is the possibility of offering higher bandwidth in remote
areas where ADSL throughput is no longer sufficient and fibre
may not be economically viable compared with LTE. In those areas
the same LTE infrastructure will deliver mobile services as well as
broadband access at home, bringing economies of scale.

With the recent introduction of HSDPA and EV-DO Rev A, we
have observed a significant increase in mobile data traffic, with
some operators quadrupling their Packet Switched traffic in one
year. At this growth rate, and with the proliferation of new
applications on the network, cells in hot spots will be quickly
saturated and the network will require densification in these
overloaded areas. This can be delivered by using a higher capacity
solution such as LTE.

LTE and Multimedia Broadcast Multicast Service
The Multimedia Broadcast Multicast Service (MBMS) enables
multiple users to receive data over the same radio resource. This
creates a more efficient approach for delivering content, such as
video programming, to which multiple users have subscriptions.
However, with HSPA, MBMS does not match the capabilities of
broadcasting and/or broadband wireless technologies (such as
DVB-H or WiMAX). With an OFDM/SC-FDMA (Orthogonal
Frequency Division Multiplex /Single-Carrier Frequency Division
Multiple Access) system, LTE provides the possibility of operating
MBMS in a single frequency network mode where significant
performance gains (up to five times existing capacity) can be
achieved without additional receiver complexity. LTE will
consequently dramatically enhance MBMS, and match DVB-H
and WiMAX, capabilities.

Reducing the Total Cost of Ownership
Another key driver behind LTE is the reduction of the cost per
byte, which is expected to decrease by a factor of six compared with
HSPA today. This cost reduction is derived from
network simplification, with flat IP architecture and the enhanced
capacity delivered by the new radio technologies implemented by
LTE.


What Is LTE Technology?
In order to prepare for wireless operator’s future needs and to
ensure the competitiveness of their mobile systems over the next
ten years, a progression of network architecture, as well as an
evolution of the radio interface is required. This is being evaluated
in the 3GPP System Architecture Evolution (SAE), Long Term
Evolution (LTE) and HSPA Evolution (HSPA+) Study Items. From
a network deployment perspective it is likely that HSPA
enhancements will be introduced first followed by the progression
to a radio interface (LTE).
LTE will allow operators to achieve even greater peak throughputs
in higher spectrum bandwidth, and to benefit from greater
capacity at a reduced cost. Initial deployments are targeted for
2009.
LTE characteristics include:
• Peak LTE throughputs (high spectral efficiency)
− DL: 100 Mb/s SISO (Single Input Single Output);
− 173 Mb/s 2x2 MIMO (Multiple Input Multiple Output);
− 326 Mb/s 4x4 MIMO; for 20 MHz
− UL: 58 Mb/s 16 QAM
− 86 Mb/s 64 QAM (based on 1 Tx UE)
• Increased Spectrum efficiency over Release 6 HSPA
− DL: 3-4 times HSDPA for MIMO (2,2)
− UL: 2-3 times E-DCH for MIMO(1,2)
• Ultra low Latency
− less than 10 msec for round-trip delay (RTD) from UE to
server
− Reduced call setup times (50-100ms)
− =>wired user experience
• Capacity per cell
− 200 users for 5 MHz, 400 users in larger spectrum
allocations
• Flexible spectrum use maximizes flexibility
− 1.4, 3/3.2, 5, 10, 15, 20 MHz
− All frequencies of IMT-2000: 450 MHz to 2.6 GHz
LTE is being developed by the 3GPP (3rd generation Partnership
Project) standards body that is also responsible for GSM and W-
CDMA. LTE standards are currently being developed and are
expected to be finalized in early 2008.
In order to reach this performance, LTE will make the best use of
the latest technologies on the market. For radio, a new modulation
scheme is being used based on OFDM, and the latest antenna
technologies, such as MIMO will be deployed. For the core
network, an IP based network topology will also be introduced to
considerably reduce network complexity.
LTE uses Orthogonal Frequency Division Multiple Access
(OFDMA) on the downlink, which is better suited than W-CDMA
for achieving high peak data rates in high spectrum bandwidth.
On the uplink LTE uses SC-FDMA (Single Carrier Frequency
Division Multiple Access), a technology that provides advantages
in power efficiency and resulting terminal battery life versus a pure
OFDM approach.

