Exit Zen
12
../../glossary.rst:48
English
ARPANET
0/100 · 7
12
../../exercises/ex-sharing.rst:231
English
With CSMA, hosts need to listen to the communication channel before starting their transmission. Consider again a 2 kilometers long cable where hosts send frames at 100 Mbps. Show in the figure below the correct transmission of frames with CSMA.
0/2450 · 245
12
../../principles/security.rst:155
English
Eavesdropping and pervasive monitoring are not the only possible attacks against a network. Another type of attacker is the active attacker. In the literature, these attacks are often called `Man in the middle` or `MITM` attacks. Such attacks occur when one user, let us call him `Mallory`, has managed to configure the network so that he can both capture and modify the packets exchanged by two users. The simplest scenario is when Mallory controls a router that is on the path used by both Alice and Bob. For example, Alice could be connected to a WiFi access router controlled by Mallory and Bob would be a regular server on the Internet.
0/6410 · 641
12
../../exercises/dns.rst:41
English
What are the IP addresses of the resolvers that the `dig` implementation you are using relies on [#fdig]_ ?
0/1070 · 107
12
../../exercises/email.rst:27
English
On Unix hosts, a subset of the port assignments is often placed in `/etc/services`.
0/830 · 83
12
../../exercises/http.rst:33
English
Some websites are reachable over both IPv4 and IPv6 while others are only reachable over IPv4 [#fv6only]_. You can use the `-6` (resp. `-4`) option to force curl_ to only use IPv6 (resp. IPv4). Verify that `www.computer-networking.info` is reachable over IPv6 and IPv4 and then check whether your university website already supports IPv6.
0/3380 · 338
12
../../exercises/ipv6.rst:41
English
router ``R2`` uses address ``2001:db8:1341:12::2`` on its West interface, address ``2001:db8:1341:23::2`` on its South-West interface and address ``2001:db8:1341:24::2`` on its South interface.
0/1930 · 193
12
../../exercises/lan.rst:83
English
Fig. 4. Can `H0` and `H1` communicate ?
0/390 · 39
12
../../exercises/routing-policies.rst:141
English
Should `AS123` change its configuration ?
0/410 · 41
12
../../exercises/routing-protocols.rst:175
English
The ``show ipv6 ospf6`` command reports the general state of the OSPFv3 daemon. The ``show ipv6 ospf6 neighbor`` command reports the state of the connected neighbors.
0/1660 · 166
12
../../exercises/tcp-2.rst:63
English
The ``0`` indicates that the system call must be issued immediately. packetdrill_ then executes the system call and verifies that it returns ``3```. If yes, the processing continues. Otherwise the script stops and indicates an error.
0/2340 · 234
12
../../exercises/trace.rst:79
English
tcpdump_ can provide more detailed information about the packets by using the `-v` or `-vv` option.
0/990 · 99
12
../../protocols/bgp.rst:47
English
The first category of peering relationship is the `customer->provider` relationship. Such a relationship is used when a customer domain pays an Internet Service Provider to be able to exchange packets with the global Internet over an interdomain link. A similar relationship is used when a small Internet Service Provider pays a larger Internet Service Provider to exchange packets with the global Internet.
0/4070 · 407
12
../../protocols/congestion.rst:43
English
Evaluation of the TCP congestion window when the network is lightly congested
0/770 · 77
12
../../protocols/dnssec.rst:144
English
To cope with these security threats and improve the security of the DNS, the IETF has defined several extensions that are known as DNSSEC. DNSSEC exploits public-key cryptography to authenticate the content of the DNS records that are sent by DNS servers and resolvers. DNSEC is defined in three main documents :rfc:`4033`, :rfc:`4034`, :rfc:`4035`. With DNSSEC, each DNS zone uses one public-private key pair. This key pair is only used to sign and authenticate DNS records. The DNS records are not encrypted and DNSSEC does not provide any confidentiality. Other DNS extensions are being developed to ensure the confidentiality of the information exchanged between a client and its resolvers :rfc:`7626`. Some of these extensions exchange DNS records over a TLS session which provides the required confidentiality, but they are not yet deployed and outside the scope of this chapter.
0/8850 · 885
12
../../protocols/email.rst:61
English
the `body` that contains the message itself.
0/440 · 44
12
../../protocols/ethernet.rst:81
English
The Ethernet frame format shown above is specified in [DIX]_. This is the format used to send both IPv4 :rfc:`894` and IPv6 packets :rfc:`2464`. After the publication of [DIX]_, the Institute of Electrical and Electronic Engineers (IEEE) began to standardize several Local Area Network technologies. IEEE worked on several LAN technologies, starting with Ethernet, Token Ring and Token Bus. These three technologies were completely different, but they all agreed to use the 48 bits MAC addresses specified initially for Ethernet [IEEE802]_ . While developing its Ethernet standard [IEEE802.3]_, the IEEE 802.3 working group was confronted with a problem. Ethernet mandated a minimum payload size of 46 bytes, while some companies were looking for a LAN technology that could transparently transport short frames containing only a few bytes of payload. Such a frame can be sent by an Ethernet host by padding it to ensure that the payload is at least 46 bytes long. However since the Ethernet header [DIX]_ does not contain a length field, it is impossible for the receiver to determine how many useful bytes were placed inside the payload field. To solve this problem, the IEEE decided to replace the `Type` field of the Ethernet [DIX]_ header with a length field [#ftypelen]_. This `Length` field contains the number of useful bytes in the frame payload. The payload must still contain at least 46 bytes, but padding bytes are added by the sender and removed by the receiver. In order to add the `Length` field without significantly changing the frame format, IEEE had to remove the `Type` field. Without this field, it is impossible for a receiving host to identify the type of network layer packet inside a received frame. To solve this new problem, IEEE developed a completely new sublayer called the Logical Link Control [IEEE802.2]_. Several protocols were defined in this sublayer. One of them provided a slightly different version of the `Type` field of the original Ethernet frame format. Another contained acknowledgments and retransmissions to provide a reliable service... In practice, [IEEE802.2]_ is never used to support IP in Ethernet networks. The figure below shows the official [IEEE802.3]_ frame format.
0/22230 · 2223
12
../../protocols/http.rst:53
English
Open standards and open implementations
0/390 · 39
12
../../protocols/http2.rst:68
English
Evolution of the size of the web pages (source: https://httparchive.org/reports/page-weight)
0/920 · 92
12
../../protocols/ipv6.rst:87
English
However, in parallel with these short-term solutions, which have allowed the IPv4 Internet to continue to be usable until now, the Internet Engineering Task Force started working on developing a replacement for IPv4. This work started with an open call for proposals, outlined in :rfc:`1550`. Several groups responded to this call with proposals for a next generation Internet Protocol (IPng) :
0/3940 · 394