程序代写 CS 6843 CS 6843 Fall 2019 Final Eam

CS 6843 CS 6843 Fall 2019 Final Eam
QUESTION 1 DNS 20 pts
1.1 i. 2 / 2
✓ – 0 pts Correct; describes example.com as the domain/zone name, and/or the start of the DNS zone file in the namespace

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– 1 pts Partially Correct; restates that it is the zone file, makes assumptions about zone hierarchy, and/or incomplete/inaccurate description regarding ORIGIN.
– 2 pts Incorrect;
1.2 ii. 1 / 2
– 0 pts Correct; the TTL field refers to the amount of
time that elapses prior to which a domain name client must discard the record and perform a new resolution operation.
✓ – 1 pts Partially correct; merely restating TTL without explaining what it is, or offers incomplete/inaccurate explanation
– 2 pts Incorrect
1.3 iii. 0 / 2
+ 1 pts Start of authority
+ 0.5 pts Primary name server
+ 0.5 pts Hostmaster email
+ 0.5 pts Serial Number; Time-to-
refresh/retry/expire; min TTL
✓ – 2 pts Incorrect
1.4 iv. 1 / 2
– 0 pts Correct; NS records identify the DNS servers
responsible (authoritative) for a zone, and/or ns.example.com is the nameserver for example.com ✓ – 1 pts Partially Correct;
– 2 pts Incorrect
1.5 v. 2 / 2
✓ – 0 pts Correct; backup name server for example.com
– 1 pts Partially Correct – 2 pts Incorrect
1.6 vi. 0 / 2
+ 2 pts mail.example.com is the mailserver for
example.com (with priority 10)
+ 1 pts Did not specify one of the following: domain
(example.com), mail exchange, or mailserver (mail.example.com); or, insufficient explanation
✓ + 0 pts Incorrect. MX means mail exchange. mail.example.com is the mailserver for example.com (with priority 10)
1.7 vii. 2 / 2
✓ + 2 pts Maps domain example.com to IPv4 address 192.0.2.1
+ 0 pts Incorrect. Maps domain example.com to IPv4 address 192.0.2.1
1.8 viii. 2 / 2
✓ + 2 pts Maps nameserver ns.example.com to IPv4 address 192.0.2.2
+ 1 pts Wrote “ns” instead of “ns.example.com” or other minor minor error
+ 0 pts Incorrect. Maps nameserver ns.example.com to IPv4 address 192.0.2.2
1.9 ix. 2 / 2
✓ + 2 pts www.example.com is an alias for example.com
+ 1 pts Mentioned www.example.com but unclear/insufficient explanation
+ 0 pts Incorrect. www.example.com is an alias for

example.com
1.10 x. 2 / 2
✓ + 2 pts Maps mail.example.com to IPv4 address 192.0.2.3
+ 0 pts Incorrect. Maps mail.example.com to IPv4 address 192.0.2.3. (Must write “mail.example.com” for credit)
QUESTION 2
2 DHCP T/F 18 / 20 – 2 pts a
– 2 pts b – 2 pts c – 2 pts d – 2 pts e – 2 pts f – 2 pts g
✓ – 2 pts h
– 0 pts Correct
QUESTION 3 MPLS 30 pts
3.1 a 3 / 5
✓ + 2 pts A label-switch path (LSP) is a path through an MPLS network.
✓ + 2 pts LSPs are represented by the series of ingress/egress labels of the MPL routers in the path.
+ 1 pts Unidirectional
+ 1 pts LSP is set up manually or by a signaling protocol such as RSVP.
– 5 pts Incorrect/Unanswered – 1 Point adjustment
3.2 b 4 / 5
✓ + 2 pts An LER is a router on the edge of the MPLS network.
✓ + 2 pts On ingress, it checks on the final destination and decides which of the LSPs to use. It
then assigns a label as it sends packets into the MPLS network
✓ + 1 pts On egress it removes the label and the packet is delivered by standard routing protocols.
– 1 Point adjustment
3.3 c 4 / 5
✓ + 3 pts An LSR is an MPLS router in the interior of an MPLS network.
✓ + 2 pts It accepts labeled packets looks up the label in its lookup table and sends the packet out with a new label from the label table.
+ 1 pts Does not perform IP lookup or IP routing
+ 0 pts Incorrect
– 1 Point adjustment
3.4 d 5 / 5
+ 2.5 pts LSP is precalculated
✓ + 2.5 pts No routing lookups in LSP once set up ✓ + 2.5 pts Output interfaces are chosen by label in label table. Faster
+ 0 pts Incorrect
3.5 e 5 / 5
✓ + 2.5 pts Signaling protocol to reserve resources for the path
✓ + 2.5 pts Used for LSP setup
+ 0 pts Incorrect
3.6 f 0 / 5
– 0 pts Correct
✓ – 5 pts Incorrect. An MPLS fast reroute is a backup LSP that is used is and when the primary LSP fails for some reason. Since it is already setup, traffic quickly switches to the backup LSP
– 2.5 pts Partially correct. An MPLS fast reroute is a backup LSP that is used is and when the primary LSP fails for some reason. Since it is already setup, traffic quickly switches to the backup LSP

QUESTION 4
IP Multicast 20 pts
4.1 a 2 / 5
+ 3 pts A Multicast group is a collection of
interested receivers that are communicating using IP Multicast.
+ 2 pts Multicast groups use a single identifier for the group of receivers.
✓ + 2 pts This identifier is a class D multicast IP address (224.0.0.0 to 239.255.255.255)
+ 0 pts Incorrect
4.2 b 4 / 5
✓ + 2 pts IGMP is the group management protocol for IP Multicast.
+ 1 pts Membership query ✓ + 1 pts Membership report ✓ + 1 pts Leave group
+ 0 pts Incorrect
4.3 c 5 / 5
✓ + 4 pts Prevents hosts on a local network from receiving traffic for a multicast group they have not explicitly joined
✓ + 1 pts Snooping takes place on switches
+ 2 pts Switch listens in on IGMP traffic + 0 pts Incorrect
4.4 d 5 / 5
✓ + 5 pts Described at least one advantage
+ 0 pts Incorrect QUESTION 5
BGP 10 pts
5.1 a 3 / 3
✓ + 3 pts An autonomous system is a network under a common management and common routing protocol. An ASN is assigned to an autonomous system.
+ 0 pts Incorrect
5.2 b 2 / 2
✓ + 1 pts Exterior Border Gateway Protocol that determines how separate AS’s interact with each other.
✓ + 1 pts Directly connected on TCP port 179 so that they can share information about routes.
+ 0 pts Incorrect
5.3 c 2 / 2
✓ – 0 pts Correct
– 2 pts Incorrect. iBGP is the interior BGP which runs between the iBGP routers within an AS
5.4 d 3 / 3
✓ + 1.5 pts List of AS numbers (ASNs) that are traversed between sender and receiver
✓ + 1.5 pts Included one of the following: Indicates cost of travel and used to prevent loops, some other use case
+ 0 pts Incorrect. An AS path is a list of AS numbers (ASNs) that are traversed between a sender and receiver. It indicates the cost of travel and is used to prevent loops

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