Exit Zen
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
12
../../protocols/ppp.rst:31
English
PPP played a key role in allowing Internet Service Providers to provide dial-up access over modems in the late 1990s and early 2000s. ISPs operated modem banks connected to the telephone network. For these ISPs, a key issue was to authenticate each user connected through the telephone network. This authentication was performed by using the `Extensible Authentication Protocol` (EAP) defined in :rfc:`3748`. EAP is a simple, but extensible protocol that was initially used by access routers to authenticate the users connected through dial-up lines. Several authentication methods, starting from the simple username/password pairs to more complex schemes have been defined and implemented. When ISPs started to upgrade their physical infrastructure to provide Internet access over `Asymmetric Digital Subscriber Lines` (ADSL), they tried to reuse their existing authentication (and billing) systems. To meet these requirements, the IETF developed specifications to allow PPP frames to be transported over other networks than the point-to-point links for which PPP was designed. Nowadays, most ADSL deployments use PPP over either ATM :rfc:`2364` or Ethernet :rfc:`2516`.
0/11710 · 1171
12
../../protocols/ppp.rst:35
English
`LAPB <http://en.wikipedia.org/wiki/LAPB>`_ and `HDLC <http://en.wikipedia.org/wiki/HDLC>`_ were widely used datalink layer protocols.
0/1340 · 134
12
../../protocols/routing.rst:38
English
The Routing Information Protocol (RIP) is the simplest routing protocol that was standardized for the TCP/IP protocol suite. RIP is defined in :rfc:`2453`. Additional information about RIP may be found in [Malkin1999]_.
0/2190 · 219
12
../../protocols/rpc.rst:27
English
The encoding problem exists in a wide range of applications. In the previous sections, we have described how character-based encodings are used by email and HTTP. Although standard encoding techniques such as ASN.1 [Dubuisson2000]_ have been defined to cover most application needs, many applications have defined their specific encoding. `Remote Procedure Call` are no exception to this rule. The three most popular encoding methods are probably XDR :rfc:`1832` used by ONC-RPC :rfc:`1831`, XML, used by XML-RPC and JSON :rfc:`4627`.
0/5340 · 534
12
../../protocols/ssh.rst:87
English
compression
0/110 · 11
12
../../protocols/tcp.rst:35
English
A TCP header contains the following fields :
0/440 · 44
12
../../protocols/tls.rst:44
English
IMAP
0/100 · 4
12
../../protocols/transport-service.rst:25
English
IPv4 addresses are usually represented by using a dotted decimal representation where each decimal number corresponds to one byte of the address, e.g. `203.0.113.56`. IPv6 addresses are usually represented as a set of hexadecimal numbers separated by semicolons, e.g. `2001:db8:3080:2:217:f2ff:fed6:65c0`. Today, most Internet hosts have one IPv4 address. A small fraction of them also have an IPv6 address. In the future, we can expect that more and more hosts will have IPv6 addresses and that some of them will not have an IPv4 address anymore. A host that only has an IPv4 address cannot communicate with a host having only an IPv6 address. The figure below illustrates two applications that are using the datagram service provided by UDP on hosts that are using IPv4 addresses.
0/7820 · 782
12
../../protocols/udp.rst:54
English
a 16 bits destination port
0/260 · 26