MIMO refers to a technique that employs multiple transmit and
receive antennas, often in combination with multiple radios and
parallel data streams. This results in numerous data paths
effectively operating in parallel and, through appropriate decoding,
a multiplicative gain in throughput. For example, with a 2X2
MIMO system, a gain of a factor of 2 is expected on the peak
throughput.
LTE also requires new network architecture, with the main
functional entities being: the e-node B on the access side, and the
Serving (S) and Packet Data Network (PDN) gateways and the
Mobile Management Entity (MME) in the core network, as
depicted in the figure below.
LTE is a pure packet system, with no support for legacy circuit-
switched voice/data. This shift allows a significant simplification of
the network, reducing the number of nodes and improving
operational efficiencies. This network simplification also removes
any bottlenecks from the system, ensuring the network
permanently runs at peak efficiency.
The next figure shows the impacts of this simplification comparing
traditional UMTS elements and LTE nodes, and provides a
macroscopic mapping of User Plane and Control Plane between
nodes.


In contrast to UMTS architecture, no Radio Network Controller
(RNC) is required: the RNC’s functions are collapsed into the
eNodeB. On the Core network side, the Mobility Management
Entity (MME) assumes the role of the SGSN for the control plane,
and the serving and PDN gateways ensure the role of user plane,
routing user data traffic to the network edge, replacing the GGSN.

Tuesday, October 13, 2009

A peek into the (not-so-distant) future of wireless broadband

What are the applications and services LTE will make possible? Check out this video to find out! Connected car, crowdcasting, mobile e-commerce… these are some of the reasons people in this video are so happy!

video

Source: Alcatel-Lucent blog.

Tuesday, July 07, 2009

Ping & Traceroute Troubleshooting Example

In this example, a ping to 186.9.17.153 gave a “TTL timeout” message. Ping TTLs will usually only timeout if there is a routing loop in which the packet bounces between two routers on the way to the target. Each “bounce” causes the TTL to decrease by a count of one until the TTL reaches zero at which point you get the timeout.

The routing loop was confirmed by the traceroute in which the packet was proven to be bouncing between routers at 186.40.64.94 and 186.40.64.93.

G:\>ping 186.9.17.153

Pinging 186.9.17.153 with 32 bytes of data:

Reply from 186.40.64.94: TTL expired in transit.

Reply from 186.40.64.94: TTL expired in transit.

Reply from 186.40.64.94: TTL expired in transit.

Reply from 186.40.64.94: TTL expired in transit.

Ping statistics for 186.9.17.153:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 0ms, Maximum = 0ms, Average = 0ms

G:\>tracert 186.9.17.153

Tracing route to lostserver.confusion.net [186.9.17.153]

over a maximum of 30 hops:

1 <10>

2 60 ms 70 ms 60 ms rtr-2.confusion.net [186.40.64.94]

3 70 ms 71 ms 70 ms rtr-1.confusion.net [186.40.64.93]

4 60 ms 70 ms 60 ms rtr-2.confusion.net [186.40.64.94]

5 70 ms 70 ms 70 ms rtr-1.confusion.net [186.40.64.93]

6 60 ms 70 ms 61 ms rtr-2.confusion.net [186.40.64.94]

7 70 ms 70 ms 70 ms rtr-1.confusion.net [186.40.64.93]

8 60 ms 70 ms 60 ms rtr-2.confusion.net [186.40.64.94]

9 70 ms 70 ms 70 ms rtr-1.confusion.net [186.40.64.93]

...

...

...

Trace complete.

This problem was solved by resetting the routing process on both routers. The problem was initially triggered by an unstable network link that caused frequent routing recalculations. The constant activity eventually corrupted the routing tables of one of the routers.


Possible Reasons For Failed Traceroutes

Traceroutes can fail to reach their intended destination for a number of reasons, these include:

o Traceroute packets are being blocked or rejected by a router in the path. The router immediately after the last visible one is usually the culprit. It’s usually good to check the routing table and/or other status of this next hop device.

o The target server doesn’t exist on the network. It could be disconnected, or turned off. (!H or !N messages may be produced.)

o The network on which you expect the target host to reside doesn’t exist in the routing table of one of the routers in the path (!H or !N messages may be produced.)

o You may have a typographical error in the IP address of the target server

o You may have a routing loop in which packets bounce between two routers and never get to the intended destination.

o The packets don’t have a proper return path to your server. The last visible hop being the last hop in which the packets return correctly. The router immediately after the last visible one is the one at which the routing changes. It’s usually good to:

v log on to the last visible router.

v Look at the routing table to determine what the next hop is to your intended traceroute target.

v Log on to this next hop router.

v Do a traceroute from this router to your intended target server.

v If this works: Routing to the target server is OK. Do a traceroute back to your source server. The traceroute will probably fail at the bad router on the return path.

v If it doesn’t work: Test the routing table and/or other status of all the hops between it and your intended target.

Note: If there is nothing blocking your traceroute traffic, then the last visible router of an incomplete trace is either the last good router on the path, or the last router that has a valid return path to the server issuing the traceroute.