Session Announcement Proto col Colin P erkins < c.p - PowerPoint PPT Presentation

Session Announcement Proto col Colin P erkins < c.p erkins@cs.ucl.ac.uk > Depa rtment of Computer Science Universit y College London Go w er Street London W C1E 6BT

The new SAP draft The current sp ec (draft-ietf-mmusic-sap-v2-01.txt) is a merger of draft-ietf-mmusic-sap-00.txt (from Novemb er 1996!) � draft-ietf-mmusic-sap-sec-04.txt � draft-ietf-mmusic-sap-v2-00.txt � Aiming to get an exp erimental RF C out relatively so on. Colin P erkins/SAPv2-01/1

Overview of changes Supp o rt fo r IPv6 and directo ry sessions � Up date address/p o rt usage � Up date bandwidth recommendations � Comp ression using zlib � P a yload t yp e �eld � Authenticated announcements � Asso rted mino r bug-�xes � Colin P erkins/SAPv2-01/2

Supp o rt fo r IPv6 Add an address t yp e bit to the SAP header and allo w the � o riginating source �eld to b e an IPv6 address The IPv6 SAP address is FF0X:0:0:0:0:0 :2: 7FFE, where � X is the 4-bit scop e value. The follo wing scop e values a re de�ned in IPv6: V alue Scop e 0x1 No de-lo cal 0x2 Link-lo cal 0x5 Site-lo cal 0x8 Organization-lo cal 0xE Global Colin P erkins/SAPv2-01/3

Directo ry Sessions Allo w SAP directo ries to b e announced within SAP { due � to Ross Finla yson. SDP syntax: � v=0 o=cperkin s 28908445 26 289084280 7 IN IP4 126.16.6 4.4 s=Sample directory session m=directo ry 9875 SAP applicatio n/s dp c=IN IP4 224.2.127. 12 /25 5 t=2873397 496 28734046 96 Announced b y SAP in the usual manner. � Colin P erkins/SAPv2-01/4

Directo ry Sessions Any one ma y announce sessions within a directo ry � Do w e w ant to restrict this? { Changes to the announcement of the directo ry MUST b e � authenticated If the directo ry is deleted, MUST stop announcing { sessions within it If the directo ry moves, MUST move announcements { of sessions to the new group Colin P erkins/SAPv2-01/5

P o rts and TTLs Announcements MUST use p o rt 9875 with TTL 255. � Previous versions allo w ed TTL scoping - w e do not - and � admin scop ed sessions w ere allo w ed to sp ecify a di�erent p o rt. What do current implementations do? � Colin P erkins/SAPv2-01/6

Bandwidth recommendation s Bandwidth limit fo r each group is no w 4 kbps - p revious � versions used 200 bps fo r global scop e groups, and 2 kbps fo r lo cal groups. Minimum timeout is increased from 30 minutes to 1 hour. � Colin P erkins/SAPv2-01/7

Comp ression Sp ecify zlib instead of gzip. � Use of gzip w as a mistak e, and only implementation used � zlib. Colin P erkins/SAPv2-01/8

P a yload t yp e W e no w allo w an optional pa yload t yp e to b e included in each announcement. Ma y b e ommitted, in which case default is SDP � All implementations MUST supp o rt application/SDP � Use of non-SDP pa yloads is NOT RECOMMENDED due � to interop erabilit y concerns Colin P erkins/SAPv2-01/9

Encryption The SAP header retains a single bit to indicate that the � pa yload is encrypted. W e do not sp ecify any encryption algo rithms in this � draft: leave to other drafts if supp o rt is desired. Encrypted announcements a re NOT RECOMMENDED � on groups where there ma y b e many receivers without the decryption k ey , due to w aste to bandwidth. Colin P erkins/SAPv2-01/10

Authenticatio n Sp ecify authentication using either Op enPGP o r CMS � As in SAP securit y drafts, but up dated fo r new versions � of the authentication sp ecs. Colin P erkins/SAPv2-01/11

P ack et fo rmat 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+ -+-+-+- +-+-+-+- +-+-+-+ -+-+-+-+ -+-+-+-+ | V=1 |A|R|T|E|C| auth len | msg id hash | +-+-+-+-+-+-+-+-+-+-+-+-+-+ -+-+-+- +-+-+-+- +-+-+-+ -+-+-+-+ -+-+-+-+ | | : originating source (32 or 128 bits) : : : +-+-+-+-+-+-+-+-+-+-+-+-+-+ -+-+-+- +-+-+-+- +-+-+-+ -+-+-+-+ -+-+-+-+ | optional authentication header | : .... : +-+-+-+-+-+-+-+-+-+-+-+-+-+ -+-+-+- +-+-+-+- +-+-+-+ -+-+-+-+ -+-+-+-+ | optional timeout | *-*-*-*-*-*-*-*-*-*-*-*-*-* -*-*-*- *-*-*-*- *-*-*-* -*-*-*-* -*-*-*-* | optional payload type | + +-+- - - - - - - - - -+ | |0| | + - - - - - - - - - - - - - - - - - - - - +-+ | | | : payload : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+ -+-+-+- +-+-+-+- +-+-+-+ -+-+-+-+ -+-+-+-+ Colin P erkins/SAPv2-01/12

Op en Issues Should the SDP syntax fo r directo ry sessions b e de�ned � here? Calculation of announcement interval is not w ell sp eci�ed � Colin P erkins/SAPv2-01/13