Post on 20-Jan-2016
transcript
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Requirements for Internet Routers (Gateways) and Hosts
Relates to Lab 3. (Supplement)
Covers the compliance requirements of Internet routers and hosts.
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What does it mean to be IP compliant?
• Requirements for Internet Routers and hosts have been document in Request for Comments (RFCs) of the Internet Engineering Task Force (IETF):
• RFC 985: Requirements for Internet Gateways – Draft (1986)• RFC 1009: Requirements for Internet Gateways (1987)• RDC 1716: Towards Requirements for IP Routers (1994)• RFC 1812: Requirements for IP Version 4 Routers (1995)• RFC 1122 (STD 3): Requirements for Internet Hosts - Communication
Layers (1989)• RFC 1123 (STD 3): Requirements for Internet Hosts - Application and
Support (1989)• Updated in many other RFCs
Language of Requirements
MUST – absolute requirement of the specification.
MUST IMPLEMENT – Implementation is required, but need not be enabled by default
MUST NOT – absolute prohibition of the specification.
SHOULD – there may exist valid reasons to, but full implications must be understood and weighed (recommended)
SHOULD NOT – there may exist valid reasons to include, but full implications must be understood and weighed (not recommended)
MAY / OPTIONAL – optional
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Robustness Principle
"Be liberal in what you accept, and conservative in what you send”
• The principle should be applied by all protocols to increase robustness and interoperability
• Other hosts and routers may use deficient implementations
”Be Adaptive to Change" • Assume that protocol will be extended in the future, and
options will be added
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HOST REQUIREMENTS: IPv4 (partial list)
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HOST REQUIREMENTS: IPv4 (partial list)
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HOST REQUIREMENTS: IPv4 (partial list)
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Definition of an IP router (gateway)
1. Conforms to specific Internet protocols, including IP and ICMP
2. Interfaces to two or more packet networks– Encapsulation/decapsulation, MTU, address translation
3. Receives and forwards Internet datagrams. – Recognizes error conditions, Drop when TTL=0, perform
fragmentation
4. Chooses next hop
5. Supports a routing protocol
6. System Support (debugging, status report, etc.)
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ROUTER REQUIREMENTS: IPv4 (partial list)
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ROUTER REQUIREMENTS: IPv4 (partial list)
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See RFC’s for more rules.
HOST REQUIREMENTS: IPv4 (partial list)
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HOST REQUIREMENTS: IPv4 (partial list)
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HOST REQUIREMENTS: IPv4 (partial list)
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Definition of an IP router (gateway)
1. Conforms to specific Internet protocols, including IP and ICMP
2. Interfaces to two or more packet networks– Encapsulation/decapsulation, MTU, address translation
3. Receives and forwards Internet datagrams. – Recognizes error conditions, Drop when TTL=0, perform
fragmentation
4. Chooses next hop
5. Supports a routing protocol
6. System Support (debugging, status report, etc.)
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ROUTER REQUIREMENTS: IPv4 (partial list)
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ROUTER REQUIREMENTS: IPv4 (partial list)
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See RFC’s for more rules.